Why Does Kidde Specify A Non-GFCI Protected Circuit For Their Smoke Alarms ?

if the gfci triggers, they don't work. you may not notice the triggering for quite some time.

One reason that I can think of is that their products work better when they have power and GFCI-protected circuits are more likely than ones that are not to be continuously powered. A minute circuit fault that will never be noticed in a regular circuit may well kill one with a GFCI

-- exactly what you want most of the time but not so with an alarm.

That's probably to avoid the risk of electrical leakage to ground on that circuit, like from an unoticed roof water leak finding it's way into an electrical box, could trip the breaker and render the smoke alarm system useless, without your being aware of it.

For the same reason, it's probably wiser to put the smokes on their own breaker if possible. It'd be a fine mess if another appliance on the same circuit as the smokes decided to overheat, catch fire, and then pop that circuit's breaker before the smokes went off.

HTH,

Jeff

Are there really that many AC-only smoke detectors out there anymore? When I was shopping around for a wired-in system, pretty much all of them had a battery backup.

- Rich

I believe code addresses it.

GFCI's are oriented to protecting personel from electricution(from conductors to ground). The risks of nucience trip, vs electrical danger is too great. No need to risk losing a whole house's smoke detectors because of a flawed gfci.

hth,

tom @

Jeff Many localities require that the smoke detectors be installed on a lighting circuit so that it is inconvenient to open the breaker to silence an alarm.

-- Tom H

Yeah this is a good idea, and so much so, I think it's in the electrical code somewhere. Like it says don't run a dedicated smoke detector branch, something else needs to be on it.

Have to check, since I can't remember where in the NEC it is, I might be mistaking this for boca, or something else.

later,

tom @

When the fire melts the wire insulation and ground faults before the smoke reaches the alarm they want the alarm to still have a chance to go off

Ah yeah.... that's the ticket!

:-P

GFCI's can have nuisance trips. Even a thunderstorm nearby can sometimes trip a GFCI. This could greatly shorten backup battery time for the smoke detector, or even cause complete failure if the circuit isn't promptly reset before the battery dies. The smoke detectors should also be on the same circuit as often used lighting to make it very obvious if the circuit is open.

For similar reasons, it's not a great idea to put a refrigerator on a GFCI circuit.

Not exactly the same situation, but a similar principal:

The US Electrical Code has exceptions for overload protection for fire pumps in residential appartment dwellings. The theory is that you want power to be supplied to the fire pump no matter what, even if it burning up do to an overload.