RCBO

jstrong · 30 Mar 2013

Hello all

I have an MK Sentry CU and was chatting to a friend who said I should have a 6amp RCBO fitted instead of the 6amp RCD I already have for my kitchen lighting curcuit. (The CU is situated inside a cupboard in the kitchen). Any ideas why I would need to change it?

bernardgreen · 30 Mar 2013

He probably meant you should have a 6 amp RCBO in place of the existing MCB I have never seen a 6 amp RCD

Or did he mean your sockets needed an RCBO ?

Does your CU have an RCD ? If you are not sure then an RCD is most often a switch with a test button. Will be labelled 30 mA

ericmark · 30 Mar 2013

I have never seen a 6A RCD. So please start again.
MCB - detects current and opens if it exceeds the thermal limit for a long time or magnetic limit immediately.
RCD - detects leakage current and trips if too much leaks to earth.
RCBO - Combines both.

jstrong · 30 Mar 2013

Bernard & Eric

Many thanks for your replies.

Right..... I think I've got my facts straight now so I'll start again!

I've got an MK sentry CU which is split.

From left to right I've got the main switch which is red and marked 100A

Then I've got.....

1. B40 MCB (Cooker)
2. 6A MCB (Kit lighting)
3. B6 MCB (Lights FF)
4. B6 MCB (Lights GF)
5. B16 MCB (Spare)
6. B40 MCB (Induction hob)

Then I've got a blank plate followed by an 80A RCD with test button followed by from left..........

7. B32 (Kit Sockets on island)
8. B32 (GF Ring) plus spur off to garden shed.
9. B32 (FF Ring)
10. B32 (Kitchen Ring)
11. B16 (Patio Lighting)

The person I was speaking to siad I should change MCB No2 from 6A MCB to a 6A RCBO. Any ideas as to if this is neccassary?

Sorry about the first post, got my wires crossed between RCD's and MCB's!
Any advice appreciated

ricicle · 30 Mar 2013

No it is not necessary unless you have any work done on that lighting circuit involving burying cables at a depth less than 50mm.

martinxxxxxx · 30 Mar 2013

Or you install a new bathroom

ricicle · 30 Mar 2013

martinxxxxxx said:
Or you install a new bathroom

The circuit in question is in a kitchen

AndyPRK · 30 Mar 2013

An RCBO would prevent/reduce a shock you got while changing light bulbs if you left the switch on etc....

Isn't it a worry that the cooker/hob are not RCD protected? but I guess it would have overloaded the RCD.

martinxxxxxx · 30 Mar 2013

Ok

...or you add an ensuite shower cube to your kitchen

phatboy · 30 Mar 2013

The ideal solution would be to replace everything with RCBO's.... or replace the board with a split RCD one, and then re-arrange the circuits to protect at least 1 lighting circuit from each RCD

ricicle · 30 Mar 2013

phatboy said:
The ideal solution would be to replace everything with RCBO's.... or replace the board with a split RCD one, and then re-arrange the circuits to protect at least 1 lighting circuit from each RCD

Why carry out un-necessary work?

phatboy · 30 Mar 2013

ricicle said:
phatboy said:

The ideal solution would be to replace everything with RCBO's.... or replace the board with a split RCD one, and then re-arrange the circuits to protect at least 1 lighting circuit from each RCD

Click to expand...

Why carry out un-necessary work?

Maximum safety I suppose......

martinxxxxxx · 30 Mar 2013

phatboy said:
ricicle said:

phatboy said:

The ideal solution would be to replace everything with RCBO's.... or replace the board with a split RCD one, and then re-arrange the circuits to protect at least 1 lighting circuit from each RCD

Click to expand...

Why carry out un-necessary work?

Click to expand...

Maximum safety I suppose......

Plus the inconvenience in the case of a fault on the RCD side of this board would warrant it being improved in some way.
7. B32 (Kit Sockets on island)
8. B32 (GF Ring) plus spur off to garden shed.
9. B32 (FF Ring)
10. B32 (Kitchen Ring)
11. B16 (Patio Lighting)
A waterlogged patio light or leak down at the shed could be a bit of a nightmare with all of these sockets on the same RCD, and I wonder what rating it is?

Adam_151 · 30 Mar 2013

AndyPRK said:
Isn't it a worry that the cooker/hob are not RCD protected? but I guess it would have overloaded the RCD.

Only if the cooker isolators incorporate socket outlets, otherwise its no issue at all

phatboy · 30 Mar 2013

Adam_151 said:
AndyPRK said:

Isn't it a worry that the cooker/hob are not RCD protected? but I guess it would have overloaded the RCD.

Click to expand...

Only if the cooker isolators incorporate socket outlets, otherwise its no issue at all

Assuming the CPC is terminated correctly. I can't think of many reasons at all why something would not be better protected by an RCD

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