MPP LV6548 Ground/Neutral Safety?

[Tetawon]

I understood that the MPP LV6548s were manufactured for compatibility with the US 240Vac Split Phase standards, until I found this post on youtube:

This homeowner DIYer only has Neutral bonded at his Mains panel, but metering ground loop voltage/current when the LV6548s are in Utility Mode. Seems these Inverters are bonding N & G when "utility" is prioritized. I was going to order 4 LV6548s....anyone else experiencing this? Thanks!

 

[Lt.Dan]

I have it in writing from MPP solar stating the neutral ground bond is only active when inverting from solar/battery. When bypassing power from the grid, it will disconnect the neutral/ground bond

 

[Tetawon]

I have it in writing from MPP solar stating the neutral ground bond is only active when inverting from solar/battery. When bypassing power from the grid, it will disconnect the neutral/ground bond

Thanks for the reply! Seems the author of the youtube link I shared has the exact opposite situation. Is placing a neutral jumper conductor between the inverter's AC in/out N terminals is not a solution then, as was repeatedly recommended for the LV5048?

 

[timselectric]

With the meter in that location, it has nothing to do with the inverter n/g bonding. He's got a problem with his downstream wiring.

Edit: I'm assuming that this is the sub panel that he's testing at.

 

[Tetawon]

I just got off the phone with Watts247. The tech there said there IS a bonding screw within the LV6548s that needs to be removed for US split-phase 240 operations, when using grid bypass....same as Growatts, so not truly US or UL out of the box.

Seems that removing the bonding screw within the inverters, and jumpering AC In/Out Terminal Neutrals will solve the issue. Followed up with email and will share any written reply.

Paul West
Thu 3/3/2022 1:21 PM


To:

• sales@watts247.com

Hi,

I just got off the phone with your tech there. He said there IS a bonding screw within the LV6548s that needs to be removed for US split-phase 240Vac operations, when using grid bypass (Utility Priority setting), and that this won't invalidate the warranties. Can you provide either schematic or drawing of the exact location of the bonding screw? I wish to order 2 sets of your dual LV6548 inverters, need to need to know this first.

Others are experiencing ground loop current from these inverters and posting such on YouTube and DIY solar forums. It seems that the LV6548s have no issues when supplied by either solar or batteries. But when powered by Utility, the AC Output inverter panel terminals short N & G. This is not US/UL compatible!

Unless a special case (separately derived system as defined by the NEC), only the initial mains panel can be the single neutral to ground bond point. If I can remove the bonding screw (knowing exactly which one), then placing a jumper conductor between the inverter's AC In/Out Neutral terminals will then properly function within a US 240Vac split phase configuration.

Paul West

 

[timselectric]

Interesting

 

[Lt.Dan]

Amazing the different information you can get, this is from Andy at MPP Solar directly:

Hi Daniel

Due to the original design of this unit, when this unit works in battery mode, the N-G terminal of AC output will be short. When this unit works in the line mode, the N-G terminal will be open. Thank you.
Best regards,
Andy Y. ¦ Support Team, MPP Solar Inc.

 

[12VoltInstalls]

FYI
mpp solar; USA Mpp Solar & watts247 are two different things

I think I’d lean in the watts247 direction for accurate info.
Other people explaining what they clearly don’t understand to someone who doesn’t know either seems a dubious task

“Due to the original design of this unit, when this unit works in battery mode, the N-G terminal of AC output will be short. When this unit works in the line mode, the N-G terminal will be open.”

^^^this seems to indicate it’s fine

 

[timselectric]

Amazing the different information you can get, this is from Andy at MPP Solar directly:

That's how these are supposed to work. lol

 

[timselectric]

FYI
mpp solar; USA Mpp Solar & watts247 are two different things

I think I’d lean in the watts247 direction for accurate info.
Other people explaining what they clearly don’t understand to someone who doesn’t know either seems a dubious task

That's why I opened mine up and made it work the way it should. Now, I sleep peacefully at night.

 

[Tetawon]

Amazing the different information you can get, this is from Andy at MPP Solar directly:

The he/he said honestly sux! Hoping that a forum member that actually has an LV6548 split phase system installed will switch to utility bypass, place a clamp meter on their ground conductor, and advise of the findings (assuming the N & G are only bonded in their Mains panel at service termination).

 

[timselectric]

I find it hard to believe that a split phase inverter isn't set up correctly.

 

[Lt.Dan]

I have 2 set up in split phase ill check tonight

 

[Lt.Dan]

Just confirmed 12a on the Neutral and .1a on the Ground conductor. It works as advertised.

 

[timselectric]

Testing at the main panel?

 

[Lt.Dan]

Thats at the panel right after the inverter. Should I check it at the main panel?

 

[timselectric]

Yes
You have to test it before the inverter.

 

[timselectric]

n/g bond loop happens between the two n/g bonds.

 

[timselectric]

When the neutral is bonded to ground in more than one place.
Current travels on the ground between the two points.
The current is shared between the neutral and the ground wires.

 

[Lt.Dan]

At the main panel:

Neutral:



Ground: