Do I need a RCD on my Shower

[Papabob]

Hi Forum, I would be grateful for some advice. I intend to change my 7kw shower for a 7.5 Shower. The reason I am not going any bigger is that I don't want to change the 6mm Twin and Earth cable. The cable is less that 10 metres long and travels through a plastic trunking and under floorboards on its own. The shower is protected by it's own 30a MCB in it's own consumer unit placed next to the main consumer unit. The main consumer unit is an old WYLEC, but I have replaced the wired fuses with plugin MCB's. Do I need to change the shower's consumer unit with a RCD? The one I have seen is a 63A 30mA RCD with a 50A MCB. Is this too big? Also can someone tell me the difference between a RCD, a RCCB and a RCBO. Thanks,
Papabob

 

[securespark]

Your installation method reduces the CCC of the cable to somewhere like 38A, iirc. That's OK for a 7.5kW shower.

I assume your consumer unit has a 100A main switch?

If so, I would fit a 35A fuse. Also, fit an RCD (40A, 30mA) external to the CU & make sure your isolating switch is >30A.

If the rest of the circuits in the bathroom are not RCD-protected, I would fit supplementary equipotential bonding. Also, make sure your PEB's and main earthing conductor are up to standard.

Usual "notifiable job" stuff applies.

An RCD and an RCCB are essentially the same BEAST. They give additional protection against electric shock by monitoring earth leakage and tripping when that rises to a dangerous level. They offer no overcurrent or short-circuit protection.

An RCBO does the job of both an MCB and an RCD.

 

[davy_owen_88]

Showers should be RCD protected (along with pretty much everything else mind you) but whether you can add an RCD/RCBO safely depends on your installation and will require testing to ensure that it is effective at doing what it is meant to.

Could you provide a picture of your meter, service fuse, and all consumer units? If you do that we might be able to offer you further advice that will be more suited to your specific installation rather than going into autopilot and giving you advice that might not be suitable.

Oh an RCD/RCCB is a residual current device/residual current operated circuit breaker - it only detects inbalances between phase and neutral but does not provide protection against overcurrents or fault currents.

RCBO's cobine the function of an RCD and an MCB so provide both overcurrent/fault current protection and earth leakage protection.

Davy

 

[Papabob]

Thanks Dave,
My Main fuse is 60A. The shower consumer unit is fed directly from the consumer side of the Meter. This consumer unit was fitted by the Electricity Board years ago and has an isolating switch and a 30A MCB. I assume I would change this CU to a RCD or a RCBO. Thanks,Bob

 

[sparkyspike]

Er, an RCD is a general term for a residual current device. RCCBs and RCBOs are types of RCD.

 

[davy_owen_88]

Thanks Dave,
My Main fuse is 60A. The shower consumer unit is fed directly from the consumer side of the Meter. This consumer unit was fitted by the Electricity Board years ago and has an isolating switch and a 30A MCB. I assume I would change this CU to a RCD or a RCBO. Thanks,Bob

Unless we know what type of consumer unit the shower is connected to we can't really help you much because it could be the case that you will not get a RCD/RCBO for the CU and you will need to fit a modern replacement.

If the shower CU is fed directly from the meter then before you are going to be able to carry out any work you are going to need to get the DNO to fit an isolator between the meter and the CU as I'm guessing the isolator you talk of is actually within or a fitted part of the consumer unit?

Also, you can't change a CU (consumer unit) for a RCD as you need the consumer unit to actually house the RCD/MCB/RCBO etc. I'm sure you know that already though and you have just got your acronyms muddled up

If you can supply a picture it would really help to get you the most effective responses.

 

[Papabob]

Thanks Dave.
I have taken the photos but can't find out how to attach them! Sorry to mess you about, you must think "what a fool!"
Bob

 

[Papabob]

Dave, I'm trying again with the photos. Bob

 

[Spark123]

//www.diynot.com/forums/viewtopic.php?t=129539

 

[Papabob]

Dave, try this. Bob

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