Author Topic: Efficient smoke detectors  (Read 881 times)

tcjones

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Efficient smoke detectors
« on: January 23, 2017, 09:34:36 AM »
Does anyone have recommendations for an efficient hard-wired smoke detector?

This is related to this MMM post:
http://www.mrmoneymustache.com/2015/03/25/cut-your-power-bill/comment-page-3/#comment-1432021

My current smoke detectors draw about 7W each and I have 8 of them.
They are hardwired  interconnected (not wireless) which I want to keep.
MMM mentioned in the article that he replaces some with a model that draws about 1W, but he could not yet recommend a hardwired model (see the comments of the about post).
So I am hoping someone can recommend one.

Spork

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Re: Efficient smoke detectors
« Reply #1 on: January 23, 2017, 10:03:33 AM »

I believe we have 5 of these:
https://www.amazon.com/Kidde-i4618-Hardwired-Battery-Backup

I don't know the wattage on it, but I can disrecommend them.  We had loads of false alarms when they were about 4 years old.  It was almost always at night and by the time you'd get up to investigate, it would be quiet again.  One of the 5 was bad... and it took a while to figure out which one.  We finally disconnected them one at a time for a few days... until we got several nights of peace.

Maybe that's a fluke and they're fine... but I won't be buying that model again.
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FIRE me

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Re: Efficient smoke detectors
« Reply #2 on: February 07, 2017, 03:30:36 PM »

I believe we have 5 of these:
https://www.amazon.com/Kidde-i4618-Hardwired-Battery-Backup

I don't know the wattage on it, but I can disrecommend them.  We had loads of false alarms when they were about 4 years old.  It was almost always at night and by the time you'd get up to investigate, it would be quiet again.  One of the 5 was bad... and it took a while to figure out which one.  We finally disconnected them one at a time for a few days... until we got several nights of peace.

Maybe that's a fluke and they're fine... but I won't be buying that model again.

I think you cut that link a bit short.

https://www.amazon.com/Kidde-i4618-Hardwired-Battery-Backup/dp/B00PC5TJJQ/
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robartsd

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Re: Efficient smoke detectors
« Reply #3 on: February 07, 2017, 04:49:32 PM »
My current smoke detectors draw about 7W each and I have 8 of them.
The power usage of a hardwired smoke detector is primarily waste in converting the AC to DC. Battery powered smoke detectors consume less than 0.5mW when idle. Unfortunately no one seems to be looking at the power draw of these devices.

Metric Mouse

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Re: Efficient smoke detectors
« Reply #4 on: February 11, 2017, 02:48:40 AM »
My current smoke detectors draw about 7W each and I have 8 of them.
The power usage of a hardwired smoke detector is primarily waste in converting the AC to DC. Battery powered smoke detectors consume less than 0.5mW when idle. Unfortunately no one seems to be looking at the power draw of these devices.
Interesting... I wonder if the price per watt of a battery offsets the differential in power usage at grid rates.
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paddedhat

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Re: Efficient smoke detectors
« Reply #5 on: February 11, 2017, 05:56:53 AM »

I believe we have 5 of these:
https://www.amazon.com/Kidde-i4618-Hardwired-Battery-Backup

I don't know the wattage on it, but I can disrecommend them.  We had loads of false alarms when they were about 4 years old.  It was almost always at night and by the time you'd get up to investigate, it would be quiet again.  One of the 5 was bad... and it took a while to figure out which one.  We finally disconnected them one at a time for a few days... until we got several nights of peace.

Maybe that's a fluke and they're fine... but I won't be buying that model again.

In dozens of new homes I built, using random brand hard wired units (per code requirements) I had this situation occur only one time. After investigating, I found that it was caused by an insect problem inside unit.  The house was clean, there was no evidence of bugs anywhere, but they somehow had an attraction to the smoke units, and would somehow trip them randomly.

Spork

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Re: Efficient smoke detectors
« Reply #6 on: February 11, 2017, 07:46:49 PM »

I believe we have 5 of these:
https://www.amazon.com/Kidde-i4618-Hardwired-Battery-Backup

I don't know the wattage on it, but I can disrecommend them.  We had loads of false alarms when they were about 4 years old.  It was almost always at night and by the time you'd get up to investigate, it would be quiet again.  One of the 5 was bad... and it took a while to figure out which one.  We finally disconnected them one at a time for a few days... until we got several nights of peace.

Maybe that's a fluke and they're fine... but I won't be buying that model again.


In dozens of new homes I built, using random brand hard wired units (per code requirements) I had this situation occur only one time. After investigating, I found that it was caused by an insect problem inside unit.  The house was clean, there was no evidence of bugs anywhere, but they somehow had an attraction to the smoke units, and would somehow trip them randomly.

I haven't seen any insects.  Well... we get an annual line of ants (downstairs) that are generally easily dealt with. The faulty unit was upstairs. We get an occasional scorpion (which is an upgrade over the building 50 ft south of us where we used to live).  This is a pretty new home and there is so much boric acid hidden in the walls and under the baseboards... I can't imagine there is much insect life.  We did narrow the problem down to a single detector.  And it's been replaced for about a year and a half now... so I am pretty sure it was localized to the one spot.

But... that's an interesting possibility nonetheless.  I will try to keep my eyes open.  We've got 6 cats... so anything that creeps and crawls might be caught, dismantled and eaten before I saw it.
Some will sell their dreams for small desires
Or lose the race to rats
Get caught in ticking traps
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tyler.close

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Re: Efficient smoke detectors
« Reply #7 on: February 17, 2017, 04:52:11 PM »
My current smoke detectors draw about 7W each and I have 8 of them.

Did you measure that 7W or get it by multiplying the amps given in the documentation by 120V? Going by that calculation, my smoke detector also draws 8W. However, by measuring the watts, I see it's only using 0.7W. Smoke detectors seem to be a place where power factor matters a lot. See:

https://en.wikipedia.org/wiki/Power_factor


matthixson

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Re: Efficient smoke detectors
« Reply #8 on: February 18, 2017, 05:01:19 PM »
Just thought I'd mention that the Protect smoke detector from Nest operates for over a year on 6 AA batteries. There is also a wired version.

tcjones

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Re: Efficient smoke detectors
« Reply #9 on: February 20, 2017, 07:38:24 AM »
Did you measure that 7W or get it by multiplying the amps given in the documentation by 120V?

I did measure 62W on the smoke alarm circuit using an Efergy power monitor.  I also measured 0.54A on the circuit using a clamp-on meter.  I verified the 8 smoke detectors where the only thing powered on that circuit at the time.  I also measured the current at each individual smoke detector to attempt to find an outlier, but they all were very similar and about (0.54)/8 amps.

In MMM's article, he mentioned he replaced some faulty detectors drawing 5W with ones using under 1W.
So I was looking for recommendations with something under 1W.
What model are yours?
Maybe I can't go wrong with any new model.

tyler.close

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Re: Efficient smoke detectors
« Reply #10 on: February 20, 2017, 08:15:37 PM »
Did you measure that 7W or get it by multiplying the amps given in the documentation by 120V?

I did measure 62W on the smoke alarm circuit using an Efergy power monitor.

It looks like Efergy has two models: the "classic" and the "true". Only the "true" will account for the power factor. Which model did you use for your measurement?

I also measured 0.54A on the circuit using a clamp-on meter.  I verified the 8 smoke detectors where the only thing powered on that circuit at the time.  I also measured the current at each individual smoke detector to attempt to find an outlier, but they all were very similar and about (0.54)/8 amps.

Since the issue here is power factor, any measurement of the amperage alone will be misleading. You need to get a simultaneous measure of the voltage x the amperage. I used a kill-a-watt wired up to the smoke detector for my measurement. I saw a measurement of 7.6 VA, as expected based on the documentation for the smoke detector, but only 0.7W, due to the power factor effect.

In MMM's article, he mentioned he replaced some faulty detectors drawing 5W with ones using under 1W.
So I was looking for recommendations with something under 1W.
What model are yours?
Maybe I can't go wrong with any new model.

I still suspect your existing detectors are using 10x less power than you think. Seems unlikely they are all faulty at the same time.

My detector is:

https://camelcamelcamel.com/First-Alert-Hardwire-Photoelectric-Ionization/product/B00O8MVW44

tcjones

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Re: Efficient smoke detectors
« Reply #11 on: March 13, 2017, 08:17:02 AM »
tyler.close, you are correct.
Thanks for setting me straight.
I have the the Efergy Classic.
I powered up one of my smoke detectors through a Kill-A-Watt.
It has a 0.08 power factor, I assumed nothing in my home would have a PF that low, and therefor assumed the W would always be somewhat close to the VA.
Obviously that was a bad assumption.
The smoke detector measured 8.3 VA and 0.6 W throught the Kill-A-Watt, pretty close to your measurements.
So what I thought was costing me about $4/month is actually only about $0.30/month.
Thanks again.
Now I wish I would have bought the Efergy True.

dcozad999

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Re: Efficient smoke detectors
« Reply #12 on: March 13, 2017, 01:05:42 PM »
Check with your local fire department.

I asked a firefighter buddy of mine what smoke alarms they recommend and he said free ones installed by the fire department.

Maybe it's just my town, but our city fire department got a grant to install free fire alarms in houses in their jurisdiction. We just had to fill out a form and mail it in. They just installed 3 in my house last week. And they put 10 year batteries in them.