Type A or Type B RCD/RCBO for solar pv

[Bhav101]

Hi which RCD / RCBO should be installed for solar pv, the manufacture instructions says Type A but posts online say Type B should be used.

 

[Murdoch]

Could be no rcd protection required

 

[binky]

Hi which RCD / RCBO should be installed for solar pv, the manufacture instructions says Type A but posts online say Type B should be used.

retro fitting usually means cable runs outside of requirements for RCDs, ie cables not buried in plaster on walls etc, so personally I prefer to fit without RCDs at all. Plus most inverters have built in protection for the AC and DC side these days.

 

[Bhav101]

If I'm installing in an existing consumer unit that has Type A RCD would I need to make any changes if I'm wiring under that RCD?

What's your interpretation of the following quote, what is meant by simple separation?

Where an electrical installation includes a PV power supply system without at least simple separation between the a.c. side and the d.c. side, an RCD installed to provide fault protection by automatic disconnection of supply must be type B RCD according to BS EN 60898 (IEC 60755, amendment 2).

 

[binky]

If I'm installing in an existing consumer unit that has Type A RCD would I need to make any changes if I'm wiring under that RCD?

What's your interpretation of the following quote, what is meant by simple separation?

Where an electrical installation includes a PV power supply system without at least simple separation between the a.c. side and the d.c. side, an RCD installed to provide fault protection by automatic disconnection of supply must be type B RCD according to BS EN 60898 (IEC 60755, amendment 2).

Ideally yes, but I suspect any existing RCD is already protecting other circuits in your house, it would therefore be dangerous to share the RCD with solar aswell. Inverters have a max shutdown time of 5 seconds. So if say you run over the lawnmower cable, your RCD will trip at 30 mAmps in under 0.3 of a second, but your solar will carry on trying to kill you with multiple Amps....

 

[ExArmy]

If I'm installing in an existing consumer unit that has Type A RCD would I need to make any changes if I'm wiring under that RCD?

What's your interpretation of the following quote, what is meant by simple separation?

Where an electrical installation includes a PV power supply system without at least simple separation between the a.c. side and the d.c. side, an RCD installed to provide fault protection by automatic disconnection of supply must be type B RCD according to BS EN 60898 (IEC 60755, amendment 2).

you don't want to connect the inverter to that RCD if it's shared with other circuits. if the Existing RCD feeds 5 MCB's for example, get rid of the RCD and MCB's and fit 5 RCBO's instead

The quote you have in italics comes from a book dating back to 2006, i'm really not sure what it means
AFAIK most inverter don't have simple transformers that are electrically separated, the are mostly transformer-less now. theres a bit in section 8 of the IET solar CoP (2022) that says if the inverter is transformerless they recommend designing the supply circuit to the inverter so that an RCD isn't required.
Manufacturers instructions are a good place to look for the specific inverter too

 

[Murdoch]

What do the manufacturers instructions say about this?

Do not connect the PV to a shared RCD and please be aware that this comes under Part P of the building regs too

 

[Bhav101]

What do the manufacturers instructions say about this?

Do not connect the PV to a shared RCD and please be aware that this comes under Part P of the building regs too

I've installed a new consumer unit for the solar with an RCBO, I prefer to do this than making changes to an existing consumer unit. Yes I'm aware of the Part P.

The quote you have in italics comes from a book dating back to 2006, i'm really not sure what it means
AFAIK most inverter don't have simple transformers that are electrically separated, the are mostly transformer-less now. theres a bit in section 8 of the IET solar CoP (2022) that says if the inverter is transformerless they recommend designing the supply circuit to the inverter so that an RCD isn't required.
Manufacturers instructions are a good place to look for the specific inverter too

This was given to me by Flexi-Orb, I've signed up to them while I become MCS. Currently trying to prepare for the MCS assessment and I'm using EasyMCS which has a list of checklists for commissioning and handover but these weren't covered in my solar pv course!

 

[binky]

I've installed a new consumer unit for the solar with an RCBO, I prefer to do this than making changes to an existing consumer unit. Yes I'm aware of the Part P.

Best way, that way you don't get involved in existing electrics, as well as from avoiding shared RCDs issues.

Wouldn't worry too much about type of RCD, my preference is, and remains, no RCDs at all for solar, which can usually be achieved quite easily and is compliant with regs. Inverters have RCD protection built in anyway.

 

[binky]

Forgot to say, inverters also check AC and DC side every time they start up aswell, so your solar circuits are the most monitored, 'inspected' circuits you will ever come across, bar hospital surgerys.

 

[dipesh]

Forgot to say, inverters also check AC and DC side every time they start up aswell, so your solar circuits are the most monitored, 'inspected' circuits you will ever come across, bar hospital surgerys.

Thanks for your advice @binky you're a great help in this forum to newcomers!

 

[stuboy]

Just to add for reference, I've used Wylex type A RCBO's and never had any problems..... yet, mainly because my OCD likes a nice row of matching breakers But as binky says the Inverter checks its self every time it starts up so a correctly rated MCB is fine. What is not fine is sharing one!