topic Re: Short cycling and message about furnace issue in Nest Thermostats

Short cycling and message about furnace issue

fedino82 — Wed, 03 Nov 2021 06:34:24 GMT

My Nest keeps telling me that the furnace shuts down every 15 mins and to check filters (see img attached). The furnace does show an overheating error / limit circuit fault code 33.

I changed the filters and had the furnace checked by a technician: he had the furnace running for 2 hours and never stopped nor give an error code.

I then removed the thermostat and connected red and white wires: the furnace works continuously, never stops and no error code.

Hence, this error is caused by the thermostat.

Re: Short cycling and message about furnace issue

mprasek — Wed, 03 Nov 2021 15:37:03 GMT

I'm having the same issue. I also am starting to suspect it is the Nest causing the furnace 33 error. I've checked several things on the furnace itself. Going to run furnace without Nest manually like you did to test the theory.

Re: Short cycling and message about furnace issue

fedino82 — Wed, 03 Nov 2021 16:29:38 GMT

Yesterday we did a few test with the google support team via chat. They asked me to switch fan and heat wires and run the furnace for 30 mins. It seems like the flow is still cycling but the furnace is always on so I decided to wait for a full day and watch the history tomorrow. So far I could only see small cycles (see attached) because of the "error" so I expect/hope the bars to be a bit wider tomorrow...

Re: Short cycling and message about furnace issue

mprasek — Thu, 11 Nov 2021 01:02:18 GMT

Problem solved. It turns out that it was a problem with how the humidifier was wired. My HVAC buddy says the humidifier 24VDC was pulling power from the wrong place in the furnace. It was likely draining power from the furnace main control board causing the fault. Apparently, fault 33 can be a lot more things than just a flame sensor. It's been 5 days now and no short cycles. PS ... HVAC guys don't like Nest thermostats.

Re: Short cycling and message about furnace issue

Jake — Thu, 13 Jan 2022 20:29:48 GMT

Hey fedino82,

Sorry for the late reply. I wanted to follow up and ensure you are good to go. Please let me know if you are still having any trouble from here, as I would be happy to take a closer look and assist you further.

Best regards,
Jake

Re: Short cycling and message about furnace issue

fedino82 — Thu, 13 Jan 2022 22:11:58 GMT

No I'm not. The issue persists and the customer support said it's my problem.

There's nothing Google can help with.

I have been told there's no refund option and nothing is planned to address this well-known issue.

Attaching highlight of the transcript and marking this as an answer so everyone in the community can see it, return their device and switch to something else before it's too late.

Re: Short cycling and message about furnace issue

jmblitch — Wed, 10 Aug 2022 14:46:30 GMT

My NEST is short cycling on AC. I had zero success with support and was told to change my filter. I told them I found a solution when I purchased an Amazon Smart Thermostat for $59.