Changing batteries in hard wired smoke detectors

wngsprd · Jan 4, 2016

One of mine kept chirping after replacing the battery, so I had to flip the circuit breaker...of course when one goes off, it triggers the others...and of course it happened in the middle of the night.

k0ua · Jan 4, 2016

Industrial Toys said:
This is news to me that hard wired (110) detectors have batteries.

The concept is, how would the detector work if the 120 volt power was out?. Which is a practical scenario because an electrical problem could easily start a fire which might blow the breaker killing power to the smoke detector as you slumber peacefully (for the longest sleep of your life). But with battery backup, you are awakened in a rude manner, and get up to either fight the fire and/or escape to live another day.

Industrial Toys · Jan 4, 2016

That's what I always maintained. 110 units were code here but power goes out, detectors go out and out come the candles. lol

But battery back-up must be a fairly new thing. I have never seen it and if so, I would have expected nicads or other rechargeables. So what is the point of ac powered units when you have to change the batteries anyway?

kcflhrc · Jan 4, 2016

The A/C powered units have a 3rd wire to connect them all together, so when one goes off they all go off. My 1970 Home was not wired for smoke detectors so I bought the sealed units that last 10 years and then you throw them away. I have never seen an 110 volt detector that didn't have battery backup, pretty sure that is code most everywhere.

aczlan · Jan 4, 2016

110v smoke detectors have had batteries since at least the early to mid 1990s. Dad put in wired smoke detectors somewhere around that time and they all took 9v batteries as backup for the 110v.

Aaron Z

Industrial Toys · Jan 4, 2016

I just googled it. I have never seen such a thing and I have worked in enough homes with 110 (to code) units although not lately. Alkaline batteries have a rather long shelf life. Curious if there is any draw on them when the detector is powered up on 110. Otherwise, those batteries should be good for five years.

Unrelated, but we used to have no end to the problems of those red LED lights attracting very small insects that would go into the sensing chamber.

charlz · Jan 4, 2016

Coyote machine said:
The 7-10 year replacement chirp is NOT the same as the replace battery chirp. When the 7-10 year one goes off the useful life of the detector is DONE and needs to be replaced. I thought they were closer to 5 years lifespan- but not sure on that detail.....
Also vacumm out cobwebs etc., when changing the battery. If doing painting/sanding in the area of a detector put a plastic bag over them until the entire room is dust free.

The CO2 detectors are the ones that you are supposed to replace the entire until every 5-7 years. I know the ones in the RV I had said it right on them.

rhunt · Jan 22, 2016

The reason the hard wired smoke detectors are required to have battery back-up is that should the building loose power from the power company, you still have protection via the battery.

Ford850 · Jan 22, 2016

I changed out my batteries in the wired detectors last week. I had marked them with dates so I knew when I installed them, which was over 4 years ago, and each had a battery date of later this year. I tested each after removing, and they varied from 9.3v to 10v.

k0ua · Jan 22, 2016

Ford850 said:
I changed out my batteries in the wired detectors last week. I had marked them with dates so I knew when I installed them, which was over 4 years ago, and each had a battery date of later this year. I tested each after removing, and they varied from 9.3v to 10v.

Hm.. those were still in fair shape, and would be usable in some devices.