Nest thermostat and c wire


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Old 06-26-19, 03:48 PM
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Nest thermostat and c wire

I'm trying to get the nest thermostat to functione with the Honeywell Aquastat L8148e. There is a stand alone air handler in the attic. My wires are Rh and w1 from the Aquastat and Rc and G and Y1 from the air handler. I get 24 volts at the aquastat between the Rh wire and W . Zero volte between the white wire T at the Aquastat and at the thermostat. 24 volts between Rh and C at the thermostat. When I connect the C wire to the nest, it tells me it recognizes that a wire is there but there is no power. Without the c wire I get an E30 code saying there is no power to the y1 terminal. the air conditioner will not work. Is there something wrong with the Nest or do I need to make some other adjustments?
 
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Old 06-26-19, 09:20 PM
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Welcome to the forums.

When I connect the C wire to the nest,
What C wire ? You don't have one in your description.

The C wire must come from the air handler.
Rh and W1 is strictly for the heat.
You need a fourth wire to the air handler.

If you wanted to go with a poor mans C wire...... you change wiring at both ends.
At the nest...... Rc is Rc - Y1 is Y1 - G wire becomes C.
At the air handler.... Rc is Rc - Y1 is Y1 & G and G wire becomes C.

In other words.... you lose the FAN ON position on your thermostat. The G wire becomes your C wire.
 
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Old 06-27-19, 04:56 AM
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I'm sorry I didn't completely explain. I ran an extra wire from the thermostat to the Aquastat on the boiler and attached it to the W terminal on the Aquastat. Are you saying that I must get the C wire from the air handler and not the Boiler?
 
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Old 06-27-19, 05:02 AM
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The air handler is in the attic and the wire connections are difficult to see. I did notice there was a block where the wires connected that was numbered 1-5 or 6. Is there any way to tell which connection would be for the C wire. Extra wires are already there if I just knew where to connect one.
 
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Old 06-28-19, 07:03 AM
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Hi, can you post a pic of the control board at the AH so we can see what you have.
Geo
 
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Old 06-28-19, 01:56 PM
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Name:  IMG_0039.jpg
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Size:  113.1 KBHere are three pictures of the terminal. I don't know what the red and white wires on # and #7 are. I have Blue,Green and Red at the thermostat with the white and Yellow Free. The second picture is the condensate pump
 
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Old 06-28-19, 02:00 PM
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I'm not happy with the way the pictures showed, but I don't know how to fix them. Hopefully you can see the situation and advise me. I have a free yellow and white wire, if I just knew where to connect the wire at the air handler I think I would be in business.
 
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Old 06-28-19, 02:21 PM
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Hi, it appears that #s 6&7 go to the condenser unit outside , there also appears to be a transformer there with a Black and Blue wire coming off of it, where does the Black wire connect? Do you have a volt meter? If measure between the Black &Blue, you should get 24 VAC, if that is the case you can connect one of the spare conductors to the Black and the other end to C on the Tstat
Geo
 
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Old 06-28-19, 10:23 PM
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It's a little tricky posting pictures.

That looks like an old system. That will more than likely have the C line grounded. Connect your white wire to any screw on the metal frame. Give that a try..... it can't hurt anything.
 
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Old 06-29-19, 07:47 AM
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If I get the C wire properly installed, where should I check for 24 volts? At the red wire or the blue wire? The blue wire is Y1 in the thermostat and the red wire is Rc.
 
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Old 06-29-19, 08:23 AM
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Between the Red and C C will be which ever color wire you connected to the common at at the AH.
Geo
 
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Old 06-29-19, 08:56 AM
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Thanks for the replies. I really appreciate your help. This system belongs to my daughter. Iíll have to go to her house and give it a try. Iíll be sure to let you know how everything worked out. Thanks again
 
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Old 06-30-19, 02:26 PM
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Had 24 volts between the blue and black wires. I connected a wire to the black wire and connected it to the C terminal on the nest. All is working well right now. Thanks for all the help. You guys are awesome
 
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Old 06-30-19, 02:45 PM
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Good job. Name:  thumb.jpg
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Size:  1.6 KB Thanks for letting us know how you made out.
 
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Old 06-30-19, 02:55 PM
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Ya, put yourself in for a raise.
Geo
 
 

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