topic Re: Furnace and heat pump both running simultaneously in Nest Thermostats

Furnace and heat pump both running simultaneously

tonygeorge_ca — Tue, 28 Nov 2023 18:22:54 GMT

Hi,

I've seen a couple of posts mentioning something similar to this issue, but I haven't quite seen a resolution.

I moved in to a home that had a Carrier forced air furnace and heat pump controlled by a Nest Learning second generation thermostat. I noticed that when the furnace comes on as "Aux Heat", the heat pump condenser is also running outside. It's not just during the defrost cycle. Both systems are running the whole time that the furnace is on. The heat pump runs fine on its own.

The Heat Pump Balance is set to off. The Compressor lockout is set to -12 C and Auxiliary heat lockout is set to 10.5 C.

Is there any other place to configure this behaviour in the thermostat?

Thanks!

Re: Furnace and heat pump both running simultaneously

zoeuvre — Sun, 03 Dec 2023 15:32:20 GMT

Hi tonygeorge_ca,

Yikes! I'm sorry to hear that your furnace and heat pump are both running simultaneously with your Nest Learning Thermostat. The behavior you described in the Nest Learning thermostat, where both the furnace (auxiliary heat) and the heat pump condenser are running simultaneously, could indicate a configuration issue or a compatibility concern. Are you located in North America or Europe? And could you help us with a photo of your previous thermostat wiring configuration and a photo of how you connected the wires to the Nest Learning Thermostat? Also, check that the wiring connections between the Nest Learning Thermostat and your HVAC system are accurate and correctly configured. A miswiring or incorrect setup could cause abnormal behavior, such as both systems running simultaneously.

Keep us posted. We're happy to help.

Best,

Zoe

Re: Furnace and heat pump both running simultaneously

tonygeorge_ca — Mon, 04 Dec 2023 01:47:02 GMT

Thanks for the reply. To answer your questions:

1. I'm in North America.

2. I've attached a screenshot of the wiring from the Nest mobile app and a photo of the actual wiring. I'm a new owner of the house and it was the previous owner who had the thermostat installed so I'm not sure what the original wiring looked like.

Any additional guidance would be great.

Tony

Re: Furnace and heat pump both running simultaneously

Markjosephp — Tue, 19 Dec 2023 17:43:35 GMT

Hello there,

I'm dropping by to see how I can help.

Thanks for your assistance here, Zoe.

@tonygeorge_ca, it sounds like you've got an interesting situation with your Carrier forced air furnace, heat pump, and Nest Learning Thermostat. If you're noticing that both the furnace and the heat pump condenser are running simultaneously during "Aux Heat" mode, there are a few things you can check on your Nest Thermostat.

Firstly, you've mentioned that the Heat Pump Balance is set to off, which is a good step. However, it's always worth double-checking the thermostat settings to ensure there are no conflicting configurations. Additionally, seeing how your thermostat has been installed can be confusing with the standard wiring configuration. Can you share with us another photo of your HVAC system control panel showing how the wires from your thermostat are labeled? This would help us check the correct configuration.

Warm regards,
Mark

Re: Furnace and heat pump both running simultaneously

tonygeorge_ca — Fri, 22 Dec 2023 14:27:47 GMT

Thanks for your reply.

Can you elaborate what you mean by conflicting configurations?

I took a look at how the wires are plugged into the control panel. Unfortunately, there are no labels. I've taken a photo, but it doesn't look like I have permission to upload the image.

Re: Furnace and heat pump both running simultaneously

tonygeorge_ca — Fri, 22 Dec 2023 14:30:19 GMT

Re: Furnace and heat pump both running simultaneously

zoeuvre — Sat, 10 Feb 2024 21:51:48 GMT

Hi there,

I'm sorry for the delayed response. I see that your control panel has the non-standard labels of 1, 2, 3, 4, 5...15 which means that your system is proprietary. Proprietary systems aren’t compatible with Google Nest Thermostats. However, some proprietary systems can be rewired by a pro installer to be compatible.

Thanks,

Zoe