Question:
I am trying to review the power and sensor wiring for an Alarm Industry Products Heat Detector AI281B. I was wondering if anyone knew where I could find the specifications and wiring diagram as I have one of these detectors without the manual and do not know which of the connection pairs is for the DC power (and which is the + screw and which is the - screw) and which pair is for the alarm circuit itself. I did not notice any markings on the unit itself to provide this information. Thank you for any assistance. I tried to find AIP on the web but couldn't locate them.

Answer: That's most likely a private labeled Edwards 281B. The unit is a rate-of-rise detector with a 135єF fixed temperature sensor as well. It detects a rapid increase in temperature typical of a fast-burning, flaming fire. These are often used in places where smoke detectors are not permitted, such as enclosed furnace rooms, laundry rooms, kitchens and garages. There is some difference of opinion among installers as to whether to use them in kitchens and garages due to the potential for a rapid temperature increase. The rate-of-rise part of the sensor is self-restoring. The fixed thermal sensor is sacrificial. Once it reaches 135єF the detector must be replaced. The connection is simple enough. These sensors are open circuit. That is, they close on alarm. There are two screw terminals on each side of the sensor. Connect the fire alarm zone loop (also called an Initiating Device Circuit, or IDC) to two of the screw terminals. Connect the EOL resistor or the wires leading to the next detector to the other two screws. For an explanation of fire alarm circuits, EOL resistors and other stuff, you may wish to browse my FAQ site.