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Old 04-12-2013, 01:14 PM   #1
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Wiring 2 baseboard heaters to 1 thermostat


Hi everyone,

I have a Honeywell programmable thermostat (RLV4300) with what looks like a 4-wire installation (judging from the junction box). My wonderful girlfriend decided to take out baseboard heaters to paint the walls (yes, breakers were shut off) but she forgot to take notes on which wires were going where.

I've attached a quick diagram of my current wiring. The real problem is that the baseboard heaters are always ON regardless of what's set on the thermostat. What am I doing wrong?

Troubleshooting done so far...

1 - I've confirmed which wires were hot...which led to the attached diagram.

2 - I have tried removing the first baseboard (and feed only 2 baseboards instead of 3) in case it was defective somehow (that said, it worked fine before). No luck, same problem.

3 - I've triple checked to make sure the diagram and the real wiring is right...and it is.

4 - I've tried changing the cable at the baseboard level (while keeping red to red and black to black for parallel) although given that both ends of the baseboard has a sensor, it shouldn't have/ didn't do different. Same problem.

5 - Even if it worked before, I checked to make sure the hot/feed cables at the thermostat level were properly connected, which they are.

*EDITED*

6 - I've also checked the ground wire (copper) to make sure there wasn't any current which would have meant it was tripping somewhere. No current on ground so we can rule that out as well.

What am I doing wrong???

Any help is appreciated.

PS: I'm in Canada, we run 240 heaters up here...so don't ask about the white cable...we have red / black wiring which in my case, is used from the panel all the way to the heaters. Heaters have 2 black cables (which confirms (i believe) that I have 240 heaters.
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Wiring 2 baseboard heaters to 1 thermostat-wiring.jpg  


Last edited by AlexandreSauve; 04-16-2013 at 09:23 AM. Reason: Correction
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Old 04-12-2013, 01:55 PM   #2
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Wiring 2 baseboard heaters to 1 thermostat


Based on the fact the heaters are running the whole time I would guess that taking a multimeter to the heater side of the thermostat shows voltage flowing to them?

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Old 04-12-2013, 02:06 PM   #3
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Wiring 2 baseboard heaters to 1 thermostat


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Originally Posted by OCPik4chu View Post
Based on the fact the heaters are running the whole time I would guess that taking a multimeter to the heater side of the thermostat shows voltage flowing to them?
I have a little voltage tester that beeps if current is going through but it's not fancy enough to tell me the actual voltage. That said, yes. Both red and black wires in all the heaters have current going through.

I've done a fair bit of electricity at my place such as installing ceiling lights, put-lights, replacing plugs, switches and dimmers. I've replaced my thermostats which were working fine until we took out the heaters. Replugging/re-wiring them has proven to be a pain more than anything else...

I should add that in the junction box, I have 1 red wired that is hot as well as 1 black wire that is hot. There's no way for me to tell which has X amount of voltage but based on how the splits were made , the thermostats have always been plugged/triggered using the black wires...as shown in the diagram.

Last edited by AlexandreSauve; 04-12-2013 at 02:09 PM.
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Old 04-12-2013, 02:14 PM   #4
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Wiring 2 baseboard heaters to 1 thermostat


Quote:
Originally Posted by AlexandreSauve View Post
I have a little voltage tester that beeps if current is going through but it's not fancy enough to tell me the actual voltage. That said, yes. Both red and black wires in all the heaters have current going through.

I've done a fair bit of electricity at my place such as installing ceiling lights, put-lights, replacing plugs, switches and dimmers. I've replaced my thermostats which were working fine until we took out the heaters. Replugging/re-wiring them has proven to be a pain more than anything else...

I should add that in the junction box, I have 1 red wired that is hot as well as 1 black wire that is hot. There's no way for me to tell which has X amount of voltage but based on how the splits were made , the thermostats have always been plugged/triggered using the black wires...as shown in the diagram.
So then is there a possibility that the thermostat has stopped working? If you disconnect the thermostat and leave the black wire disconnected I'm guessing the heaters dont turn on, right?
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Old 04-12-2013, 02:22 PM   #5
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Wiring 2 baseboard heaters to 1 thermostat


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Originally Posted by OCPik4chu View Post
So then is there a possibility that the thermostat has stopped working? If you disconnect the thermostat and leave the black wire disconnected I'm guessing the heaters dont turn on, right?
In theory, they shouldn't but i'll have to try that (given that red does have voltage going through. One of 2 things might happen...

1 - Black (where thermostat would push) is cold and therefor heaters stay cold.

2 - Even if situation #1 is true, the voltage from the other end (red wire) pushes enough current to heat the baseboard heaters and die where the black wire (at thermostat level) stops.

Scenario #1 is more likely but honestly, at this point, I wouldn't be surprised to see scenario #2.

That said, I'll try that tonight and update this thread with my findings.
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Old 04-13-2013, 11:22 PM   #6
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Wiring 2 baseboard heaters to 1 thermostat


First, verify that the total watts of your 3 heaters isn't more than 3000W total - that's the rating of your t-stat.

If you are less than 3000W total, do this:
Turn off power.
Pop off the tstat from the baseplate, which will take the tstat out of the picture.
Turn power back on and check the heaters.

If the heaters are ON, you have a miswire, (OR if the tstat's relay is part of the baseplate, you may have a bad relay).
If the heaters are OFF, your issue is most likely the t-stat itself.
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Old 04-15-2013, 09:20 AM   #7
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Wiring 2 baseboard heaters to 1 thermostat


Quote:
Originally Posted by williswires View Post
First, verify that the total watts of your 3 heaters isn't more than 3000W total - that's the rating of your t-stat.

If you are less than 3000W total, do this:
Turn off power.
Pop off the tstat from the baseplate, which will take the tstat out of the picture.
Turn power back on and check the heaters.

If the heaters are ON, you have a miswire, (OR if the tstat's relay is part of the baseplate, you may have a bad relay).
If the heaters are OFF, your issue is most likely the t-stat itself.
Thank you, I will try that.
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Old 04-16-2013, 08:22 AM   #8
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Wiring 2 baseboard heaters to 1 thermostat


Quote:
Originally Posted by williswires View Post
First, verify that the total watts of your 3 heaters isn't more than 3000W total - that's the rating of your t-stat.

If you are less than 3000W total, do this:
Turn off power.
Pop off the tstat from the baseplate, which will take the tstat out of the picture.
Turn power back on and check the heaters.

If the heaters are ON, you have a miswire, (OR if the tstat's relay is part of the baseplate, you may have a bad relay).
If the heaters are OFF, your issue is most likely the t-stat itself.

Ok so I tested a few things to really narrow down the problem. Willis, your response helped me a lot.

1 - I've switched my baseboard setup to 2 baseboard heaters now (both are 1250W for a total of 2500W on that line). That said, I tested with only one for the most part to really find out what was going on...

2 - Removed the thermostats (and left the wires hanging, securely of course) and turn on the breaker. As expected, lines were hot but heaters stayed OFF.

3 - I took the same thermostat from my office (which I know works) and tested my living room (which is where the problem was) with it. As expected, the heaters would only go on if I manually increased the temperatures but would turn off if temps were good. In other words, it worked. I switched back to my "faulty" thermostat and again, heaters would go ON and never stop.

Result? 2 Thermostat (out of 5) in my home stopped working (only within 5 months after install). I'm not impressed but I'll stop by ranting here...

That said, thanks everyone for your responses. It really helped a lot. Glad to have found this forum.

Alex

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