Doorbell circuit

[Ed MacLaren]

I know modern signal (Class 2) transformers are supposed to be thermally protected, but have any of you ever heard of residential doorbell circuit wiring overheating and causing a fire?

Do you think this would be possible if the pushbutton stuck in the "on" position?

Ed

 

[roger]

Re: Doorbell circuit

Ed, I can't say I've heard of one starting a fire, but I've seen one that blackened a stud next to the box it was mounted to. The scenario you mentioned was the culprit.

The service call was due to the owner hearing the chime buzzing.

When I got to the house you could smell the wood burning. This was in the early 80's and the transformer was in the attic.

Roger

 

[pierre]

Re: Doorbell circuit

Are they thermally protected by some device, or is the impedance of the windings on a class two doorbell transformer the thermal protection?

Pierre

 

[hbiss]

Re: Doorbell circuit

Pierre, I've seen both. Some will have an internal fuse. Unfortunately if you inadvertently short these types you have to buy a new transformer.

 

[macmikeman]

Re: Doorbell circuit

About 3 years back I got a call from a customer telling me his smoke alarms were going off and his house was full of smoke. Turns out that he just had his house painted, and the painter dripped enough paint into the flush button that when dry it caused the switch to stay closed after the button was pushed in. This in turn overheated the 16v xfmr and it melted the varnish on the windings which was the source of all the smoke. How close was it to burning?. Hard to say exactly but it sure looked like it was about to go.

 

[jimwalker]

Re: Doorbell circuit

Have replaced more than a few chimes over painted buttons.The nutone $10 ones usually melt the plunger.Maybe if they got the backcharge for this they would learn to be more carefull.Door chime $10 labor $100.The problem in backcharging is some use it to make a high profit from an accident.We don't want the painter charging us $100 to paint that spot on the ceiling we made so usually we don't make a big deal out of that rare time he paints our button.As to a fire i have not seen anything close to that.
Have replaced far more chimes and transformers over our helpers installing them wrong than over painters.How often have you heard,sure i know how to install a chime ?

[ January 27, 2004, 02:04 PM: Message edited by: jimwalker ]