Wiring a Homeline load center. Green ground screw question.

Watch Me Build

Solar Enthusiast
Ok I'm running an MPPSOLAR pip-1012-LV. 1000w inverter system in an off-grid setup from a DIY 280ah LifePo4 battery bank and 600w of panels.

Until today I was just using a cut extension cord hooked directly into the output of the MPPSOLAR for 120v.

I hooked up a load center with 3 breakers (a double slot 30amp to the inverter out, to power both bus bars. And 2 single slot double pole breakers each hooked to 2 outlets in my tiny house.)


I wired it up with the separate ground bar because I thought that would be the way to do it... But now I'm not sure if I should have used the included Green ground bonding screw for the neutral bar and just hooked the ground and neutral into there?

Here are some photos.

Should I use the green ground screw to link the neutral bar to the panel casing, or leave it off?
 

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FilterGuy

What, me worry?
I am struggling to make heads or tails of the pictures.

  • Is the green wire coming out of the bottom right of the inverter the DC positive line and is the blue wire the DC negative line?
  • What is the brown wire coming out of the bottom center of the MPPT.?
  • Is it correct to say the ground wire from the MPP AC output is going to the ground bar in the breaker box?
  • Are you running a generator into the system?
  • Is there any connection between the inverter and a grounding electrode(a ground rod driven into earth)? (I don't see it anywhere)
  • Is the DC negative tied to earth ground anywhere? (I don't see it anywhere)

Preliminary answer to your question:
I have never used an MPP, but from my research I believe the MPP has an internal Neutral-Ground bond while running off of battery. (See below for the LV2424 grounding scheema). Therefore the Equipment Grounding wires and the AC neutral should be kept separate in the breaker box.

There should also be one of the following but NOT both:
1) A Grounding electrode tied to the grounding lug on the MPP chassis. Since the AC ground and MPP Chassis are tied together, this would give a proper earth ground for your.
2) A grounding electrode tied to the ground bar inside the breaker box.

Finally, even though it is not required by code for a 12V system, I would tie your DC neg to earth ground. However, be sure to check the MPP manual. If the MPP has internal PV Ground Fault protection, the DC is almost certainly already tied to ground and doing it again would disable the Ground Fault Protection.


1617848086724.png
 

iamrich

Solar Enthusiast
Is any of your system grounded? I would just run all the grounds to the ground bus bar in the Homeline and then to a ground rod. That is how I have my (sorta) similar setup run.
 

Watch Me Build

Solar Enthusiast
I am struggling to make heads or tails of the pictures.

  • Is the green wire coming out of the bottom right of the inverter the DC positive line and is the blue wire the DC negative line?
  • What is the brown wire coming out of the bottom center of the MPPT.?
  • Is it correct to say the ground wire from the MPP AC output is going to the ground bar in the breaker box?
  • Are you running a generator into the system?
  • Is there any connection between the inverter and a grounding electrode(a ground rod driven into earth)? (I don't see it anywhere)
  • Is the DC negative tied to earth ground anywhere? (I don't see it anywhere)

Preliminary answer to your question:
I have never used an MPP, but from my research I believe the MPP has an internal Neutral-Ground bond while running off of battery. (See below for the LV2424 grounding scheema). Therefore the Equipment Grounding wires and the AC neutral should be kept separate in the breaker box.

There should also be one of the following but NOT both:
1) A Grounding electrode tied to the grounding lug on the MPP chassis. Since the AC ground and MPP Chassis are tied together, this would give a proper earth ground for your.
2) A grounding electrode tied to the ground bar inside the breaker box.

Finally, even though it is not required by code for a 12V system, I would tie your DC neg to earth ground. However, be sure to check the MPP manual. If the MPP has internal PV Ground Fault protection, the DC is almost certainly already tied to ground and doing it again would disable the Ground Fault Protection.


View attachment 44210
Yeah I probably shouldn't have included the entire setup in this and just put the inside of the breaker box.

The only thing going from the mpp unit to the box is the piece of yellow romex.

To answer your questions.

1. Yes. I had 4 gauge welding wire available for free. So they're weird colors.

2. Probably referring to the cutoff end of an extension cord to be able to hook a generator into it and recharge the battery or run ac appliances.

3. Yes I have the hot wire into the double slot breaker with a jumper to energize both bars. The neutral into the neutral bus, and the ground into the ground bus.

4. Occasionally if it rains for 4+ days to recharge the battery. I've never used it in passthrough mode to power things through the mpp unit. But I'd like to be able to if it's possible.

5 and 6. I have no grounds run to earth.
 

Watch Me Build

Solar Enthusiast
Is any of your system grounded? I would just run all the grounds to the ground bus bar in the Homeline and then to a ground rod. That is how I have my (sorta) similar setup run.

If I did that. Should I use the green ground screw to bond the neutral bus to the Homeline case then?
 

iamrich

Solar Enthusiast
If I did that. Should I use the green ground screw to bond the neutral bus to the Homeline case then?
I did not. My neutral is completely separate from my ground in the Homeline panel. Actually now that I think about it, the only place I have N-G bonding is possibly inside the LV2424 as referenced in FilterGuy's post above.
 

Watch Me Build

Solar Enthusiast
I did not. My neutral is completely separate from my ground in the Homeline panel. Actually now that I think about it, the only place I have N-G bonding is possibly inside the LV2424 as referenced in FilterGuy's post above.
Ok this was my first instinct with this, but I wasn't sure.

Do you ever hook up to a generator and use it as passthrough?
 

Watch Me Build

Solar Enthusiast
I have not tried that. I have only tested charging the batteries with my Ryobi generator and that was only for a couple of minutes.
Ok thanks. I haven't tried it either yet. Only charged the battery a few times.

I'm thinking the ground lug from the generator would be the way to go.
 

Zak923

New Member
Don’t bond it unless the panel is grounded(earth ground or chassie ground). If you bond it without a good ground you could put power on the ground from the neutral. Meaning what is plugged in with 3 prongs could now have power on the metal case.
 

FilterGuy

What, me worry?
4. Occasionally if it rains for 4+ days to recharge the battery. I've never used it in passthrough mode to power things through the mpp unit. But I'd like to be able to if it's possible.
Most generators do NOT have a N-G bond, but the MPP will disable the N-G bond when the AC-in is energized. Therefore the Generator needs an N-G bond. The best way to do this is with a plug that has Neutral and ground plugged together. This is plugged into one of the sockets on the generator and the MPP is plugged into another socket.

You can run without earth ground, but it is not recomended. I would tie a wire from the breaker box ground bus to a grounding electrode.
 

FilterGuy

What, me worry?
Don’t bond it unless the panel is grounded(earth ground or chassis ground). If you bond it without a good ground you could put power on the ground from the neutral. Meaning what is plugged in with 3 prongs could now have power on the metal case.
Correct, I would not do anything with grounding the generator chassis. Leave the generator chassis floating.


BTW: This is a N-G bonding plug that can be used to add an N-G bond to a generator that does not have one.
Like I said before, you plug this into one socket of the generator to create an N-G bond.
 

Watch Me Build

Solar Enthusiast
Correct, I would not do anything with grounding the generator chassis. Leave the generator chassis floating.


BTW: This is a N-G bonding plug that can be used to add an N-G bond to a generator that does not have one.
Like I said before, you plug this into one socket of the generator to create an N-G bond.

Ok. I actually have a grounding rod that I haven't installed. I can get on it though.

I just added that plug to my cart. Thanks.


Thanks for the input everyone. It's working fine. But I want to make sure I'm doing it ok so no problems arise.
 

FilterGuy

What, me worry?
BTW: If you want to learn a bit more about grounding, you may want to look at the series of 4 papers I put up in the resources section. The first one his here and has links to the others:
 
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