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philipv avatar image
philipv asked

multiplus 48v 3000 50amp output earth and neutral bond

hi looking for some advise after installing a multiplus into my total offgrid house, with no generator ( yet) having issue's with earth and neutral relay, my multiplus is before the house switchboard with rccbs fitted, i have tried grounding the ac INPUT as per manual and tried both positions on the number one dip switch open and closed ( position n appendix b).

i have also tried removing the multiplus housing earth also the link pins between earth and neutral buzz bars in the house switchboard but ever time a slight load comes it trips RCCB, the house lights, fridge freezer etc are all fine but as soon as u go to use anything else even a cordless drill charger it trips. also have had new RCCBS fitted and whole house checked by a qualified sparky. who saying it must be issue with inverter and then left after leaving a large bill.

is there any anything else to external to try as losing hair at a great rate !!!!

thanks for your time

MultiPlus Quattro Inverter Charger
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5 Answers
wkirby avatar image
wkirby answered ·

It's a pity your sparky has run off because we really need him around.
If you can forgive me, I'm going to explain some technical things which are necessary to help you understand how earthing systems work. Please ignore me if you already know this.
Being totally off-grid would most likely mean that you have a TT earth system. This basically means that you have to provide your own earth reference for your electrical installation. A TT earth system should comprise of at least one long earth rod which is hammered into the ground. You connect the earth of the MultiPlus and the earth of your installation here. The Neutral and the Live come out of the MultiPlus and go into the consumer unit. You have Live, Neutral and Earth going into the consumer unit.
Neutral is derived as being the side of the output transformer that is connected to the chassis and down to Earth. The N-E relay closes and makes this connection.
This is important for making RDC's work. Power goes through the RCD on live, through the load and back via neutral through the RCD and back into the transformer. The RCD is happy as long as the current going through it's live and neutral are the same. If they are not the same, then it assumes that the power has gone back to the transformer another way - via the earth wire and this causes it to trip.

So, the MultiPlus is correctly performing the Neutral - Earth bond. There should not be an N-E bond anywhere else. You MultiPlus is correctly positioned at the head of the installation.
So, has your sparky installed the earth rod correctly? Is there a good bond to it and to the earth buss bar in the consumer unit? If this is all done, then your sparky shouldn't be afraid just because the energy provider is bit different. The MultiPlus is just a transformer, just like the one up the street in a urban setting. From a wiring standpoint, the system needs to be regarded as a TT earth system. The consumer unit should be wired according to current standards and regulations and if it doesn't work, then there is a wiring fault somewhere in the consumer unit or house.

Try switching off all circuits in the consumer unit and then try introduce them one at a time to isolate the fault.
Get your sparky back in to fix the fault you contracted him to in the first place.

Edit: This sparky explains earth systems very well. Make yourself a cup of tea.

https://www.youtube.com/watch?v=AWxeb2MI37c

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philipv avatar image philipv commented ·

hi Wkirby,

thanks for the reply, yes even put a extra 6ft earth in and linked the two together, but did you say the multiplus earthing stud /chassis should go Neutral ? ( not the ground wire) as at the moment it is linked to the earth.

i just checked switch board and pushed the test button on RCCB and it didnt trip as it should . even with disconnecting the output from the RCCB before hitting the mcb's. so the house side disconnected after RCCB.


should the ac INPUT ground wire be connected to ac OUTPUT ground wire ?

what position should the dip switch be in ? as changing position i can hear a relay click over.

thanks for your help .

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philipv avatar image philipv commented ·

hi Wkirby,

thanks for the reply, great video, yes even put in a extra 6ft rod and linked both together, you mention that the chassis should be connected to neutral, does this mean the chassis/ box of the multiplus should be connected to neutral?

going back to basics , should the AC INPUT ground be connected to AC 1 OUTPUT ground be linked ?

what position should the dip switch 1 be in ?

next to the dip switch for the ground there is a socket with + and - for a external ground relay is this used or should be linked ?

after disconnecting output from the Rccb so no house wiring connected it appears that pushing the test button on the new Rccbs does NOT trip unit. tried reconnecting and test button still not working.

so its looking at upstream from switchboard?

almost time to test the strength of the walls by banging ones head against it !

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philipv answered ·

sorry should also mention that i'm in N / Zealand where we use the MEN (multiple earthed neutral) system . ie the neutral and earth buzzbars are linked by a removable pin inside the switchboard

reading through the manual it says the multiplus should be able to decide if the automatic bond is needed.

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Rob Duthie avatar image Rob Duthie commented ·

Do not remove the Neutral - Earth link in a switch board it very dangerous under the NZ regulations to do so!!!

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philipv avatar image philipv Rob Duthie commented ·

Hi Rob, it was only while checking but if the automatic relay works as it should then it should be ok as mutiplus links them maybe????

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Rob Duthie answered ·

It must never be disconnected under any circumstances, under current Electrical regulation this MEN link is called high risk work, and must be signed off by a Electrical inspector.

If you want help i can help but i will need to know the switch board layout and how many RCD's and installed for the loads that re supplied etc. Photos etc.

Note depending on the type of RCD used here type A they are could trip on any pulsed DC signals from certain appliances etc. which could be a issue when tied up with the inverter

and cause a harmonic signal which might trip under certain conditions.

Note i am based in Rotorua

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philipv avatar image
philipv answered ·

That would be greatly appreciated Rob. The sparky has checked the house with no issues on the output side of things. But showed me the switch board with only the master switch and one Rccb. The Rccb didnt trip using the test button with the inverter on. He tested the automatic bond link relay by removing Men link for checking only.the relay clicked in instantly combining earth and neutral And the Rccb still didnt trip with the test button with no connection after the Rccb. He tried 3 different makes and a few different models. . After removing Rccbs and testing house with only master switch and mcbs all power points lights tested fine. But of course illegal with out Rccbs what model Rccbs are you using ?

The current ones supplied with switch board are schneider 2pole 63amp with 30ma-a. Part number dom16696

Thanks

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Rob Duthie avatar image
Rob Duthie answered ·

Hi

So one RCB protecting all circuits? These days it is a maximum of three circuits to one RCD

as the leakage currents in the cable will trip a RCD if to many cables are placed on one RCD

to monitor, Did he test the circuits using a Fluke or similar power tester to test for RCD trip times and current ratings for leakage etc? Did he HiPOT test the insulation etc?

The RCD trip button should work with the inverter running?

I have just re tested with my Mulitplus2 Inverter changer unit all OK using a standard RCD unit

form Voltex eletrical.


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