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Trying to install a thermostat but only have black and wires

Customer Question
Trying to install a thermostat...
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: 1 year ago.Category: HVAC
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Answered in 5 minutes by:
11/10/2016
HVAC Technician: airheatman, HVAC Technician replied 1 year ago
airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8,502
Experience: Furnace, A/C and heat pump specialist.
Verified

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

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Customer reply replied 1 year ago
Honeywell rth221b
Customer reply replied 1 year ago
I only have white and black wires and need to know where to put them, labeling and manual isnt helping
Customer reply replied 1 year ago
Heating only, no AC
Customer reply replied 1 year ago
Are you there?
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

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

Is this a gas or electric furnace?

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Customer reply replied 1 year ago
Oil burner hot water baseboards
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

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

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Customer reply replied 1 year ago
Either wire to those?
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

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

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Customer reply replied 1 year ago
No idea, straight from burner
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

Are you replacing a thermostat?

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Customer reply replied 1 year ago
Lookslike it
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

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

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Customer reply replied 1 year ago
Doesn't say model#, it's an old honeywell with an on off type switch
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

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

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Customer reply replied 1 year ago
12
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

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

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Customer reply replied 1 year ago
They are stained over
HVAC Technician: airheatman, HVAC Technician replied 1 year 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?

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Customer reply replied 1 year ago
Vno voltmetr at the moment and I now gotta leave for work, been at this for 2 hours
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

Would you like to continue later?

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Phil
Phil
Phil, Mechanical Engineer
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