Loop (fire and security alarm) - an electrical circuit connecting the output circuits of the detectors, including auxiliary elements and connecting wires and designed to transmit notifications to the control panel, and in some cases to supply power to the detectors.
A set of signaling loops, connecting lines for transmission via communication channels or separate lines to the control panel, devices for connecting and branching cables and wires, underground sewers, pipes and fittings for laying cables and wires is included in the linear part of the alarm system.
plumes fire alarm, as a rule, are carried out by communication wires, if technical documentation the use of special types of wires or cables is not provided for fire control devices. For fire alarm loops, only cables with copper conductors with a diameter of at least 0.5 mm can be used. Required automatic control the integrity of the loop along the entire length.
With parallel open laying, the distance from fire alarm loops with voltage up to 60 V to power and lighting cables must be at least 0.5 m. It is possible to lay loops at a distance of less than 0.5 m from power and lighting cables, provided they are shielded from electromagnetic interference .
In rooms where electromagnetic fields and tips have high level, fire alarm loops must be protected from interference.
At the end of the loop, it is recommended to provide a device that provides visual control of its on state, as well as a junction box for assessing the state of the fire alarm system, which must be installed at an accessible place and height. Such a device can be used manual call point or loop control devices.
Scheme of a constant-sign loop
The integrity of the constant-sign loop is controlled using a terminal device - a resistor installed at the end of the loop. The higher the value of the terminating resistor, the lower the current consumption in standby mode, respectively, the lower the capacity of the backup power source and the lower its cost. The state of the loop of the control panel is determined by its current consumption or, which is the same, by the voltage across the resistor through which the loop is powered. When smoke detectors are included in the loop, the loop current will increase by the amount of their total current in standby mode. Moreover, its value for detecting a break in the loop should be less than the current in the standby mode of an unloaded loop.
Scheme of alternating loop
The method of monitoring the alarm loop with power supply of the loop with alternating pulsed voltage provides an increase in the load capacity of the loop for powering current-consuming detectors. A resistor and a diode connected in series are used as remote elements of alarm loops; in the direct voltage cycle, it is connected in the opposite direction and there are no losses on it. In the reverse cycle, due to its short duration, the losses are also insignificant. The signal "Fire" is transmitted in the positive component of the signal, "Fault" - in the negative. To continue operation when a “Fault” signal is issued due to the detector 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, a linear one) does not block the “Fire” signal from a manual call point.
An 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 panel, since the control of the detector removal is mandatory requirement norms fire safety for all PKPs.
The control method with power supply of the alarm loop with pulsating voltage is based on the analysis of transient processes in the loop loaded on the capacitor.
In addressable fire alarm interrogation systems, fire detectors are periodically polled, their performance is monitored and a faulty detector is identified by a control panel. The use of specialized processors with multi-bit analog-to-digital converters, complex signal processing algorithms and non-volatile memory in fire detectors of this type makes it possible to stabilize the sensitivity level of the detectors and form various signals when the lower limit of auto-compensation is reached when the optocoupler is dirty and the upper limit when the smoke chamber is dusty.
Address polling systems are quite simply protected from breakage of the address loop and short circuit. In polling addressable fire alarm systems, any type of loop can be used: ring, branched, star, any combination of them and no end elements are required. In polling address systems, it is not required to break the address loop when the detector is removed, its presence is confirmed by responses when the receiving and control device is requested at least once every 5 - 10 seconds. If the receiving and control device does not receive a response from the detector at the next request, its address is displayed on the display with a corresponding message. Naturally, in this case, there is no need to use the loop break function, and when one detector is turned off, the operability of all other detectors is maintained.
Fire alarm loops, as a rule, are carried out by communication wires, if the technical documentation for fire control devices does not provide for the use of special types of wires or cables. For fire alarm loops, it is possible to use only cables with copper conductors, with a cross section of at least 0.5 sq. mm. Automatic control of the integrity of the loop along the entire length is required.
With parallel open laying, the distance from fire alarm loops with voltage up to 60 V to power and lighting cables must be at least 0.5 m. Loops at a distance of less than 0.5 m from power and lighting cables are possible, provided they are shielded from electromagnetic interference.
In rooms where electromagnetic fields and pickups are high, fire alarm loops must be protected from pickups.
At the end of the loop, it is recommended to provide a device that provides visual control of its on state, as well as a junction box for assessing the state of the fire alarm system, which must be installed at an accessible place and height. As such a device, a manual call point or loop control devices can be used.
Fixed-sign (constant current) fire loops
The mode of operation of the constant-sign loop. 1-standby mode, 2-attention, 3-fire,
4 - short circuit, 5 - break.
The integrity of the constant-sign loop is controlled using a terminal device - a resistor installed at the end of the loop. The higher the value of the terminating resistor, the lower the current consumption in standby mode, respectively, the lower the capacity of the backup power source and the lower its cost. The state of the loop of the control panel is determined by its current consumption or, which is the same, by the voltage across the resistor through which the loop is powered. When smoke detectors are included in the loop, the loop current will increase by the amount of their total current in standby mode. Moreover, its value for detecting a break in the loop should be less than the current in the standby mode of an unloaded loop.
Variable loops
Operating mode of the alternating loop. 1-standby, 2-attention, 3-fire, 4-short circuit, 5-break, 6-fault
The method of monitoring the alarm loop with power supply of the loop with alternating pulsed voltage provides an increase in the load capacity of the loop for powering current-consuming detectors. As remote elements of alarm loops, a series-connected resistor and diode are used; in the direct voltage cycle, it is connected in the opposite direction and there are no losses on it. In the reverse cycle, due to its short duration, the losses are also insignificant. The signal "Fire" is transmitted in the positive component of the signal, "Fault" - in the negative. To continue operation when a "Fault" signal is issued due to the detector 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, a linear one) does not block the "Fire" signal from a manual call point.
An 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 control panel, since the control of the detector removal is a mandatory requirement for fire safety standards for all control panels.
Loops with pulsating voltage
The control method with power supply of the alarm loop with pulsating voltage is based on the analysis of transient processes in the loop loaded on the capacitor.
Address loops
In addressable fire alarm interrogation systems, fire detectors are periodically polled, their performance is monitored and a faulty detector is identified by a control panel. The use of specialized processors with multi-bit analog-to-digital converters, complex signal processing algorithms and non-volatile memory in fire detectors of this type provides the ability to stabilize the sensitivity level of the detectors and generate certain digital signals when the lower limit of auto-compensation is reached when the optocoupler is contaminated and the upper limit when the smoke chamber is dusty, and also a digital signal in the presence of smoke.
Address polling systems are quite simply protected from breakage of the address loop and short circuit. In polling addressable fire alarm systems, any type of loop can be used: ring, branched, star, any combination of them and no end elements are required. In polling address systems, it is not required to break the address loop when the detector is removed, its presence is confirmed by responses when the receiving and control device is requested at least once every 5 - 10 seconds. If the receiving and control device does not receive a response from the detector at the next request, its address is displayed on the display with a corresponding message. Naturally, in this case, there is no need to use the loop break function, and when one detector is turned off, the operability of all other detectors is maintained.
To protect the addressable loop from short circuits, insulating bases are used, which, with the help of electronic keys automatically disconnect the short-circuited section of the address loop.
Good day to all.
Today about the address-threshold loops of the PPK. The word "addressable" means that each detector in the loop has its own unique address, this allows the control panel to localize the place of fire to the accuracy of the detector. we considered just threshold loops, where the detector's activation is localized to the loop: the detector in the loop worked - run along the entire loop (the Code of Rules allows one loop to be pulled through adjacent rooms up to ten pieces), open the rooms, see where the sensor glows if there is no smoke. IN this case everything is simpler - the control panel will inform the upstream device of the address of the triggered detector in the loop. This solution is intermediate between threshold and address-analog loops (about them the next chapter).
In reality, I know of only one device with such loops: the previously mentioned Bolidovo "Signal-10". This is a relatively inexpensive control panel with ten programmable threshold loops - smoke thermal, security, etc. Everything is strictly like Signal-20, which was discussed in. But there is an additional 14th type of loop - the same address-threshold. By programming the loop type “14”, you can connect only special detectors to it: a DIP-34PA smoke detector and a S2000-IP-PA heat detector, up to 10 in total. With the help of some button manipulations, they can program the address from 1 to 10, and the device will catch alarms up to the detector. The detectors are powered by a loop, the connection diagram from the same Bolida website is below:
The connection diagrams are exactly the same. AND appearance detectors is the same (pictured at the beginning of the chapter). Please note: the terminating resistor in the address-threshold mode has a nominal value of 10 kOhm, and in the usual threshold mode - 4.7 kOhm (you can see the connection diagrams of threshold loops in the previous chapter).
Another feature of these detectors is that they give an "Accident" signal in case of a detector malfunction. Thus, in accordance with the Code of Rules, it is possible to seriously save on the number of detectors: in some cases it is allowed to install a smaller number of them than in the case of a threshold loop. This allows you to compensate for more high cost detector with greater functionality of the fire alarm system.
Something I looked at the previous picture - it looks too abstruse. Here is the wiring diagram directly from the detector label:
So, I think, it’s clearer, only for some reason the tip sticks out at the beginning of the line, kindly it should be at the end: this will make it possible to distinguish a banal break from the theft of detectors.
Well, that's all for now: next will be a chapter on the most advanced type of detectors - analog addressable. And one more thing: while I was composing this post, I thought that I often refer to the Code of Rules, it will be necessary to collect some extracts from it with comments and roll it out as a separate chapter. I think a lot of people will be interested. Well, for now, I bow out.
Ask questions in the comments, who needs it, subscribe - the form at the bottom of the page.
At present, the regulatory framework that determines the procedure for performing maintenance work on the fire protection system is also based on the base developed in the USSR. When concluding agreements between the Contractor and the Customer, there are often different readings of the same documents. If the Contractor makes a reference to some Guiding Document (RD), then the Customer disputes its provisions, referring to the time the document was created and outdated wording. For example, "on objects National economy, regardless of their departmental affiliation. or "Industry standards of time for Maintenance PA and OPS installations", which no one has ever seen, or "The cost of services is determined by the price list wholesale prices for the repair of instruments, machines and equipment No. 26-05-48. ”, Also hopelessly outdated. Although no one has repealed these norms, and they are in force, nothing better has yet been developed in the Russian Federation.
The modern developed norms of time for maintenance and repair, which are developed by the housing and communal services and the Ministry of Internal Affairs, are mandatory for use throughout the country. The main document regulating the work on maintenance and scheduled preventive maintenance, at the moment is RD 25.964-90 "Maintenance and repair system automatic installations fire extinguishing, smoke removal, security, fire and security and fire alarm". This document defines the types of work and repairs, gives unambiguous wording, samples of contracts, survey reports, and the response procedure.
All other GOST, PPB, RD, RM, etc., which mention the need for maintenance of fire alarm systems, give regulations, duties of responsible persons, a list of works, etc.
Under the influence of moisture, high and low temperatures, dust, caustic fumes, gases, over time, the quality of the insulation of wires and cables deteriorates and the risk of electrical injury increases. To prevent this danger, a megohmmeter is used to periodically measure the insulation resistance of wires and cables. RD 78.145-93 says: p.11.6. “When accepting for operation the completed installation and adjustment of technical means of signaling, the working commission performs: measurement of the insulation resistance of the signaling loop, which must be at least 1 MΩ”, which corresponds to the PUE: Chapter 1.8. Acceptance test standards, electrical apparatus, secondary circuits and electrical wiring up to 1 kV.
The check is carried out after 3 years, and there is a nuance, the organization conducting the measurement of insulation resistance must have permission to carry out this type of work. Carrying out work on measuring the insulation of electrical circuits is carried out jointly with the person responsible for the electrical facilities of the facility.
If there is no emergency lighting panel or a free group on it at the facility, the Customer installs an independent power supply panel for the appropriate number of groups. The power supply panel installed outside the protected premises must be placed in a lockable metal cabinet and blocked from opening. Power supply of alarm systems is the prerogative of the Customer. It is not only not necessary to independently enter the electrical panel of the facility where maintenance is carried out, but it is also prohibited by PTEEP. Painlessly, as part of the maintenance, we can measure the insulation resistance of the supply circuits, in the area from circuit breaker fire alarm systems to control panel or power supplies. Those. where, under the influence of moisture, high and low temperatures, dust, caustic fumes, gases, over time, the quality of the insulation of wires and cables deteriorates and the risk of electrical injury increases.
Checking other cables, electrical panels, devices, etc. at this facility, this is the task of the person responsible for the electrical facilities of this facility, which he must carry out according to the schedule of the enterprise and in accordance with the PUE and PTEEP. Including the section from the electrical panel to the OPS machine.
Insulation resistance of alarm loops when performing installation work carried out after laying the cable before connecting the OPS elements to them (this is according to RD 78.145-93). The technique is the same as for power cables. The expediency of measuring the insulation resistance of alarm loops, once every 3 years, seems to me personally unnecessary work, which does not make any sense not from the point of view of safety (getting electrical injuries from 12-20V) and equipment failure. According to GOST 16962-71, the insulation resistance is measured between electrically unconnected circuits, electrical circuits and the housing. Electrical circuits containing semiconductor devices and microcircuits, must be disconnected and, if necessary, tested separately.
The main monthly type of maintenance work is an external inspection and performance check. Health Check - Definition technical condition by monitoring the implementation technical means and setting as a whole part or all of their inherent functions.
The alarm loop is a wired line that electrically connects the remote element (elements), the output circuits of security, fire and security fire detectors with the input of the control panel. From the point of view of the need to maintain the elements of the fire alarm system, the alarm loop is one of the most vulnerable elements of the on-site fire and security alarm system, which is most exposed to various external factors. Practice shows that one of the main reasons for the unstable operation of devices at the facility are violations of the alarm loop. They represent a failure in the form of an open or short circuit in the loop, which occurs as a result of a gradual spontaneous deterioration of its parameters. Places electrical connections the alarm loop, as well as the contacts for connecting detectors during operation are exposed to prolonged exposure high humidity V wide range temperatures, and in some cases - the impact of aggressive environments. Thin surface films appear on the surface of the loop contacts, which leads to a change in the resistance of the alarm loop (the main parameter).
The technical goal of carrying out maintenance of fire alarm systems that work with non-address detectors via wired communication lines (the vast majority of all serviced alarm fire alarm systems) is the task of maintaining R ss, in the denomination when the control panel provides information about the status of the "Norma" loop. From this it follows that checking the resistance of the alarm loop during monthly maintenance "... by means of control, the nomenclature of which is established by the relevant documentation" is not at all superfluous. The measurement is carried out by a tester in ohmmeter mode. The alarm loop is disconnected from the control panel and connected in parallel to the measured wire. According to the resistance readings of the signaling loop, one can judge the physical state of the loop (poor contact, corrosion, oxidation lead to an increase in Rshs, humidity, together with a violation of the wire insulation, to a decrease in Rshs and shunting of the loop section, etc.).
Therefore, it is advisable to monthly work on external inspection and performance check, add a paragraph on checking the resistance of the alarm loop.
To provide smooth operation fire alarm sensors are connected to warning devices and the dispatcher's console by means of wires (loops). The cables also transmit control messages, optical signal, etc. The types of fire alarm loops are divided according to their structure, the requirements for them are specified in SNiP and Federal Law No. 123.
The terminal device of the loop is provided with constructive additional or any other fire protection.
According to the Federal Law, cable standards are regulated by a decree of 07/10/2012. In particular, it states:
To determine the location of a fire, it is necessary that all systems are in working order. For fire alarms, a cable resistant to open fire must be used. The fire resistance limit is calculated according to the requirements of the PPB for load-bearing structures in the room.
For some categories of premises, the PPB establishes certain restrictions on loops. Installation of exclusively non-flammable wire, inadmissibility concealed wiring, laying in a cable tray - these and other restrictions are described in SNiP 3.05.06-85 and VSN 116-87.
The brand of wire for installation is determined by the fire hazard category of the building and installed system alerts. The decision to use a thermal cable and other types of materials is made during the development of project documentation. When choosing a cable, the following indicators play an important role:
The norms for laying loops depend on the alarm system used and the current requirements of the FSP. The list of cables acceptable for use is given in SNiP and PUE. Violation of the recommendations leads to a malfunction of the PS.
If the cable does not meet the standards, upon detection of this, the inspector of the Ministry of Emergency Situations will write out an explanatory note and bring to administrative responsibility indicating the timing of the replacement of existing loops.
