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HVAC Guru
HVAC Guru, HVAC TECH
Category: HVAC
Satisfied Customers: 14877
Experience:  15yrs in the HVAC industry with certificates and degrees.
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Installing a new Honeywell TH8320ZW thermostat. Replacing an

Customer Question

Installing a new Honeywell TH8320ZW thermostat. Replacing an old mercury thermostat that only had two wires. Red and white. Instructions call for a C common but the transformer on my furnace only has two connections T T. What can should I do from here? I already pulled a four conductor cable just don't see what I can connect to.
Submitted: 1 year ago.
Category: HVAC
Expert:  HVAC Guru replied 1 year ago.

Hello and thanks for using this service, if you have been waiting do not worry or get upset I am just one of the techs on here and I try to get to as many customers as I can and I just picked up your question now. Please give me time to respond sometimes I get your replies late so there may be a delay in my response.

Can you get to the low voltage transformer? One side of the transformer has 120 volts to it and out the other side are the 24 volt HOT and COMMON wires you need to splice the wire you are using for your C to the COMMON on that transformer.

We are on the honor system for our time, all I ask is please rate my service using the STAR RATING LINK on your page before you leave. If you are not happy with the service please let me know before leaving a negative rating. This is the only way I am paid or credited through the site for my time. This will also allow you to get directly back to me for FREE follow up questions and tips are greatly appreciated! Thanks

Expert:  HVAC Guru replied 1 year ago.

Just like this, all transformers have to have a supply in and supply out.

CLICK HERE

Customer: replied 1 year ago.
my common splices with my white on the low side?
Expert:  HVAC Guru replied 1 year ago.

Hello and thanks for using this service, if you have been waiting do not worry or get upset I am just one of the techs on here and I try to get to as many customers as I can and I just picked up your question now. Please give me time to respond sometimes I get your replies late so there may be a delay in my response.

Yes that is a common issue you need a new interface board.

CLICK HERE

We are on the honor system for our time, all I ask is please rate my service using the STAR RATING LINK on your page before you leave. If you are not happy with the service please let me know before leaving a negative rating. This is the only way I am paid or credited through the site for my time. This will also allow you to get directly back to me for FREE follow up questions and tips are greatly appreciated! Thanks