3000Watt Inverter Ground Fault and 12k BTU Mini Split AC Shutting Off

[Adventuretrips1221]

Hello all,

I am looking for guidance troubleshooting AC installation issues that I am experiencing with a 12K BTU Mini Split AC in my build. Upon completing the installation of the outdoor unit on my first test run, the AC fan turned on momentarily then the inverter shut off with a Ground Fault light coming on. Immediately I thought it was a grounding issue so I researched how to test ground faults but I was not able to find any grounding problems in my system. I also looked for damaged wires to make sure there weren't any breaks and all the wires turned up clean. I checked the terminals on the AC for continuity and all good on that end as well. The breaker inside my distribution panel never tripped during my test run but just in case, I replaced the 20/20 amp tandem breaker to a standard single 20 amp breaker. I tried testing the AC again after each troubleshooting step but the inverter still shut off just after a couple of minutes with the same ground fault light on the inverter. The compressor in the outdoor unit of the mini split never gets to turn on, only the fan, I am thinking maybe the AC unit is too big for my battery bank but through my research I thought I had enough juice to power it. I also tried turning off all other breakers to make sure there wasn't any power going other appliances and tested again but same problem persists. I looked at my battery monitor with each test, and there wasnt a huge draw on the batteries when I tried turning on the AC. I'm assuming because the compressor doesn't even turn on, I wouldn't be able to see the real draw on the batteries. I have run a wall AC unit on this same system before without any issues, that unit was 9,000 BTU.

Here goes my disclaimer, I most definitely am not an expert in solar or any electrical for that matter. I was able to put together my battery bank and solar panels through research through and asking advice and recommendations from experts. Also, I will be adding shore power but I am holding off on getting the equipment until a later time. I am including a diagram of my set up with as much detail as I can put together to give a clear picture and below I have listed the main components with the wiring and fuse info in case it helps clarify further....

Solar Array
8 - 100W Renogy Compact Solar panels in parrallel/series connection (800 Watts of Solar)
Wire - 10AWG
Fuse - 50A
Shut off Switch

Solar Charge Controller
150v/85A MPPT Victron Charge Controller
Wire - 4AWG
Fuse - 100A

Battery Bank
8 - 100ah 12V Lead Acid Batteries connected in parallel ("800Ah" Battery Bank)
Wires - 4/0
Fuse - 400A
Shut off Switch

Inverter
3000W Renogy Pure Sine Inverter
Wire - 4/0
Fuse 400A

Distribution Panel
WFCO WF8930/WF-8950
Wire - 6/3 Connected to inverter
AC - 30A Main Breaker
DC - 6AWG
Fuse - 30A

Mini Split AC
Pioneer 12K 1 Ton Air Conditioner/Heat Pump for 110/120V
Wire - 12/3 Triplex Marine Wire
20A Tandem Breaker

All components and batteries run through separate positive and negative bus bars. My negative bus bar has a shunt with a battery monitor and is also grounded with a 4/0 AWG wire to the chassis of my rig.

My next move this weekend is to test the Mini Split with direct residential power to make sure it isnt defective but I am throwing this in here to see if there are any recommendations for what might be the problem and hopefully come to a solution. I really appreciate anyone taking the time to read this and I am hoping I can find a solution to move forward with finishing up my build.

It has been very difficult finding an electrician that would take on the trouble shoot on a non residential application. I am located in Florida, South Miami. If by chance anyone is near.

Thank You!

[magnakansas]

Look for a place that does electrical work on boats


william

[Adventuretrips1221]

That's a good suggestion, i'll start looking tomorrow. Thank you.

[Jay Brand]

I'm no expert in solar or electrical so please take what I say with a grain of salt.
GFCi plugs can be twitchy at times. When a ac system fires up, a huge power draw has to come from the system. Some GFCi plugs see this as a surge in the system and can trip to protect that system. Also, GFCi can only be tripped so many times before the plug becomes weaker and in turn trips without much surge in the system.
I would also check the capacitor on the AC unit. Back in the day, a cap would last for decades but the cheap Chinese ones are more prone to crap out on you. Always keep a spare stashed away.
If the cap looks swollen, change it. Honestly, for the cost, I would change it anyway. Most of them are under $20 from a appliance parts store.
IF the cap is bad, it will trip Everytime. Caps are super easy to change.
Depending on your ac system it will have either one or two caps on it. If you have any questions on caps hit me up and I can walk you through it.

[djdalfaro]

Can't comment yet on your issue, but one thing I see is that your parallel batteries should be wired better to allow balanced charging/discharging. See this pamphlet for an explanation and wiring diagram. This WILL improve your battery life.

https://www.solar-electric.com/lib/w...d_charging.pdf

[djdalfaro]

Here's a balanced 8P config. Luckily for you there isn't much modification necessary to your wiring. It looks like you just need to redo the connections between the "Right" and the "Left". The key things are to make all the "short" cables the same length, and both the "long" cables the same length. The leads from the battery bank to the inverter should be made as short as possible, but don't need to be the same length.

I've shown the electrical path through each battery and you'll notice that the path goes through the same number of short and long cables for each battery, regardless of how many of them are red or black. Three short lengths and one long length. That keeps the resistance through each battery even which means each battery has the same charging/discharging amperage per Kirchoff's current law.

[djdalfaro]

Also, 4/0 cable is rated to 90F at 260 amps. You have a 400 amp fuse protecting your wiring. That means your fuse is much too high to protect the wiring at it's rated capacity. This could be because you are attempting to make sure your system doesn't trip if you have a surge in consumption(6000w / 12v = 500amps), and you don't think you'll reach 400 amps regularly. As long as you realize that fuse will not prevent you sending witches and heretics to their fiery doom.

[Adventuretrips1221]

Originally Posted by djdalfaro

Here's a balanced 8P config. Luckily for you there isn't much modification necessary to your wiring. It looks like you just need to redo the connections between the "Right" and the "Left". The key things are to make all the "short" cables the same length, and both the "long" cables the same length. The leads from the battery bank to the inverter should be made as short as possible, but don't need to be the same length.

I've shown the electrical path through each battery and you'll notice that the path goes through the same number of short and long cables for each battery, regardless of how many of them are red or black. Three short lengths and one long length. That keeps the resistance through each battery even which means each battery has the same charging/discharging amperage per Kirchoff's current law.

Oh nice! I did come across that same article on balancing through my research but wasn't sure my interpretation of it was good. Once I can put some extra funds together for extra 4/0 cable I will definitely review my connections. Thank you for the diagram!

[Adventuretrips1221]

Originally Posted by Jay Brand

I'm no expert in solar or electrical so please take what I say with a grain of salt.
GFCi plugs can be twitchy at times. When a ac system fires up, a huge power draw has to come from the system. Some GFCi plugs see this as a surge in the system and can trip to protect that system. Also, GFCi can only be tripped so many times before the plug becomes weaker and in turn trips without much surge in the system.
I would also check the capacitor on the AC unit. Back in the day, a cap would last for decades but the cheap Chinese ones are more prone to crap out on you. Always keep a spare stashed away.
If the cap looks swollen, change it. Honestly, for the cost, I would change it anyway. Most of them are under $20 from a appliance parts store.
IF the cap is bad, it will trip Everytime. Caps are super easy to change.
Depending on your ac system it will have either one or two caps on it. If you have any questions on caps hit me up and I can walk you through it.

During testing with residential power this weekend I will look for any cap issues and let you know. One other person did mention the capacitor might be the issue. Thanks!

[djdalfaro]

Originally Posted by Adventuretrips1221

Oh nice! I did come across that same article on balancing through my research but wasn't sure my interpretation of it was good. Once I can put some extra funds together for extra 4/0 cable I will definitely review my connections. Thank you for the diagram!

Yours isn't terrible, it's mostly balanced. As a thought exercise I'm working up the calcs to see what the actual difference will be.

[Rucker]

I'm wondering if your inverter is a floating ground and needs a bond between ground and neutral (at the inverter).

[rossvtaylor]

A capacitor will often trip a GFCI, just because of they way they work. They compare the current on the "out and in" (line and neutral) and if they aren't similar, the assumption is that current is going somewhere else...maybe bad, like through you. Until a capacitor is charged up, the "in and out" won't match. It's like a tiny bucket of pixies and until the bucket is filled, no pixies spill out the overflow. I've had this issue with inverters, in residential systems, and it could be a factor here. As a test, try resetting the GFCI and restarting the air conditioner several times. If you find that, after a few times, it stays on then you know a capacitor issue is probably the cause.

The most likely solution would be to remove the GFCI for the mini split and run it off a standard breaker.

On an unrelated note...don't expect that 800W of solar will allow you to run your mini split for long. Watch your battery drain.

[Rucker]

Originally Posted by rossvtaylor

A capacitor will often trip a GFCI, just because of they way they work. They compare the current on the "out and in" (line and neutral) and if they aren't similar, the assumption is that current is going somewhere else...maybe bad, like through you. Until a capacitor is charged up, the "in and out" won't match. It's like a tiny bucket of pixies and until the bucket is filled, no pixies spill out the overflow. I've had this issue with inverters, in residential systems, and it could be a factor here. As a test, try resetting the GFCI and restarting the air conditioner several times. If you find that, after a few times, it stays on then you know a capacitor issue is probably the cause.

The most likely solution would be to remove the GFCI for the mini split and run it off a standard breaker.

On an unrelated note...don't expect that 800W of solar will allow you to run your mini split for long. Watch your battery drain.

The most correct answer, I think!

Some clever guy elsewhere recommended using a resistor to charge the inverter to avoid the arc. I wonder if this would also prevent the breaker from tripping?

Here's the one I use:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I put it in line for a few seconds and the capacitors in the inverter charge up properly.

If all of this makes sense, and you plan on flipping that breaker often enough, you can hard wire the resister in line, around the breaker, and use a momentary switch to put the pixies in the buckets.

[Adventuretrips1221]

Hello again!

I have been really busy with work so I have not had a chance to update the results of trouble shooting this past weekend. I do appreciate the input everyone gave.

I was able to run a 10AWG Wire from the 3000W Inverter directly to the chassis for ground. I tested turning on the mini split with my battery system after doing that but the inverter still shut off after a few seconds. I proceeded to run a line directly from residential 110/120V with a dedicated 20A breaker in the house and tested the mini split that way. The mini split ran without any issues. I ran it for a couple of hours to make sure there wasn't any other issues. It cooled the space without any problems. That tells me the mini split is not malfunctioning and the problem very likely has to do with the capacity of my inverter.

I decided to connect and test the mini split one more time with my battery system after testing with residential power. I turned the mini split on and the inverter did not shut off this time. I ran the mini split for a few hours to monitor the power draw and the behavior of the inverter and batteries and take inventory of the added power power draw along with all the other appliances already connected to the system. The power draw is concurrent with the specs of the mini split and also the inverter was not suffering any drastic changes or elevated temperature. Once the mini split cools the area to the desired temperature, the power draw lowers significantly to the equivalent of running a small fan. I do not know exactly what is allowing the mini split to run on my system now after running it through residential but I am sure glad it is working without any signs of it damaging my system.

I did see mention of double checking the capacitor or adding an easy start to the mini split to give the compressor a slow start and less of a power draw on the inverter. On that note I reached out to Micro-Air who manufactures the "Easy Start" that can be added to RV AC units or residential units. I furnished them with the details of my application and the issue I was experiencing and they replied with the following:

"An EasyStart is not required for mini-split systems as they already supply the low current starts....

Mini splits typically have their own built in inverter and Easy Start is not necessary."

They also asked for a diagram of the mini split's internal components to review further. I am still waiting on a response. As I mentioned before, I will be adding components to be able to run my appliances from shore power and even generator to alleviate the wear and tear on the batteries.

I am interested to read on what you all think is allowing the mini split to run now. Thanks all in advance for your feedback.

[Rucker]

Originally Posted by Adventuretrips1221

Hello again!

I furnished them with the details of my application and the issue I was experiencing and they replied with the following:

"An EasyStart is not required for mini-split systems as they already supply the low current starts....

Mini splits typically have their own built in inverter and Easy Start is not necessary."

My guess (informed largely by Ross' comment) is that the capacitors initial charging was the issue. So once you ran it from the house it would appear to work normally when you switched over. Did you say the system is on a GFCI circuit?

And/or, can you monitor the voltage sag and inrush current at the unit, just in case there's a loose wire or unusual length that, taken together with the capacity of the inverter, is interfering even with the soft start/easystart components?

[Jay Brand]

I'm going to agree with Ross and Rucker. If the inverter wasn't able to charge the cap for the first firing if the system, shore power was able to do it.
Start up draws a large load and your cap is there to boost it.
I hope that cures the issue for years to come.
I'd still recommend keeping a spare cap in the tool box or garage of your bus. It's the most prone part of a air conditioning system to fail.

[ewo1]

Originally Posted by Adventuretrips1221

Solar Array
8 - 100W Renogy Compact Solar panels in parrallel/series connection (800 Watts of Solar)
Wire - 10AWG
Fuse - 50A
Shut off Switch

Solar Charge Controller
150v/85A MPPT Victron Charge Controller
Wire - 4AWG
Fuse - 100A

Battery Bank
8 - 100ah 12V Lead Acid Batteries connected in parallel ("800Ah" Battery Bank)
Wires - 4/0
Fuse - 400A
Shut off Switch

Inverter
3000W Renogy Pure Sine Inverter
Wire - 4/0
Fuse 400A

Distribution Panel
WFCO WF8930/WF-8950
Wire - 6/3 Connected to inverter
AC - 30A Main Breaker
DC - 6AWG
Fuse - 30A

Mini Split AC
Pioneer 12K 1 Ton Air Conditioner/Heat Pump for 110/120V
Wire - 12/3 Triplex Marine Wire
20A Tandem Breaker

. I am located in Florida, South Miami. If by chance anyone is near.

Thank You!

Hi,

Where about in south Miami are you?
I am in cutler bay!

I got two buses in progress and one is ready for solar. I would love to come by and take a look. I know almost nothing about solar but would like to learn off what you did so far.

I’ll pm you my tel. number.

Thanks,
Ed..

[Rucker]

Originally Posted by Jay Brand

I'm going to agree with Ross and Rucker. If the inverter wasn't able to charge the cap for the first firing if the system, shore power was able to do it.
Start up draws a large load and your cap is there to boost it.
I hope that cures the issue for years to come.
I'd still recommend keeping a spare cap in the tool box or garage of your bus. It's the most prone part of a air conditioning system to fail.

And/or perhaps the Capacitor in the minisplit is bad. Pretty easy to identify by getting an amp clamp with a 'max' or 'inrush' setting to see how much the current spikes right at start.

You may not be able to pick up the spike just by monitoring it with a regular amp clamp.

Also, perhaps that minisplit capacitor is going on the fritz.

Okay, second thing, and this may be what's up: You have #4 from the batt to the panel and #6 from the panel to the inverter (edit: your diagram doesn't specify the wire size but does list a 400A fuse-good-but your specs are a bit unclear)? Barely enough for the inverter to run 6 or 8 amps of load on the 120VAC side! That inverter can draw up to 250 amps on the DC side to feed a 25 amp load. Kind of danger Will Robinson there if your wires are not fused for their max carrying load.

If your inverter is tripping, I'm guessing there may be significant draw through the wire feeding it from the panel. You can experiment a little to check by firing up the inverter and putting some loads on it while checking amperage (again, DC amp clamp) and/or a thermal gun, or hands on the wire.

If it's heating up, that may be an indication....

Does that make sense?