AC Compressor problems after PV install

[Tony808]

Aloha,

I have an odd situation going on since my solar install. My AC compressor will not turn off. The installer put the PV on the same circuit as my AC. Now, whenever the thermostat sends a signal to power on the central AC equipment, everything turns on but the compressor never turns off. Just runs and runs and runs until the circuit breaker is turned off. When the breaker is turned back on, the compressor stays off until the thermostat signals the system to start again. To make this even more curious, it only seems to happen at night when there is no power being generated by the PV panels.

Has anyone heard of this? Or have any ideas of where to start troubleshooting? The AC system is in a newer home (3 years old) and has been serviced regularly and has never had a problem, until PV. My gut feeling is that the installer is going to push back and say it's not his problem.

Any help would be greatly appreciated.

Tony

[Naptown]

Why on earth did he tie it into your AC unit and how did he do it?

[Tony808]

Well, not being an electrician I can't really answer. All I know is that when the electrician was showing me the finished panels, he said that he tapped into the same circuit as the AC. Said it shouldn't be a problem. I just agreed as I figured since they have installed many systems in the area and have a good reputation, he knew what he was doing.

[Naptown]

Is this one of the lennox solar AC units?

[Tony808]

No. It's a regular AC unit (Carrier). The PV system is grid-tie. 20 enphase converters, 20 Hyundai panels. I think it's pretty standard.

[Naptown]

This should not be tied into the AC system circuit it should go directly into the panel on its own circuit. This does not sound like a legal or inspected connection.
That said i can see no reason why you are experiencing the issue you have. Sounds more like a sticking contactor or other control within the condensing unit. or the thermostat depending on the type it is an if you have a heat pump

[Sunking]

Bet he was not licensed nor pulled a permit.

[Volusiano]

It may just be a coincidence, too. Maybe you started having a bad relay in your AC system that's stuck and doesn't turn off the compressor at around the same time of your PV installation. Last year my AC blower kept running even though the compressor was stopped after the thermostat disengaged. Turned out to be a stuck relay and after I replaced the relay, it worked just fine again.

This is not to say that it's OK to backfeed the PV output into the same AC circuit. Just that it may be a coincidence.

Isn't there a separate shutoff switch for the PV output just before going into the service panel? Can't you just use that shutoff switch to determine if the AC compressor will stop running if you shut off the PV? That is a total disconnect switch just as if you didn't have the PV system connected. If the compressor still doesn't stop running, then you know that there's something wrong with the AC system without interference from the PV system.

[Tony808]

He was licensed and pulled a permit. We are awaiting the inspection.

Yes, it could be coincidence. I just went home, however, and tested the system. Turned the thermostat back on (I turned it off when I left this morning) and the air handler came on, compressor came on, house cooled, compressor turned off, air handler turned off. Everything worked as expected. I tried 3 times. No failures.

So, the ONLY common denominator is that this happens at night, when there is no power being produced by the PV system.

As for being tied into the AC system, there is a label on the main circuit breaker feeding the house that says AC - PV TAP. I assume based on what the electrician told me that it is indeed sharing the same circuit as the AC.

If it IS a stuck relay, is it possible it was damaged by this install. On Monday the electrician had to replace a 30amp breaker for the air handler. This is about the time this issue started. PV was installed the previous Friday/Saturday and I can' remember having issues with the condenser. I still was not sure what the electrician was doing at the house on Monday afternoon. I came home and he was there. When he left, I noticed AC wasn't working so I called him, he came back and replaced the 30amp breaker. It's all been a little weird.

Yes, there is a shutoff switch that turns off both the AC and PV.

[Sunking]

He was licensed and pulled a permit. We are awaiting the inspection.

If he tied the inverters to the AC CB's it will not pass inspection. If it does pass then the inspector is also incompetent, or Hawaii does not have codes. .

[Tony808]

That is good to know. Will be interesting to see what the inspectors make of it.

I think I am going to call my AC guy to come out. He is a straight shooter and if he sees something he doesn't like, he will not hesitate to say something.

Fortunately, no money has changed hands as of yet.

Thanks for everyone's input!

[Tony808]

There is also the possibility (as I sit here and think about it) that whenever the electrician said "I tapped into your AC" or "this will turn off your PV and AC" he meant alternating current and not air conditioning. And that this all IS coincidental. And I am an idiot

The AC on the main panel (where the electric company meter is) has to mean alternating current and not air conditioning. THAT breaker is in another box next to the compressor.

So yeah, maybe just coincidence. Just kind of odd timing.

[Volusiano]

There is also the possibility (as I sit here and think about it) that whenever the electrician said "I tapped into your AC" or "this will turn off your PV and AC" he meant alternating current and not air conditioning. And that this all IS coincidental. And I am an idiot

The AC on the main panel (where the electric company meter is) has to mean alternating current and not air conditioning. THAT breaker is in another box next to the compressor.

So yeah, maybe just coincidence. Just kind of odd timing.

You can just open up the panel and see for yourself whether the solar backfeed has its own breaker or goes into the AC system's breaker, right? It should be obvious to see right away. We didn't bring this up because we assumed you already opened up the service panel and looked for yourself.

[Tony808]

I did open up the panels. Here is what I have:

- Main panel with electric company meter. This has two breakers. One is labeled AC / PV - TAP. The other breaker is unlabeled.

- Panel with four breakers. Three are labeled PV Array 1,2,3 and the third is for the EMC unit

- Panel that has a arm type cut off switch. This is labeled PV/AC Shutoff

- Panel over by the air compressor which has three sets of breakers. One is for AC System Power, one is for Air Handler and one is for Compressor.

Apologies for not being clear.

[Volusiano]

- Main panel with electric company meter. This has two breakers. One is labeled AC / PV - TAP. The other breaker is unlabeled.

There's got to be more than just 2 breakers in the main panel. There should be the main breaker on the top of the panel, and below it are several breakers. One (big one) for the AC system, one for the range/stove, one for refrigerator, one for washer, then dryer, water heater, then several for the kitchen and bedrooms, garage, and lightings, and so on... You get my gist.

If you see a breaker labelled PV or something like that (and it looks like you do) that is SEPARATE from your original breaker for the AC system, then the electrician probably did the right thing and tapped into the main panel with its own breaker, and didn't tie the PV backfeed into the breaker of the AC system.