# "Green" doorbell?



## TradEddie (Feb 23, 2014)

Last night I discovered that my doorbell transformer died. This transformer is directly mounted onto my breaker box, and although I can replace it myself, it will be a PITA to kill power to the whole house and re-wire a new transformer. Then I got to thinking that this is one of those "phantom loads", that transformer is powered 24/7 so maybe I don't want to replace it. I've temporarily put a battery onto the transformer outlet wires, and that works just fine. Quick research shows that typical doorbell transformers draw about 5w with an open circuit, but I'm sure I could re-wire an old phone charger with a switched mode transformer that would draw less

Am I crazy to care? Perhaps some of you OCD energy misers have already done the research? Should I buy a new transformer, reuse an old phone charger, buy a battery-powered wireless, plug-in wireless, or just wire up a pp3 battery in the bell box?

TE


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## fossil (Feb 23, 2014)

The possibilities are endless...

https://www.google.com/#q=door+knocker


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## TradEddie (Feb 23, 2014)

fossil said:


> The possibilities are endless...
> 
> https://www.google.com/#q=door knocker



I guess I deserved that! 

TE


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## GaryGary (Feb 23, 2014)

TradEddie said:


> Last night I discovered that my doorbell transformer died. This transformer is directly mounted onto my breaker box, and although I can replace it myself, it will be a PITA to kill power to the whole house and re-wire a new transformer. Then I got to thinking that this is one of those "phantom loads", that transformer is powered 24/7 so maybe I don't want to replace it. I've temporarily put a battery onto the transformer outlet wires, and that works just fine. Quick research shows that typical doorbell transformers draw about 5w with an open circuit, but I'm sure I could re-wire an old phone charger with a switched mode transformer that would draw less
> 
> Am I crazy to care? Perhaps some of you OCD energy misers have already done the research? Should I buy a new transformer, reuse an old phone charger, buy a battery-powered wireless, plug-in wireless, or just wire up a pp3 battery in the bell box?
> 
> TE




The 5 watts is 5*24*365/1000 = 44 KWH a year and maybe 70 lbs of CO2 emissions -- seems worth going after to me.

I like the mechanical door knockers -- both aesthetically and for performance.

Gary


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## bsruther (Feb 23, 2014)

I'm not sure they even make the transformer kind anymore. I did away with mine and installed a driveway motion sensor.
I know when someone's here before they turn their car off.

Here you go...
http://lmgtfy.com/?q=doorbell


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## Circus (Feb 24, 2014)

If you disable the little lights a battery would probably die of old age before draining.


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## peakbagger (Feb 24, 2014)

Most heating systems have a 24 volt AC transformer that is active 24/7 as long as the heating system is running. It may not be strictly code but I wonder if you could just feed the doorbell off it, since it has to be on all the time anyhow?


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## Ashful (Feb 24, 2014)

First, that transformer is not likely wired to the mains, but a sub circuit, so it should not be necessary to kill the house to replace.  Second, the draw of a transformer is simply its load divided by its efficiency.  Your transformer is not drawing 5 watts, the little lightbulbs in your doorbell buttons are.  That will be the same with a switch mode power supply.  Third, tapping off the heating system transformer will not save energy, as it's the same load/efficiency, simply displaced to another transformer.


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## bmblank (Feb 24, 2014)

Transformers draw power whether there is a load on the 24v side or not, barring some sort of "smart" transformer. That's why you're supposed to unplug phone chargers with wallwarts to stop "energy vampires".


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## Ashful (Feb 24, 2014)

bmblank said:


> Transformers draw power whether there is a load on the 24v side or not, barring some sort of "smart" transformer. That's why you're supposed to unplug phone chargers with wallwarts to stop "energy vampires".


In theory, this is correct.  There is a no-load current (imaginary, almost zero real component) associated with magnitizing the primary under no load condition.  The fact that the real component is near zero is why there is very little power loss associated with this current.  Any power loss due to no-load currents is VERY small, compared to the actual load rating of the transformer.

Size your transformer to the load, choose one with high efficiency, and focus on reducing loads.  Focusing on the transformer itself is time spent for very insignificant returns.


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## bmblank (Feb 24, 2014)

I guess I can dig that.


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## velvetfoot (Feb 24, 2014)

They sell battery operated wireless models at HD.


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## Ashful (Feb 24, 2014)

velvetfoot said:


> They sell battery operated wireless models at HD.


Are batteries more green than central power?  Perhaps we should go back to local battery telephones?


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## bmblank (Feb 24, 2014)

I haven't had much luck with the battery wireless ones. Then again I'm a hard wire kinda guy.


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## peakbagger (Feb 24, 2014)

The old crank style phones need a battery for the DC circuit that handles the voice but the bell is run by the crank and doesnt require a battery. Therefore the crank from the telephone could be mounted outside with the bell inside. When I was growing up army surplus crank generators were easy to get and some folks used them to get earthworms for fishing. These days I think they are no regarded as antiques.


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## Highbeam (Feb 24, 2014)

I haven't had a doorbell for the last 8 years. It would appear that they weren't always installed 50 years ago when my house was built. Can't say I've missed it.


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## TradEddie (Feb 24, 2014)

Joful said:


> First, that transformer is not likely wired to the mains, but a sub circuit, so it should not be necessary to kill the house to replace.  Second, the draw of a transformer is simply its load divided by its efficiency.  Your transformer is not drawing 5 watts, the little lightbulbs in your doorbell buttons are.  That will be the same with a switch mode power supply.  Third, tapping off the heating system transformer will not save energy, as it's the same load/efficiency, simply displaced to another transformer.



The transformer is mounted directly onto a conduit hole on the breaker panel, and wired directly to one of the breakers, there is no (safe) way to remove or replace the transformer without killing power to the panel. I'm fine with doing all that, its just a PITA.
I don't have any lights on the bells, and since the old transformer is dead I have no way to measure its open circuit draw, but don't want to buy a new one and find it has a high draw, so for now, I've repurposed an unused 5v switched mode transformer and it draws little enough to not even register on the kill-a-watt.

TE


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## Ashful (Feb 24, 2014)

peakbagger said:


> The old crank style phones need a battery for the DC circuit that handles the voice but the bell is run by the crank and doesnt require a battery. Therefore the crank from the telephone could be mounted outside with the bell inside. When I was growing up army surplus crank generators were easy to get and some folks used them to get earthworms for fishing. These days I think they are no regarded as antiques.


Best idea I've seen in a while.  I actually have three of those, but they're mounted in 100 year old phones (which we still use, actually).  I just replace the local battery circuit with a transformer from a Western Electric 302, which are plentiful.


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## Jo191145 (Feb 24, 2014)

Visitor powered.


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## bsruther (Feb 24, 2014)

More cowbell.


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