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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a bryant air handler model fb4anf036. It has blown

Customer Question

I have a bryant air handler model fb4anf036. It has blown 5amp fuses a couple of times in last 3 months. Now thermostat is blank again however this time the fuse did not blow. I checked the voltage on my transformer. The primary read 120v on both primary wires. The transformer secondary side read 0 while still wired inside fan coil. I removed transformer and checked it in wall socket and secondary read 15v. I discovered that a 60A breaker at my house box was only 45V. I replaced the bad breaker and verified 240V. I replaced with new transformer in the fan coil unit. I still have 0volts on secondary side of transformer. Why cant I get voltage through the transformer ? I have no low voltage, therefore my t stat is still blank. Please help. Its cold here. Thanks
Submitted: 6 years ago.
Category: HVAC
Expert:  BillyHvac replied 6 years ago.




did you replace the transformer?



Customer: replied 6 years ago.
Expert:  BillyHvac replied 6 years ago.

Was transformer a multifit or OEM replacement?


Customer: replied 6 years ago.



Expert:  BillyHvac replied 6 years ago.


All unused leads capped separately?



Customer: replied 6 years ago.
yes i did
Expert:  BillyHvac replied 6 years ago.


What 2 colors did you hook up on primary side?


What model transformer ?


And are you measuring for 24v wire to wire or wire to ground?


Customer: replied 6 years ago.

orange and white

Jard tf402424-b51c84k

wire to ground

Customer: replied 6 years ago.

i was having computer issues but i think its good now Are you still here


Expert:  BillyHvac replied 6 years ago.


Last question....when measuring primary (220)...are you reading each wire to ground or wire to wire?



Customer: replied 6 years ago.
wire to ground
Expert:  BillyHvac replied 6 years ago.


Thank you....


you said you tested transformer in wall outlet...but that would be 115v. We need 220 and I hope you used the 2 wires on primary for 230v.


Now you need to measure supply wire to wire. With 220 you must measure wire to wire because it is possible to have only one leg and be reading that same leg on both sides.


Verify wire to wire for 220v

Verify primary wires on transformer are for 230v

Then check 24 v side wire to wire and not ground


let me know results