Switching to nest thermostat from Honeywell (with dehumidifier)

[b21morales]

I want to replace an existing Honeywell T10 thermostat with the nest. I have tried using the wiring compatibility tool with Google but there is no U1 and U2 wire equivalent to the Honeywell thermostat (see the 2nd image).  These control the standalone dehumidifier. From what I can tell, it looks like:

• U1 (cyan) is connected to the 'DEHUM' (compressor + fan operation)
• U2 (brown) is connected to the 'R' (24 VAC Output)

**this dehumidifier has a dedicated return to dedicated supply in our house. meaning it is not ducted to the HVAC system: 

***the fresh air supply fan does not activate the Air Handler blower when running. It only receives pass-through power from it and I believe has it's own controller/settings.

I have included some images of my wiring/control diagram, current thermostat wiring, the air handler/furnace circuit, the dehumidifier circuit, and fresh air supply circuit.

I'd appreciate any help or advice!

Fig 1: wiring diagram

Fig 2: Honeywell T10 thermostat wall plate/wiring

Fig 3: Air Handler/Furnace Circuit

Fig 4: Standalone Dehumidifier Wiring

Fig 5: Fresh Air Supply Wiring

Equipment List/Installation Guide Links:

• Air Handler/Furnace: American Standard (Trane) S8X1
• Dehumidifier: Honeywell DR90 A3000 Home Dehumidifier
  • https://digitalassets.resideo.com/damroot/Original/10015/33-00298EFS.pdf
• Compressor: Trane 4TTR6061 Condensing Unit 
• Fresh Air Supply: Broan FIN-180P(power cord plugs into outlet)
• Thermostat: Honeywell T10+ Pro Smart Thermostat 

One note on the Dehumidifier: the installation guide lists some compatible optional thermstats/controllers, but doesn't include the Nest. Does that really mean that I CAN'T use the nest to control it??

Thank you in advance for helping me!

[b21morales]

Switching from a Honeywell thermostat to Nest Learning therm. The two 'U' wires connect to a standalone dehumidifier that's plugged into a 120V outlet. It has it's own dedicated supply/return vents so it's not attached to the rest of the HVAC system. Below is how it flows:

U1 (cyan)-> DEHUM (compressor and fan op)

U2 (brown) -> R (24V hot output)

Where would I connect these to on the nest?

wiring diagram (different angle)and the nest wiring for reference

I have more detail/information on my system on a previous post: https://www.googlenestcommunity.com/t5/Nest-Thermostats/Switching-to-nest-thermostat-from-Honeywell-...

but this is a more specific question about the dehumidifier wiring.

Thanks

[ByronP]

Hi b21morales,

Thank you for posting here in the community. I understand you want to check the compatibility of the dehumidifier with the Nest thermostat. Help's here.

Please follow this humidifier and dehumidifier compatibility. There are a few options and steps to guide you in choosing the best Nest thermostat for your device.

Let me know if you need more assistance.

Regards,

Byron

[b21morales]

Thanks. I'm hoping someone in the community might help me determine where to connect those two particular wires on the nest learning thermostat. My intuition tells me its * and Rh, but i'm not 100%. I've had an OnTech person come out and they weren't sure what to do.

[ByronP]

Hi b21morales,

Thank you for posting. I understand sometimes it could be confusing. But not to worry, let me check other options.

We would need to investigate and dive deep into your issue. Please fill out this form, and our specialist team will reach out to you for further assistance.

Let me know once you're done.

Regards,

Byron

[YL1]

I have the same issues and would like to connect my nest thermostat as stand-alone on my old humidistat