The Difference Between a Single-Circuit and Dual-Circuit Heat Detector

Heat detectors are installed in places that are unable to accommodate smoke detectors, and assist in safeguarding against fire. Several models are available with multiple configurations according to the desired temperature rating, activation and circuit. Heat detectors are applied using either a single-circuit or a dual-circuit system, which must be in compliance with the National Electric Code.

Wiring Guidelines

• When wiring heat detectors, accessory devices such as the alarm control panel are connected using color-coded conductors. Heat detector wires should not be mixed with other electrical wiring, and are usually installed in a separate grounded conduit. This limits the possibility of wiring errors, which is important as incorrect connections increase the risk of fire.

Operation

• Heat detectors are a long standing technique used in fire detection. Some heat detectors also operate as sprinklers and extinguish potential fires. Heat detectors perform best in confined spaces as they generate a relatively slow response compared to other detection devices. They issue a response when either a fixed temperature is reached, or the rate of temperature increase changes.

Connection

• Heat detectors are available as either single-circuit or dual-circuit models. Single-circuit detectors have two screw terminals where wires are connected to an adjacent detector or an end of line resistor, while dual-circuit detectors have double this amount. Thus dual-circuit models are able to connect to four other detectors, and single-circuits only connect to two.

Other Differences

• Dual-circuit detectors are mainly used to send two independent electrical signals, while single-circuit detectors only send one. The single-circuit model is available with one normally open dry contact, compared to the dual-circuit model that has two. Dual-circuits are capable of accommodating two auxiliary devices on one circuit; however, the single-circuit detector only accommodates one.