MPP HV2-5048 Earthing of output

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TyTower
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MPP HV2-5048 Earthing of output

Post by TyTower »

MPP HV2-5048 Earthing of output

I have this inverter on a 48v battery and producing 240 volts A/C.
Its wired up normally as is the 240v A/c output but I ran the output through a RCD first then to the outlet plug. All the earths are connected up to each other BUT I have not yet connected the main earth to the ground peg.

Before doing so I ran the inverter and measured the A/C voltage from the unconnected earth to the earth ground peg proper and found it had a 48v A/c potential.

Is this correct? Is it how it should show at this time ?
Or is that telling me something is amiss.?
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Re: MPP HV2-5048 Earthing of output

Post by coulomb »

TyTower wrote: Fri, 15 Jan 2021, 08:09 MPP HV2-5048 Earthing of output

I have this inverter on a 48v battery and producing 240 volts A/C.
...
Before doing so I ran the inverter and measured the A/C voltage from the unconnected earth to the earth ground peg proper and found it had a 48v A/c potential.

Is this correct? Is it how it should show at this time ?
This is a hybrid model, so I don't know much about them. If the AC input was connected to the mains at the time, then I would expect some voltage at the earth terminal. There are often small "Y" capacitors to earth from both live and neutral at the input and output of the inverter, so I'm surprised you didn't see more than 48 VAC at the earth.

So yes, this is expected, and you should connect the inverter earth to the house earth.
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Re: MPP HV2-5048 Earthing of output

Post by antiscab »

When testing potentials, did you use the meter in LOZ mode?

Otherwise you will be measuring with 1MOhm of meter resistance. 48v measured at 1MOhm suggests 4MOhm of isolation between the two
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Re: MPP HV2-5048 Earthing of output

Post by TyTower »

Firstly the inverter is not connected to the grid in any way.

Second I have no idea what the second post is about ?
What is LOZ mode?
I had the multimeter turned to 400 volts A/C with one probe on the joined up earth wires and one probe on the earth rod.
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Re: MPP HV2-5048 Earthing of output

Post by antiscab »

Fluke explains it better than I:
https://www.fluke.com/en-au/learn/blog/ ... ultimeters

I'm suggesting the 48vac difference measured is more a ghost voltage than anything to be concerned about. A cheap way to do it without a LoZ capable meter would be to put a light globe across as well. if there's no current available, the voltage will just fall to 0.

Are you operating with a MEN?
An RCD won't work without one (though you could use a RVD, though they're somewhat more expensive)
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Re: MPP HV2-5048 Earthing of output

Post by TyTower »

Dunno about ghost voltage . The way I found this was I touched the earth wire while sitting on a damp cement block and felt a definite tingle . Also if you would explain your Acronyms the first time you use them it would make it a bit easier to understand .
MEN?
I went searching and I guess this is what you meant . No I dont have neutral connected to earth in my Inverter or elsewhere as far as I know .
Should I have with this inverter?
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Re: MPP HV2-5048 Earthing of output

Post by antiscab »

Yep fair point
MEN = multiple Earth neutral

I would use one, though if the inverter doesn't like the neutral being connected to earth for some reason (some don't), then residual voltage detector it would have to be
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Re: MPP HV2-5048 Earthing of output

Post by TyTower »

antiscab wrote: Fri, 15 Jan 2021, 18:52 Fluke explains it better than I:
https://www.fluke.com/en-au/learn/blog/ ... ultimeters

I'm suggesting the 48vac difference measured is more a ghost voltage than anything to be concerned about. A cheap way to do it without a LoZ capable meter would be to put a light globe across as well. if there's no current available, the voltage will just fall to 0.

Are you operating with a MEN?
An RCD won't work without one (though you could use a RVD, though they're somewhat more expensive)
Didn't know of that as my 50 years of experience has mostly been with DC
Thanks for the post! There does not seem to be any other ways to say thank you on this forum.
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Re: MPP HV2-5048 Earthing of output

Post by paulvk »

An RCD measures the current in the neutral and active should the current become imbalanced by more than the RCD is set for it will trip,
so it will trip without an earth if their is enough parasitic current flow and sometimes this causes problems.
Also in the above diagrams having an earth stake at a sub board is rarely done the out buildings would have to be a long distance away
and doing so prevents you having an RCD up stream, with my inverters I only earth the neutral while the inverter is running
as the neutral and active are disconnected from generator/grid input in this mode I use a relay driven by the inverter dry contacts.
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Re: MPP HV2-5048 Earthing of output

Post by TyTower »

paulvk wrote: Sun, 17 Jan 2021, 05:53 Also in the above diagrams having an earth stake at a sub board is rarely done.... the out buildings would have to be a long distance away
and doing so prevents you having an RCD up stream,...... with my inverters I only earth the neutral while the inverter is running .......
as the neutral and active are disconnected from generator/grid input ......in this mode I use a relay driven by the inverter dry contacts.
I've put dots where I think you mean to stop but its not making full sense to me yet.
OK on the sub-boards . That has been my experience also but why does putting one on prevent an RCD upstream?
as the neutral and active are disconnected from generator/grid input
can you explain that bit for me please.

.
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Re: MPP HV2-5048 Earthing of output

Post by paulvk »

TyTower wrote: Sun, 17 Jan 2021, 06:01

I've put dots where I think you mean to stop but its not making full sense to me yet.
OK on the sub-boards . That has been my experience also but why does putting one on prevent an RCD upstream?

can you explain that bit for me please.

.
If there there is an earth on the neutral down stream from an RCD unbalanced current will flow as current will flow on the earth back to the MEN link so it will trip.

With my inverters they disconnect both incoming from grid/generator active and neutral when in inverter mode so the MEN link is no longer there
Note my inverters are the 4048 MS so no feed to grid you would have to check how your ones operate.
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Re: MPP HV2-5048 Earthing of output

Post by TyTower »

paulvk wrote: Sun, 17 Jan 2021, 10:44 If there there is an earth on the neutral down stream from an RCD unbalanced current will flow as current will flow on the earth back to the MEN link so it will trip.
Nope still not with it . Must be a bit thick . down stream meaning ?

If the inverter produced A/C goes through an RCD before the power points and the earthing has a neutral link where will current flow?
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Re: MPP HV2-5048 Earthing of output

Post by coulomb »

TyTower wrote: Sun, 17 Jan 2021, 14:40 down stream meaning ?
After the RCD (on the load side of the RCD).
If the inverter produced A/C goes through an RCD before the power points and the earthing has a neutral link where will current flow?
Your diagram does not show a neutral to earth link on the load side of the RCD. If there is, then some of the neutral current will flow through the earth, bypassing the RCD, causing an imbalance and likely causing a trip even though there isn't a life threatening fault.
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Re: MPP HV2-5048 Earthing of output

Post by TyTower »

OK I think I understand now thanks.
Downstream being from the viewpoint of power flowing in from the source -->load.

Of course that's not what my intention was anyway after the RCD but I guess if the plug outlet earth is joined to the earthing network as it should be then the RCD would operate correctly as it is shown above as no current flows to earth unless in a fault condition. Am I right in that?

Simple things can get very complicated and messed up in your head if you think about them too much..
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Re: MPP HV2-5048 Earthing of output

Post by coulomb »

TyTower wrote: Sun, 17 Jan 2021, 19:03 I guess if the plug outlet earth is joined to the earthing network as it should be then the RCD would operate correctly as it is shown above as no current flows to earth unless in a fault condition. Am I right in that?
Yes, exactly.
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5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
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Patching PIP-4048/5048 inverter-chargers.
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