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Transformer (90-T40F3) replacement on a Carrier HVAC. 120VAC…

Transformer (90-T40F3) replacement on...

Transformer (90-T40F3) replacement on a Carrier HVAC. 120VAC input White to common Black to power (208-240 capped) Secondary 24V blue/yellow. From the units circuit board connection "C" is brown and connection "T" is red. What do I connect the blue lead to, red or brown

Contractor's Assistant: Are you an HVAC professional?

NOPE

Contractor's Assistant: Do you plan on doing the work yourself?

YEP

Contractor's Assistant: Anything else we should know to help you best?

That should do it, the capacitor checked good.

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Answered in 1 minute by:
9/12/2017
airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 9,531
Experience: Furnace, A/C and heat pump specialist.
Verified

It makes no difference blue or yellow can go either place

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I usually use blue for Common just because Carrier uses blue to common at thermostat

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Customer reply replied 1 year ago
Thanks, ***** ***** sure before I smoke test.

LOL.Totally understand. Let me ask this, if old transformer burned up, have you determined cause?

airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 9,531
Experience: Furnace, A/C and heat pump specialist.
Verified
airheatman and 87 other HVAC Specialists are ready to help you
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If you had a short that burned up transformer, I recommend installing a little 3 or 5 amp fuse in one of the low voltage wires just in case something shorts again it will pop fuse instead of frying transformer.

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Customer reply replied 1 year ago
The unit is 19 years old, I did an oms check between the secondary coil and it was open. Don't know if there is other problems down stream. I'll let you know

Sounds good.

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