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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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
 

calida82

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Hi, I have a Syrio Power SI5000MKS II inverter which is like a Pip 5048MG, the inverter is downstream of a 0.3A domestic RCD and it worked like this for 2 years without any problem, two weeks ago at night the power went out, I don't know if it is due to my power supplier or the occurrence of error 08 which caused the inverter to restart, after restart when the inverter tries to bypass so the RCD jumps.
Have you solved the problem?
 

GoneDiving

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.Have you solved the problem?
I didn't worry about it as I only wanted to plug the inverters in once to commission and charge the battery pack. It's for a boat that will very rarely be plugged in to a mains socket.

Note that when I initially used one 5048 it did work as a charger while downstream of the RCD. It was only after I added the second unit in parallel that it tripped the house RCD. As I said, I haven't investigated further as it's a problem I don't need to fix.

Perhaps read some of the previous posts and see if the info on neutral earth bridging is applicable to you.

Good luck
 

Roland W

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Hi, I have a Syrio Power SI5000MKS II inverter which is like a Pip 5048MG, the inverter is downstream of a 0.3A domestic RCD and it worked like this for 2 years without any problem, two weeks ago at night the power went out, I don't know if it is due to my power supplier or the occurrence of error 08 which caused the inverter to restart, after restart when the inverter tries to bypass so the RCD jumps.
Have you solved the problem?
In general, all those generic PIP units do not have a N-G bond. Its only some models which do come with a Bonding Relay which can be set in the UI as described in previous postings.
It is easy to check if there is a connection between N and G by measuring the resistance between those two terminals, but you will find, there is as well not OL there. This is because of a measuring circuit from the PIP monitoring the two lines.
I personally would not install a Power Generator downstream of a RCD, as such internal monitoring circuits do cause a permanent leakage current to flow and thus it works at all, may only take a bit extra leakage to trip the upstream RCD. You must treat the Inverter equal to any other Power Source and keep it as an upstream device, protected by Over Current Devices embedded in a general distribution setup between all possible other Sources you are mixing together there...
 

GoneDiving

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My information from the manufacturer is that my MK model does have a fixed bridge. Again it's not a major concern for me but if it becomes one, I'll consider installing a MEN and manually open and close the bridge as required.

Does anyone know if the bridge is a removable busbar (that can be replaced with a switch) or is it incorporated into circuitry?
 

calida82

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In general, all those generic PIP units do not have a N-G bond. Its only some models which do come with a Bonding Relay which can be set in the UI as described in previous postings.
It is easy to check if there is a connection between N and G by measuring the resistance between those two terminals, but you will find, there is as well not OL there. This is because of a measuring circuit from the PIP monitoring the two lines.
I personally would not install a Power Generator downstream of a RCD, as such internal monitoring circuits do cause a permanent leakage current to flow and thus it works at all, may only take a bit extra leakage to trip the upstream RCD. You must treat the Inverter equal to any other Power Source and keep it as an upstream device, protected by Over Current Devices embedded in a general distribution setup between all possible other Sources you are mixing together there...
hi, my inverter has a double throw relay which connects neutral to earth when it is in island mode or off. I checked the diagram above the relay, its datasheet and I made measurements with a multimeter. when it is isolated I have continuity between earth and neutral in output.
I don't find it normal to have ground despairs, my inverter has been working under a 0.03A differential for a long time. I had to mount a 0.3A differential because when it rained the differential would jump. since I mounted the 0.3A one it hasn't jumped even under the flood until 2 weeks ago. despair is not normal. there is because something has gone wrong. I tried to change this relay with one of similar characteristics (not the same) and now my differential no longer jumps when it enters bypass, but now it jumps when it returns to the island ...
I checked the instruction booklet of my inverter, the parameter you are referring to is 38, but I think it does what you think. in my manual that relay (setting 38) refers to the Nc / No relay which has green outputs next to you have PV cables and is used to connect a grounding box. this is what my manual says. unfortunately my firmware has been updated and now I don't have that setting anymore. someone has some shred of wiring diagram regarding the relay that connects neutral / earth?
 
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