NDR: HVAC Blowing fues on the low voltage side

Carl

Carl

Moderator
Staff member
My HVAC (Heat Pump) keeps blowing the 5 amp blade fuse on the controller card on the low voltage side. Happened over Christmas, replaced the thermostat (wanted a new one anyway) and the fuse and it worked fine until last night.
When I put a new fuse in & turn the breaker on & turn the thermostat to heat, it immediately pops the fuse.

Any one have any ideas?
I'm thinking I have a short in the low voltage wires either from the thermostat to the control panel or from the control panel to the outside unit.
 
Carl,

That's what ours was, short between the thermostat and the furnace. Installer ran the thermostat wire through holes through the duct work without putting grommets in the holes. DUH!!!

George
 
I would agree with checking for a short in the wiring first, sometimes construction work done on the house, new picture being hung or follow the wires and check for grounding, check low voltage outside wires going into the condensor.Try turning the outside disconnect off then turn on the system, see if unit runs sometimes with wet wheather or critters can short out your condensor contactor and give you a high voltage feed back.
 
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AC guy was here at 8:30, done by 9:00. Which is good, it was 48 degrees in the house this morning.
Last time the AC blew a fuse, we couldnt track down the short. This time, the wire had worn enough to be easy to see it. It was in the outside unit, on one of the low voltage wires coming from the inside.
 
Carl if I had a problem like that I would not know about it for five months and maybe not then...You don't want to buy some snow...Hee hee

 
This was on a heat pump that runs both the AC & the heat, so we knew about it pretty quickly!
It was chill here this weekend, not upper midwest chilly, but chilly none the less!
 
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