MPP LV6548 AC Wiring Question

Blueprint24

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Your picture has a ground loop. Lose the green EGC from the junction box to the 3-pole double throw switch. The EGC running through the inverter circuit will do
I was wondering about connecting all of these grounds together! Will do, thanks for taking time to look.
 

Blueprint24

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I was wondering about connecting all of these grounds together! Will do, thanks for taking time to look.
Question though - I do keep the EGC from there on, right. So the only EGC I’d remove is between the JBOX and the 3PDT switch
 

acdoctor

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My main had 42 in use. I figured I would size it the same, so I could move the existing circuits over 1 for 1.

Is the neutral (from the inverters) combined at the main neutral lug or before? Could I take both 4 awg wires (for nuetral) from both inverters and inside them into the main neutral lug?

If I only got with 1 breaker (in the main box), do I need what technodave was talking about (Back fed main breaker lock down kit part)?

If you intend to power all circuits consider moving the utility to a new panel and feed the current one with the inverters.
 

raurre

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Your equipment grounding can be connected all together as many times as necessary to insure a constant connection. The only time that you would have any restriction is were it is also bonded to the neutral. By NEC code it should only be at the Main service entrance. Every time after that it should be separated. The only time you would do it again would be if you are creating a new source of electricity. That was the original question are the inverters considered a new source like a generator and transformer or a appliance since they have a bypass capability.
 
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Zwy

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Your picture has a ground loop. Lose the green EGC from the junction box to the 3-pole double throw switch. The EGC running through the inverter circuit will do
If the double throw is in inverter bypass, is it possible there will not be a ground to subpanel?

I can't recall but is the ground input thru the inverters pass thru?
 

Blueprint24

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If the double throw is in inverter bypass, is it possible there will not be a ground to subpanel?

I can't recall but is the ground input thru the inverters pass thru?
My understanding is that they do pass through. Earlier in this thread someone mentions this. MPP solar reviewed my wiring and approved it, but before they did, I had to separate my neutrals as I didn’t originally have them switched. You cannot have the AC IN and AC OUT neutrals connected anywhere. As far as the grounds, I was with @raurre on the connect grounds everywhere, because they’re all going back to main regardless. But seems to be a lot of controversy over the grounding of these inverters. I’m going to contact MPP and see if the ground passes through… but I read earlier that it did.
 

Blueprint24

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It won’t matter, because the 3PDT switch will have grounding from the Main side. Those grounds (unless I disconnected that ground - as @eabyrd suggested). Then the inverters would NEED to be pass through for the ground.
 

eabyrd

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Question though - I do keep the EGC from there on, right. So the only EGC I’d remove is between the JBOX and the 3PDT switch
Yes, the grounds pass through the LV6548. EGC in, EGC out, and Chassis ground on those units are all connected at all times. Reading the posts that follow, I must say I am not an electrician, and I am not sure the loop is a huge deal if you leave it, but all I have read says you want no loops either neutral or earthing.
 

eabyrd

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I read Dan's problem here and the issue is confusing to say the least. https://diysolarforum.com/threads/lv6548-grounding-issues.21531/

What I gathered there was there was a ground loop somewhere in the junction box. One thing that also comes up is the neutral and ground are bonded in the LV6548.
Dan’s problem was a current on the EGC running directly from the main to the sub panel. I think he goes into it more in the comments to his YouTube video on the issue.

yes, the LV6548 creates a bond (annoyingly I admit) when in inverter mode. There is no bond when passing through grid power, however the fact it creates one at all necessitates isolating the neutral. Hence the 3-pole switch in this case.
 
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Blueprint24

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Dan’s problem was a current on the EGC running directly from the main to the sub panel. I think he goes into it more in the comments to his YouTube video on the issue.

yes, the LV6548 creates a bond (annoyingly I admit) when in inverter mode. There is no bond when passing through grid power, however the fact it creates one at all necessitates isolating the neutral. Hence the 3-pole switch in this case.

Yes, I totally agree, should be an UNBONDED pass through.

I have everything run already, with the ground connected, but will probably disconnect that between the double throw and the JBOX before powering the circuit and thinking of a way to test. Working on the final connections (waiting on more wire) from and to the inverters AC IN/AC OUT from the 3PDT switch from AC OUT as well as the 3P disconnect for the AC in. I do have the neutrals switched, as MPP confirms it is required to separate them from IN AND OUT. I will most definitely be checking the current on the ground wire at all places.

I am happy to run any tests or checks once I have this wired to confirm any questions or if anyone knows a way to properly test if this is needed.

Matt
 

eabyrd

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Yes, I totally agree, should be an UNBONDED pass through.

I have everything run already, with the ground connected, but will probably disconnect that between the double throw and the JBOX before powering the circuit and thinking of a way to test. Working on the final connections (waiting on more wire) from and to the inverters AC IN/AC OUT from the 3PDT switch from AC OUT as well as the 3P disconnect for the AC in. I do have the neutrals switched, as MPP confirms it is required to separate them from IN AND OUT. I will most definitely be checking the current on the ground wire at all places.

I am happy to run any tests or checks once I have this wired to confirm any questions or if anyone knows a way to properly test if this is needed.

As to testing
1. I tested continuity of the the EGC from the main panel to each and every component connection & their chassis (scrape a bit of paint if need be) in the system.
2. I tested continuity between neutral and the EGC at the output of each unit in both bypass, and inverting modes to confirm that there was no continuity (no bond) when bypassing, but there was continuity (bonding) when inverting.
3. I tested the voltage to EGC to make sure I had a bond at all times. (voltage to EGC and Voltage to Neutral should be the same since they're bonded.
4. I tested for current on the EGC to make sure there wasn't in (except trace amounts that is)

I didn't bother with any resistance testing, but I have read of others doing it.
 

Zwy

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As to testing
1. I tested continuity of the the EGC from the main panel to each and every component connection & their chassis (scrape a bit of paint if need be) in the system.
2. I tested continuity between neutral and the EGC at the output of each unit in both bypass, and inverting modes to confirm that there was no continuity (no bond) when bypassing, but there was continuity (bonding) when inverting.

This is the important test, I thought possibly the neutral and EGC were bonded in the unit when in bypass mode. His problem only occurred when running on bypass.

Thanks, appreciate the input.

3. I tested the voltage to EGC to make sure I had a bond at all times. (voltage to EGC and Voltage to Neutral should be the same since they're bonded.
4. I tested for current on the EGC to make sure there wasn't in (except trace amounts that is)

I didn't bother with any resistance testing, but I have read of others doing it.
 

Blueprint24

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As to testing
1. I tested continuity of the the EGC from the main panel to each and every component connection & their chassis (scrape a bit of paint if need be) in the system.
2. I tested continuity between neutral and the EGC at the output of each unit in both bypass, and inverting modes to confirm that there was no continuity (no bond) when bypassing, but there was continuity (bonding) when inverting.
3. I tested the voltage to EGC to make sure I had a bond at all times. (voltage to EGC and Voltage to Neutral should be the same since they're bonded.
4. I tested for current on the EGC to make sure there wasn't in (except trace amounts that is)

I didn't bother with any resistance testing, but I have read of others doing it.
This is great, I will be running the same tests and appreciate the feedback!! I can’t wait to Finish up the wiring. I only have the AC IN and AC OUT wires left, then need to find some good priced panels.
 

Sanwizard

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This is great, I will be running the same tests and appreciate the feedback!! I can’t wait to Finish up the wiring. I only have the AC IN and AC OUT wires left, then need to find some good priced panels.
Try Qcell 330W from Alt-e store. Mine were about $185 each.
 

eabyrd

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This is great, I will be running the same tests and appreciate the feedback!! I can’t wait to Finish up the wiring. I only have the AC IN and AC OUT wires left, then need to find some good priced panels.
Good luck with that, I happened upon used 260 watt panels from Lightway for $65 back in may. I bought 8, and now wish I had bought double that... Of course my wife probably wouldn't let me string them across the yard any more than I already have.
 

Zwy

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This is great, I will be running the same tests and appreciate the feedback!! I can’t wait to Finish up the wiring. I only have the AC IN and AC OUT wires left, then need to find some good priced panels.
It all depends on what you want. I decided on 16 530w panels from San Tan. They are sold out after dropping to $239 each. I can only run 4S with 4 strings however I could go 4S2P and then split each PV string in 2, so one wire to each PV input. This splits the amps back down under max rated.

For the LV6548, something like this 350W https://store.santansolar.com/product/rec-350w/ actually is a good panel considering the PV limits. You can go 5S2P per string and remain in the limits. VOC is 43.7 and ISC is 7.98a. Each string would be 3487.26w max and with 2 PV inputs gets you up to just under 7Kw. That's 20 panels per LV6548. With 2 units in parallel, 40 panels and just under 14Kw array size.
 

Blueprint24

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It all depends on what you want. I decided on 16 530w panels from San Tan. They are sold out after dropping to $239 each. I can only run 4S with 4 strings however I could go 4S2P and then split each PV string in 2, so one wire to each PV input. This splits the amps back down under max rated.

For the LV6548, something like this 350W https://store.santansolar.com/product/rec-350w/ actually is a good panel considering the PV limits. You can go 5S2P per string and remain in the limits. VOC is 43.7 and ISC is 7.98a. Each string would be 3487.26w max and with 2 PV inputs gets you up to just under 7Kw. That's 20 panels per LV6548. With 2 units in parallel, 40 panels and just under 14Kw array size.
I like this!! I’m going to be roof mounting, so the wife shouldn’t be an issue on this one lol that’s funny though. I’ll be going up this weekend to get good measurements, try to figure out the rack, check panel dimensions, math, but this is great! Thank you all for the input and this seems like exactly what I want, if I can fit it all. I do have a roof and garage south banks to fill, so might be doable.

Side note - $65 a panel!!! , wow I wish they weren’t gone too, because space is limited and I was to get as much up there as possible now.
 

Zwy

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I like this!! I’m going to be roof mounting, so the wife shouldn’t be an issue on this one lol that’s funny though. I’ll be going up this weekend to get good measurements, try to figure out the rack, check panel dimensions, math, but this is great! Thank you all for the input and this seems like exactly what I want, if I can fit it all. I do have a roof and garage south banks to fill, so might be doable.

Side note - $65 a panel!!! , wow I wish they weren’t gone too, because space is limited and I was to get as much up there as possible now.
San Tan inventory changes daily. It's best to determine how much room you have, then look at various panels they have about every 2 days, then determine what VOC works best to get close to the LV6548 max 250VOC.

If you want cheap used panels, https://store.santansolar.com/product/santan-solar-t-series-250w-snail-trails/
 
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