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Nest 2020 Short Cycling Furnace

TJC129
Community Member

Hi all,

I felt the need to share my recent experience in installing my Google Nest Thermostat 2020, and the issues and eventual solution to the problem I was having.

On 12/28/21, my wife and I decided to buy a Google Nest from Lowe's, as we're starting to transition our home into a "smarter" home.  We did some digging, found our HVAC system should be compatible and decided on the Nest 2020. 

Removal of the old thermostat was easy, it was wired with the Y, G, W, C & R wires right away and I felt the install of the Nest would be a breeze, which it was.  We got the Nest wired, mounted and installed in about 20 minutes.  The Nest was on, the temperature was set but the house never started heating up.  We weren't receiving any error codes, wiring showed accurate, it said it was heating (the furnace was running) but the vents were blowing cool air.

I went and checked our gas furnace and it would start to cycle and it would ignite the burners for a couple seconds before the furnace would click and the flames would die out.  The house began cooling off fairly quickly and it was starting to get late. We decided to call it a night and turned on our fireplace and an electric heater, grabbed a couple extra blankets just in case and went to bed.

At 0330 in the morning on 12/29, I woke up and the house was reading at 62° F.  Not bad all things considered but still cooler than we should have woke up to.  I started looking at different fixes, different issues other people have had and started getting ideas on things to do to try to fix it.  I completed a factory reset before going to work and reinstalled the Nest but had the same issue.

I left work early and came home to try some of the different things I had seen people say worked for them.  I tried removing only the Y wire to check the power pull on the system, I connected the W & R wires to verify the problem was with the thermostat and not the furnace, and the furnace worked with them connected. I installed an old thermostat (not the one I replaced) and it also short cycled the furnace. I reinstalled the old thermostat and low and behold the furnace worked again.  I once again wired the Nest back in and we were back to the short cycling so I cleaned the flame sensor hoping that might help, but once again it didn't.

I finally contacted Google for help.  They had me swap Y & W wires, change the thermostat to cooling and change source type from gas to electric. This also did not work.  I worked with the Google rep for a little over an hour before we got disconnected and she told me that she would have to have a supervisor help me figure out what's happening.

While waiting to hear back, I shut the furnace down at the breaker box, and decided to cut and strip the wires at the thermostat hoping for a cleaner connection. I put the wires back in place and went out and turned the furnace back on at the breaker box.  As the furnace began to cycle up, I remembered we had changed the source type from gas to electric so I changed it back to gas. After changing it to gas, the furnace stopped and shut down and cycled up again.  The ignitor lit and the burners all began blowing flames.  This time, they stayed lit.  I was beside myself and ecstatic.

I adjusted the temps from my phone to verify the furnace would shut off when necessary but also come back on.  It has done both for us so far and we couldn't be happier.

I don't know what exactly was the final solution but I wanted to share to somebody having a similar issue: 

•clean the flame sensor

•change source type to electric

•trim and strip wires for clean contact

•start running your cycle and from your phone or tablet change source from electric to gas and wait for it to run it's next cycle.

It's not perfect and doesn't make much sense to me but, it's working, we're warm again and are having fun set up our new thermostat.

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