I. Neplohov, Ph.D., Technical Director according to PS company ADT/Tyco
PART 1
Lack of loop classification fire alarm and communication lines in systems fire automatics in domestic standards is a significant drawback that determines the low level of performance of fire alarm, warning and fire protection. The principles of constructing threshold, multi-threshold and addressable analog loops have already been repeatedly discussed in the industry press, however, increased regulatory requirements in terms of ensuring the operability of loops and communication lines in fire conditions have led to the need to return to this topic once again.
It is obvious that only the use of fire-resistant FRLS and FRHF cables does not provide a significant increase in system performance; disconnecting one detector blocks the “FIRE” signal from all other detectors in this loop. What is the use of using an expensive cable with 3-hour fire resistance at a temperature of 750 ° C if the device connected to it burns out 5 minutes after the start of the fire and thereby ensures a break or short circuit in the communication line. Requirements for the performance of non-addressed and addressable fire alarm loops, Unfortunately, they have not undergone any changes in terms of ensuring full or at least partial operability in the event of a break or short circuit of loops and communication lines. True, in new version GOST R 53325, apparently, short-circuit insulators will be introduced for ring and radial stubs, but when the requirements for their mandatory use will be determined and in what form is still unknown.
On the other hand, the manuals of foreign non-addressable devices and addressable modules of non-addressable sub-loops define the possibility of creating and programming various styles and classes of loops and communication lines, but the methodology for selecting them taking into account our regulatory requirements is not given. The first part of the article mainly examines the classification of loops according to NFPA72, and the second part of the article will analyze the technical characteristics of addressable modules of non-addressable sub-loops and addressable control modules when programming various styles and classes.
CLASSES AND CABLE STYLES ACCORDING TO NFPA72
Communication lines with actuators, with sirens, alarm loops with fire detectors, and so on can only be either class A or class B. Alarm loops and communication lines with actuators, which in the event of a single break or not simultaneously in the event of a single short circuit to the ground of any conductor retains the ability to generate an alarm signal from any fire detector of this loop or which ensure the operation of all devices connected to that communication line are defined as class A.
Table 1. Classes and styles of loop with detectors
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Break of one conductor |
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Conductor short circuit to ground |
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Short circuit of loop conductors |
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P - Fire; N - Malfunction; N+P - Fire in the presence of a malfunction
Alarm loops and communication lines with actuators, which under these conditions ensure the transmission of an alarm signal only from fire detectors to the point of the break and do not ensure the operability of devices beyond the point of break or a single ground fault of any conductor of the alarm loop or communication line, are defined as class B.
Moreover, if a loop conductor or communication line breaks, or if it is shorted to ground, a fault signal should be generated within 200 seconds. No other classes of loops with other properties, for example, which do not ensure the operation of detectors not only after the break point, but also before it, are classified, and their use in fire automatic systems is not allowed.
Class B loops are divided by style into A, B and C. They all must provide fault detection in the event of a single break in any loop conductor or a single short circuit to ground. When a short circuit occurs in style A and B loops, a “Fire” signal is generated, and a “Fault” signal is generated in the style C loop. In style B and C loops, a fault such as a single conductor short circuit to ground should not block the formation of the “Fire” signal (Table 1).
Class A trains are divided by style into D and Ea. They must provide fault detection in the event of a single break in any loop conductor or a single short circuit to ground. When the D style loops are short-circuited, a “Fire” signal is generated, and a “Fault” signal is generated for the Ea style loops. In D and Ea style loops, a fault such as a single loop conductor break or a single conductor short circuit to ground should not block the formation of the “Fire” signal (Table 1).
Thus, taking into account the requirements of GOST R 53325 on monitoring loop faults not only during a break, but also during a short circuit, when programming the loop style, you can only select style C for a class B loop and style Ea for class A. In loops of style A, B and D, if the loop is short-circuited, a false alarm will be generated.
To make the technical implementation clear when meeting the requirements for class A and B loops, let’s consider what recommendations are given in NFPA72 Appendix C on the methodology for testing them.
CHECKING LINES OF DIFFERENT CLASSES AND STYLES
It is recommended that the functionality of Class B two-wire loops (Style A, B and C) with fire smoke detectors be checked as follows. Break the loop by removing the detector from the base or disconnecting the loop conductor. Activate the smoke detector, which is located between the control panel and the loop break, as recommended by the manufacturer of this type of detector. After this, install the removed detector into the base or restore the loop connection, or do both. The control panel must indicate a malfunction after a loop break and generate an alarm signal when the detector is activated, despite the presence of a loop break. It should be noted that class B can include both radial loops (Fig. 1a) and ring loops (Fig. 1b), while all detectors remaining connected to the alarm loop output must be able to detect a fire, and detectors located behind the break in the loop are in a disabled state. Class B ring loops are formed in non-addressable threshold systems when the terminal element of the loop is located in the receiving and control device. In this case, there is significantly more reliable information about the change in the state of the loop during operation by analyzing the change in voltage at the input and output of the loop compared to a traditional radial loop with a terminal element at the end of the loop.
Rice. 1. Class B cables (style A, B or C)
Rice. 2. Class A train (style D and E)
It is recommended to check the functioning of two-wire class A loops (style D and Ea) with fire detectors as follows. Break the conductor in the middle part of the loop by removing it from the broadcaster and disconnecting the conductor from the base contact. Activate the detectors on both sides of the loop break (Fig. 2). After this, reset the device to standby mode, restore the loop connection and install the detector. Then repeat the test when any loop conductor is shorted to ground in the place where the detector was disconnected. In both tests, an audible and visual fault indication must first be activated, followed by an alarm indication followed by restoration. Unlike the Class B ring loop, the Class A ring loop is converted into 2 radial loops when a break is detected, and all detectors continue to function despite the presence of a fault. This is checked during testing.
Communication lines with devices of any type used in fire automatics are classified in a similar way. For all types of devices included in the communication lines, it remains necessary to fulfill the requirement to ensure the operability of devices connected before the communication line break in class B, and maintaining the operability of all devices regardless of their location relative to the break in class A. But for each individual type of device, depending from fulfilling other requirements when various types device faults identified various styles, which are designated by various letters or numbers. For example, communication lines with class B sirens (Fig. 3), in addition to the obligatory provision of operability of sirens before the communication line is broken, must satisfy additional requirements defined for style W or style Y. And communication lines with class A sirens (Fig. 4), in addition to ensuring the operability of all sirens before and after a communication line break, must satisfy additional requirements specified for style X or style Z.
Rice. 3. Communication lines with class B sirens, styles W and Y
Rice. 4. Communication lines with class A sirens, styles X and Z
The principle of separation into classes B and A must also be followed when using communication lines with devices various types. For example, Figure 5 shows loops with addressable and addressable-analog devices of various types: detectors and sirens. A radial loop of class B ensures the operability of all devices until the loop breaks, and a ring loop of class A ensures the operability of all devices, both in standby mode and in fire mode, despite the presence of a malfunction. In the addressable system, if there is no response from devices beyond the break point when polling, the output circuits of the ring loop are switched to operate in the mode of two radial loops. The fault is automatically localized by the distribution of devices between two radial loops formed and it is determined between which addressable devices the loop break occurred.
It must be emphasized that devices with communication lines or loops that do not meet the requirements for Class A or B are not classified and cannot be used in fire automatic systems according to NFPA72. For example, if, when a radial loop breaks, the detectors that remain connected to the device are not able to generate a “FIRE” signal, perceived by the device against the background of a malfunction, then such a system does not meet the requirements for class B loops and cannot be operated, despite its operability when no malfunction. Likewise, if the ring cable breaks anywhere, it is not allowed for at least several devices to stop functioning in standby mode or in “Fire” mode.
Rice. 5. Loop with class B detectors and sirens
Rice. 6. Loop with class A detectors and sirens
REQUIREMENTS GOST R 53325-2009
In our regulatory framework similar requirements for the classification of loops are completely absent, although, obviously, it is impossible to compensate for their low fault tolerance by installing three detectors instead of one. In GOST R 53325-2009, clause 7.2.1.1, there is a requirement that the control panels must ensure “preferential registration and transmission to external circuits of fire notifications in relation to other signals generated by the control panel.” Despite the fact that the same wording was already present in the NPB 75-98 of the last century, there are a lot of certified control panels on our market, in which a fire notification is not registered if there is a signal about a faulty loop, even if its end-of-line resistor and all alarms are turned off remain connected to the device and detect a fire, the “Fire” signal is blocked.
Ring addressable loops, despite their potential advantages over radial non-addressable ones, in our design cannot always be classified as class A. Methodology for checking the functioning of devices in the event of a malfunction in our regulatory documents is absent, and checks to ensure operability in the event of a cable break are not carried out. In addition, the loopback loop outputs can be combined on the board, and then a single loop break is not detected by the device. True, if the cable cross-section is chosen to be minimal, then in the event of a break, the voltage drop can be significant and a large number of addressable devices cease to function.
Sometimes installers, even on foreign addressable analog devices with separate loopback outputs, parallelize them in order to “eliminate” a malfunction that occurs due to a significant voltage drop on the loop with a small cable cross-section. But if the loop breaks, this error manifests itself in the form of a drop in the loop voltage below the permissible value and shutdown of a significant part of the devices.
For clarity, let’s consider an abstract example: a ring loop with a voltage of 20 V, approximately 1 km long, with a total current consumption of addressable devices of the order of 100 mA. The total cable resistance with a core cross section of 0.2 mm2 is about 200 Ohms. Assuming a uniform distribution of devices along the length of the loop, the current at each output of a parallel loop will be approximately equal to 50 mA, and taking into account the linear change along the loop, the average current in each half of the loop can be considered 25 mA. Accordingly, at a distance of 500 m at a resistance of 100 Ohms, the voltage will drop by approximately 2.5 V. That is, the loop is powered in parallel, and due to this, a relatively small voltage drop is obtained. And if you disconnect one of the loop inputs from the device, then the average loop current will be summed up and increase to approximately 50 mA. Accordingly, along the entire length of the loop with a resistance of 200 Ohms, the voltage drop will increase 4 times and amount to 10 V!
Rice. 7. Fail-safe loop
REQUIREMENTS OF Federal Law No. 123 AND GOST R 53316-2009
On the other hand, we have been living for more than three years under Federal Law No. 123, where Article 82 clearly states the requirements for ensuring the preservation of operability in fire conditions cable lines and electrical wiring, fire protection systems, means of supporting the activities of departments fire department, fire detection systems, warning and management of evacuation of people in case of fire, emergency lighting on evacuation routes, emergency ventilation and anti-water protection, automatic fire extinguishing, internal fire-fighting water supply, elevators for transporting fire departments in buildings and structures for the time necessary to perform their functions and evacuate people to a safe area.
To fulfill this requirement, fire-resistant low-smoke FRLS cable and even smokeless and halogen-free FRHF cable with a fire resistance of more than 3 hours began to be used everywhere. However, it soon became clear that the fire resistance of such a cable is not ensured if there is no mechanical fastening when exposed to high temperature. Accordingly, a fire-resistant cable must have a fire-resistant fastening and it is no longer allowed, as before, to put it in a corrugated cable with fastening on polyethylene dowels, which instantly burn at a temperature of 750 ° C, which leads to the destruction of the fire-resistant cable.
GOST R 53316-2009 was issued, which defined test methods for cable lines that are subject to requirements for maintaining operability in fire conditions. This GOST defines a cable line: “a line intended for the transmission of electricity, its individual pulses or optical signals and consisting of one or more parallel cables with connecting, locking and end couplings (seals) and fasteners, laid in accordance with the requirements of technical documentation , in boxes, flexible pipes, on trays, rollers, cables, insulators, free hanging, as well as directly on the surface of walls and ceilings and in the voids of building structures or in another way.”
But the cable lines and electrical wiring of fire protection systems, means of supporting the activities of fire departments, fire detection systems, warning and management of evacuation of people in case of fire, emergency lighting on evacuation routes include automatic and manual call points, sound and warning lights and so on, which must also retain, if not operability, then the ability to “transmit electricity.” In essence, they are “connecting... couplings” and must also be tested according to GOST R 53316-2009 as part of a cable line.
How can the requirements of the Technical Regulations be considered fulfilled when using a fire-resistant cable, if in the room where the fire occurred, after a few minutes the burnt-out siren short-circuits or breaks the communication line and turns off all other sirens, without waiting for people to evacuate to a safe area? A burnt-out detector can block the formation of the “Fire” signal until the procedure for rechecking it is completed by resetting and waiting for confirmation from other detectors. One of possible solutions This problem is solved by the use of ring loops and communication lines while constructively ensuring that there is no short circuit in the device terminals in the event of a fire and when the loop short circuit insulators are turned on (Fig. 8). It is quite possible that there are more optimal solutions this problem. Obviously, a reliable assessment of the correctness of the chosen solutions can be determined by analyzing the results of “full-scale tests” of systems under fire conditions, which, unfortunately, we have in abundance.
PART 2
In the first part of the article, published in issue No. 5 of the journal “Safety Algorithm” for 2012, the foreign classification of fire alarm loops and communication lines in fire automatic systems was considered. The second part of the article discusses the technical implementation of loops of different classes and styles. The electrical parameters of class B radial loops, style C, are given, which ensure the operability of detectors up to the point where the loop breaks, and class A ring loops, styles D and E, which ensure the operability of detectors before and after the break. The use of a D-style cable makes it possible to distinguish between the operation of automatic and manual fire detectors.
In conclusion to the first part of the article, it was said that the lack of classification of loops in domestic standards is a significant drawback that determines the low level of performance of fire alarm, warning and fire protection systems. Indeed, to what style and class can the loops of domestic control and control devices be classified? Maybe everything is fine with us anyway? Not at all, regulatory requirements have changed more than once recently; many additional requirements have been introduced to improve the performance of fire automatic systems in fire conditions. In the Technical Regulations on the requirements fire safety Article 82. paragraph 2 states: “Cable lines and electrical wiring of fire protection systems, means of supporting the activities of fire departments, fire detection systems, warning and management of evacuation of people in case of fire, emergency lighting on evacuation routes, emergency ventilation and smoke protection, automatic fire extinguishing, internal fire-fighting water supply, elevators for transporting fire departments in buildings and structures must remain operational in fire conditions for the time necessary to perform their functions and evacuate people to a safe area.”
To fulfill this requirement, fire-resistant FRLS and FRHF cables began to be used in communication lines and fire alarm loops, but its break still puts the loop into the “Fault” mode, and “Fire” signals from fire detectors are blocked in almost all domestic fire equipment . There are no requirements to maintain the operability of communication lines and loops with detectors and alarms in fire conditions. Foreign experience ensuring full (class A) and partial (class B) operability of fire alarm loops in the event of a break is also not used. The new version of GOST R 53325, as well as NPB 75-98, states that the control panel should provide only “preferential display and transmission to external circuits of fire notifications in relation to other signals generated by the control panel.” There is no clear requirement in our standards that it is inadmissible to block “Fire” signals by any other signals, and, accordingly, technical solutions are not used to ensure compliance with this requirement.
Not only do we not have non-addressable devices with ring loops of class A, but also radial loops do not fit into class B of style D. But almost all control panels are multi-threshold, which determines the low level of performance even when maintaining the integrity of the loop, not to mention the operation of fire detectors with broken loop.
Unacceptably high probability of false alarms from smoke fire alarms due to lack of protection against electromagnetic interference, regular Maintenance and for many other reasons, the result was that the “Fire” signal from the fire detector ceased to be considered as such. Paradoxical as it may seem, it has already become commonplace for many that now in domestic fire alarm systems any fire detector generates only the “Attention” signal, and the “Fire” signal is generated by the combined efforts of two fire detectors.
The use of this terminology led to the development of an appropriate algorithm for the operation of control panels. An approximate algorithm for the functioning of domestic devices is given in Table 1. The “Attention” signal from the first fire detector can be blocked by the “Fault” signal with an appropriate reaction to it. Although in conditions of development open hearth fire, there is a high probability of a break or short circuit in the loop before the second fire detector is activated. Protection against false alarms cannot be achieved by reducing the level of fire safety. Why don’t security loops use similar methods of protection against false alarms? There are no “Attention” signals, no two-threshold loops with at least 3 security detectors in the room. Moreover, in the event of a break, a short circuit in the loop, or even just a change in the resistance of the loop, an “Alarm” signal is quite logically generated. Perhaps the likelihood of theft is much higher, but the lack of fire protection creates a real threat to the population, not to mention incomparable material losses.
Perhaps many readers who have become familiar with foreign requirements for the classification of fire plumes and communication lines have the impression that this is only a theory. It is technically difficult to ensure that a fire detector generates a “Fire” signal when the loop breaks. And that ring loops are used only in addressable systems, but certainly not in traditional non-addressable ones.
Let's look at the principles of constructing class B loops, styles B, C, and class A, styles D, E, using the example of the multifunctional module of non-addressable sub-loops DDM800 addressable-analog fire system Zettler (Fig. 1). This module can be programmed to operate in various modes, including supporting two radial loops of class B, style C (short circuit of the loop is defined as a fault), or style B (short circuit generates a “Fire” signal) (Fig. 2), either one class A loop cable, style E (a short circuit of the loop is defined as a fault), or style D (a short circuit generates a “Fire” signal) (Fig. 3), with terminal elements in the form of resistors or zener diodes, when using detector bases with diodes , and operate in 4-20 mA protocol mode. Different durations for resetting detectors and a polling interruption mode without verification or with verification are programmed with different times for rechecking the confirmation of the “Fire” signal, depending on the type of detectors (Fig. 4). Depending on the operating mode, it can occupy from one to four addresses. Power supply for non-addressable sub-loops can be provided either from an addressable analog loop (Fig. 2) or from an additional power source with galvanic isolation (Fig. 3).
Table 1. Algorithm of fire plume operation
Rice. 1. Electronics of the DDM800 module
Rice. 2. Two Class B radial loops powered by an addressable analog loop
Rice. 3. Class A loopback cable with external power supply
Table 2. Operating modes of the non-addressable sub-loop
Table 3. Algorithm of operation of a non-addressed loop of class A and B
In addition, the DDM800 module works as part of analogue addressable system and transmits to the panel not the “Fire” and “Fault” signals, but much more informative and convenient for analysis analog values associated with loop currents. These numerical values are broadcast with a polling period of 5 s and displayed on the panel display (Fig. 5-7).
What parameters should the loop have to ensure the possibility of receiving the “Fire” signal from fire detectors in the event of a break in the radial loop? First of all, it should be noted that in class A and class B loops, the use of series-connected broadcasters with normally closed contacts is not allowed. An indispensable condition for their operation is the absence of a cable break. If the loop breaks, all detectors before and after the break point are not able to change the voltage and current of the loop. In class A and B fire loops of any style, only fire detectors connected in parallel to the loop can be used.
For radial loops of class B, the parameters must be selected in such a way that, with sufficiently large technological reserves, it is possible to identify the standby mode of the detectors and the activation of the detector both with a working loop with an end-of-line resistor, and if the loop breaks anywhere. Table 2 shows the operating modes of the non-addressable loop. Maximum permissible current consumption of firefighter broadcasters in standby mode is 2.5 mA, which is significantly less than the loop break current threshold of 3.2 mA. Consequently, even if there is a break at the end of the loop, the current consumption of the detectors in standby mode will be less than the break current, and the fault will be identified. The minimum loop current in standby mode due to the terminal resistor is 4.2 mA; with a maximum number of fire detectors, it can increase to 6.7 mA. A wide range of loop currents in the “Fire” mode from approximately 10.5 mA to 24.5 mA ensures reliable generation of the “Fire” signal both in the case of a maximally loaded loop and in the event of a break. Even if only one of the broadcasters remains connected to the module as a result of a cable break, then if the detector current in “Fire” is more than 10.5 mA, the control panel fixes the “Fire” mode. On the other hand, as a rule, foreign and domestic detectors have zener diodes, which prevent the loop from going into short circuit mode even if several detectors go into fire at the same time. In this case, as a rule, no additional resistors are required to be connected to the detectors.
Rice. 4. Programming operating modes of the DDM800 module in the MZXConsys program
Unlike the algorithm of operation of domestic receiving and control devices, the logic of operation of foreign loops ensures unconditional priority of the “Fire” signal. Regardless of the previous state of the loop, as soon as its parameters fall into the range corresponding to the “Fire” mode, it is fixed by the addressable analog panel (Table 3).
To ensure the operability of all detectors in the event of a cable break, a class A loop structure without branches is used (Fig. 3). In standby mode, power is supplied only from the A terminals, and the loop end-of-line resistor is connected to the B terminals. This can be seen in the analog values associated with the loop current, which are transmitted to the control panel when polled. With a detector current in standby mode equal to 2.5 mA and a total loop current of 6.7 mA, the analog value at output A is 035. Output B is disabled, and its analog value is correspondingly equal to 001 (Fig. 5).
If a loop break occurs, the part of the loop connected to terminals B remains without power while the fault is identified. By regulatory requirements the time for detecting a fault should not exceed about 100-200 s; in reality it takes about 60 s. If a break occurs near terminals B, then the current at output A is reduced by the amount of current consumption of the terminal resistor and becomes equal to 2.5 mA, the analog value is reduced to 015, and the current at output B remains zero for 60 s, and its analog value remains equal to 001 (Fig. 6).
After detecting a break in the loop cable, output B is turned on and two radial loops are formed, respectively, the value of the analog value at output B becomes equal to 023, which corresponds to a current of 4.2 mA, which is consumed by a 4.7 kOhm terminal resistor connected to terminals B (Fig. 3).
Rice. 5. Loop loop readings in standby mode
Rice. 6. Class A loop in break detection mode
Rice. 7. A loop cable with a break has been converted into two radial cables
When using automatic and manual detectors in one loop, the type of activated detector can be determined. The “Fire” signal from a manual call point operates by interrupting the polling of the addressable analog loop, in the so-called Fast CallPoint mode. The response to activation of the automatic detector is programmed separately and can also be with interruption of the survey, or with verification by re-querying the status, or without verification. The control panel indicates the activation of manual and automatic call points at different addresses, indicating the type of detector. Accordingly, when using two radial loops of class B in Fast CallPoint mode, a total of four addresses are used, and when using a loopback loop of class A, two addresses are used. Moreover, a manual call point with normally open contacts is connected without an additional resistor and transmits the “Fire” signal by short-circuiting the loop, that is, loops of class A, style D, and class B, style B are implemented. The use of these modes at present, according to our standards, is problematic, since the serviceability of the loop must be monitored for open circuits and short circuits, but the interest in the experience of implementing the 2-threshold mode is obvious.
In addition to the fact that in the Fast CallPoint mode, to introduce the second threshold, the signal from manual call points is transmitted by short-circuiting the loop, the short-circuit current of the loop is doubled, to 50 mA. Accordingly, the range of operating currents of the loop expands (Table 4). As a result, the loop current range from 0 to 50 mA is divided into 4 parts, corresponding to the loop break mode, standby mode, “Fire” mode from an automatic detector, and “Fire” mode from a manual call point. Naturally, “Fire” modes are also formed in the presence of a cable break.
For comparison, in domestic devices the range of loop currents is half as large, from 0 mA to 20-25 mA, there are 5 modes for the smoke loop and 7 modes for the combined loop, and if the loop breaks, the only reliable signal remains “Fault”, and the signals “Fire” from detectors that were subsequently triggered are not accepted by the control panel.
Table 4. Class A loop thresholds, style D with detection of automatic and manual call points (Fast CallPoint mode)
Thus, the use of class A loop cables, style E, makes it possible to ensure the operability of all detectors in the event of a loop break, not only in addressable analogue systems, but also in non-addressable traditional systems. When laying a loop cable through various zones, this can significantly increase the performance of the loops in fire conditions.
LITERATURE:
1. Not bad I. Classes and styles and trains. Ensuring performance. Part one // “Security algorithm”. -2012. - No. 5.
2. Not bad I. Loop control, protection against breakage and short circuit // “Safety Algorithm”. - 2005. - No. 5.
3. Not bad I. Addressless sub-loop in an addressable analogue system // “Security Algorithm”. - 2007. - No. 6.
4. Neplohov I. Gas fire extinguishing: requirements of British standards // “Security systems”. - 2007 - No. 5.
5. Neplohov I. Classification of non-addressable loops, or Why there are no two-threshold devices abroad // “Security Algorithm”. - 2008. - No. 3.
6. Neplohov I. Analysis of the parameters of a two-threshold PPKP loop // “Security Algorithm”. - 2010. - No. 5.
7. Neplohov I. Analysis of the parameters of a two-threshold PPKP loop. Part 2 // “Security algorithm”. - 2010. - No. 6.
8. Neplohov I. Analysis of the parameters of a two-threshold PPKP loop. Part 3 // “Security algorithm”. - 2011. - No. 1.
9. Neplohov I. Problems of connecting heat detectors with indicators // “Fire Safety - 2011”. - "Grotek".
10. GOST R 53325-2012 Fire fighting equipment. Technical means fire automatics. Are common technical requirements. Test methods.
11. NFPA 72, National Fire Alarm Code.
PART 3
In the first and second parts of the article, published in Nos. 5, 6 of the Safety Algorithm magazine for 2012, the foreign classification of fire alarm loops and communication lines in fire automatic systems was considered. The third part of the article discusses the technical implementation of communication lines of different classes and styles. The parameters of class B radial communication lines according to the NFPA72 classification are given, ensuring the operability of sirens up to the point of a loop break, and class A ring communication lines, ensuring the operability of sirens before and after a communication line break.
FEDERAL LAW REQUIREMENTS
Federal Law of July 22, 2009 No. 123-F3 “ Technical regulations on fire safety requirements" introduced requirements to ensure the operability of fire protection systems in case of fire. In Article 51 “The purpose of creating fire protection systems”, paragraph 3 says: “Fire protection systems must be reliable and resistant to exposure hazardous factors fire within the time necessary to achieve fire safety objectives.” Further in paragraph 4 it is said: “The composition and functional characteristics of fire protection systems for objects are established by regulatory documents on fire safety.” In addition, in article 84 “Fire safety requirements for systems for warning people about fire and managing the evacuation of people in buildings and structures”, paragraph 7 says: “Systems for warning people about fire and managing the evacuation of people must function for the time required to complete the evacuation of people from a building or structure.” Also in Article 84, paragraph 6. “ Design and characteristics of smoke protection elements of buildings and structures, depending on the purposes of smoke protection, should ensure proper work supply and exhaust smoke ventilation systems for the time necessary to evacuate people to a safe area, or for the entire duration of the fire.”
NORMATIVE BASE
Accordingly, requirements were introduced to improve performance fire protection systems in fire conditions into the regulatory framework. In the first edition of the Code of Practice SP 6.13130.2009 “Fire protection systems. Electrical equipment. Fire safety requirements" it was stated that "cable lines of fire protection systems must be made of fire-resistant cables with copper conductors that do not propagate combustion when laid in groups according to category A according to GOST R IEC 60332-3-22 with low smoke and gas emissions (ng-FRLS ) or halogen-free (ng-FRHF)”, and “cable lines of warning and evacuation control systems (SAEC) and fire alarm systems involved in ensuring the evacuation of people in case of fire must remain operational in fire conditions for the time required for complete evacuation people to a safe zone."
On February 25, 2013, a new Code of Rules SP 6.13130.2013 came into force, in which there is no mandatory requirement to use fire-resistant cable, it only states that “Electrical cable lines and electrical wiring SPZ must be made with cables and wires with copper conductors.”
In addition, Code of Practice SP 3.13130.2009 “Fire protection systems. Warning and management system for evacuation of people in case of fire. Fire Safety Requirements" contains a general technical requirement: "Cables, wires of SOUE and methods of their installation must ensure operability connecting lines in fire conditions for the time necessary to completely evacuate people to a safe area.”
Thus, the domestic regulatory framework considers ways to ensure the operability of communication lines when using fire-resistant cables and installation methods. Circuit solutions that improve the performance of communication lines are, for some reason, still not being considered. An expensive fire-resistant FRLS and FRHF cable is used, but there is no protection of the communication line from a simple break. The new version of GOST R 53325-2012 introduces requirements for short-circuit insulators (SCI) for addressable loops and communication lines, but the Codes of Practice do not define requirements for their mandatory use. Moreover, in most domestic addressable systems, the mandatory introduction of IKZ into addressable loops is a half-measure, since communication lines with the RS-485 protocol, through which modules with addressable loops are connected to the hub, still remain unprotected from breakage and short circuit. If a malfunction occurs in these communication lines, the entirety of one, several or all addressable loops with all detectors, modules, sirens and IKZ is switched off. The introduction of requirements to ensure the failure of no more than 32 devices, in the event of a break or short circuit of any communication lines, and not just loops, automatically leads to the use of loop communication lines.
Another significant drawback Our spontaneously emerging heuristic principles for constructing communication lines with control modules are the lack of control of the communication line with the power source and the presence of voltage at the module input. Usually only the control line to the relay module is controlled, which also determines the low performance of the system.
LINES OF COMMUNICATION WITH ANNOUNCERS ACCORDING TO NFPA72-2013
The 2002 version of NFPA72 defined communication lines with Class A, Style Z and Class B, Styles W, X, and Y sirens. In subsequent editions, only Classes A and B were retained for sirens without their division into styles. Class B lines ensure operability when one conductor is short-circuited to ground with the formation of fault signals (Fig. 1), but do not ensure the operability of sirens beyond the break point. Class A communication lines have a backup channel and ensure operability in the event of a single break or a single short circuit of one of the conductors to ground with the generation of fault signals (Fig. 2).
Moreover, class A communication lines made using physical conductors, for example, copper or optical fiber, must be laid separately: outgoing conductors and conductors returning to the control unit. Single path installation using 4-conductor cable is permitted, provided that the communication line is no more than 10 feet (3.0 m) long, only one device is connected, or several sirens are installed in the same room with an area of no more than 1000 ft2 (93 m2 ).
In addition, there is a requirement that loops or communication lines do not pass through the same room twice. Thus, when using short circuit insulators, high system performance is ensured as in normal conditions in case of mechanical damage to the loop, as well as in fire conditions.
ADDRESSABLE ANALOG MODULES
There is no mistake in the subtitle, as it might seem to some readers who are not familiar with the equipment of the world's leading manufacturers. In fact, to increase the level of monitoring of the state of communication lines in an analogue addressable system, the modules transmit to the panel not the fault codes “Open” and “ Short circuit”, and analog quantities associated with the resistance of the communication line. Depending on the level of current consumption of the sirens in the “Fire” mode, various technical solutions can be used. In the simplest case, with relatively small load currents, for example up to 75 mA, the sirens are powered from an addressable analog loop, and controlled through transistor switches. The LPS800 siren control module has two pairs of outputs S+ S- and R+ R-. A class B radial communication line with an end-of-line resistor is connected to the S+ S- outputs (Fig. 3). The class A ring communication line is connected to the S+ S- and R+ R- outputs, and the end-of-line resistor is connected to the R+ R- terminals (Fig. 4). In this case, the sirens are powered from both outputs simultaneously and, despite the communication line being broken, they all remain operational.
In both cases, the analog-addressable panel monitors open and short-circuited communication lines using analog values of current and voltage, determined in standby mode by an end-of-line resistor. Figure 5 a, b, c shows the analog values on the display of the analogue addressable panel received from the LPS800 module with address A249, respectively, for standby mode, communication line break mode and communication line short circuit mode.
Sounders with high consumption currents of up to 2 A are powered from an external power source so as not to overload the addressable analog loop, and control is carried out using a polarized relay. Accordingly, the SNM800 siren control module, in addition to two pairs of outputs S+ S- and R+ R- for connecting sirens, additionally has two pairs of terminals I+ I- for connecting an external power source and connecting power to the next module (Fig. 6, 7). When using a class A ring communication line, the sirens are powered from both outputs and, despite the communication line being broken, they all remain operational (Fig. 7). In this case, the addressable analog panel monitors the voltage of the external power source at the module input based on the readings of analog values transmitted by the SNM800 module, and generates the “Fault” and “Sounder Fault” signals when the supply voltage decreases.
a) standby mode; b) communication line interruption mode; c) short circuit mode of the communication line
UNADDRESSED MODULES
To control sirens with high current consumption up to 15 A, additional non-addressable modules can be used - sound boosters (Fig. 8). 
The module contains 2 relays, dual terminals for connecting an external power source and for connecting a radial communication line with sirens. Inflows up to 10 A can be connected to codinary terminals; for higher currents, it is necessary to use a parallel connection of each conductor, as shown in Figure 9. The SB520 module is connected to the communication line of the LPS800 module or SNM800 module through the I/P terminals, and the end-of-line resistor is connected to the EOL terminals. The sound booster relay module provides control of communication lines with sirens and control of external supply voltage at the input. If a fault is detected, the SB520 module turns off the EOL resistor and thereby transmits a fault signal via the LPS800 or SNM800 address module to the control panel.
Thus, modern technical solutions with class A communication lines according to NFPA72 classification, ensuring the operability of all sirens when the communication line is broken, and relay modules with control of the communication line and voltage of the external power source can significantly increase the level of operability of fire protection systems in fire conditions. It should also be noted that in domestic standards there are no requirements for the classification of loops and communication lines, which leads to the widespread use of only radial communication lines, which are inoperative when broken. The lack of clear requirements in regulatory documents for monitoring communication lines allows the use of relay modules without monitoring the presence of supply voltage, which significantly reduces the level of control over the performance of fire protection systems.
To be continued...
LITERATURE
1. Not bad I. Classes and styles and trains. Ensuring performance. Part 1 // “Security algorithm”. - 2012. - No. 5.
2. Not bad I. Classes and styles and trains. Ensuring performance. Part two // “Security algorithm”. - 2012. - No. 6.
3. NFPA 72-2013, National Fire Alarm Code.
4. No. 123-FZ Technical regulations on fire safety requirements.
5. Set of rules SP 6.13130.2009 “Fire protection systems. Electrical equipment. Fire safety requirements."
6. GOST R IEC 60332-3-22-2005 Testing of electrical and optical cables under flame conditions. Part 3-22. Flame propagation along vertically located bundles of wires or cables. Category A.
7. Set of rules SP 6.13130.2013 “Fire protection systems. Electrical equipment. Fire safety requirements."
8. Code of Practice SP 3.13130.2009 “Fire protection systems. Warning and management system for evacuation of people in case of fire. Fire safety requirements."
9. GOSTR 53325-2012 Fire fighting equipment. Fire automatic equipment. General technical requirements. Test methods.
Fire alarm (FS) is a set of technical means, the purpose of which is to detect fire, smoke or fire and promptly notify a person about it. Its main task is to save lives, minimize damage and preserve property.
It may consist of the following elements:
- Fire alarm control device (FPKP)– the brain of the entire system, exercises control over loops and sensors, turns on and off automation (fire extinguishing, smoke removal), controls sirens and transmits signals to the remote control security company or a local dispatcher (for example, a security guard);
- Various types of sensors, which can react to factors such as smoke, open flame and heat;
- Fire alarm loop (SHS)– this is the communication line between sensors (detectors) and the control panel. It also supplies power to the sensors;
- Annunciator- a device designed to attract attention, there are light - strobe lamps, and sound - sirens.
According to the method of control over loops, fire alarms are divided into the following types:
PS threshold system
It is also often called traditional. The operating principle of this type is based on changing the resistance in the fire alarm system loop. Sensors can only be in two physical states "norm" And "fire" If a fire factor is detected, the sensor changes its internal resistance and the control panel issues an alarm signal on the loop in which this sensor is installed. It is not always possible to visually determine the location of the trigger, because in threshold systems, an average of 10-20 fire detectors are installed on one loop.
To determine the fault of the loop (and not the state of the sensors), an end-of-line resistor is used. It is always installed at the end of the loop. When using fire tactics “PS triggered by two detectors”, to receive a signal "attention" or "possibility of fire" An additional resistance is installed in each sensor. This allows the use of automatic fire extinguishing systems at the facility and eliminates possible false alarms and property damage. The automatic fire extinguishing system is activated only in the event of simultaneous activation of two or more detectors.
PPKP “Granit-5”
The following PPCPs can be classified as threshold type:
- "Nota" series, produced by Argus-Spectrum
- VERS-PK, manufacturer VERS
- devices of the “Granit” series, manufactured by NPO “Sibirsky Arsenal”
- Signal-20P, Signal-20M, S2000-4, manufacturer of NPB Bolid and other fire-fighting devices.
The advantages of traditional systems include ease of installation and low cost of equipment. The most significant disadvantages are the inconvenience of servicing fire alarms and the high probability of false alarms (resistance can vary from many factors, sensors cannot transmit information about dust levels), the number of which can only be reduced by using a different type of substation and equipment.
Address-threshold PS system
A more advanced system is capable of automatically periodically checking the status of sensors. Unlike threshold signaling, the operating principle is based on a different algorithm for polling sensors. Each detector is assigned its own unique address, which allows the control panel to distinguish them and understand the specific cause and location of the malfunction.
The Code of Rules SP5.13130 allows the installation of only one addressable detector, provided that:
- The PS does not control fire alarm and fire extinguishing installations or type 5 fire warning systems, or other equipment that, as a result of startup, can lead to material losses and reduced human safety;
- the area of the room where the fire detector is installed is not larger than the area for which this type of sensor is designed (you can check it using the technical documentation for it);
- the performance of the sensor is monitored and in case of a malfunction a “fault” signal is generated;
- It is possible to replace a faulty detector, as well as detect it by external indication.
Sensors in addressable threshold signaling may already be in several physical states – "norm", "fire", "malfunction", "attention", "dusty" and others. In this case, the sensor automatically switches to another state, which allows you to determine the location of a malfunction or fire with the accuracy of the detector.
PPKP “Dozor-1M”
The address-threshold type of fire alarm includes the following control panels:
- Signal-10, manufacturer of airbag Bolid;
- Signal-99, produced by PromServis-99;
- Dozor-1M, manufactured by Nita, and other firefighting devices.
Addressable analog system PS
The most advanced type of fire alarm to date. Has the same functionality as address-threshold systems, but differs in the way signals from sensors are processed. The decision to switch to "fire" or any other condition, it is the control panel that accepts it, and not the detector. This allows you to adjust the operation of the fire alarm to external factors. The control panel simultaneously monitors the status of the parameters of installed devices and analyzes the received values, which can significantly reduce the likelihood of false alarms.
In addition, such systems have an undeniable advantage - the ability to use any address line topology - tire, ring And star. For example, if the ring line is broken, it will split into two independent wire loops, which will fully retain their functionality. In star-type lines, you can use special short-circuit insulators, which will determine the location of the line break or short circuit.
Such systems are very convenient to maintain, because Detectors that require purging or replacement can be identified in real time.
The addressable analogue type of fire alarm includes the following control panels:
- Two-wire communication line controller S2000-KDL, manufactured by NPB Bolid;
- Series of addressable devices “Rubezh”, manufactured by Rubezh;
- RROP 2 and RROP-I (depending on the sensors used), manufactured by Argus-Spectrum;
- and many other devices and manufacturers.
Scheme of an addressable analogue fire alarm system based on PPKP S2000-KDL
When choosing a system, designers take into account all requirements terms of reference the customer and pay attention to the reliability of operation, the cost of installation work and the requirements for routine maintenance. When the reliability criterion for a simpler system begins to decrease, designers move to using a higher level.
Radio channel options are used in cases where laying cables becomes economically unprofitable. But this option requires more money for maintenance and maintaining devices in working condition due to periodic replacement of batteries.
Classification of fire alarm systems according to GOST R 53325–2012
Types and types of fire alarm systems, as well as their classification are presented in GOST R 53325–2012 “Fire fighting equipment. Fire automatic equipment. General technical requirements and test methods".
We have already discussed addressable and non-addressable systems above. Here we can add that the former allow the installation of non-addressed fire detectors through special extenders. Up to eight sensors can be connected to one address.
Based on the type of information transmitted from the control panel to the sensors, they are divided into:
- analog;
- threshold;
- combined.
According to the total information capacity, i.e. The total number of connected devices and loops are divided into devices:
- low information capacity (up to 5 shs);
- average information capacity (from 5 to 20 shs);
- large information capacity (more than 20 shs).
According to information content, otherwise according to the possible number of notifications issued (fire, malfunction, dust, etc.) they are divided into devices:
- low information content (up to 3 notices);
- medium information content (from 3 to 5 notices);
- high information content (from 3 to 5 notices);
In addition to these parameters, systems are classified according to:
- Physical implementation of communication lines: radio channel, wire, combined and fiber optic;
- In terms of composition and functionality: without the use of computer technology, with the use of computer technology and the possibility of its use;
- Control object. Control various settings fire extinguishing means, smoke removal means, warning means and combined ones;
- Expansion possibilities. Non-expandable or expandable, allowing installation in a housing or separate connection of additional components.
Types of fire warning systems
The main task of the warning and evacuation control system (WEC) is to timely notify people about a fire in order to ensure safety and prompt evacuation from smoke-filled rooms and buildings to a safe area. According to Federal Law-123 “Technical Regulations on Fire Safety Requirements” and SP 3.13130.2009, they are divided into five types.
The first and second types of SOUE
Most small and medium-sized facilities, according to fire safety standards, must install the first and second types of warning.
At the same time, the first type is characterized by the mandatory presence of an audible siren. For the second type, “exit” light signs are added. A fire alarm must be triggered simultaneously in all premises with permanent or temporary occupancy.
The third, fourth and fifth types of SOUE
These types refer to automated systems, the triggering of an alert is completely assigned to automation, and the human role in managing the system is minimized.
For the third, fourth and fifth types of SOUE, the main method of notification is speech. Pre-developed and recorded texts are transmitted that allow evacuation to be carried out as efficiently as possible.
In the 3rd type additionally, illuminated “exit” signs are used and the order of notification is regulated - first service personnel, and then everyone else in a specially designed order.
In the 4th type there is a requirement for communication with the control room inside the warning zone, as well as additional light indicators for the direction of movement. Fifth type, includes everything that is listed in the first four, plus the requirement for separate inclusion of light signs for each evacuation zone is added, full automation of control of the warning system is provided and the organization of multiple evacuation routes from each warning zone is provided.
New technologies, energy-saving components, ability software fulfill certain actions and other innovations in last years changed not only the manufacturing technology of fire detectors, but also the methods of their installation and installation. This, in turn, caused changes in existing standards and regulations for the design of fire alarm systems. For example, the radial stub topology, which has long been used and was considered traditional until recently, is now increasingly being replaced by a ring topology. The ability to install a large number of fire detectors in one loop without reducing their reliability and performance makes the use of ring loops quite attractive compared to radial ones. Modern ring loops are multifunctional and allow, in addition to connecting automatic and manual fire detectors, to control additional equipment using various I/O modules.
Advantages of using analog ring loops:
Fig.1. Radial loops Fig.2. Ring loop
- Maximum information content of the loop, achieved by using intelligent fire detectors and their full addressing;
- High reliability of the ring loop, compared to the radial one - in the event of a break or short circuit, the radial loop partially or completely fails; in the ring loop, devices called insulators automatically cut off the damaged area, and the loop continues to function as two radial branches. If the loop breaks, the insulators are not activated;
- Possibility to create radial branches if necessary for optimization cable diagram;
- Less labor costs and consumption of cable materials with the same number of detectors.
Esserbus - maximum reliability, minimum costs
ESSER fire control panels support esserbus and esserbus-PLus ring loops. The esserbus ring loop is a two-wire loop with the following features:
- Maximum cable length 3500 m;
- Up to 127 devices per loop;
- Up to 127 groups of detectors per loop;
- Up to 63 radial branches (up to 32 devices per branch) per loop;
- Up to 32 transponders per loop (up to 100 transponders per control panel);
- The voltage in the loop is 27.5 V.
In addition to the features of the esserbus technologies described above, there is the esserbus-PLus ring loop with improved characteristics. The new loop supports IQ8Quad series automatic detectors with built-in notification devices, IQ8Alarm series addressable notification devices and IQ8Wireless wireless devices. No wiring required to connect all these devices additional wires, i.e. Data transmission, signals and power supply for all loop devices are carried out over just two wires. The esserbus-PLus loop is supported only by the IQ8Control series control panels.
Fire alarm loop- this is the communication line between the fire control panel, fire detectors and other devices designed to work in this line. Physically, the loop can be made using wire lines communications, fiber-optic communication lines, over a radio channel, etc. Most often, loops perform two main functions: receiving (transmitting) information from fire detectors and supplying power to the detectors. Wired loops, depending on the number of wires, are divided into two-, three-, four-wire, etc. As a rule, the connection between addressless control panels and addressless fire detectors is realized using a two-wire loop, i.e., information is received (transmitted) from fire detectors and power is supplied to the detectors via the same two-wire line. In this case control panel carries out continuous monitoring of the current flowing in the loop and, depending on the magnitude of this current, can issue notifications: “Normal”, “Attention”, “Fire”, “Open”, “Short circuit”. Addressable loops fire alarm with addressable fire detectors included in them, they allow you to register and display on the addressable control panel not only the operating mode of the detector, but also its address. Data exchange between the addressable control panel and detectors (exchange protocol), as well as power supply to detectors can be carried out different ways. In order to separate the information exchange lines and the power lines of detectors, three- and four-wire loops are often used, however, to reduce the cost of wired communication lines, many manufacturers of addressable systems transmit the supply voltage and exchange information between the device and the detectors via a two-wire loop. The exchange protocol (sequence, time characteristics, amplitude and information content of pulses) in addressable fire alarm systems is not standard. Most often, it is developed by manufacturers of address systems for specific equipment or series. The advantages of addressable loops are obvious, but there are certain difficulties in their development and use related to problems of electromagnetic compatibility. The presence of digital information exchange using pulse sequences leads to the fact that the introduction of pulse noise from external sources of electromagnetic radiation onto wired communication lines can lead to errors in the operation of the system. In this regard, it is advisable, and in some cases mandatory, to use shielded wire or wires made in the form of “twisted pair” as wire communication lines in address loops.
Plume(Ray) security and fire alarm system - electrical circuit from detectors to control panels (control panels) or to the junction box. Plume, connecting the output circuits of detectors (sensors) and the control panel (PKP), may include auxiliary elements (monitoring devices, visual indication devices, etc.). Purpose plume- transmission of notifications to the control panel, and in some cases, for supplying power to the detectors.
Loops alarms (in Fig. ШС1 ... ШС5) together with communication lines with external devices are part of the linear part of the alarm system. Plume has its own normal current, determined by the value of the terminal resistance, and also, to a lesser extent, by the internal resistance of the sensors.
Some requirements for fire alarm loops ( NPB 88-2001 ):
♦
One train fire alarm with fire detectors that do not have an address, it is allowed to equip a control zone that includes:
- premises located no more than 2 communicating with each other floors, with a total area of premises of 300 m2 or less;
- to ten isolated and adjacent premises with a total area of no more than 1600 m2, located on one floor of the building, while isolated rooms must have access to a common corridor, hall, vestibule, etc.;
- up to twenty isolated and adjacent premises with a total area of no more than 1600 m2, located on one floor of the building, while isolated rooms must have access to a common corridor, hall, vestibule, etc., with a remote light alarm indicating the activation of fire detectors above the entrance to each controlled room;
- trains fire alarms must unite the premises in such a way as to ensure the necessary time to establish the location of the fire.
♦ Fire detectors installed under a false floor, above a false ceiling, must be address or connected to independent plumes fire alarms, and it must be possible to determine their location. The design of the false floor and false ceiling must provide access to fire detectors for their maintenance.
♦ Control panel capacity reserve (number loops), designed to work with non-addressable fire detectors, must be at least 10% with the number loops 10 or more.
♦ Selection of wires and cables, methods of laying them for organization loops and fire alarm connecting lines must be made in accordance with the requirements of PUE, SNiP 3.05.06-85, VSN 116-87, the requirements of this section and technical documentation for devices and equipment of the fire alarm system.
♦ Loops fire alarm must be carried out with the condition of ensuring automatic integrity control them along their entire length.
♦ Loops fire alarms should be made with independent wires and cables with copper veins. Loops fire alarms should generally be carried out using communication wires if technical documentation The control panel does not require the use of special types of wires or cables.
♦ In cases where the system fire alarm not intended for control automatic installations fire fighting, warning systems, smoke removal and others engineering systems fire safety object to connect loops For radial type fire alarms with voltage up to 60 V, connecting lines made by telephone cables with copper conductors of the complex communication network of the facility can be used to receive and control devices, provided that communication channels are allocated. At the same time, free pairs are allocated from the cross-connection to the distribution boxes used during installation loops Fire alarms should generally be located in groups within each distribution box and marked with red paint.
♦ Connecting lines made with telephone and control cables must have a reserve supply of cable cores and junction box terminals no less than 10% each.
♦ Loops radial type fire alarms, as a rule, should be connected to the control panel via junction boxes and cross-connections. Allowed trains Radial type fire alarms should be connected directly to fire appliances if the information capacity of the appliances does not exceed 20 loops .
♦ Loops fire alarm ring type should be carried out with independent wires and communication cables, while the beginning and end of the ring plume must be connected to the corresponding control panel terminals.
♦ The diameter of the copper cores of wires and cables must be determined based on the permissible voltage drop, but not less than 0.5 mm .
♦ Power supply lines for control panels and fire control devices, as well as connecting control lines for automatic fire extinguishing, smoke removal or warning installations should be made with separate wires and cables. It is not allowed to lay them in transit through explosive and fire hazardous premises (areas). In justified cases, it is allowed to lay these lines through fire hazardous rooms (zones) in the voids of building structures of class KO or fire-resistant wires and cables or cables and wires laid in steel pipes according to GOST 3262.
♦ Joint laying is not allowed loops and fire alarm connecting lines, control lines for automatic fire extinguishing and warning systems with voltages up to 60 V with lines with voltages of 110 V or more in one box, pipe, harness, closed channel building structure or on one tray.
The joint laying of these lines is allowed in different compartments of boxes and trays that have solid longitudinal partitions with a fire resistance limit of 0.25 hours made of non-combustible material.
♦ In case of parallel open installation, the distance from fire alarm wires and cables with voltage up to 60 V to power and lighting cables must be at least 0.5 m.
It is allowed to lay the specified wires and cables at a distance of less than 0.5 m from power and lighting cables, provided they are shielded from electromagnetic interference.
It is allowed to reduce the distance to 0.25 m from wires and cables loops and fire alarm connecting lines without interference protection to single lighting wires and control cables.
♦ In rooms where electromagnetic fields and interference exceeds the level established by GOST 23511, trains and fire alarm connecting lines must be protected from interference.
♦ If necessary protection loops and fire alarm connecting lines against electromagnetic interference, shielded or unshielded wires and cables should be used, laid in metal pipes, boxes, etc. In this case, the shielding elements must be grounded.
♦ External electrical wiring for fire alarm systems should generally be laid in the ground or in a sewer.
If it is impossible to lay them in the specified way, it is allowed to lay them on the outer walls of buildings and structures, under canopies, on cables or on supports between buildings outside streets and roads in accordance with the requirements of the PUE.
♦ The main and backup cable power supply lines of fire alarm systems should be laid along different routes, eliminating the possibility of their simultaneous failure during a fire at the controlled facility. The laying of such lines, as a rule, should be carried out through different cable structures.
Parallel laying of these lines along the walls of premises is allowed with a clear distance between them of at least 1 m.
The joint laying of the specified cable lines is allowed, provided that at least one of them is laid in a box (pipe) made of non-combustible materials with a fire resistance limit of 0.75 hours.
♦ Loops It is advisable to divide fire alarm systems into sections using junction boxes.
At the end plume It is recommended to provide a device that provides visual control of its switched on state (for example, a device with a flashing signal other than red, with a flashing frequency of 0.1–0.3 Hz), as well as a junction box or other switching device for connecting evaluation equipment conditions of the fire alarm system, which must be installed at an accessible location and height.
According to the method of monitoring the integrity of the loop, they are distinguished:
| Sign-constant loops | Alternating loops |
| Integrity of constant sign plume controlled using a terminal device - a resistor installed at the end plume. The higher the value of the terminal resistor, the lower the current consumption in standby mode; accordingly, the lower the capacity of the backup power source and the lower its cost. The condition of the control panel loop is determined by its current consumption or, what is the same, by the voltage across the resistor through which it is powered plume. When included in a loop smoke detectors the loop current will increase by the amount of their total current in standby mode. Moreover, its value to detect a broken loop must be less than the current in the standby mode of an unloaded loop. |
Integrity of alternating plume controlled using a terminal device - a resistor and diode installed at the end of the loop. The “Fire” signal is transmitted in the positive component of the signal, “Fault” - in the negative component. To continue operation when a “Fault” signal is issued due to the detector being removed from the base, a Schottky diode is installed in the base. Thus, the “Fault” signal due to a removed detector or a malfunction of a self-testing detector (for example, linear) does not block the “Fire” signal from a manual call point. The alternating loop allows the use of self-testing detectors in threshold loops. When a malfunction is detected, the detector automatically removes itself from the alarm loop, and this allows it to be used in conjunction with any fire alarm remote control, since the control of detector removal is mandatory requirement fire safety standards for all control panels. |
Address loops:
(material under development)
Intrinsically safe loops:
(material under development)
