House has a fairly ancient (like 20 years old) 16kW guardian whole home that came with it when we bought it. The mechanics are built like a tank, everything on it runs great, and I maintain it regularly. House has 2 X 3-ton AC units with separate start timers so they cannot both try at once. Both have hard starters added. Previous outages this summer have seen the generator kick in, everything runs fine, even the pool pump.

Yesterday, generator kicked on when power went out, everything ran but the 2 outdoor condenser units. Attic units were circulating 78 degree air. I also had a bunch of gfci's blinking alternating orange and green which I couldn't reset.

I tried shutting off most of the other breakers and one of the AC units at both the breaker and thermostat to fire the other with no luck. Tried re-setting the units by turning thermostat on/off and re-setting breaker, then waiting 30 minutes to mess with thermostat with no luck.

Clearly the outside condenser was not getting power, but I am unsure what has changed, why it could be, or a workaround. When electricity came back on, everything went back to normal and both outside condensers started right up. Any tips or suggestions for other things to check?

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Posted by good_2_geaux

Member since Feb 2015

796 posts

Posted on 8/1/23 at 7:37 pm to man in the stadium

Timers damaged?

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Posted by bapple

Capital City

Member since Oct 2010

12194 posts

Posted on 8/1/23 at 8:53 pm to man in the stadium

I don't know if maybe they wired in some load shedding equipment in with the generator but that definitely is strange. I also have some protections on my compressors with solid state contactors that have built-in brownout protection. My soft starters also have brownout protection and stagger their starts. But once all those timers are done my compressors will kick on and give me cold air. I imagine it is usually the same for you.

When it's night time or not ridiculously hot, do a simulated outage by turning off power to the breaker in the auto transfer switch enclosure. Then after the generator starts and the switch transfers see what your compressors do. Pull the disconnects at the compressors (or switches if that's what you have) and verify you have 240V by measuring on a meter. That's the only way to try and repeat the conditions from last night and see if in fact you aren't getting power to them.

If you confirm you aren't getting 240V to the compressor disconnects, you'll need to see if there's some special wiring in your ATS to load shed or prevent the generator from powering the compressors. If you have 240V volts at the disconnects, the issue is with your compressor or the electronics associated with it.

This post was edited on 8/1/23 at 8:54 pm

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Posted by man in the stadium

Member since Aug 2006

1444 posts

Posted on 8/2/23 at 8:52 pm to bapple

Thanks. I think the issue definitely lies somewhere in the 240 connection between gen and house since the compressors jumped right back on when grid power came back on. Somehow the generator is supplying 120 but not 240 since everything else worked in the house with gen running. Having an electrician buddy come by to hunt for the gremlin.

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Posted by Enadious