Installed Ecobee 4, now Lennox Furnace Behaving Oddly


Old 01-08-19, 08:52 AM
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Installed Ecobee 4, now Lennox Furnace Behaving Oddly

Hi all

I am working with a Lennox gas furnace, model G60UHV-36A-070-06

As I mentioned in my Ecobee install thread (Specifically THIS message in that thread), I had noticed odd behavior immediately after the install:

Initially, after setup, I noticed (after setting the Ecobee to 79 degrees--it was 74 at the time) the burner kicked on, then off after 5-10 seconds. It did this two or three times. Then the LEDs for DS1 and DS2 started alternating blinking, slowly. After running through the diagnostics with Ecobee (burners first stage 1 and stage 2--both fired right up), I decided to shut the power to the furnace off and wait 5 minutes before turning back on. I set the thermostat to 74 (it had dropped to 71 at this point) and the furnace fired up (DS1 and DS2 blinking rapidly, burner on and stayed on). Is this a reasonable behavior on furnaces?
After shutting off the furnace, and then turning it back on, everything seemed to be running fine for literally the one full month I have been running with the new stat.

Yesterday, I came home, late, and noticed my upstairs bedroom was 66 degrees (we keep it 72). I checked the Ecobee, and it was set to hold at 74 (which keeps bedrooms 72), but the thermostat registered 70 degrees.

I went down to the furnace, popped the panels off and--sure enough-- the diagnostic LEDs were blinking 'alternate slow flash'. The label says this indicates 'WATCHGUARD'... Either the burners failed to ignite (a) or limit open more than 3 minutes (b) or lost flame sense 5 times on one cycle (c)

This is "kind of" the issue I had at install-- although that was the burner IMMEDIATELY shutting off (after like 15-30 seconds). Same LED blink pattern. I turned off furnace for 2 mins. Then turned back on. Furnace lit up. House warmed up. So I called it a fluke, and enjoyed rest of evening. At bed time, I realized the bedroom was cold again. This was about 2 hours later. Sure enough, furnace had same issue. So, I restarted it, and went to bed.

I woke up this am, and everything SEEMS ok. Temps are normal in the house.

But, I am worried. This is a furnace installed in 2004, I believe. I know its at the end of any reasonable expectation of service life. Is this an indication of imminent failure?

A google search yielded suggestion of dirty flame sensors... I have lived in this house two years, and didnt know they are supposed to get cleaned-- could that be the issue? Any advice I can get is very much appreciated. I folded and called an HVAC company to troubleshoot it. I would like to be educated on this so I know what they are talking about.

As an aside, one think that is great about Ecobee is the amount of data it collects. I have a chart that shows exactly when the home ambient temp deviated (you can see that it usually it right on the money otherwise) from the thermostat desired temp

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Many thanks for all who take the time to read and respond to this thread. This website is truly unique in its valuable exchange of advise and recommendations.
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Old 01-08-19, 11:13 AM
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Resolved. Tech came in. Dirty flame sensor. I now know how to clean it, and also how to safely check/clean out pressure switch.

At $175, I will call this an HVAC lesson fee, lol
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