MPP solar neutral to ground bond is doing both of my brain cells in.

[pablo131]

Hi Guys and Gals,
I have a problem here in the uk with my 240VAC system. As you can see from the pictures, I tried to solve the neutral ground bond problem when running on solar and/or batteries by using a transfer switch. Could you gurus please cast an eye over my setup to see where I have failed. The system is working well but.... when on solar/batteries, I have no earth according to the socket tester. I can measure 105VAC between neutral and earth and 122VAC between live and earth. The output is 240VAC give or take 2 volts. All is good when (earth is there on the socket tester) running on mains, either through the MPP or direct. I have an earth.
My MPP system only supplies a few select items and does not back feed to the main consumer unit (panel) I only use the grid power to feed the MPP when solar and power is exhausted and the grid also feeds the transfer switch. I thought the internal changeover relay inside the MPP would autobond the neutral to earth when running on solar/battery. It looks like it partially does it as the earth indicator on the socket tester is faintly alight some of the time and the 30mA Residual Current Device RCD protection (in the critical load consumer unit) trips when I push to test

My background was as a marine radio/radar tech and ROV plough pilot technician so I am not completely thick.

 

[pablo131]

bump

 

[mikefitz]

See,

MPP LV6548 Ground/Neutral Safety?

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...

diysolarforum.com

There may be more useful info with an Internet search

If the diagram you posted of the MPP Internal relay is correct, there should be no volts on the 'neutral'

The test button on the RCD only confirms the unit mechanically functions with a resistor simulating an unbalanced flow. It does not confirm the unit will trip in your system under fault conditions.( it won't trip without earth or neutral bonding.)

Mike

 

[pablo131]

See,

MPP LV6548 Ground/Neutral Safety?

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...

diysolarforum.com

There may be more useful info with an Internet search

If the diagram you posted of the MPP Internal relay is correct, there should be no volts on the 'neutral'

The test button on the RCD only confirms the unit mechanically functions with a resistor simulating an unbalanced flow. It does not confirm the unit will trip in your system under fault conditions.( it won't trip without earth or neutral bonding.)

Mike

thanks Mike, I am nearly there. I am suspecting that the MPP internal relay is not making a good connection between neutral and earth when in battery/solar inverting mode. Will keep digging and then throw the question at MPP. Cheers, for the info

 

[pablo131]

I have thrown the question to MPP,..... still waiting an answer. In the meantime, i have been rubbing both my braincells together......would this work. The transfer switch has some passive contacts. see pics.

 

[Casper1234]

Hi, I know your post was some time ago but we have the exact same issue and in the UK. Did you ever get a resolution and find out how to fix the problem with the Earth issue?

 

[pablo131]

Hi, I know your post was some time ago but we have the exact same issue and in the UK. Did you ever get a resolution and find out how to fix the problem with the Earth issue?

Hi, yes I did. See below the reply i got from James MPP

Hi Paul

By design the 2524GE does NOT come with a N-G ground screw, which means under battery/solar mode, output N-G will not bond and so it will behave per original design to be "floated". This is why you will measure a differential between N-G and this is perfectly normal. Reason N-G screw is not added on all the models is that some customers prefer dealing with N-G bond at the load distribution panel side by themselves, so in that case they will need to remove the screw.

Some models come with N-G screw by default, and when this happens:
1. LINE MODE -- N-G output will remain open, letting the AC mains panel decide (which should be closed anyway).
2. BATTERY MODE -- N-G output will bond (closed).

If you require the N-G bond feature, simply add a screw at the following location, marked in BLUE, on MAIN BOARD and this should resolve your problem.

to get at the board:-

PIP1212GE & 2524GE disassembly guide 20220402.pdf

drive.google.com

 

[Casper1234]

Thank you so much for your help and reply, much appreciated as it has been worrying us?