rcd rating is this suitable

[neilyboy]

quick question,
80a/30ma rcd protecting 5 32a circuits
2 ring mains
1 oven
1 shower
1 hob
ive been told the shower and hob need upgraded to 40a mcbs
is the rcd still suitable
one ring main supplys 4 bedroom sockets the other kitchen/living area with 7 sockets.

 

[brianmoooore]

536.4.202 is the reg., and here is the last time it was discussed in a thread on here: Installing dual RCD boards 18th edition - https://www.electriciansforums.net/threads/installing-dual-rcd-boards-18th-edition.194962/#post-1713950

 

[neilyboy]

Regulations do not need to be applied retrospectively but if you are making changes then all changes must be made to current standards..

You could contact the DNO and ask them, I can't remember the exact section but Brian is correct, as standard now if fitting a dual RCD board which I tend to fit RCBO boards I would fit dual 100A type A RCD's, as if you cannot be sure what the size of the fuse is you should assume it is worst case scenario of 100A..

Here's the thing then, the guy doing the EICR has said the shower is underrated and the hob is underrated and advised changing the whole board instead of me uprating the 2 mcb's.This is where the problem is, yes the board is not dual RCD and yes its not to current standards but he has already passed a few of the boards with only C3's and C1's (blanks missing from front of board

 

[Rockingit]

Yes, as others have said, every part of the circuit chain needs to be capable of handling the current of its upstream CPD - so in this case if that’s a 100A service fuse then it needs to be a 100A rated device. If for arguments sake there was a KMF between the incomer and that consumer unit that was fused at 63A then it would be fine. As for what’s downstream - diversity applies.

 

[brianmoooore]

What is the rating or model number for the shower?
Same for the hob.

 

[Intoelectrics]

Here's the thing then, the guy doing the EICR has said the shower is underrated and the hob is underrated and advised changing the whole board instead of me uprating the 2 mcb's.This is where the problem is, yes the board is not dual RCD and yes its not to current standards but he has already passed a few of the boards with only C3's and C1's (blanks missing from front of board

Why has he determined the mcb's are underrated?

 

[neilyboy]

Why has he determined the mcb's are underrated?

not sure,unless he's assumed the shower is a 10.5kw currently on a 32a mcb
and the halogen hob is currently on a 32amcb ,the hob is completely built in so there is no rating plate available I googled the make/manufacturer and they recommend a 32a mcb.
the shower and hob have both been in place for at least 10 years now the flat has had had 2 EICR's carried out on it but this is the first time this has been flagged up

 

[brianmoooore]

The two previous EICRs have been carried out by someone who a) Is incompetent to complete EICRs, OR understands the concept of diversity, or b) The recent EICR has been carried out by someone who is incompetent to complete EICRs and doesn't understand the concept of diversity, OR by someone who is competent, and does understand the concept of diversity.
The challenge is to work out which is wrong.
Unfortunately, there is no diversity allowable on the electric shower, so if it does exceed 7.36kW, when the probable 240V rating is corrected for 230V, then the 32A MCB needs to go, and the "regs. not applying retrospectively" argument ceases to apply.
I take it that this CU only has one RCD, and the lower rated circuits are not RCD protected?
Best solution would be a board change, so that all circuits are RCD protected, and if 40A MCBs are not available, that is the way to go. Shower cable size will need to be looked at as well, of course.
If the 40A MCB is needed, and can be obtained, possible solutions are: confirm that the supplier fuse is not greater than 80A, fit a 80A s/fuse isolator between meter and CU, Move the shower supply to a separate small CU.

 

[neilyboy]

The two previous EICRs have been carried out by someone who a) Is incompetent to complete EICRs, OR understands the concept of diversity, or b) The recent EICR has been carried out by someone who is incompetent to complete EICRs and doesn't understand the concept of diversity, OR by someone who is competent, and does understand the concept of diversity.
The challenge is to work out which is wrong.
Unfortunately, there is no diversity allowable on the electric shower, so if it does exceed 7.36kW, when the probable 240V rating is corrected for 230V, then the 32A MCB needs to go, and the "regs. not applying retrospectively" argument ceases to apply.
I take it that this CU only has one RCD, and the lower rated circuits are not RCD protected?
Best solution would be a board change, so that all circuits are RCD protected, and if 40A MCBs are not available, that is the way to go. Shower cable size will need to be looked at as well, of course.
If the 40A MCB is needed, and can be obtained, possible solutions are: confirm that the supplier fuse is not greater than 80A, fit a 80A s/fuse isolator between meter and CU, Move the shower supply to a separate small CU.

yep only one rcd ,lights,boiler smoke alarm not on rcd,I got 40a mcbs compatible with the board I need to go back down and check shower rating,and confirm supplier fuse and what size the isolator there is already.
you say a board change,this would necessitate 25 new boards although the tester did pass a few flats with only C3's .ie board not to current standard/combustible materials and these boards also have the same shower/hob combo
The company has just come out of 2 years with literally no income due to hospitality being shut down so obviously new mcbs in place of complete board changes would suit them.
I'm thinking of changing the hob back to a 32a which would mean the 80aRCD protecting 3 x socket circuits (1 with 4 sockets and the other with 6 sockets) and 1 40a mcb for the shower .how would that do ?

 

[neilyboy]

What is the rating or model number for the shower?
Same for the hob.

sorry just seen this,I'd no time to check the shower type but its 10 years old and the manufacturer of the hob recommends 32a mcb full drawn current is 27a on full load

 

[brianmoooore]

We now know that the latest EICR is incorrect on the need to replace the hob MCB, so it all hinges on whether the existing 32A for the shower is acceptable, or the supplier fuse is not more than 80A.
The existing CU stills gets C3s on multiple points, and a strong recommendation that it is upgraded so that all circuits are RCD protected, but if the existing stuff was installed before the 18th, then there's no C2s (unless visible damage), and it can stay.
We all know that there's only one way to check for sure what fuse is in the cut out, and if it's a reasonably modern head, that's what I would have done by now.

 

[neilyboy]

We now know that the latest EICR is incorrect on the need to replace the hob MCB, so it all hinges on whether the existing 32A for the shower is acceptable, or the supplier fuse is not more than 80A.
The existing CU stills gets C3s on multiple points, and a strong recommendation that it is upgraded so that all circuits are RCD protected, but if the existing stuff was installed before the 18th, then there's no C2s (unless visible damage), and it can stay.
We all know that there's only one way to check for sure what fuse is in the cut out, and if it's a reasonably modern head, that's what I would have done by now.

Thanks for that reply making a lot of sense, I live 140 miles away from the job so when I get back down (had to come home after a positive test...) I was concentrating on the FI's on the reports while I was there but I will certainly look more closely at the service fuse. Not so easy opening these as opposed to the bad old days when a terminal driver and a pair of pliers could open a seal and replace it without anyone knowing...

 

[brianmoooore]

I can assure you that no one cares about the seals, although I would replace it with one of my own before I left.
Plenty of seals are put on so loose that you can pull the carrier out far enough without breaking the seal, and I've also come across cut outs where the little bit of plastic with the hole for the seal wire has been accidently broken off at some time, and the fuse can be removed with the seal intact..