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Growatt 3kw wiring question

Jim in NH

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I have installed a 6 circuit Reliance Controls generator sub panel transfer switch 30 amp 120v. It has 6 circuit breakers in it that I have wired to 6 circuits in my main panel. Three of the circuits in my main panel that I connected are GFI breakers. The generator panel is fed with the Growatt 3kw inverter. When I switch the 3 circuits on the sub panel to be fed from the inverter, that trips the GFI circuits in the main panel. The circuits on the sub panel are running fine. I am not sure why this is happening and if it is an issue (I assume it is)? I have successfully wired these panels in other houses, but never to GFI breaker circuits in the main panel.

BTW, I did the generator subpanel so I could also switch and feed it directly with a generator if I had to.

Any help is appreciated!
 

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I have installed a 6 circuit Reliance Controls generator sub panel transfer switch 30 amp 120v. It has 6 circuit breakers in it that I have wired to 6 circuits in my main panel. Three of the circuits in my main panel that I connected are GFI breakers. The generator panel is fed with the Growatt 3kw inverter. When I switch the 3 circuits on the sub panel to be fed from the inverter, that trips the GFI circuits in the main panel. The circuits on the sub panel are running fine. I am not sure why this is happening and if it is an issue (I assume it is)? I have successfully wired these panels in other houses, but never to GFI breaker circuits in the main panel.

BTW, I did the generator subpanel so I could also switch and feed it directly with a generator if I had to.

Any help is appreciated!
I need some kind of circuit diagram to understand what your set-up is doing and what the problem might be.

However, my guess is that you are ending up with two Neutral-Ground bonds in the system. This will cause current on the Equipment Grounding wire and if the GFI breakers are part of the circuit they will pop.
 
Thanks for your response!

The generator sub panel is wired:

White to Neutral Bar in main panel
Green to Ground Bar in Main Panel
Hots from the 6 critical circuits, to the specific circuits in the main panel. 3 of the breakers in the main panel that are run to the generator box are GFCI breakers, which are the ones that are popping when I switch them to Generator (Growatt)

The AC being fed into the generator box from the Growatt box is:

Black in Growatt to Black in Sub Panel
White in Growatt to White in Sub Panel
Ground in Growatt to Ground in Sub Panel

So I will need to look for a Neutral / Ground bond in the Generator Box as well. The Growat documentation seems to state that the Neutral & Ground is not bound by default which is my setting:

1614022856252.png

Per your comment, there should only be one in the system.

I will review my gear & settings next weekend and report back.

Thanks!!

Jim
 
Thanks for your response!

The generator sub panel is wired:

White to Neutral Bar in main panel
Green to Ground Bar in Main Panel
Hots from the 6 critical circuits, to the specific circuits in the main panel. 3 of the breakers in the main panel that are run to the generator box are GFCI breakers, which are the ones that are popping when I switch them to Generator (Growatt)

The AC being fed into the generator box from the Growatt box is:

Black in Growatt to Black in Sub Panel
White in Growatt to White in Sub Panel
Ground in Growatt to Ground in Sub Panel

So I will need to look for a Neutral / Ground bond in the Generator Box as well. The Growat documentation seems to state that the Neutral & Ground is not bound by default which is my setting:

View attachment 38167

Per your comment, there should only be one in the system.

I will review my gear & settings next weekend and report back.

Thanks!!

Jim
2 things

1) The description helps, but I need a diagram or at least make and model of every component so I can figure out what you are saying.

2) The manual may be outdated. I have been collecting info on various inverter grounding scheems. You can see what I have here:

I have tried but failed to get good details on growatt, but this is what I found for MPP
1614025047583.png

Here is a blow up from the MPP manual. (It is too blury above)

1614025106525.png

Notice how similar it is to the configuration of the Growatt. These two inverters clearly share a similar/same design.

Now notice what MPP support told me:

Emails From MPP Solar Support:
1) Is the AC-In ground, AC-out ground and Chassis ground all tied together? yes
2) Is there any bonding between the AC Neutral out and AC-Out Ground? If not, is there any problem if there is a Neutral-Ground bond in the circuit after the inverter?
The output N-G is handled this way - when under line mode (AC bypass), N-G is open, but when under inverter mode, then N-G will short. There shouldn't be any problem
to the inverter itself if you wish to N-G short manually, however we're told some countries (like Australia) require N-G to stay open when grid passes through so that’s the reason it's designed this way.
When asked about the configuration setting above, They said:
Please ignore this setting as essentially it is the same as what I've described in the last message about how OUTPUT N-G is handled under different modes so it's already now done internally and this setting would have no use.
thanks
This makes me wonder if the Growatt documentation is out of date as well.
 
>>1) The description helps, but I need a diagram or at least make and model of every component so I can figure out what you are saying.

Will do. I will put together a stick drawing and include the make and model number of the equipment involved...

Stay tuned.

Jim
 
I have attached the instruction manual from the ProTran Generator Box.

More info coming.
 

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I have attached the instruction manual from the ProTran Generator Box.

More info coming.
Does the generator box come pre-wired with the wires hanging out of it?

I am 90% sure this transfer switch only switches the Hot wire(s) and not the Neutral wire. That is not necessarily bad, but it means the N-G bond can only be at *one* of the following three places:

Generator
Inverter
Main Breaker Box.
 
>>Does the generator box come pre-wired with the wires hanging out of it?

Yes is does. I just hooked the White to the Neutral Bar and the Green to the Ground bar in my main panel.

System drawing:

Drawn using https://app.diagrams.net/

Am I getting closer to the information that you require?

Best,

Jim
 

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>>I am 90% sure this transfer switch only switches the Hot wire(s) and not the Neutral wire. That is not necessarily bad, but it means the N-G bond >>can only be at *one* of the following three places:

>>Generator
>>Inverter
>>Main Breaker Box.

I am 99% sure the Neutral and Ground on the transfer box are just "pass through" (just the Hot wires are switched). And since my main panel is Neutral/Ground bonded, that leaves the Growatt as the culprit. This leaves us to straighten out the ambiguity in the manual(s) and your correspondence with MPP Support.
BTW, I recall Will Prowse stating that the MPP & Growatt were nearly identical boxes MFG by the same MFG. The only difference being better documentation (which is why I went with the Growatt in the 1st place).

Maybe we can have Ian Roux of Watts247 reach out to Growatt corporate (since he is a distributor) and get this question answered properly?
 
I did quite a bit of research on my configuration a couple of weekends ago and here are my findings:

See "Solar System Drawing" attached above for reference.

The the Neutral and Ground on the transfer box are just "pass through" (just the Hot wires are switched). My main panel is Neutral/Ground bonded.

The GFI & Arc Fault Breakers in the main panel that are are fed through the 6 Circuit Transfer Switch only pop when the panel is being fed from the Growatt. That leaves the Growatt as the culprit and I did not open it up to look at the configuration inside because I would have to cut the warranty seal. I have been told by Ian Roux (Watts247) that there is NO Neutral/Ground bond inside the unit. We put a Fluke Amp meter on the Neutral and could see a momentary surge on the Neutral when the circuit in the transfer switch was changed from "Line" to "Gen" (Growatt as the source) and that is most likely the cause of the trip of the breaker in the main panel.

The other thing that was pointed out to me is than the breakers in the Transfer Switch Sub Panel are not GFCI so when running on Gen (Growatt) I would not have GFCI protection. I then put GFCI outlets in the first outlet in the string on that circuit and removed the GFCI breaker in the main panel. This resolved the tripping of the GFCI breaker in the main panel and protected everything on those circuits whether they are running on Grid or Growatt.

Keep in mind that I can feed the Transfer Switch Sub Panel with either the Growatt or a Generator if I had to. I did it this way so that if I ever had a prolonged power outage and the batteries were not sufficient, I could just run off of an Inverter Generator.

As always any commentary is welcome.
 
Nice setup.
Did you ever try to connect an actual generator to your transfer switch (not the Growatt) and see whether the GFCI breakers pop?
As I understand it, the GFCI breakers monitor current on hot and neutral, then pop when there is any imbalance. Somehow the Growatt or transfer switch is delivering unbalanced current?
 
>>Did you ever try to connect an actual generator to your transfer switch (not the Growatt) and see whether the GFCI breakers pop?

Great question... I did not have access to the generator at this 2nd home. However, through the process of elimination I traced the issue to the Growatt unit and a friend of mine used his Fluke Clamp on amp meter to detect a surge on neutral when swapping from "Line" to "Gen" (going from grid to Growatt). This is when the breakers tripped. However, the breakers could not be reset and would continue to trip while on Gen (Growatt) and we could not see anything wrong. I did not want to open the Growatt box to dig around in there because that would have involved breaking the warranty sticker...

My main panel had a combination of GFI and Arc Fault breakers on the circuits going to the subpanel and both were popping.

An oversight that came up while doing all of this work is that the sub panel had standard breakers in it and the down stream outlets were not being GFI protected when on Gen (Growatt). To remedy this situation I removed the GFCI breakers from the main panel and put GFI protection on the outlets down stream. This now gives me GFI protection on those circuits regardless of whether I am on Grid or Growatt. There has been no issues with any of the GFI outlets after I did this when running on Grid or Growatt.

Trying to understand the original Growatt issue was beyond my abilities and I think that this final solution has solved the original issue as well as the new issue that popped up (no GFI on the circuits when on sub panel).
 
Great info, thanks. The GFCI breakers are somehow more current-sensitive than the downstream outlet, I guess. Hopefully someone who knows what was really going on with the popping breakers will chime in and shed more light.
Are you now without arc fault protection, though?
 
I had 3 Arc Fault breakers and 3 GFI breakers. I replaced all 6 breakers with standard breakers and down stream, put GFI outlets on all 6 circuits. I think think this will cover all safety issues. This is how my other homes have been configured as GFI outlets were cheaper than GFI breakers, but less convenient because they may be hidden behind things.

If anyone sees issues with this I would love to hear them.
 
From the above description and the Xfer switch instructions, I tried to draw out one of the circuits as it was when it was not working.

Is this correct?
1616537359496.png

And this is what you did to make things work
1616538117800.png
However, through the process of elimination I traced the issue to the Growatt unit and a friend of mine used his Fluke Clamp on amp meter to detect a surge on neutral when swapping from "Line" to "Gen" (going from grid to Growatt). This is when the breakers tripped.
Did you happen to put the clamp-on meter on the ground wire once you got it working? If there is current on that ground wire, then I would be fairly confident that there is a N-G bond inside the Growatt (despite what Growatt support said). Furthermore, any current on ground is considered a hazard.

However, the breakers could not be reset and would continue to trip while on Gen (Growatt)
This reinforces my suspicion that there is a N-G bond in the growatt
 
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These drawings you provided represent before and after my reconfiguration.

I did not test for current on the ground and will recheck this weekend.
 
I did not test for current on the ground and will recheck this weekend
I am looking forward to the results.

BTW: Test it when there is a load (Even with a N-G bond in the grow-watt there might not be a measurable current if there is no load.)
 
I had 3 Arc Fault breakers and 3 GFI breakers. I replaced all 6 breakers with standard breakers and down stream, put GFI outlets on all 6 circuits. I think think this will cover all safety issues. This is how my other homes have been configured as GFI outlets were cheaper than GFI breakers, but less convenient because they may be hidden behind things.

If anyone sees issues with this I would love to hear them.

Just FYI, arc fault protection is now required by code at most rooms in a house, unless your jurisdiction still has not adopted this reqt. Existing homes are exempt until any change is made to the system, then the reqt kicks in.

 
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