My Consumer Unit and RCD

[mstizomad]

Hello,

The house that we have bought has a CU that was last tested in 2016.

It has a 100A supply Main Switch and then a single 63A RCD that protects 7 x MCB:

1 x 40A Shower - 10mm Cable
1 x 32A Cooker - 6mm Cable
1 x 32A Ground Floor Ring Main - 2.5mm Cable
1 x 32A First Floor (small) + Kitchen Ring Main - 2.5mm Cable
1 x 6A Ground Floor Lights Radial - 1.5mm Cable
1 x 6A First Floor Lights Radial - 1.5mm Cable
1 x 20A Outdoor Socket/Shed Radial - 2.5mm Cable

Does this seem OK, or should i get a sparky to come and have a look and install an 80A RCD?

Also, in a few months time, we will be completely removing the 40A shower circuit, as we will be switching to a Combi Mixer Shower. So that will obviosuly be less load on the system.

Thanks

 

[ban-all-sheds]

It's fine - when anybody adds up all of the ratings of their fuses/MCBs, they always come to more than the RCD rating, more than the main switch rating, more than the supply fuse rating.

It's because you never have everything going flat out at the same time.

http://www.tlc-direct.co.uk/Book/6.2.1.htm

 

[OwainDIYer]

If there are 2 spare modules in the CU you'd be better getting the circuits split over 2 RCDs.

Or at least shuffle the RCD along one and put the shed on iots own RCBO

 

[Brian shepherd]

Diversity

 

[winston1]

Someone wasted money using 1.5mm cable (note lower case c) for lights instead of 1.0mm, but it is not worth changing now.

 

[Taylortwocities]

As above. The load is fine.
What is wrong is having one RCD for everything.

One simple fault on any circuit will kill every circuit in the house.

Yes, get an electrician to advise if s second RCD can be installed and the board split to mean that you’ll only lose half of everything if there’s an earth fault.
Or (better) have the MCBs changed for RCBOs.

 

[sparkwright]

If you go for all RCBOs, you would remove the 63A RCD.

 

[sparkwright]

Someone wasted money using 1.5mm cable (note lower case c) for lights instead of 1.0mm, but it is not worth changing now.

Sigh.

What's this rubbish doing here?

 

[Taylortwocities]

Untitled

• Taylortwocities
• 21 Mar 2014
• 1

 

[mstizomad]

As above. The load is fine.
What is wrong is having one RCD for everything.

One simple fault on any circuit will kill every circuit in the house.

Yes, get an electrician to advise if s second RCD can be installed and the board split to mean that you’ll only lose half of everything if there’s an earth fault.
Or (better) have the MCBs changed for RCBOs.

Hi, ok thanks. What is the main advantage of RCBOs? Is each like a combined RCD and MCB for each individual circuit?

 

[EFLImpudence]

Yes.

 

[Taylortwocities]

Hi, ok thanks. What is the main advantage of RCBOs? Is each like a combined RCD and MCB for each individual circuit?

Exactly.

As i said in my earlier post, if you have one RCD at the origin, you lose everything if there is one earth fault.
With a split-load board (eg two RCDs) you lose half of everything if there is an earth fault.

With RCBOs, you only lose the circuit where the fault is. That is a much better segmentation of circuits, but more expensive as MCBs average about £5 each, RCBOs can be between £25-£40 depending on the make and supplier.

 

[ban-all-sheds]

Sigh.

What's this rubbish doing here?

Ask the Mods - they are the ones who want it here.