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Replacing thermostat for electric baseboard heaters--- what do I have right now?

Replacing thermostat for electric baseboard heaters--- what do I have right now?

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  #1  
Old 08-31-08, 06:43 PM
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Replacing thermostat for electric baseboard heaters--- what do I have right now?

I take it that thermostats are a bit different from other electric heating devices. and I needs some help in determining what I have and what replacement I should get.

Current Setup
Current is supplied by a twinned 30 amp breaker on a 240v system. Tests on the lead wires indicate 120v on each (testing black-to-ground and then white-to-ground) and 240v when testing black-to-white. The heaters include 2x 1500 watt electric baseboard heaters and 1x 1000 watt fan-forced electric heater. So total wattage is 4000.

Power supply comes in to the thermostat by a single heavy-gauge black wire. This runs through the thermostat and then returns to a cap which sends the current on through separate wires to all three heaters. The white wires are all capped together and do not run through the thermostat. When I test the supply at all three heaters, I read 240v so that part seems to be working fine.

Current thermostat is a circa-1978 White Rodgers model (166-133?). It is a fairly simple dial-based model with four connectors which are are arranged in an "X" pattern. Supply comes in to top-left and returns to the heaters via top-right. The bottom-left and bottom-right connectors are connected by a single red jumper wire.

Questions
1. Does the current wiring make sense?
2. What type of thermostat can I replace this with? 2-pole? 4-pole? Any other restrictions or specifications?
3. Can someone recommend a simple programmable thermostat that can handle 4000w at 240v?
4. How would the replacement be wired in? Okay, I understand that this is going to be model-dependent.
5. Is this a simple job or should I leave this to a professional?

Thanks,
 

Last edited by Viso1964; 08-31-08 at 07:33 PM.
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  #2  
Old 09-02-08, 06:59 AM
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Originally Posted by Viso1964 View Post
The white wires are all capped together and do not run through the thermostat. When I test the supply at all three heaters, I read 240v so that part seems to be working fine.
So at the t-stat, only 3 of the 4 wires are used?

1. Does the current wiring make sense?
Are you able to draw or take a photo and put on here for us to see your set up?

2. What type of thermostat can I replace this with? 2-pole?
4-pole? Any other restrictions or specifications?
Any of them can work.

3. Can someone recommend a simple programmable thermostat that can handle 4000w at 240v?
Not sure about your area if Home Depot has it, but down here we have the Honeywell Line Voltage t-stat that can work. It's model #RLV430A

5. Is this a simple job or should I leave this to a professional?
I don't think it's going to be too bad... Seems like you got a good ideal of what's going on there when you did a voltage reading.
 
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Old 09-02-08, 09:15 AM
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Jay, thanks for the reply. Here is some additional info.

Originally Posted by Jay11J View Post
So at the t-stat, only 3 of the 4 wires are used? Are you able to draw or take a photo and put on here for us to see your set up?
Here's a very rudimentary wiring diagram that I put together. The wiring seemed pretty simple. The ground wires are hooked up identically to the white whires - twisted together.


I guess the thing that has me most concerned is that I did try to install a simple non-programmable 4-pole t-stat. It was a Honeywell model CT410B. It had connections for two black leads and two red leads, so I just connected each of the loose blacks to one of the black leads and connected the two reds together - same as the old model. Initially it seemed to work but then the next day the breaker kept blowing. I removed it and reinstalled the old one and the breaker stopped blowing so I figured that I must be doing something wrong.
 
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Old 09-02-08, 02:51 PM
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Originally Posted by Jay11J View Post
Not sure about your area if Home Depot has it, but down here we have the Honeywell Line Voltage t-stat that can work. It's model #RLV430A
Looks like that model is only rated up to 3,500 watts and I'm going to need 4,000 watts. Any other suggestions? I guess I can keep doing the Ohm's law thing on several models until I find one that fits the bill.
 

Last edited by Viso1964; 09-02-08 at 05:35 PM.
  #5  
Old 09-03-08, 07:00 AM
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Originally Posted by Viso1964 View Post
Looks like that model is only rated up to 3,500 watts and I'm going to need 4,000 watts.
Shoot... I didn't look at the wattage... I will keep digging to see what I can find...

Oh by the way, nice drawing!! What did you use for that?

Everything is done right as I can see.
 
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Old 09-03-08, 01:42 PM
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The drawing is just done in MS Paint, which comes with MS Windows. Make your drawing, save your BMP as JPG, upload JPG to the web, and then link JPG via IMG code to your post. Easy!

Now about the CT410B t-stat ... I mentioned that I kept blowing my circuit breaker when I had it wired in. I should describe how I had wired it and perhaps you can tell me where I went wrong. The CT410B is a 4-pole model (the 410A is 2-pole) and it has the following connectors:

L1 (black wire)
T1 (black wire)
L2 (red wire)
T2 (red wire)

I had connected black power supply to L1, connected the two reds L2 and T2 together with a cap, and then connected my black feed to the heaters to T1. I did it this way because it seemed similar to my old White-Rodgers t-stat. But it shorted out so I guess that wasn't quite right.

Looking again at the wiring diagram, I'm guessing that I should have run black supply to L1, white supply to L2, and then T1 back to feed the black heater wires and T2 to feed the white heater wires. This would be a slightly different setup that I currently have. So I'm just looking to see if I have correctly understood the wiring diagram. I'd still rather get a programmable model if I can find one that handles 4000 watts.
 
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Old 09-03-08, 07:06 PM
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I had connected black power supply to L1, connected the two reds L2 and T2 together with a cap, and then connected my black feed to the heaters to T1. I did it this way because it seemed similar to my old White-Rodgers t-stat. But it shorted out so I guess that wasn't quite right.
I can't see why it would short out like that.. The way you wired it would been a single pole vs double pole.

Looking again at the wiring diagram, I'm guessing that I should have run black supply to L1, white supply to L2, and then T1 back to feed the black heater wires and T2 to feed the white heater wires. This would be a slightly different setup that I currently have. So I'm just looking to see if I have correctly understood the wiring diagram.
That is correct, wire it that way and see what happens.
 
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Old 09-04-08, 01:03 PM
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Alright, I've revised the wiring and it seems to be working properly now so that's all fine. Thanks very much for you help with this matter.
 
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Old 09-04-08, 07:22 PM
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For the benefit of other brave souls who want a clearer picture of what I did (rightly or wrongly), here's a picture. I take no responsibility if your house burns down! It's starting to make sense to me. Note that the L1 and L2 on the thermostat have black and red leads (respectively) which I capped to the black and white power supplies, but I've shown the L2 as a single white supply wire to emphasize the origin.
 
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