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djdemond avatar image
djdemond asked

UK ESS Multiplus-II 48/5000/70-50 RCD tripping - Ground relay clarification

I am setting up an ESS attached to the UK grid in my home. The battery has not yet been connected but will be a self-built 2S16P LiFePO4 system with 250 amp Daly BMS.

I am just testing things so far. The battery pack is not connected yet.

The only connections to the inverter are AC out 1 mains which is connected by a 4mm2 twin and earth to a small consumer unit with RCD and 2 MCBs, then back via that unit to my main consumer unit. Also, USB mk3 adaptor going to either a Raspberry Pi running venus OS, or to a tablet PC with VE configure.

Initially, I made an Earth link cable from the AC-1out Earth to the chassis earthing point inside the inverter but this instantly tripped the house RCD when power was connected. I removed that.

I have read the wiring unlimited guide and can see the purpose of the ground relay in off-grid and especially mobile systems where there is no guarantee that there will be a neutral-to-earth bond anywhere. However, in a stationary grid-connected system, there is always a neutral-to-earth bond by the utility so the unit never needs to connect the neutral to earth it will always trip the rcd.

I could turn the ground relay off in ve configure but when I set UK country code, this option ceases to be available. When I connect the power the unit closes the ground relay and the rcd trips.

Any ideas? In order to configure it I presently do not have the earth connected to the inverter - not ideal.

Is this anything to do with the battery being absent?

ESS
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4 Answers
Alexandra avatar image
Alexandra answered ·

@DJDemonD

The Victron is a battery referenced system.

Not designed to work without one attached.

Suggest waiting until it can be set up and configured fully before thinking there is some deep issue.

The ground relay internally only activates when there is no grid present. See the block diagram in the manual or here.

The action of the ground relay is described here.


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djdemond avatar image
djdemond answered ·

Thank you. I will wait until I have some batteries attached before proceeding. They are on the slow boat from China. Thanks for taking the time.

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pau1phi11ips avatar image
pau1phi11ips answered ·

Although I use a Daly in my van. I wouldn't recommend it as it can't balance big batteries. The 250mA balance current does nothing.

This driver will allow you to see the details from the Daly in Venus though: https://github.com/Louisvdw/dbus-serialbattery

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djdemond answered ·

Thank you. I will use active balancers if required.

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pau1phi11ips avatar image pau1phi11ips commented ·
If you've got a BMV, you can use the relay to only turn it on at a high state of charge. You don't want it balancing all the time.
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