I have a smoke detector that is nearing the end of its life and needs to be replaced. It has a 9V battery and is also wired into my condo’s electric supply. I bought a new detector yesterday that is battery-only (I couldn’t find the wired type at the store). However, reading the instructions, it says “WARNING! Do not install this alarm over an existing electrical box. Only AC powered units are intended for installation over electrical boxes.”
Is it as dangerous to install my new detector as the instructions imply? Should I try to return it and find the proper type of detector elsewhere?
They are designed to be up against a flat surface. If there is an extra hole underneath it, the air movement may cause a slight risk of false nuisance alarms.
I looked elsewhere online and there is speculation of concerns of EM interference. That seems less likely to me, but again the main problem would be false nuisance alarms.
My concern would be that someone that does that might not do it safely. If they don’t put a cover on the box, they could run the risk of a wire getting into the smoke detector or someone getting a shock when they take it down to change the batteries some day.
I was also thinking there could be a very, very small risk of an alarm being delayed because smoke could escape above the ceiling, but that would be the case for a hardwired smoke detector as well, so that’s probably not it.
If the old j-box has a cover on it, I really can’t see what difference it would make.
ETA…I know what it (probably) is. Putting the new smoke detector over the electrical box may be considered a code violation (NEC). Since the smoke detector has a bracket that gets screwed to the ceiling, it would make the junction box behind it inaccessible (which is a violation). The hardwired smoke detector OTOH is the cover for the box.
If you have AC powered smoke alarms, they are very, very likely to be interconnected with other smoke alarms. If any individual smoke alarm activates, it will sound the other alarms on the circuit.
If you have a battery-only alarm, it is not generally able to be interconnected (wireless alarms notwithstanding). The overall alarm system is designed to have all devices go into alarm if one device activates, you lose this functionality if you install the battery one.
The smoke alarm will work fine as a single-station alarm, but it will not alert you outside of where you can hear that specific alarm. Similarly, if another device activates elsewhere, it will not cause the battery alarm to activate.
Check your state building codes. Many states require wired, interconnected smoke alarms (with battery backup) on all living levels, with at least one detector in each bedroom. If you decide to rent out your condo, or even sell it, you may be prohibited from doing so if your smoke detectors do not meet code.
Duckster has the right answer. There is nothing dangerous about putting a smoke detector over an electrical box as long as the electrical box has a cover. But the problem is that code now requires that at least one smoke detector be operated by 110 VAC with battery back up. The Idea is if the home owner does not change out the batteries and all the batteries in the smoke detectors go dead then there will be at least one smoke detector will still work, and that detector will have a battery in it incase the power goes off.
When I purchased my brand-new home the upstairs smoke detector was powered by AC. When I replaced it to meet code the new detector had to be powered by AC and with a battery backup.
When I sold that home and purchased a new home all living spaces had to have working smoke detectors with at least one operating off AC with battery backup. My real estate agent was very definite about this. If we did not meet the detector qualifications during appraisal the house would not be appraised, and the sail would not go through until the problem was corrected and the house would be appraised.
So, it is not really dangerous, but your condo will no longer meet building code. And you will have problems selling it, and to rent it out would be a violation of the law.
Any Hardware store that sells smoke detector should have dual powered smoke detectors. Ask.