Breaker Box wiring for MPP Solar LV2424

[ChrisW123]

Hi Everyone!

I'm a newb solar guy building my first portable solar generator using an MPP Solar LV2424 all-in-one inverter box, and two 12v 100ah batteries in series.

I have a couple questions though, maybe someone here can help or offer advice:

1) With this setup, is a breaker box required or good to use? Or does this all-in-one unit already have cover-current protection?

2) If it needs a breaker box, is my wiring diagram correct? Any changes or something not right?

Thanks in advance! -Chris.

 

[Hedges]

One issue I see is a 10 awg neutral from inverter to breaker panel, carrying current for 20A + 30A = 50A total circuits.
(Of course, LV2424 might not deliver enough current to be a problem.)

Neutral and ground aren't shown as bonded together. In U.S., we bond them at one location.
A few inverters aren't compatible with that, however. But many are. Assuming this one is, the breaker panels I use have a green bonding screw to connect the box to neutral busbar, which gets both neutral and ground wires.

Using a breaker panel is good to have disconnects for multiple circuits. It lets you have 20A protection for a 20A circuit and also feed a 30A circuit. If you use 12 awg, good to have 20A breaker.

 

[ChrisW123]

This box doesn't have a green bonding screw to connect the neutral bar to the panel. I can't find info in the MPP Solar manual on whether or not I need to bond neutral and ground in the box.

But tell me if this is correct (I'm a newb at this): Without using the breaker box, wouldn't my circuit wiring be connected (the ground and neutral wires) as being NOT bonded? So would mean the invertor box IS bonded? If that guess is correct, then it makes sense that I should NOT be bonding the ground and neutral in my breaker box. Just my guess, is it correct?

 

[iamrich]

LV2424 only has 2400 watts AC out (~22a total)?

 

[Hedges]

If your inverter has AC input and AC output terminals, almost certain it does not bond neutral to ground inside the box. The AC is receives would come with neutral bonded to ground.

My Sunny Island have no bonding internally. They are fed from the grid so neutral and ground on AC input were bonded earlier, at my main breaker panel.
If I was using off-grid, I would probably do the bonding inside the first breaker panel their AC output connects to.

If you do decide to bond inside this box, just get a longer ground busbar to install and use that for both neutral and ground.

With inverter switched off, you can use an ohm meter to check for continuity neutral to ground.
Switched on, use volt meter from hot to ground. But due to capacitive coupling, could be inconclusive. I would then connect a lightbulb from hot to ground and again check voltage (don't touch chassis while lightbulb is connected; it will electrify a floating ground).

Besides bonding neutral to ground, put in a ground rod and wire to that.
I'm assuming a fixed installation. We also tie to any other metal we see, like metal water pipe going into the earth and foundation steel (which I doubt is connected very well.)

 

[ChrisW123]

LV2424 only has 2400 watts AC out (~22a total)?

Yes that's correct. I know it won't fully power the 30 amp circuit but that's OK for now.

 

[iamrich]

My plan is to ground everything to my AC panel in the workshop so that is where I will bond to neutral. Panels, mounting rails, building (it is metal), inverter will all ground to the panel which will ground to a metal rod. I will bond the ground/neutral in this panel as it will be the main disconnect for the garage.

 

[ChrisW123]

If your inverter has AC input and AC output terminals, almost certain it does not bond neutral to ground inside the box. The AC is receives would come with neutral bonded to ground.

"The AC it receives" will come from the grid (plugged into an outlet), from batteries, and from solar panels. So then while plugged in to my wall outlet, the bonding is done in my house main breaker panel, is that correct? And in this scenario my small breaker box (pic above) I would NOT need to bond the N and Ground. Is this correct?

My Sunny Island have no bonding internally. They are fed from the grid so neutral and ground on AC input were bonded earlier, at my main breaker panel.
If I was using off-grid, I would probably do the bonding inside the first breaker panel their AC output connects to.
....

And yes, this was my next guess.... When I unplug my unit from the wall outlet (this unit is portable) that is when I would need to bond the N and ground in my small breaker box, and also probably tie my inverter to a grounding rod. Is this correct?

Thanks again for your replies, this is very helpful!

 

[Hedges]

"The AC it receives" will come from the grid (plugged into an outlet), from batteries, and from solar panels. So then while plugged in to my wall outlet, the bonding is done in my house main breaker panel, is that correct? And in this scenario my small breaker box (pic above) I would NOT need to bond the N and Ground. Is this correct?



And yes, this was my next guess.... When I unplug my unit from the wall outlet (this unit is portable) that is when I would need to bond the N and ground in my small breaker box, and also probably tie my inverter to a grounding rod. Is this correct?

Thanks again for your replies, this is very helpful!

Basically yes.
There is some UL standard for mobile/marine inverters, where they have a relay to make the neutral/ground bond internally when not plugged into shore power.
Those might encounter a shore power pedestal with hot/neutral reversed. I think people carry adapters wired backwards to address it.

I plan to mount one of my Sunny Island on a vehicle. What I will do is have a power cord wired to its input, and when not plugged into "shore power" I'll plug it into a socket that is dead but has neutral and ground wired together. (rather than bonding in the breaker panel on its output.)

Another approach would be an NC relay with 120V coil, which would open when fed AC from shore power, close shorting neutral to ground when absent. If plugged into an outlet that's backwards, what's supposed to be neutral is hot, the relay will not be happy.

What ground means for a portable system is more up in the air. It is probably the chassis of a motor home.
If you'll carry it around, having a ground rod is less likely.
If you'll use it outside or anywhere you could get wet, GFCI outlets or breakers would be good.

 

[iamrich]

The lv2424 is n to gr. Bonded in the unit itself, so don't n to gr. Bond in sub panel. Usually can only have 1 n to gr. In total system

I distinctly remember when I hooked up my (green) LV2424 that there was no ground on the output (verified by my tester) until after I bonded the ground and neutral in the sub panel. My LV2424 is not actually grounded other than the AC out line that goes to the subpanel, so maybe that is why it works. I don't recall the part circled below on my unit. My unit is standalone off grid (not connected to grid). Might need to take a look at it again this weekend.

Here is a post I got from the resources page.

Grounding details for specific make/model of inverters

To get to the paper, click on the orange button at the top of the screen. It is important to understand how an inverter handles grounding in order to set it up correctly. Unfortunately, many inverters do not provide adequate documentation on...

diysolarforum.com

 

[LithiumSolar]

I'm referring to lv2424msd model the guy from "Lithium Solar" channel showed us how to break the n,b connection in the inverter so you can n,bond in subpage. Said can't have 2 n to bond in the system, only 1. The more I read the more confusing it gets...lol

I removed the N+G bond screw on the LV6548 after checking with the manufacturer (MPP Solar). I have not done this on (or asked about) the LV2424 MSD.

 

[Vafarmer]

Can I just hard wire the output on the lv2424 straight to the main input in my RV breaker box? I would just remove the main power coming in and replace it with the output wire coming from the lv2424. My RV is only going to be off grid and it will never be moved..