Maximising 10mm SWA to garage CU.

[MattH]

My new build house has the following supply to the garage.

45A B curve RCBO suppling a 10mm SWA 2 core cable, armour being used as the CPC,
In the garage is a sub CU with a 100A dual pole isolator:



This seems very conservative and is I suspect based on the fact the the RCBO from fusebox are limited to 50A.

Would I be ok replacing the 45A RCBO with a 63A MCB C curve in the house CU and:
Replace the 100A isolator with a 100A dual pole RCB in the garage CU to still provide fault protection?

Will the armour be able to provide the earth impedance required to support the required disconnection times on a C curve MCB?

Thanks in advance.

 

[Welderpaul]

Blanks missing in the garage DB. That busbar will be live

 

[Barking Mat]

10mm2 cable, what's the run to the garage consumer unit in meters ?

 

[Barking Mat]

No RCD'S ?

 

[Anguz]

Rcbo s in the house db

 

[MattH]

10mm2 cable, what's the run to the garage consumer unit in meters ?

Less than 10 metres. RCBO's currently on every circuit. No RCD's.

 

[MattH]

Blanks missing in the garage DB. That busbar will be live

TBF the house hasn't been handed over yet so the sparky might not be finished. Although I think he has.
I will be fully populating the board and if not I would fit blanks.
Interesting if it stays that way if it will pass inspection.

 

[dobbslc]

Looks like reference method D is used for the garage cable so that means buried or in a duct so should be ok for a 63A RCBO.

 

[MattH]

Looks like reference method D is used for the garage cable so that means buried or in a duct so should be ok for a 63A RCBO.

Issue is they don’t do a 63a RCBO, so can I switch to an MCB with an RCD at the other end?

 

[GRW]

Issue is they don’t do a 63a RCBO, so can I switch to an MCB with an RCD at the other end?

You can get combination 63A 2-pole MCB/RCD units?

 

[qwakers]

Single Pole 63 Amps RCBO 6kA C Curve EUC7R.63/1C

EN 61009 , 230V, Type A, 30mA Trip.

www.cpelec.co.uk

 

[MattH]

Single Pole 63 Amps RCBO 6kA C Curve EUC7R.63/1C

EN 61009 , 230V, Type A, 30mA Trip.

www.cpelec.co.uk

I was under the impression that mixing makes in a CU was not allowed.

 

[qwakers]

its not ideal but its not strictly against regs iirc

 

[MattH]

You can get combination 63A 2-pole MCB/RCD units?

Don’t think so:

Products – FuseBox

fusebox.co.uk

 

[MattH]

its not ideal but its not strictly against regs iirc

That’ll be plan B then

 

[GRW]

Don’t think so:

Products – FuseBox

fusebox.co.uk

You can get them for Din Rail mount. I used to fit them in smaller industrial generators that I'd reconfigured to single phase on rental jobs (has to have an RCD on).
Dunno if you can get one in the brand you want, but Schneider & Merlin Gerin do them from memory

 

[GRW]

A quick Google & this popped up at CEF, cheap too (63A RCBO)

63A Double Pole 2 Module C Curve 10kA 30mA Type A Mini RCBO

Compact modular design

www.cef.co.uk

 

[MattH]

A quick Google & this popped up at CEF, cheap too (63A RCBO)

63A Double Pole 2 Module C Curve 10kA 30mA Type A Mini RCBO

Compact modular design

www.cef.co.uk

Qwakers RCBO above is probably a better fit if I go down the mixed manufacturer road.

 

[brightspark]

its not ideal but its not strictly against regs iirc

here https://www.voltimum.co.uk/articles/q-day-can-bsen-devices-different

 

[AdventuresInMetal]

Personally at these sort of currents, i've never been a fan of 63A MCB's, I would rather split the meter tails with henley blocks and move the garage submain to a switch fuse isolator instead.