Setting Requirements for Bus Short-Circuit Isolators
Bus short-circuit isolators are mainly used to isolate components on the bus, isolating fire detectors, combustible gas detectors, manual alarm buttons, sound and light alarms, etc., in certain areas or segments, to avoid affecting the reliable operation of the unisolated area system. This is crucial for maximizing the overall functionality of the system without being impacted by faulty components.1. Setting of Short-Circuit IsolatorsFire safety standards in the “Design Specifications for Automatic Fire Alarm Systems” stipulate:Short-circuit isolators should be set up on the system bus, and the total number of fire detectors, manual fire alarm buttons, and modules protected by each short-circuit isolator should not exceed 32 points; when the bus crosses fire compartments, short-circuit isolators should be set at the crossing points.This regulation requires the installation of short-circuit isolators on the bus, with the number of field components protected by each isolator not exceeding 32 points. This is to ensure that if a field component fails, the isolator can isolate the faulty component, thereby maximizing the overall functionality of the system.Note:1. The 32 points mentioned refer to the number of fire-fighting devices, not considering device addresses. Standardized modules (such as input/output modules or multi-input/output modules) are counted as one device, while for module boxes, the total number of modules within the box is counted.a. One input module connects to one device.b. One input/output module connects to one device.Standardized multi-input/output modules (regardless of how many addresses they occupy) are counted as one point. For example, the GST-LD-8303 dual input/output module is counted as one device when calculating the number of devices, even though it has two encoding addresses.The GST-LD-8303 dual input/output module is a bus-based control interface used for controlling dual-action devices such as two-step fire shutter doors, water pumps, and smoke exhaust fans. It is primarily used for position control of fire shutter doors, capable of controlling the door from the upper position to the middle position and from the middle position to the lower position, while also confirming whether the door is in the upper, middle, or lower position. This module can also function as two independent GST-LD-8301 single input/output modules. The GST-LD-8303 dual input/output module has two encoding addresses that are consecutive.2. The bus mentioned includes alarm buses and power lines, and the short-circuit isolators should be able to isolate faulty alarm buses and power lines.3. The term “crossing” includes entering another fire compartment from one fire compartment.2. The settings of bus short-circuit isolators can be divided into tree structure and ring structure.Tree Structure:Tree structure system diagramWiring of tree structure bus short-circuit isolatorsSettings when crossing fire compartments in tree structureRing Structure:Ring structure diagramWiring of ring structure bus short-circuit isolatorsSettings when crossing fire compartments in ring structureNote1. In the diagram, if the bus only passes through a fire compartment without connecting any devices within it, a short-circuit isolator is not required in that fire compartment. The short-circuit isolators in the ring structure can be set on either side of fire compartment 1 or fire compartment 2.2. Some manufacturers’ bus short-circuit isolator products occupy address numbers, which are calculated according to the manufacturer’s declared address numbers.3. Short-circuit isolators may be placed inside module boxes or wall-mounted along the route, with a bottom edge height of 2.2m. When installed in ceilings, the bottom edge should be 0.2m from the ceiling, and there should be a maintenance access point with clear markings nearby. The short-circuit isolators in tree structures can also be concentrated in weak current vertical shafts.4. Products of bus short-circuit isolators in ring structure and tree structure generally cannot be used interchangeably.5. If the fire detector itself has an isolation function, a separate short-circuit isolator is not required.6. Whether the bus circuit adopts a tree structure or a ring structure is determined by the designer, who should select the appropriate products.
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