Nest Thermostat install on gas package unit

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  #1  
Old 07-30-19, 06:12 PM
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Nest Thermostat install on gas package unit

Hi there, I'm new to this forum and this is my first post. I bought my first house a few years ago and it came with an old Goodman GPG13 gas package unit sitting up against the house (I live in the south). So I bought a Nest thermostat on sale and installed it no problem. About a week later the unit started acting up because the thermostat needs a common wire installed (I think). My system already has a 6 strand thermostat wire and the basic Honeywell thermostat i'm still using only needs 4 wires.

I've read a lot about this subject and have reviewed my wiring diagram for this HVAC unit but I'm still a bit unsure where to connect this common wire. I understand the concept of why it's needed and how to physically install it but I need someone more knowledgeable than me to look at my control board and provide some direction. I've attached some photos below (notice someone was already mixing wire colors before I got here).Name:  IMG_20190729_211352.jpg
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Let me know if you need more photos or other information.
Thanks,
Chris
 
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Old 07-30-19, 08:43 PM
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Goodman uses blue for C/common. Bottom left connections on the transformer in the middle. Then see a blue going to the contactor on top. Then other blue wires going down the left side. Can't quite tell but there might be a loose blue with black tape on it in the lower left.
 
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Old 07-31-19, 08:07 AM
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Hi, what are the spare wires tucked into the wall behind the Stat? At the furnace where is that Red conductor spliced to the blue landed?
Just trying to see if the wiring can be set up to more standard colors. Red to R Blue to C. White to W .
Geo
 
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Old 07-31-19, 10:25 AM
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The blue wire with black tape on it is the "C" wire that shows up on the wiring diagram. I was confident that was the wire I needed but I tried it out by connecting it to the red Stat wire and then connecting the red wire to the C terminal at the Nest (as a test before I correct all of the wire colors). After doing so the Nest said it wasn't getting power from that wire. That's when I decided to ask for help - the last thing I want to do is fry my new thermostat or the wire by connecting the wrong thing.
 
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Old 07-31-19, 10:32 AM
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Currently, the spare wires are a white and red. Whomever wire this originally connected an off-white (it may have been purple orignally) wire to the White. They also connected Red inside the unit to the blue Stat wire. At the very least, I will correct the red wire so that my spares are blue and white.
 
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Old 07-31-19, 05:03 PM
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Hi, the cable you’re holding is the one to the Tstat, correct ? Do you have a voltmeter ? Measure between the Red/Blue to the blue on that transformer should be 24VAC.
GEO
 
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Old 07-31-19, 05:13 PM
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Last time I checked Nest t stat is a power robbing t stat and may shorten the life of the electronics with in your HVAC equipment. Be warned.

https://www.ecobee.com/2014/01/the-p...ower-stealing/

If you want a gimmick go with ecobee..

I would use neither as its all gimmickes.

A simple honeywell t6 pro and its algorithm is all you need..

Just my opinion

Oh read here also

http://greyghost.mooo.com/nest-thermo/
 
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Old 08-01-19, 07:50 PM
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Turn the power off to the unit. Disconnect the blue thermostat wire from the red wire. Connect the blue wire to the metal chassis. Any available screw in the area is fine. Connect the red thermostat wire to the red wire in the splice area.

At the thermostat.... connect the red wire to Rh on the nest and blue to C on the nest.

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