Had to revert back to an older thermostat, BUT it didn't work.


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Old 05-27-12, 05:50 AM
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Had to revert back to an older thermostat, BUT it didn't work.

Good morning all. Here is a little history on my set up. Had two thermostats upstairs, one for heating and one for cooling. Decided to combine them into one stat. Got all the wires into one room, installed the NEST, no problems. Used it during winter months, worked flawlessly. Well, decided to use the A/C last night and the NEST went into a delay mode. Contacted their customer support, and it was determined I need a C wire installed. They are sending someone.
PROBLEM: I go to put an older stat back in, just to get some A/C and the A/C would not kick on, what gives? I wired everything right. So, I put the NEST back in just to see and the A/C did go back on, it went to standby mode again, But it worked. Any advice since I may need a temporary A/C stat.
PS: Five wires all together. RED/WHITE/YELLOW/GREEN/RED
 
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Old 05-27-12, 02:18 PM
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Advice is wait until some gets there to help you. The wire loom that contains the red green yellow, if you wire nut them together the ac should run.
 
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Old 06-03-12, 05:53 PM
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I would like to add to this thread. A tech came out and hooked up a wire for constant power for the NEST. He tested the wires and there was power. All good, right? Nope. The nest was so dead, they had to overnight another one. So, I get another one and go to install it and problems again. It does not go on. I call NEST support and he asks me a bunch of questions. He has me remove the NEW "C" wire and now it works, strange. It works like before and it can't stay this way because it will need constant power, not just battery power. I take out my tester and measure the volts between the NEW wire and the RC, NOTHING. Now the tech is baffled. He asks me for my A/C info, which I gladly provide and will consult the engineers and get back to me. So, why post here, any thoughts from anyone out there? Thanks!
PS: Lennox A/C system, harmony III(that's where the wire was hooked up to)
Thanks!
 
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Old 06-03-12, 05:59 PM
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Harmony III is a zoning system not an A/C system. That is why you are having problems. The tech should be able to figure it out. Are you putting in multiple thermostats? You should have more than one stat with a zoning system.
 
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Old 06-03-12, 06:24 PM
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First, thanks for the reply. Yes, there are two stats, one downstairs, not a nest, works fine. What the tech did is, he an unused wire in the the bundle. He hooked it up to something in the HARMONY III board. Any advice? Thanks!
 
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Old 06-03-12, 06:30 PM
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I would need a picture of the control board with the wires. I would need to know which wire exactly he used wnad what terminal it was installed to.
 
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Old 06-03-12, 06:40 PM
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OK, I'll take a picture tomorrow and post it for you.
FYI, if you can check out page 5
http://www.lennox.com/pdfs/manuals/L...III_Manual.pdf
Thanks!
 
 

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