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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Power out of transformer but nothing at thermostat. Replaced

Customer Question

Power out of transformer but nothing at thermostat. Replaced t stat wire checked common, this is a heat pump system. Stuck. System is less than a year old carrier 5 ton unit all electric
Submitted: 2 years ago.
Category: HVAC
Expert:  airheatman replied 2 years ago.
Hello. My name is ***** ***** I'll do my best to help. Let's get started and see what we can do.If we have 24v out of transformer but not at thermostat, we have to have a break in circuit somewhere. Can you take a photo of the wiring diagram on lable in air handler and follow the hot and common low voltage wire from transformer and tell me where they go?
Customer: replied 2 years ago.
for the 24 volt or 120 v
Expert:  airheatman replied 2 years ago.
The 24 volt side. We should have a hot and a common 24 wire. They should go from transformer to thermostat. WE need to find what components they go through to determine which is not allowing the circuit to thermostat.
Customer: replied 2 years ago.
From the transformer the red and brown are the 24 volt hot legs. Red runs to a fuse and then to the t stat brown, which is the common, runs to a crimp point where 4 wires split off one to the t stat one to a # ***** terminal and one to a 3 terminal both connected to the fan motor
Customer: replied 2 years ago.
The red also connects to the condenser unit outside
Customer: replied 2 years ago.
The brown wire connects to both the condenser unit and fan oil as well.
Expert:  airheatman replied 2 years ago.
Can you upload a photo?
Customer: replied 2 years ago.
I have replaced the t stat wires, the transformer, though the other was still ok, the fuses to the disconnect, the breakers and I have a new t stat. It worked fine and then one day it just stopped. I have tried to jumper the t stat nothing, I am thinking it may have something to do with the circuit board in the fan coil unit though I checked voltage out of that and it seemed fine.
Customer: replied 2 years ago.
Yes of what the circuit or the actual unit guts
Customer: replied 2 years ago.
Customer: replied 2 years ago.
2 more pics