Can’t connect alarm to smoke detector?
My house (built in 2000) has hardwired smoke detectors. I’m told by my security system company that these can’t be connected to the alarm system because “the voltage is different”, so I would have to use their smoke detectors (at $90 a pop!). Seems to me that converting a signal at one voltage to a signal at a different voltage isn’t exactly rocket science. What’s the real deal?
Pete
Replies
Even if the voltage were the same, they might not be sending out the same signal.
...Also the issue of UL approval for that particular application. Even if it were easy to create a jury-rigged interface between the two, without UL approval, one would have code and underwriting issues.
E.g., hardwired DS usually are powered off the house AC. SDs designed for alarm system use are usually powered off 12-24V from the alarm panel (with a supervision circuit that lets you know if the signal and power leads are broken). Even if the signaling were compatible, the possibility of ground loops and insulation failures would require some changes in design, and the supervision logic would certainly not work.
Just to clarify, I'm looking for something ready-made and approved, not a jury rig. Seems to me that if code requires hardwired smoke detectors, there have to be a lot of new houses out there that people want to add alarms to.
Pete
Simple answer: Hardwired smoke detectors are the same cheap-o battery models connected to the hall light circuit. Smoke detectors that can be tied to an alarm system require a central station, battery back-up (not the 9v), and separate low voltage wiring. $
...that's not a mistake, it's rustic
Although the smoke detecting part of the design are pretty much the same for all the smoke detetors, the interface circuitry is pretty much incompatable. Much of the UL approval is around that part of the design. The margins on the detectors are so thin, that there would be no percentage in designing one for multiple applications. It would be priced out of the market.
Edited 5/15/2002 12:15:37 AM ET by DonH
generally smoke detectors are to save lives and heat detectors to save property. I do many homes with hardwired smokes(required) interconnected (also called local smokes) and heat dets on the alarm system. This prevents many false alarms going to central monitoring stations. Another option is just one system smoke on the system in addition to required line volt smokes in the home. I have wired hundreds of elderly housing units this way. (line smokes system heat dets.) If you really wanted it they do make relays that connect to the line smokes to operate other things such as a connection to the alarm system. If the relay is made by the smoke manufacturer they will be ul listed But not UL listed by the alarm system.