100A Main Service Fuse and 63 AMP rated RCD

[wilburwilbur]

I'm soon to have an Electric Shower installed and i am going to purchase the parts required in advance and just pay for the labour costs on PART P sparky. I have been doing some research, my service fuse states 100A. My Fuse Board has no RCD protection. I will run the shower from a second consumer unit taken from the Service Fuse & leave the Fuse Board that protects my other circuits in the property in place. My question is - most second consumer units designed for a shower seem to have an RCD rated at 63A included. Can i use this or will i need to find a consumer unit with a 100A rated RCD as my Service Fuse is 100A? I am not going to replace my present Fuse Board and i'm not seeking for advice on other aspects of this install, thanks.

 

[Spark123]

It just means the RCD contacts are rated at 63A, as long as the connected circuits don't exceed this then a 63A one is fine.
Best check out with the sparky first to see what they want though if you expect them to certify it! I hate cheap consumer units, a sparky may be able to get a better one at a reasonable price through trade.

 

[EFLImpudence]

my service fuse states 100A.

That is the rating of the fuse holder and no indication of the rating of the fuse.

 

[wilburwilbur]

well, it's not going to be greater than 100A Service Fuse in a domestic situation is it?

 

[EFLImpudence]

well, it's not going to be greater than 100A Service Fuse in a domestic situation is it?

No, definitely not.

Fuse could be 60A, 80A or 100A.

 

[securespark]

No. Some fuses I have seen in London are 125A, but I guess they would be marked as such.

But I think the point EFLI is making is that if your fuse is <100A you will need to have your intake upgraded so it will be capable of running the additional load.

Talk to your DNO.

 

[wilburwilbur]

So - it will be Ok to provide a 63A RCD with the MAIN Fuse being maximum 100A ? I will ask the Sparky to check the main fuse if he can, also The property is not in the London area.

 

[EFLImpudence]

So - it will be Ok to provide a 63A RCD with the MAIN Fuse being maximum 100A ?

You seem to be looking at things and doing things the wrong way round.

The 63A refers to the loads downstream of the RCD, not the fuse upstream of it and...

you should be discussing this with the electrician who will be able to see your existing installation and, if you insist on buying the parts yourself, telling you what he needs to do the job properly.

 

[wilburwilbur]

I just like to have some prior knowledge of what i am paying for - i have been poorly advised in the past by so called pro's of trades. It in no way means that i am doing this work myself and i have found that it also means that i have more respect from Sparks / plumbers and so on if i have SOME knowledge of what is to be done and what is involved in a job. Also, i like the refer to up / downstream - i think i understand.

 

[ban-all-sheds]

i am going to purchase the parts required in advance and just pay for the labour costs on PART P sparky.

1. Have you found an electrician who is happy with this arrangement?
2. If so, has he specified the parts you should buy?
3. You do realise that not only will it cost you more overall to do it this way but also that you may not get a warranty from the electrician?
   
   

 

[wilburwilbur]

Yes, i have a Sparky recommended to me. I may not purchase the parts in advance - i just wanted advice on the research i have done so far.

 

[ricicle]

For your own piece of mind, leave all the purchasing of equipment to the electrician. Therefore if there is a problem with any kit or workmanship then it has to be remedied at his cost. If you get the kit, it all becomes a tangled web of costs etc to rectify it.
And you will not be able to buy it cheaper than him (unless you want a fire risk with cheap chinese carp off fleabay !)

 

[ericmark]

Inside a consumer unit it does not really matter which comes first as there should be no way anything can get short circuited inside the unit.

So a 63A RCD followed by an MCB or MCB's who's total does not exceed 63A is fine.

I would agree that where the total of MCB's exceeds the 63A then there may be an issue.

 

[Taylortwocities]

I will run the shower from a second consumer unit taken from the Service Fuse

Oh no you would not. I think you have forgotten the issue of the meter that tells the supply company how much juice you have used!

So, per the above advice. You need to get your spark on board first.
There's ather stuff on top of the shower consumer unit
Henley blocks
25mm² double insulated tails
16mm² earth cable

oh yes, and your existing bonding may need to be brought up to date

and you have not mentioned the small issue of running the cable to the shower itself.

Again, an electrician can advise on this as the size of the cable needed will depend on many factors.

 

[wilburwilbur]

Well - it's obvious this would be connected after the Meter & i've already stated that i'm getting a PART P Sparky to install anyway and advice i was seeking was limited only to that of the rating of the RCD, but thanks for your concern.