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Aug 22, 2011
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nomdesplumes wrote:
Jan 9th, 2018 1:11 pm
Glad I went wireless thermostat so I don't have to deal with stuff like this. Sometimes it is better to invest the money now than to invest later.
What make and model is your wireless tstat.
How does it communicate with your furnace?
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Dec 14, 2008
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Whitby
You could use an ohm meter to match the wires at the furnace to the wires at the thermostat.

Turn off the power to your furnace. Unhook all the wires from your furnace control board, and all of the wires from your thermostat. Take a jumper wire and attach it to one of the wires at the furnace, and attach the other side of the jumper to ground. At the thermostat wires, take one lead of your meter while on the ohm scale, and attach it to ground and with the other lead touch each wire one at a time until you find the one with a very low ohm reading. When you find the match, put an ez code sticker, or piece of tape on each end of the wire and mark it with the same designation. Continue to do this with every wire, until you have matched them all.
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Dec 12, 2009
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vkizzle wrote:
Jan 9th, 2018 1:47 pm
What make and model is your wireless tstat.
How does it communicate with your furnace?
I posted the thermostat model in the OP. It is a Honeywell RTH-7400D. I am not sure what you mean by how the thermostat communicates with the furnace. It is from the wiring, demand for heat, AC, fan???
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kryton619 wrote:
Jan 9th, 2018 2:37 pm
You could use an ohm meter to match the wires at the furnace to the wires at the thermostat.

Turn off the power to your furnace. Unhook all the wires from your furnace control board, and all of the wires from your thermostat. Take a jumper wire and attach it to one of the wires at the furnace, and attach the other side of the jumper to ground. At the thermostat wires, take one lead of your meter while on the ohm scale, and attach it to ground and with the other lead touch each wire one at a time until you find the one with a very low ohm reading. When you find the match, put an ez code sticker, or piece of tape on each end of the wire and mark it with the same designation. Continue to do this with every wire, until you have matched them all.
I bit the bullet and did this last night. As it were, the blue and red wires are ganged together somewhere. So, even though I have 5 wires at the thermostat, it is effectively a 4 wire set up with no C wire. I think I answered my own question about the compatibility of the ecobee thermostat. I will either have to unbundle the red and blue wires somehow and repurpose on the blue wire for the common or use the PEK kit.
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Aug 22, 2011
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will888 wrote:
Jan 10th, 2018 9:34 am
I posted the thermostat model in the OP. It is a Honeywell RTH-7400D. I am not sure what you mean by how the thermostat communicates with the furnace. It is from the wiring, demand for heat, AC, fan???
Oh, I wasn't asking about your's; it was about nomdesplumes.
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After spending an inordinate amount of effort dealing the the green on installation company, I finally managed to convince them that my wiring is fine and they should proceed with the furnace installation. On the second visit, I got a different crew that once again knew enough to be dangerous. They claimed my furnace was not compatible with a smart thermostat. After a second round of runaround with the installation company, I had to escalate my case to the program administrator. That got the installation company to stop the charades. The third guy that came did the installation. I think this guy was learning on the job. He messed up the wiring at the thermostat and so the thermostat issued an error messaged about a wiring error. He starts to point the finger at the cable from the thermostat to the furnace may be faulty. He checked the wiring a couple of times, looks at the manual in his tool pouch, slaps himself on the forehead, moves a couple wires around. The thermostat worked as it should once the wiring error was corrected. Compared to the old Honeywell, the ecobee works much better particular with the ability to prescribe a temperature difference between the furnace coming on and shutting off. The Honeywell has literally zero offset which cause the furnace to cycle a like crazy especially on relatively warm days. With a half degree offset, the furnace has longer cycle times and will stay off for a good period of time.
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Jun 24, 2015
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the thermostat wire they sell in the stores does not come with yellow wire in the bundle any more, they phased out yellow and changed it to orange now. so yeah the picture in post one is good but when you get a thermostat wire installed, the yellow wire is now orange,
Hi

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