trevor4321 avatar image
trevor4321 asked

MultiPlus II GX blows 30A breaker

This is a new sysyem for ESS comprising MultiPlus II GX 48/5000/70-50, 3 Pylontech US2000C batteries with an external current transformer on the grid input.

Initially powers up fine, no batteries connected yet.

Clunking, relays?, from the MultiPlus. Display is showing the grid power, obviously batteries are showing low voltage because BMS not connected.

Connect batteries, more clunking, battery voltage now reading OK, about 49.3V. But have lost grid monitoring display says AC Disconnected also error #15 comes up. Says it's in ESS 3,4,5. After a little while longer more clunking and the 30A breaker trips out.

I have limited power on both charge and discharge to 3KW.

I have also tried running it in charger mode with the same result.

Only happens when batteries connected, runs for days if not.

I have been in touch with the supplier 3 weeks ago but they are not being very pro-active.

I am wondering if there is something wrong inside or has anyone else got any suggestions.


multplus 2 gx
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3 Answers
Alexandra avatar image
Alexandra answered ·


First of all. The battery is meant to be connected before anything else. It is a battery based system.

See the manual. It is the first thing that is mentioned.

Second. Low battery is because it is not programmed correctly, or the battery is tripping. Not because there are no comms.

Follow the guide.

Third. Probably blowing/tripping a 30A breaker (i assume you mean AC) because the default input current limit is 50A. Again points to programming. Unless you have a wiring issue? Or because of the inrush for precharging the inverter.

ESS 3, 4 & 5. Are BMS related. And temperature related.

VE Bus error #15

You did not update system components, before commisioning or programming?

Also wanted to point out you need one more battery if they are us2000s to meet the minimum requirements of a 5kVa.

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Jason - UK avatar image
Jason - UK answered ·

@Trevor4321 do you have a schematic of your system? What do you have connected to the AC out's? Photos of the connections on your unit would be helpful.

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daza avatar image
daza answered ·

I would connect back to the grid and put a clamp meter on the house to make sure your demand is staying within your 30amp limit. You know that the 48/5000 has a pass through of 50amps is there a reason why you or your installer has gone down 20amps?

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trevor4321 avatar image trevor4321 commented ·

Starting from the top when I said about connecting batteries I meant the BMS cable, batteries are physically connected.

The VRM says both the MultiPlus and GX are up to date, don't know about batteries because it trips out too quickly.

AC outs are not used, purely a self-consumption system.

There are 3 batteries at the moment, charge and discharge power is programmed to be 3KW each way. This should be within the limit of 25A per battery.

Schematic and pictures of MultiPlus connections and battery connections attached.



I also tried the charge mode and the breaker tripped as before.


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trevor4321 avatar image trevor4321 commented ·
I did try powering up the system with the BMS connected, it took the breaker out after about 5 mins.

Also display said AC disconnected, no indication of what is being used from the grid when the battery BMS cable is connected.


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nicles avatar image nicles trevor4321 commented ·

Hi Trevor, what kind of breaker are you using?

1/differential circuit breaker

2/thermal circuit breaker?


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trevor4321 avatar image trevor4321 nicles commented ·

It's a standard UK DIN rail breaker which I believe are a combination of magnetic and thermal, curve B which is short to medium tripping time, allows for short term overloads.


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daza avatar image daza trevor4321 commented ·

Can you take a pic of the earthing arrangement from the DNO and where your new earth or earth bond relay is? Is it just an MCB or RCBO? Whats your electrician saying?

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