Need advice on wiring new thermostat


I recently bought a new digital Honeywell line-voltage thermostat to replace my current one. The thermostat controls one 240V wall heater. I'm having some trouble because the wiring is different on the new one compared to the old one (and Honeywell doesn't provide directions).
This is my current thermostat and wiring:
http://www.uploaddress.com//files/855/current1.jpg
http://www.uploaddress.com//files/855/current2.jpg
Although the photo doesn't show it, the red wire from the thermostat is wire-nutted to two black wires, the black wire from the thermostat is connected to another single black wire.
Okay, so here is my new thermostat:
http://www.uploaddress.com//files/855/new.jpg
Can someone give me some advice on how to properly hook this up?
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Rob wrote:

Looks like the new one is a LineVoltPro. You can find the specific model here, then they have links to the installation instructions.
http://www.iaqsource.com/index.php?module=products&prod_cat#3
Likely your existing stat is only switching one phase, while the new stat switches both phases.
You need to bring both conductors from the wall heater back to the stat to wire it up the way they show.
Warning...the following makes sense electrically, but I'm not sure if it is acceptable to code. I'd appreciate it if someone else could verify.
Unless the thermostat does something "intelligent" to monitor load, you should be able to treat the new thermostat as a single pole switch, same as your old one. This would switch only one side of your heater, leaving the other hot all the time.
Take the single black wire connected to the black thermostat wire, and hook it up to the inner black wire. Insulate the end of the outer black wire--this will be live when the heat is on.
Split the two black wires hooked to the old red wire, connect the one going to the heater with the outer red wire, and the one going to the supply to the inner red wire.
Chris
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On Wed, 29 Nov 2006 13:49:21 -0600, Chris Friesen
I'll try this. I forgot to mention there's also 3 white wires 'nutted together in the back of the box as well. Don't know if that makes a difference.

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On Wed, 29 Nov 2006 13:49:21 -0600, Chris Friesen
Hmm. I wired it up exactly as you described. Thermostat powers up normally and runs through self test. I set the temperature, and I heard it "click" and the display shows it's turning the heater on, however, the heater never comes on. Any idea on what I could be doing wrong?

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Rob wrote:

Hmm...I'm thinking I misunderstood the old one. I forgot it had only two wires. I'm sorry, I gave you bad advice.
You should probably rewire the old one back in before continuing--the two blacks hooked to the two red leads get nutted together with the old red lead, and the other black gets nutted with the remaining black wire.
The two black wires that were nutted together with the red before should stay nutted together. These are likely one leg of the supply (but we can't be 100% certain without checking).
The black wire that was nutted to the black thermostat wire before is likely one leg of the wall heater, but again, we can't be 100% certain without checking.
The white wires may supply the other leg of the circuit to the wall heater, although ideally if they're hot they should be taped to identify them as such.
If you have a voltmeter, check the voltage between the black wires (that were nutted with the red before) and the white wires. If this is 240V then you know that the black wires are one side of your supply, and the white is the other.
If this is the case, then you can nut the black inner lead to the two black wires, and the black outer lead to the remaining black wire. Then nut the inner red to the three white wires and see if that works.
If you can identify that one of the three white wires goes to the heater, then you could pull it out and nut it to the outer red lead, leaving the inner red lead nutted to the remaining two white wires.
Chris
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Bingo! Thanks for the help, Chris. I never would have figured all that out all by myself.
On Wed, 29 Nov 2006 16:27:06 -0600, Chris Friesen

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You have to first determine which of the three cables in the box is the feed. Then determine which of the two remaining cables is the feed, continuing to another heater, which should remain spliced to the feed. Then the last cable is the one to the heater. Once you've determined this, you can connect it like the diagram. Currently the thermostat is just breaking one leg of the 240 volts. The second leg, the white wires are spliced directly. The Honeywell stat needs 240 volts to operate, so you can't just connect it to one leg like the current thermostat

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