Parallel PIP5048MK's are tripping house RCDs

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GoneDiving

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Jan 17, 2020
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I have just connected my second PIP5048MK in parallel using the OEM parallel board and cables to find that whenever the Utilities mains is connected my house RCD trips.

I originally had one 5048MK connected direct to the mains to charge and test the batteries and had no problems. It's only after installing the parallel inverter that I now have issues.

Are there any special earthing requirements or settings to parralel units?

To my knowledge, all wiring is as per the manual.
Utility mains is being connected to the inverter at a 15a powerpoint.
House RCD trips immediately upon connection
Both inverters continue to work when RCD trips.
The only error message is #04, low battery voltage. 51.0v
230vac output works fine.

Am I missing something?
 

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Roland W

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Did you connect all wires before! the RCD? As well the neutral is not used from behind the RCD? Where is the G-N bonding in regards to the inverter feed in point, etc. You cannot feed in after a RCD...

On that photo, where is the connection to your house? As it is there, it is totally isolated from your house, isn't it?
 
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GoneDiving

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Thanks. I've wired the AC Input Active, Neutral & Earth to a normal house GPO ie after the RCD.

My understanding is that when the 5048MK sees an incoming AC current it opens the internal G/N bonds on both inverters to make use of the house's at the switchboard...?? I suspected that the house RCD is being triggered as there is an internal inverter G/N link.

It's strange that the same GPO/RCD etc worked when I was only using one inverter to charge the battery.

For completeness, the intended use is in a boat, essentially off grid with solar providing the vast majority of the battery charging & inverted power. Should this run low, then I would resort to onboard genset or shore power. The genset doesn't have a internal RCD ( there is one downstream in the vessel's distribution board), shore power does have an RCD before the power outlet that I would use.

Thanks
 

Roland W

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Well, If your inverter is only using Grid to supply its AC charger, you should be able to plug it in at an outlet behind a RCB as it is just a normal load. But the OUT side of the inverter and its panel behind, must be fully isolated from the Grid, including N and Earth if it comes via an RCB. There is no such a thing like internal bonding in a inverter. That is intentionally left out to be done outside according code. That's why it is essential to use Transfer switches in case there is a hand over between Inverter and Grid for a Sub-panel.
On your boat, you will have to provide Earth and make a G-N bonding by yourself!

Maybe this of my videos can help to clarify things a bit...

 

GoneDiving

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Jan 17, 2020
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Thanks Roland

For everyones reference, I've attached messages to&from PIP.

Cheers

"Hi,

Is there a Neutral/Earth bridge within 5048MKs? If so, is the link automatic (depending on conditions) or configurable?

I have two new 5048MKs wired with parallel kits. When AC IN is connected to a power supply downstream of a RCD, then that RCD triggers immediately upon connection. When AC IN is connected to a supply with no RCD the inverter operates normally. Everything downstream of AC OUT works as expected.

Intended use is on a boat with the primary power source being solar panels. Backup supply is either shore power (with a RCD) or 3kva genset (no RCD)."

Reply:

"The inverters are not electrical appliances and they cannot sit downstream of an RCD. Any RCD protection must be after the inverter on the AC OUTPUT or load. Yes, the Neutral and Earth are bridged inside the inverter, this is a physical constant bridge.

Household RCD's are different than those found at shore power sites on marina's. "
 

Cheap 4-life

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I think I read somewhere that some inverters including some pip-mpp do internal switching of the neutral to ground connection. This enables the inverter to disconnect its neutral ground bond when the grid is connected
 
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GoneDiving

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I think I read somewhere that some inverters including some pip-mpp do internal switching of the neutral to ground connection. This enables the inverter to disconnect its neutral ground bond when the grid is connected
Yes.

A similar reply regarding their MPI models:

"sorry for the late reply. there's a menu in the monitoring software SolarPower that can adjust this.

In Solarpower under setting “Shorten N/G relay in battery mode” if it is “Enable.”

If “Enable”, inverter will short N/G in Batter Mode(Off-Grid) and open N/G if out of Battery Mode.
If “Disable”, inverter won’t short N/G under any Mode.



Should you have any other questions please feel free to ask. thank you"
 

Cheap 4-life

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Yes.

A similar reply regarding their MPI models:

"sorry for the late reply. there's a menu in the monitoring software SolarPower that can adjust this.

In Solarpower under setting “Shorten N/G relay in battery mode” if it is “Enable.”

If “Enable”, inverter will short N/G in Batter Mode(Off-Grid) and open N/G if out of Battery Mode.
If “Disable”, inverter won’t short N/G under any Mode.



Should you have any other questions please feel free to ask. thank you"

So in one reply they say it’s a physical constant bridge. In the other reply they say it can be enabled-disabled. Which is it
 

GoneDiving

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So in one reply they say it’s a physical constant bridge. In the other reply they say it can be enabled-disabled. Which is it
Different models.

Unfortunately, for other reasons, Ive got the MKs with fixed bridge. If it becomes a problem I can always open the case, find it and insert a contactor. Buy it's not an issue yet
 
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