Help Wiring Nest Learning Thermostat with PTAC ICE-AIR Unit


Old 06-20-19, 05:41 PM
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Help Wiring Nest Learning Thermostat with PTAC ICE-AIR Unit

I've recently purchased a Nest Thermostat to replace my existing thermostat connect to my ICE AIR PTAC Unit.

I've seen older posts where it seems doable, but for some reason my wiring is missing the color scheme.

I've attached my current PTAC Wiring Diagram and the actual wiring connected to the thermostat.

Does anyone have any experience with that kind of PTAC, and should it be OK if I would try to follow either of the threads above in terms of wiring the system?
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Old 06-24-19, 07:28 PM
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E4 = Low refrigerant charge
E6 = High pressure protection
E8 = Indoor coil freeze protection

Your existing thermostat has some diagnostic capability that you will lose if you try to install that Nest thermostat.

While it looks like...
H1 = W1
Cool = Y1
F2 = G
R = Rc
C = C

It is still a gamble and I would not try to install the Nest.

If I were to try this I would measure voltage from C to W1 and C to G2 for 24VAC when a heating demand is present.

Then C to Y1, G2 and O at the PTAC when a cooling demand is present.

But I wouldn't gamble some expensive boards and lose diagnostics to be able to control the stat from a phone.
guyba voted this post as helpful.

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