Heater won't start if connected as standard (W1), only if connected as Cooler (Y1)

[JeanLuc]

My system:

Basement: quiet old combined Heating/Cooling System
Old: Honeywell control, 4 wires, Y/W/G/R (only one, but bridged), no C
New: Nest Learning Thermostat, wired: Y to Y1, W to W1, G to G, R to Rh, system recognizes all connections

• The fan is working and can be switched on/off
• The heater won't start when the target temp is set > room temp, even if display turns orange and should heat
• The cooling does start

I tried the following (with Nest hotline): switched Y and W (heater <=> cooler)

• The fan is working well
• The heater (now connected to cooler) does start when I start cooling
• The cooling (now connected to heater) won't start

With the original controler everything works fine (heating at 'heat' and cooling at 'cool') so the Y and W seem to be connected right in the basement. Also, there is obviously communication between Nest and the unit, just the heater won't start when connected in the standard way.

As said, I don't have a C-wire, but charged the Nest by cable. I was told that this missing C can't be the root cause, this is only to charge the battery.

Any idea what to do? Thanks, JeanLuc

[EdwardT]

Hi JeanLuc,

Thanks for reaching out. I'm sorry to hear that you're having an issue with your Nest Thermostat. I'd love to know more about this and I have a few questions:

• Could you share a photo of your previous thermostat's wiring?
• What's the make and model of your outside unit?

Looking forward to you response.

Thanks,

Edward

[Jhonleanmel]

Hey folks, 

We appreciate your help here, EdwardT.
JeanLuc, I wanted to follow up and see if you are still in need of any help. Please let me know if you are still having any concerns or questions from here, as I would be happy to take a closer look and assist you further.

Thanks,
Mel

[Jhonleanmel]

Hi everyone,

Just one quick final check in here since activity has slowed down. We haven't heard from you in a while so we'll be locking this thread if there is no update after 24 hours. If you have any new questions, updates or just a discussion topic, feel free to start a new thread in the Community.

Thanks,
Mel