Inverter tripping main RCD

[gustaff]

Installed a Solis 3.6 inverter and 4 kw of panels on garage roof had electrician install small cu to connect to house. Worked fine for a week, now wake up to tripped RCD in main cu, when I reset works fine for rest of day. Was I ott asking for RCBOs in small cu? Any ideas of cause or how to fix appreciated.

 

[Murdoch]

Call the spark back?

 

[binky]

nothing on main board saying solar that I can see from your pictures.

 

[gustaff]

nothing on main board saying solar that I can see from your pictures.

No it is on the garage feed it would have been impossible without digging up the garden to put a new cable in. We had a small consumer unit fitted into the garage that the inverter feeds into.second picture.

 

[Murdoch]

Photos aren’t very clear imho

 

[gustaff]

Photos aren’t very clear imho

Sorry the small cu is in the garage with two RCBOs one for the inverter and the other for a socket.( Could you confirm it is correct for the inverter to be on a RCBO) this then travels to main cu along garage feed. The tripping is occuring at around 5 am when the inverter wakes up. After the reset it all works fine. Thank you for taking the time to reply any helpful pointers I can give to the electrician are welcome. He was reluctant to do the job when solar was involved.

 

[kerching]

So you've got an upfront single-RCD board, feeding a board with two RCBOs?

 

[binky]

Sorry the small cu is in the garage with two RCBOs one for the inverter and the other for a socket.( Could you confirm it is correct for the inverter to be on a RCBO) this then travels to main cu along garage feed. The tripping is occuring at around 5 am when the inverter wakes up. After the reset it all works fine. Thank you for taking the time to reply any helpful pointers I can give to the electrician are welcome. He was reluctant to do the job when solar was involved.

And this is one of the reasons solar should not be on a shared RCD.

Your main board is rather out of date, a single RCD main switch went out of fashion about 25 years ago. In short a single small fault could shut down the entire house. This is known as 'nusiance tripping'. Earth leakage from multiple appliances, plus the inverter relays chattering in the morning will trip the RCD every time. Your sparky should have done something about it, plus the RCBOs in the garage will not trip before the house as they will not be seeing earth leakage from your appliances.

Your current set up is also dangerous, the inverter has a shut down time of upto 3 seconds on loss of mains power. Your RCD is supposed to trip in milliseconds, so if you are getting belted by the electrics for some reason, the RCD may trip like it should, but the inverter will continue to try and kill you with 16Amps for up to 3 seconds. Get it changed.

 

[Murdoch]

It really worries me that basic install issues come up like this time after time.

as for up front RCD boards …… oh dear, they need to be given a C2

 

[gustaff]

And this is one of the reasons solar should not be on a shared RCD.

Your main board is rather out of date, a single RCD main switch went out of fashion about 25 years ago. In short a single small fault could shut down the entire house. This is known as 'nusiance tripping'. Earth leakage from multiple appliances, plus the inverter relays chattering in the morning will trip the RCD every time. Your sparky should have done something about it, plus the RCBOs in the garage will not trip before the house as they will not be seeing earth leakage from your appliances.

Your current set up is also dangerous, the inverter has a shut down time of upto 3 seconds on loss of mains power. Your RCD is supposed to trip in milliseconds, so if you are getting belted by the electrics for some reason, the RCD may trip like it should, but the inverter will continue to try and kill you with 16Amps for up to 3 seconds. Get it changed.

So the RCBO the inverter is wired into won't trip ? Is it meant to be in the main cu on the garage feed and an ordinary mini cu in the garage?

 

[binky]

Your house RCD will trip first.

You need to feed your garage from an MCB in the main board that isn't sharing the RCD. I am assuming your garage is fed from the main board. To do that it's easier to change the entire board, ideally to one with an rcbo per circuit, although that board may be large enough for RCBOs. You then need to replace the RCD with a main switch.

The other option is a mini board, house end tapped into the meter tails after your leccy meter. That mini board will need main switch and MCB only for the garage supply.

 

[gustaff]

Your house RCD will trip first.

You need to feed your garage from an MCB in the main board that isn't sharing the RCD. I am assuming your garage is fed from the main board. To do that it's easier to change the entire board, ideally to one with an rcbo per circuit, although that board may be large enough for RCBOs. You then need to replace the RCD with a main switch.

The other option is a mini board, house end tapped into the meter tails after your leccy meter. That mini board will need main switch and MCB only for the garage supply.

Thank you so much for the concise reply I shall pass on your recommendation to my sparky ( who is really a good guy but no knowledge of solar) and ask that he updates the electrics to current standards regards Babs.

 

[Murdoch]

Thank you so much for the concise reply I shall pass on your recommendation to my sparky ( who is really a good guy but no knowledge of solar) and ask that he updates the electrics to current standards regards Babs.

he’s not a good spark if he doesn’t understand the issues when daisy chaining RCDs incorrectly

solar is irrelevant

 

[SPECIAL LOCATION]

Thank you so much for the concise reply I shall pass on your recommendation to my sparky ( who is really a good guy but no knowledge of solar) and ask that he updates the electrics to current standards regards Babs.

he’s not a good spark if he doesn’t understand the issues when daisy chaining RCDs incorrectly

solar is irrelevant

Agree with what Murdoch says... Solar is a red-herring in this scenario...

A good electrician should have a comprehensive understanding of attempting to create discrimination between protective devices when connecting them in series.. be they Fuse wire, Cartridge fuse, MCB's, RCD's, or RCBO's...

It sounds as though your electrician doesn't fully grasp how RCD's work?

 

[gustaff]

Thank you all for your input and will get the matter resolved.

 

[Andy1733]

Imo (I'm not a sparky but experience property developer). You need a different electrician. A shock from Solar could kill you. It's not like the one you get from AC. It really shouldn't be messed with unless they know what they are doing.
From your images and explanation, he may be a good guy but a poor electrician. It may pain you but imo you need to overhaul your system and bring it to date

 

[gaxxter]

Why dont you get a registered sparks to resolve this for you ? thought this was sparks forum not a 20 questions diy?