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Leakage current on installations with solar

JohnE

I have been looking at a domestic installation that has solar and batteries

The solar and battery (Solar edge and Fox ESS ) are on their own sub board via henleys
The main house circuits on a split load board.
 
The leakage current is very high on the tails of the main board, round 350mA up to 700mA
With everything isolated, no leakage.

With solar all off and isolated, and the main switch of the house CU on, but no circuits energised,
I get a bump in leakage of about 15mA
When I switch on individual MCBs, I get a leap of about 100mA on some circuits and 40mA on others
with all house circuits on, but no real current draw,(nothing switch on)
I'm up past 700/ 800mA and it fluctuates up and down rapidly.
 
I thought about disconnecting the isolated solar boards main earth, but as I know little about solar
I do not want to start disconnecting anything really.
 
With isolated solar, can you still get leakage from it, which can find its way onto
the rest of the installation, and as circuits are closed, the leakage increases.
More parallel paths?

Any advice would be appreciated. Thanks
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  • +1
    JohnE said:
    When I switch on individual MCBs, I get a leap of about 100mA on some circuits and 40mA on others
    with all house circuits on, but no real current draw,(nothing switch on)
    I'm up past 700/ 800mA and it fluctuates up and down rapidly.
     

    I think that I am about as confused as you are.

    If nothing is switched on, where is the current flowing?

    One possibility is FCUs (with the appliances' functional switches open), but surely not on every circuit.

    If the leakage occurs when the solar is isolated (with a 2-pole switch), I cannot see how it can be relevant, so perhaps forget that it is there for the moment.

  • 0 in reply to Chris Pearson
    Chris Pearson said:
    isolated (with a 2-pole switch)

    Is it necessary to disconnect the neutral in a TN system?

  • +1 in reply to gkenyon

    Like the OP, JohnE, I claim no expertise in solar tackle.

    My understanding is that  a 2-pole switch is usually provided. If not, the possibility of a N-E fault in the solar tackle is not excluded.

  • 0 in reply to Chris Pearson

    Thanks Chris, I feel a little better knowing that others are not sure .

  • 0 in reply to gkenyon
    gkenyon said:
    Is it necessary to disconnect the neutral in a TN system?

    It is for main switches in household or similar for single phase supplies - 462.1.201 (even if as in this case we seem to have two "main switches").

      - Andy.

  • 0 in reply to JohnE

    when you measure the 100mA plus of leakage, how exactly are you measuring it ? In the sense which conductors is your meter embracing or connected to ? And is this a board with lot of RCBOs, one per circuit, or one big RCD per group, or something else.?

    If L and N really were that far out of balance, by they reached an RCD, I'd expect things to trip - so something is wrong.

    Mike.

  • 0 in reply to mapj1

    Its a 16th edition board, so sockets and such on the RCD and lighting on the non RCD side.
    I started by clamping onto the tails of the main board L-N 
    This was with the installation fully energised, and got the high reading.
    So I shut down Solar first (Own board)  Still high leakage. Then individual MCBs on the main board.
    Gradually came down to zero with all off and main switches open
    Close the main switch to the house CU and already 15mA with all MCBs open
    Close any MCB RCD side or non RCD side  and I get a leap of 100mA or 40mA per circuit



  • 0 in reply to JohnE
    JohnE said:
    Close any MCB RCD side or non RCD side  and I get a leap of 100mA or 40mA per circuit

    if the RCD is working correctly (i.e. trips at no more than 30mA?)

    If so and the RCD isn't continually tripping then the fault must be on non-RCD side. A N-PE fault could give those symptons - provided each of the circuits had some load connected (not a massive load, but something - a few tens of watts perhaps) - switching them on then increases the N current, hence raises the N voltage a little at the CU due to voltage drop in the supply which then pushes more current across the fault. Could be aggrivated if there was an extra impedance in the N somewhere (e.g. loose connection) - worst case if the N was entirely open circuit and all the N current was finding its way back via the fault.

      - Andy.

  • 0 in reply to JohnE

    CU and already 15mA with all MCBs open 

    Right, the only way that is possible is if you have a neutral earth leak between two objects either within the board before the RCD, or assuming the RCD is not defective,  on one of the branches on the non RCD side.. (a fault on the RCD side is not possible, unless the RCD is busted...)

    Note that unlike the latest compact RCBOs MCBs don't break the neutral, so this path is present even when the MCB is off..

    By having a second N-E path in parallel with the one that the DNO provides, the neutral current is split, most of it going down the low resistance meter tail of course, but a resistance dependent fraction going the other way and returning via a mixture of CPCs and bonding to plumbing etc, so when the balance is measured, the neutral tail is missing a few electrons relative to the live one.

    Even when no load is applied, note that the supply neutral may be a few volts off true earth  and also relative to any shared metal plumbing etc, due to the voltage slope in the street cables from the neighbour's loads, (the neighbours presumably share metal mains services, so current can dive down the plumbing and take a shortcut, rejoining the neutral at a house nearer the substation, )So even when you dont have any  loads, that street voltage offset drives a small current through that NE fault 

    Buzz NE in the box with the mains incomer off, so the ohm meter should not see any NE bond, and let us know what you find,

    regards Mike.

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  • 0 in reply to JohnE

    CU and already 15mA with all MCBs open 

    Right, the only way that is possible is if you have a neutral earth leak between two objects either within the board before the RCD, or assuming the RCD is not defective,  on one of the branches on the non RCD side.. (a fault on the RCD side is not possible, unless the RCD is busted...)

    Note that unlike the latest compact RCBOs MCBs don't break the neutral, so this path is present even when the MCB is off..

    By having a second N-E path in parallel with the one that the DNO provides, the neutral current is split, most of it going down the low resistance meter tail of course, but a resistance dependent fraction going the other way and returning via a mixture of CPCs and bonding to plumbing etc, so when the balance is measured, the neutral tail is missing a few electrons relative to the live one.

    Even when no load is applied, note that the supply neutral may be a few volts off true earth  and also relative to any shared metal plumbing etc, due to the voltage slope in the street cables from the neighbour's loads, (the neighbours presumably share metal mains services, so current can dive down the plumbing and take a shortcut, rejoining the neutral at a house nearer the substation, )So even when you dont have any  loads, that street voltage offset drives a small current through that NE fault 

    Buzz NE in the box with the mains incomer off, so the ohm meter should not see any NE bond, and let us know what you find,

    regards Mike.

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