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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 5648
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Trying to install a thermostat but only have black and wires

Customer Question

Trying to install a thermostat but only have black and white wires and dont know where to put them
JA: Just to clarify, do you think this is a larger HVAC problem, or something specific to the thermostat?
Customer: Thermostat
JA: Do you plan on doing the work yourself?
Customer: Yes
JA: Anything else we should know to help you best?
Customer: I just need to know the wiring, its a honeywell rth221b
Submitted: 25 days ago.
Category: HVAC
Expert:  airheatman replied 25 days ago.

I will glad to help.Tell me what kind of unit you contols

Customer: replied 25 days ago.
Honeywell rth221b
Customer: replied 25 days ago.
I only have white and black wires and need to know where to put them, labeling and manual isnt helping
Customer: replied 25 days ago.
Heating only, no AC
Customer: replied 25 days ago.
Are you there?
Expert:  airheatman replied 25 days ago.

Sorry had a customer called. One wire to R and one to W.

Is this a gas or electric furnace?

Customer: replied 25 days ago.
Oil burner hot water baseboards
Expert:  airheatman replied 25 days ago.

What thermostat are you replacing and do you know it is 24v controlled?

Customer: replied 25 days ago.
Either wire to those?
Expert:  airheatman replied 25 days ago.

Yes as long as your unit is 24v controlled. What is model on old thermostat?

Customer: replied 25 days ago.
No idea, straight from burner
Expert:  airheatman replied 25 days ago.

Are you replacing a thermostat?

Customer: replied 25 days ago.
Lookslike it
Customer: replied 25 days ago.
Expert:  airheatman replied 25 days ago.

Give me model on old and tell me where wires went on old

Customer: replied 25 days ago.
Doesn't say model#, it's an old honeywell with an on off type switch
Expert:  airheatman replied 25 days ago.

Are the wires small like about 18 gauge or thick like 12 gauge?

Customer: replied 25 days ago.
12
Expert:  airheatman replied 25 days ago.

THat sounds like it may be line voltage.If so the thermostat will not work. Any numbers at all on old stat?

Customer: replied 25 days ago.
They are stained over
Expert:  airheatman replied 25 days ago.

Do you have a volt meter to check ? I sure hate to burn the new thermostat up if it is high voltage wires. Can you attach a pic of old or where they connect at unit?

Customer: replied 25 days ago.
Vno voltmetr at the moment and I now gotta leave for work, been at this for 2 hours
Expert:  airheatman replied 25 days ago.

Would you like to continue later?