Thermostat Question ?

[Bob]

Hello,

Son is not in area, so couldn't look myself.

Has a Honeywell Thermostat (about 8 years old) that controls his A/C and heat (forced hot air).

A/C didn't work so called in a HVAC man who found that the inside of the thermostat had "lots of wires fried and shot to oblivion".

This seemed to happen right after he put in new new batteries in the Thermostat. Does this once a year, every year.

No expert, but was wondering.

What could possibly "fry" the inside of a Thermostat ? Can't see how putting in new batteries would.

Some voltage spike from the A/C ?

Eight years a reasonable life for one of these things ?

New Thermostat, and all seems happy now.

Any thoughts would be appreciated.

Bob

[trader_4]

IDK, it's strange. To start with, the thermostats I've had for decades now don't have "many wires" in them. They are essentially a circuit board. There might be a couple of wires to the batteries. The wires in the thermostat area are generally the ones that run to the thermostat from the system and it sounds like it's not those that he was talking about. Some failure mode of some component on the thermostat could probably burn up wires on the thermostat. A lightning surge could certainly do it, but a surge doing that kind of damage at the thermostat and not frying anything else seems rather unlikely. Most vulnerable devices are those that have direct connection to outside wiring, eg cable set top box, modem, phone, ectc.

[Ken]

Did he see the damaged wires, or is he simply repeating the comments from the HVAC guy? It is hard to imagine such damage based upon what you described. Unfortunately there are people in trades that pad the problem when called in for a repair.

[trader_4]

+1

I was thinking that too after hitting send. Even if there was some damage, one guys "a bunch of burned up wires" could be very different from the next. You would think the guy would show it to the customer. For all we know, if he didn't see it, it could have been a loose wire and nothing wrong with the thermostat.

[Ralph Mowery]

Would be nice to see a pix of the box. Hard to believe it could really be fried from just a couple of batteries. I could see if he put the batteries in backwards as messing it up, but not totally fried.

The wires comming from the AC are usually low voltage ( about 24) low power and only go to a small part of the control unit.

Maybe the repairman was just making small talk while telling him he needed a new one.

[Art Todesco]

Most 24 volt transformers don't have that much energy to fry wires. But, maybe if the battery was put in backwards it could fry parts, wires if the design didn't include a protection diode.