Correct RCD for a shower unit

[STI]

Hi, is it ever correct to fit a 100ma RCD for a bathroom circuit. I thought it had to be 30ma. The RCD appears to be protecting the shower circuit and two socket circuits. Each of these circiuts has its own MCB THE SHOWER IS 45A and the 2 rings are 32A.I have tried to contact the electrician who put the board in originaly but to no avail.

Thanks

 

[ColJack]

would you happen to be in a rural area?
do you have a TT earthing system? ( earth rod somewhere, wires on a pole? )

 

[STI]

Hi yes it is rural but not sure if its a TT, ill see what i can find. If this was the case then is 100ma ok

 

[ColJack]

yes and no..
that 100mA rcd incommer will be because you are on a TT system.
when it was installed, there was no reg to say that showers had to be RCD protected, unless the manufacturers instructions said so..

depending on how old your CU is, you may be able to fit RCBO's to it in place of the breakers.. this combines a breaker and an RCD into one unit..
best left to a sparky..

 

[STI]

Great thanks for the help. I will try to contact the sparky who put it in. I cant see any dates on the CU nor any suggested inspection dates. Although the CU looks fairly new the wiring is the old black and red so i guess this could date in back to pre 2006. Would you recomend putting in the RCBO given the new rules and would this be at a 30ma rating.

 

[spark1]

Hi STI.

It does appear you may well have a TT system, A Qualified Electrician will be needed to verify this for you.
If it is a TT system the 100mA RCD will have been installed for indirect protection due to the poor earthing characteristics of this type of supply system. The socket outlets would have needed 30mA protection so there is an issue about that already.
If you wish to have the system upgraded it is best to have the Electrician to give advice as to any other possible issues standing at present.A Full periodic Inspection & Test is advisable.
It would not be possible to simply add 30mA RCBOs to a system protected by a 00mA RCD unless it is of the S type time delayed variety otherwise there would be a lack of fault discrimination meaning both 30mA and standard 100mA RCDs would trip in tamden

 

[STI]

Hi Spark1, Thanks for the reply. Can you just clarify the point on the RCDs for the sockets. Its probably the way i explained it. The two socket circuits are on separate MCB's and do not go into the bathroom, they just feed the the bedrooms and the hallway. So do they need to have a rcd at all ?

The CU set up is, main switch, Kitchen circuit on a MCB , Downstairs light circuit and downstairs sockets each on their own MCB, 100ma RCD, Shower circuit on mcb 2 x Socket circuits each on a MCB Socket Upstairs light circuit.

 

[spark1]

STI
Under previous Regulations ,in general only socket outlets Likely to supply equipment outdoors required RCD protection, though in practice when rewiring or at a Fusebox upgrade All sockets where usually provided with the 30mA RCD protection.
If it is wished to fully comply with the new regs BS 7671 2008 then all sockets outlets require 30ma protection throughout the House. In additional All circuits in the Bathroom require the same protection,,,,plus any cables buried less than 50mm in the wall[Probably All of them} will require 30mA protection.

Have a qualified "PartP" registered Electrician take look ..at minimum i think you are going to require a Consumer unit [Fusebox] replacement by a dual RCD board..other options are available ,talk it over with the Spark.

 

[STI]

Oh no more expense !

Thanks for all the help I certainly wasnt aware of the requirement for RCD's on the socket circuits.