New Socket Protection Question

[alfa20ad]

I have to install 2 new sockets into a garage, but unfortunately the consumer unit has all spaces allocated. One of the circuits has a 40Amp circuit breaker that is feeding a CU out into a summerhouse.

The maximum load in the summerhouse would be around 10Amps with the summerhouse heater that is not on regularly but is taking up most of the load. Would it be easier to change the 40Amp circuit breaker out to a 20Amp, wire in the 2 new garage sockets in 2.5mm twin and earth (ran in plastic conduit), therefore creating 2 radials out from the 20Amp MCB?

Or any other guidance appreciated.

 

[Lucien Nunes]

Not a good idea IMHO - as these are totally separate areas they should have separate OCPD so that a problem in one area does not involve isolating the other. Also reasonable to think that a 13A load may be used in the garage, which with the 10A in the summerhouse would be over the 20A.

 

[alfa20ad]

Looks like i will need to install either a separate 20Amp MCB outwith the CU and fit a couple of rcd sockets or an RCBO with standard double sockets.

 

[Deleted member 26818]

What circuits does the existing board have?

 

[alfa20ad]

What circuits does the existing board have?

It has mostly separate shower, cooker, smoke alarm, upstairs/downstairs 6Amp Lighting and 32Amp protected ring main for upstairs/downstairs.

Just going to go for installing a new CU. Kill the board supply and throw in some 25mm singles from dead side of CU isolator into a combined MCB/RCD unit and take new radial circuit off that, sticker the board up with switch off mains before removing cover.

 

[Deleted member 26818]

Why can’t you come off the existing socket circuit?

 

[alfa20ad]

The garage is wired up for radial and want to keep it that way as the 20mm conduit and the amount of bends in this would be a PITA to feed 2No. twin and earths down. Plus dont think its best practice to shove 3 cables into the ring main circuit breakers.

 

[Squid]

The garage is wired up for radial and want to keep it that way as the 20mm conduit and the amount of bends in this would be a PITA to feed 2No. twin and earths down.

Would singles be allowed?

 

[alfa20ad]

Would singles be allowed?

For the 25mm? you mean. This would be done in tri-rated cable suitable for 136Amps.

 

[DPG]

What containment?

 

[alfa20ad]

What containment?

All would be carried in PVC conduit.

 

[Squid]

For the 25mm? you mean. This would be done in tri-rated cable suitable for 136Amps.

In the conduit, but I don't think the cables handling 136A would fit.....

 

[alfa20ad]

In the conduit, but I don't think the cables handling 136A would fit.....

Sorry the new consumer unit would be butted beside the old CU so just a 30mm hole on both units would do. Sorry the smaller 2.5mm Twin and Earth is in the conduit.

 

[DPG]

I'm confused. I think I've misunderstood something.

 

[alfa20ad]

I'm confused. I think I've misunderstood something.

Hey, i dont make it easy enough for myself.