Hope someone can help! Labman you've touched on this but I want to be sure.

I have a simple baseboard heater connected to an old analog thermostat with no labeling or HVAC color coding, and I would like to install a new programmable thermostat with only the Rh and W connected - I am using 2-wire heating only. (no fan, A/C, etc... ) .

There are two sets of wires in the electrical box behind the existing t-stat: 2 grounds, 2 white, 2 black. The two whites are connected to each other, and the two blacks are connected to 2 unmarked terminals on the old t-stat.

So here's what I need to know:
1. Do I leave the 2 whites connected, and connect the blacks to the R & W?
2. Does it matter which black goes to the R and which goes to W? (If so how can I distinguish between the two black wires?! )

Thanks very much!

Mark

Quote:

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Originally Posted by mpichora

Hope someone can help! Labman you've touched on this but I want to be sure.

I have a simple baseboard heater connected to an old analog thermostat with no labeling or HVAC color coding, and I would like to install a new programmable thermostat with only the Rh and W connected - I am using 2-wire heating only. (no fan, A/C, etc...) .

There are two sets of wires in the electrical box behind the existing t-stat: 2 grounds, 2 white, 2 black. The two whites are connected to each other, and the two blacks are connected to 2 unmarked terminals on the old t-stat.

So here's what I need to know:
1. Do I leave the 2 whites connected, and connect the blacks to the R & W?
2. Does it matter which black goes to the R and which goes to W? (If so how can I distinguish between the two black wires??!! )

Thanks very much!

Mark

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1. Yes
2. No. Doesn't matter

Make sure the thermostat you purchased is for line voltage. i.e. it should say that it is rated for x thousand watts and 240V.

Thanks, that was very quick!

It's an AUBE TH147-P , and it says "24V - 1A"

-Mark

Nooooo! Do not install this thermostat. It is the wrong thermostat for a baseboard heater. It is for a furnace or other low voltage system that uses an isolating relay.

Go back to where you purchased it and swap it for a line voltage thermostat. Here's an example form the same manufacturer as the one you purchased
Aube Technologies TH106, Line Voltage Thermostat, SPST 120V or 240V

Quote:

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Originally Posted by rtw_travel

Nooooo! Do not install this thermostat. It is the wrong thermostat for a baseboard heater. It is for a furnace or other low voltage system that uses an isolating relay.

Go back to where you purchased it and swap it for a line voltage thermostat. Here's an example form the same manufacturer as the one you purchased
Aube Technologies TH106, Line Voltage Thermostat, SPST 120V or 240V

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Okay, now my problem is that I have a fire on the south wall of my bedroom... just kidding! Thanks a lot for the help, I'll go exchange my thermostat.

Cheers !

Mark

If it is a 240 volt heater, you should buy a double pole thermostat and disconnect the 2 whites and connect them to the second set of contacts. I don't remember if a double pole thermostat is code, or just a good practice. The wires are heavy #12 or #10, and not the little #18 wire 24 volt thermostats use?

Quote:

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Originally Posted by labman

If it is a 240 volt heater, you should buy a double pole thermostat and disconnect the 2 whites and connect them to the second set of contacts. I don't remember if a double pole thermostat is code, or just a good practice. The wires are heavy #12 or #10, and not the little #18 wire 24 volt thermostats use?

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Thanks Labman, the response time in here is unbeatable! I just went to return my 24V thermostat for a line load version. rtw_travel recommended the TH106, but all they had left was the TH104plus, which doesn't have the same range of voltage compatibility. I haven't cracked open the heater yet to see what voltage it is, but my line registers 120V. I assume this means that a 240V t-stat is no good, i.e. I should hunt around for a TH106 and not settle for the TH104. Any thoughts? If my line is only supplying 120V does it hurt to use a 240V thermostat? Would it even work?

Appreciate the enlightenment,

Mark

No problem using a 240 volt thermostat on a 120 volt circuit. Most quick way to sort out is to look at the breaker. A double wide one with the 2 handles linked together, and it is 240 volts. A single handle is 120 volts.

Ah, that explains it. My breaker is indeed set up for a 240V circuit. I also double checked my heater and it is 240V.

Problem solved, case closed, thanks for the education. My heater piped in at 5:40 this morning as planned.

Take care,

Mark