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mpichora · Oct 31, 2007, 04:50 PM

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

rtw_travel · Oct 31, 2007, 05:00 PM

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

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.

mpichora · Oct 31, 2007, 05:14 PM

Thanks, that was very quick!

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

-Mark

rtw_travel · Oct 31, 2007, 05:22 PM

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

mpichora · Oct 31, 2007, 05:30 PM

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

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

labman · Oct 31, 2007, 06:22 PM

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?

mpichora · Oct 31, 2007, 07:34 PM

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?

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

labman · Oct 31, 2007, 09:17 PM

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.

mpichora · Nov 1, 2007, 08:41 AM

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