Nest zone still blowing cold when off

[JPColorado]

I will try to keep this brief but here is the background.

I live in a 1950s home.  It originally had forced air heat but cooling was from a separate evaporative cooler.  Last year during a major remodel we replaced all the duct work in the house and divided the house into two zones.  We also installed central air.  

The zones are upstairs and downstairs.  Both controlled by google nest thermostats.  The $129 dollar model from home depot.

All winter the zones have worked well.  We just started using the AC for the first time ever and we are having an issue.  The downstairs of our house is much more efficient than the upstairs and gets much colder.  We can't seem to shut the cold air off to the basement though.  Even if the downstairs thermostat is set to off, if the upstairs is running then cold air will be blowing downstairs.  This may be an issue with the baffles but they were working appropriately with the heat.  I'm curious if this could be a setting on the thermostat.  Any thoughts or input appreciated.  What should my next step be?  Our HVAC people are great and very responsive but they don't do anything with Nest and have been clear they won't do anything with them.

Thank you

[alejandom]

Hi @JPColorado,

First I would like to thank you for posting in our community page, on the other hand I apologize for the inconvenience that you are having with your Thermostat. Let me tell you some troubleshooting steps that you can try to fix the problem.

That's a frustrating situation! It sounds like the cold air is leaking from the upstairs zone to the downstairs even when the downstairs Nest is set to "off." Here are some possible explanations and next steps:

1. Check Nest Thermostat Settings:

• Fan Mode: While unlikely, double-check that the downstairs Nest thermostat isn't set to a fan-only mode that might be circulating cool air even when not actively cooling. The fan mode should be set to "Auto" or "Off" when cooling isn't needed.

2. Verify Zone Dampers:

• Most likely culprit: Your suspicion about the baffles (also called zone dampers) is a strong possibility. While they might have worked well for heating, they might not be closing completely for cooling. This would allow cold air from the upstairs zone to leak into the downstairs even when the downstairs cooling is off.

3. Nest Compatibility:

• Limited role: It's understandable that your HVAC company is hesitant to troubleshoot Nest thermostats. While Nest thermostats can work well with most systems, they might require specific configurations or settings depending on your HVAC setup.

Next Steps:

1. Self-check Dampers (if comfortable):

• If you're comfortable, you can try visually inspecting the zone dampers (usually located near the air handler unit). See if they are closing completely when the downstairs Nest is set to "off." Consult a professional if you're unsure about accessing these components.

2. Contact Nest Support:

• Nest Support might be able to offer troubleshooting steps specific to Nest thermostats and zone control systems. Explain your situation and the fact that you have a two-zone system. Here's a link to reach Nest Support: https://goo.gle/31i1U5t

3. Consider Limited HVAC Support:

• While your HVAC company might be hesitant to deal directly with the Nest thermostats, they might be able to offer some general advice on zone damper operation or recommend a qualified technician who can investigate the dampers and ensure they're functioning correctly for both heating and cooling.

Additional Notes:

It's important to ensure proper zone damper operation for efficient heating and cooling throughout your house. A qualified HVAC technician can diagnose the issue and make any necessary adjustments.

Since your house has undergone significant renovations, it's possible there might be some minor adjustments needed to the zone damper system to optimize performance for both heating and cooling.

Hopefully, by checking the Nest settings, contacting Nest support, and potentially consulting your HVAC company for damper verification, you can resolve the cold air issue downstairs and achieve proper zone control in your home.

Regards, 

Mario.