MPP LV6548 AC Wiring Question

davesmith87

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Hello all,

I pulled the trigger on (2) LV6548 hybrid inverters. https://watts247.com/product/2-x-lv...ar-inverter-8kw-2-x-4kw-250v-mppt-bms-ul1741/ . Also have purchased a pallet of 435 watt solar panels. The plan is to run both in split phase.

I've been studying the manual but I'm quite confused on the AC wiring.

Currently, I have 1 main panel (connected to grid), 200A service.

The instructions state, "Before connecting to AC input power source , please install a separate AC breaker between
inverter and AC input power source . This will ensure the inverter can be securely disconnected during
maintenance and fully protected from over current of AC input."

I'm not sure what size breaker to use from my main panel to the inverters. 60A? 100A? I believe the "AC In" will be for the grid assist if the solar/battery is not meeting the load.

The utility, I'm confused on what to do with the neutral. I get each hot wire, will go to a separate inverter (from a breaker in the main box). However, the diagram doesn't really show what to do with the neutral wire.

For the load, it shows the neutral being bonded and ran into each inverter.

Can I use my main panel, for both the AC In, as well as Load? So I would essentially just be installing 2 double pole breakers in the existing box.

Or should I wire up a separate sub panel for the Load? Extend existing circuits (that I want to run on solar/battery) to the new panel?

What would be the best way to handle the neutral for the load? Just use the neutral bus bar (from potential new sub panel) and run to each inverter?

Thanks in advance.

oneinverter.PNG
 

schmism

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Can I use my main panel, for both the AC In, as well as Load? So I would essentially just be installing 2 double pole breakers in the existing box.
You can not run the output from the inverters back to the grid power main panel. You CAN NOT mix the grid AC with the inverter output AC.

This is accomplished by installing a second pannel. Anything you want run off the inverter is wired from this second "sub panel"

For my 3kw growatt the breaker they recommend to be installed in the grid panel is 40a (this is detailed in the manual). The unit can charge the battery at the same time it grid bypasses drawing more than what you would expect for just 3kw of output. I would expect yours to be 50-60a.
 

Tecnodave

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Diagram is missing one connection needed, the Neutral in of both inverters go to the neutral in the main box. But do verify that with your supplier. I think that they simply omitted drawing that wire, they started it but it goes nowhere
The AC feed to the inverter needs to be 60 amps and the inverters need the “synchronization cable” , maybe called a paralleling cable to be connected.


Everything that @schism has said is exactly correct, so i will not expound on that.
 

davesmith87

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Thanks for the replies. I read different that about mixing the grid AC with the inverter output AC. Thank you for clarifying.

I picked up the panel below to be my "sub panel" for the inverter load. I went with a QO model so I could move breakers form main to it. However, I realized that this panel is designed to be a main panel, but I think I can use it as it without issue (for inverter load)?

When running the "AC Out" from the inverters into the new sub panel would that require a breaker? I think so. So I would need (2) 60 AMP breakers (one for AC in and one for AC out).

Thanks in advance.

 

Tecnodave

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That is a main panel which can have neutral and ground combined but if you want to use it as a sub-panel then you will need to remove the green lacquered grounding screw from the isolated neutral buss and add a Square D PK23GTA ground buss bar, there are threaded holes in this box to mount this ground buss at 4 locations in this panel.
Commonly available at any supply house , home cheepo, lowe’s etc.

Question 2, yes you need two two pole breakers Square D part number QO230, one in the main panel and one in the sub panel, AND you will need a back fed main lock down kit for the 60 amp main breaker installed on the buss of the sub_panel

This panel is set up for QOM2 Bolt on main but that is not available in 60 amp so use a back fed main on the plug in part of the panel. To be safe and code legal a back fed main on a QO buss must have a breaker lock down as the QO breakers have exposed terminals on the breakers which would be live when removed.

Back fed main breaker lock down kit part number PK3MB. Back fed main is to be mounted in top most right two positions and threaded holes for the lock down kit are provided at this location and the two below this one for the case of two back fed mains toggled together in a two source arrangement.

This probably will not be a lowe’s or home depot item, but will be found at any stocking distributor of Square D electrical panels.

1st pic is a Square D back fed main breaker lock down in a QO10-20M100S main panel


2nd Pic is of this two source back fed main installed in a QO8-16L100RB sub panel.
Unfortunately I do not have a pic of the lock down kit in this panel but it does the same thing as the lock down kit in the main panel, This installation required a different lock down kit

So you can add a generator feed to the either panel that you have safely and code compliant. It will be a different lock down and breaker toggle for the main as you would be toggling a QOM-2 with a QO breaker in your main panel and toggling between two QO 2 pole breakers in your sub-panel.

Yep, i am an electrician and stocking installer of Square D, ya think
 

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eabyrd

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Thanks for the replies. I read different that about mixing the grid AC with the inverter output AC. Thank you for clarifying.

I picked up the panel below to be my "sub panel" for the inverter load. I went with a QO model so I could move breakers form main to it. However, I realized that this panel is designed to be a main panel, but I think I can use it as it without issue (for inverter load)?

When running the "AC Out" from the inverters into the new sub panel would that require a breaker? I think so. So I would need (2) 60 AMP breakers (one for AC in and one for AC out).

Thanks in advance.

That's one heck of a big sub-panel. Do you really think you're going to run 42 separate circuits? There are much smaller and less expensive Square D panels out there that are intended to be sub-panels. They have both a neutral and a ground bar so you save even more money there by not having to go by another part.

You do NOT need a main breaker as the inverters themselves provide overcurrent protection (I just learned this from Will see an old dog can learn). The Line from inverter one, can go to one main lug, the line from inverter two goes to the other main lug. The neutral is combined from the two inverters and can go straight to the main neutral lug, same with the grounds.

What @Tecnodave said above regarding the neutral to ground bond is correct, most sub panels come with the bonding screw "uninstalled" but you want to confirm that there is no continuity between the neutral and ground bars
 

davesmith87

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That is a main panel which can have neutral and ground combined but if you want to use it as a sub-panel then you will need to remove the green lacquered grounding screw from the isolated neutral buss and add a Square D PK23GTA ground buss bar, there are threaded holes in this box to mount this ground buss at 4 locations in this panel.
Commonly available at any supply house , home cheepo, lowe’s etc.
Thanks for the reply. This is what it looks like I need then, https://www.lowes.com/pd/Square-D-1-in-Ground-Bar-Kit/3364862
 

davesmith87

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That's one heck of a big sub-panel. Do you really think you're going to run 42 separate circuits? There are much smaller and less expensive Square D panels out there that are intended to be sub-panels. They have both a neutral and a ground bar so you save even more money there by not having to go by another part.

You do NOT need a main breaker as the inverters themselves provide overcurrent protection (I just learned this from Will see an old dog can learn). The Line from inverter one, can go to one main lug, the line from inverter two goes to the other main lug. The neutral is combined from the two inverters and can go straight to the main neutral lug, same with the grounds.

What @Tecnodave said above regarding the neutral to ground bond is correct, most sub panels come with the bonding screw "uninstalled" but you want to confirm that there is no continuity between the neutral and ground bars
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)?

 

Tecnodave

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The main breaker in this panel is a QOM2 bolt on main, it is not available in 60 amp so the best course of action is to use a back fed main....

This panel has no lugs for line in.......where are you going to attach the feed wires, you cant just mickey mouse them anywhere and be code compliant. Look closely at that main panel.......I do not need to go look, I have that on my stock shelf, installed many of those.

Square D is my line of choice more than 95% of my installs are Square D. I do know the details of how to do these...
 
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eabyrd

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OK Reality check time. If I'm wrong forgive me, but I'd rather say this in case you haven't thought it through. First, with a panel that size you likely have 200AMP service at your house. That's 200 Amps per leg. Your inverters will give you about 55 Amps per leg. You will overload your system badly if you try to run your entire house on 2 of the 6548 inverters. Sorry it just isn't possible.

If you are going to use the panel you linked to, then yes you need to use the backfeed breaker kit, but that is, in my humble opinion, a bad idea. I suggest you pause, think about how much power & which circuits you want / need to move into the sub-panel, then spec from there
 

davesmith87

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OK Reality check time. If I'm wrong forgive me, but I'd rather say this in case you haven't thought it through. First, with a panel that size you likely have 200AMP service at your house. That's 200 Amps per leg. Your inverters will give you about 55 Amps per leg. You will overload your system badly if you try to run your entire house on 2 of the 6548 inverters. Sorry it just isn't possible.

If you are going to use the panel you linked to, then yes you need to use the backfeed breaker kit, but that is, in my humble opinion, a bad idea. I suggest you pause, think about how much power & which circuits you want / need to move into the sub-panel, then spec from there
Good idea. My other thought with the bigger panel was if I expand in the (get another 6548) that I would have ample run in the existing sub panel, but then again, I could also add another sub panel, when I expanded.

What panels would not require the backfeed breaker kit? I would like to stick with the Square D QO series, so I can reuse the existing breakers.

Would this panel, require the back feed breaker kit?

 

Tecnodave

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OK Reality check time. If I'm wrong forgive me, but I'd rather say this in case you haven't thought it through. First, with a panel that size you likely have 200AMP service at your house. That's 200 Amps per leg. Your inverters will give you about 55 Amps per leg. You will overload your system badly if you try to run your entire house on 2 of the 6548 inverters. Sorry it just isn't possible.

If you are going to use the panel you linked to, then yes you need to use the backfeed breaker kit, but that is, in my humble opinion, a bad idea. I suggest you pause, think about how much power & which circuits you want / need to move into the sub-panel, then spec from there
You are wrong, wrong, wrong....

42 spaces is probably more than needed but will not overload the inverters if the loads do not overload the inverters, extra spaces do not hurt anything
 

eabyrd

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Tecnodave

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There is another option with Square D, if you do not want to use a main breaker on this sub panel you can use bolt on lugs in place of the QOM2 main breaker but I do not suggest it as the overcurrent protection in the inverter is not user accessible and at some time you may want to shut down the sub-panel for service
 

Tecnodave

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davesmith87

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What he said is move the circuits from the main, not the main, I do believe that the OP does know the limitations of the inverters
Correct. Original thought was to get a bigger panel then I need. Move circuits over 1 by 1 and measure usage, then evaluate. Thought was to get (2) additional 6548 down the road to expand.
 

Tecnodave

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I have said that I am a stocking installer of Square D, Ive posted 2 pictures of three Square D panels, 2 Square D Homeline panels and one Square D QO panel, Ive done hundreds of Square D panels and can quote Square D part numbers from memory and i’m not qualified.....


@davesmith87 You are on the right track......Im only sharing my expereince as a qualified electrician who only installs the better grade panels.

IMHO QO is the best there is for home and industrial, that is why I have 30-40 Square D panels in my stockroom

I also use Cutler-Hammer and Seimens, but wont even touch Stak-lok, Zinsco, Challenger.....etc will not patch, repair , upgrade them....only rip them out and replace with quality

Again I suggest using a back fed main as it provides a quick shutoff of the subpanel.

The QO-260 back fed main is about $18., and maybe $10 for the lock down kit....chump change for what you are doing....

Added note......a QO260 can be used as a branch breaker without a lock down kit but as a “back fed main” it does require the lock down kit to comply with the UL listing AND the NEC.
 
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davesmith87

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I have said that I am a stocking installer of Square D, Ive posted 2 pictures of three Square D panels, 2 Square D Homeline panels and one Square D QO panel, Ive done hundreds of Square D panels and can quote Square D part numbers from memory and i’m not qualified.....


@davesmith87 You are on the right track......Im only sharing my expereince as a qualified electrician who only installs the better grade panels.

IMHO QO is the best there is for home and industrial, that is why I have 30-40 Square D panels in my stockroom

I also use Cutler-Hammer and Seimens, but wont even touch Stak-lok, Zinsco, Challenger.....etc will not patch, repair , upgrade them....only rip them out and replace with quality

Again I suggest using a back fed main as it provides a quick shutoff of the subpanel.

The QO-260 back fed main is about $18., and maybe $10 for the lock down kit....chump change for what you are doing....
I appreciate your advise. I'm definitely in the learning phase, although my wife's dad will be helping greatly with the install (he's a master electrician). At this point, I'm just trying to make sure I have all the right components, to not make dozens of trip to the hardware store.

I think I will stick with the original panel I have.

To Buy:
(1) ground bar kit https://www.lowes.com/pd/Square-D-1-in-Ground-Bar-Kit/3364862
(2) QO-260, https://www.lowes.com/pd/Square-D-QO-60-Amp-2-Pole-Standard-Trip-Circuit-Breaker/3135069. One to go into the main panel to the inverters. One to go into the new sub panel for the load.
(1) lock down kit PK3MB.

Does the lock down kit go into the sub panel or the main?
 

Tecnodave

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The lock down kit is only required when the breaker is back fed....that will be in the sub panel

your wife’s dad will verify everything that I have said.

20 years contracting after 29 years engineering for General Electric, i think that i have it down.
 

davesmith87

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The lock down kit is only required when the breaker is back fed....that will be in the sub panel

your wife’s dad will verify everything that I have said.

20 years contracting after 29 years engineering for General Electric, i think that i have it down.
Understood. One last question I promise.....

If I did get a different box to function as the sub panel (such as the one linked below), would I still need, the lock down kit? I think the answer to my question is "yes" but not 100% sure.

 
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