Solis 3G 3.8k AC Backup Earthing UK

[MSRConf]

I have a Solis 5G 3.8K Grid Tied, in the UK, with an AC backup connection, 10KWH of Batteries and 5KW East west facing Solar, all working just fine. The AC backup wasn't wired to anything. As the Inverter, batteries etc are all in the Garage they are literally about 3 feet from our Fridge freezer, which uses about 2.5KWH per day.

The fridge is really the only thing I'm concerned about in the event of a power outage, so wired in a 4 way extension block, to the AC backup, Positive, Neutral and Earth all correctly wired. Adjusted the config on the inverter, then shutdown the house supply and yey the fridge is still working. Sounds good so far, but having seen a post about the correct way to do this, with a separate distribution panel and separate earth, I plugged in a socket tester that tells me the extension block is fine but has no earth. I have unplugged the fridge, moved it back to its original socket and made everything safe.

So the question is does it need an entirely separate earth from the rest of the house ? If so, to improve my knowledge base, why would that be ?

 

[SeaGal]

I plugged in a socket tester that tells me the extension block is fine but has no earth.

This is as expected.

So the question is does it need an entirely separate earth from the rest of the house ? If so, to improve my knowledge base, why would that be ?

First of all, I'm not a sparky... have Solis inverters though!

The reason is that that when there is AC-Grid power, the Solis AC-backup port is connected to the grid and hence will receive L, N and E from the grid connection.

When the AC-Grid connection is disconnected, depending on your existing house 'searthing arrangements you are likely not to have an earth connection. Specifically that would be the case with the most common TN-C-S arrangement. So, when using the AC-backup connection in a power outage situation, you will need to provide your own earth, such as an earth rod to effectively implement a TT earthing arrangement. If you are already rural with overhead cables, your house may already have TT earthing. Either way it will be necessary to bond the backup supply's N with your PE and add an RCB in the supply line to your equipment _unless_ the only equipment you are attaching to the backup supply is double-insulated devices which don't require a PE.

The other thing to be aware is that the Solis 3.6kW inverter can only provide 3kW via battery alone before tripping and inductive loads will draw more on start up - so you should be OK for one or two fridges, but 3.6kW Solis wouldn't start up 4 fridge / freezers simultaneously - had to switch them on one at a time.

 

[MSRConf]

This is as expected.


First of all, I'm not a sparky... have Solis inverters though!

The reason is that that when there is AC-Grid power, the Solis AC-backup port is connected to the grid and hence will receive L, N and E from the grid connection.

When the AC-Grid connection is disconnected, depending on your existing house 'searthing arrangements you are likely not to have an earth connection. Specifically that would be the case with the most common TN-C-S arrangement. So, when using the AC-backup connection in a power outage situation, you will need to provide your own earth, such as an earth rod to effectively implement a TT earthing arrangement. If you are already rural with overhead cables, your house may already have TT earthing. Either way it will be necessary to bond the backup supply's N with your PE and add an RCB in the supply line to your equipment _unless_ the only equipment you are attaching to the backup supply is double-insulated devices which don't require a PE.

The other thing to be aware is that the Solis 3.6kW inverter can only provide 3kW via battery alone before tripping and inductive loads will draw more on start up - so you should be OK for one or two fridges, but 3.6kW Solis wouldn't start up 4 fridge / freezers simultaneously - had to switch them on one at a time.

Ahhh now that makes sense, many thanks !