old rewireable fuseboxes

[tawraste]

hi everyone,
just wondering about homes that still have these old rewireable fuseboxes and where the owners want some work done.
please excuse any apparent ignorance in this or other questions i have asked/will ask, i am in the process of learning and these are hypothetic situations where i am trying to link the requirements of the regs with "real world" scenarios.

this is what has got me wondering - in a couple of properties i've been in as a visitor i've noticed (always looking now i'm learning lol) that where someone's had a shower installed, the electrician has mounted a one way enclosure to house the rcd as the old rewireable board does not have one. i always think that this arrangement looks like a "make good" scenario instead of a replacement of the cu. now i can understand that certain customers won;t have the money for a new cu, and i know that if the existing installation is still safe that cost can be factored in. however, is this acceptable under the regs?

i ask this because this arrangement always seems to leave bathroom lights and kitchen sockets etc non rcd protected, so a job has been done and the tradesman has left knowing that these special locations are not protected?!

what if new bathroom downlights were installed for example and were protected by the same method? i.e one way enclosure next to the old cu. i've never seen that arrangement! but if the shower is ok then surely this would be ok?

in my mind these kind of things do not seem the right way to go about things. but surely everyone does not walk away from a job on the basis the customer won;t pay for a full modernisation of their installation? could someone please clarify this for me ?

many thanks,

tawraste

 

[telectrix]

as you rightly say, the separate enclosure RCD has been done to save money. as far as the regs. go. any work done has to be installed in accordance with current regs. there is no requirement to upgrade other circuits as they are not being altered. the only other thing is that the earthing and bonding must be checked and upgraded if necessary ( this is because it will have an effect on the new shower circuit, which has been installed ).

 

[tawraste]

"any work done", i understand. so that seperate rcd box could be for the sockets in a new extension kitchen?
i assume then that the remainder of an installation in this kind of example that was not up to date would simply be listed in the section "comments on existing installation" indicating that the contractor was aware but the client did not want the work done?

 

[Knobhead]

As you progress in life you will find installations that are pre 15[SUP]th[/SUP] edition. You can’t force the customer to upgrade but you must ensure your work is up to current regulations. If this means fitting a separate RCD protected CU then so be it.

You can only advise on, not enforce regulations. A dangerous installation notice can be enforced by the DNO if notified. But god help you in court it’s not correct! BTW I’ve seen a DNO inspector in Hitler mode, not a pretty sight!

Many years ago it was possible to get a disclaimer from the supply company to supply an unsafe installation. This usually came about with un-earthed brass light switches, the owner didn’t want them changed.

One day I’ll write down the episode of changing a baronial hall from DC to AC public mains.

 

[tawraste]

cheers guys, thats cleaned that up for me. this forum and it's members frequently provide far more in depth answers to things than the tutors/colleges and their courses. thanks again, now i shall return to the regs, find the section that describes the requirement for "any work done" and emblazon the reg number in my mind.
i'd like to read the story of that dc to ac conversion, stick a link here or pm me when you do!
regards,
tawraste

 

[malcolmsanford]

The very introduction to the regs on page 4 states

"Existing installations that have been installed in accordance with earlier editions of the Regulations may not comply with this edition in every aspec. This does not mean that they are unsafe for continued use or require upgrading"

And then onto reg 131.8 regarding the existing regluation which includes the earthing and bonding

 

[tawraste]

hi glenn,
could you post a link to that pack please? would be of interest. also, your boss installed an rcd instead of an rcbo because the main switch is the one in the old board?
cheers,
tawraste

 

[tawraste]

cheers malcolm!

 

[malcolmsanford]

hi glenn,
could you post a link to that pack please? would be of interest. also, your boss installed an rcd instead of an rcbo because the main switch is the one in the old board?
cheers,
tawraste

I would have assumed he fitted a double pole RCBO rather than an RCD/MCB. I would class a sub board like that as a seperate installation and so to reg 537.1.3 it should have main linked switch or a linked circuit breaker that will isolate boih LIVES.

If he had Henly blocked the tails as is normal, then by isolating the main switch on the existing CU, will not isolate the other installation covered by the sub board, and so technically then it is "another installation"

 

[telectrix]

hi, malcolm. did that CU thursday. look at the pic on my thread called yesterdays job. (incoming L tail).

 

[malcolmsanford]

hi, malcolm. did that CU thursday. look at the pic on my thread called yesterdays job. (incoming L tail).

Not to hijack the thread mate .......................bit of red tape??

 

[telectrix]

Not to hijack the thread mate .......................bit of red tape??

only had brown with me. not really a hijack tho, was a 3036 board so slightly relevant

 

[tawraste]

where there are seperate boards i can see that they will have their own means of isolation of supply, but the kind of arrangement i had in mind is where someone has literally attached a 2 way enclosure to the wall next to the old cu and wired in the protective device to the old rewireable boards' rails.
i've seen showers done this way twice, and that prompted my initial enquiry.
my question about the rcbo was based on the requirement for an rcd not to be a main switch. i.e, in the above arrangement where there is not an existing rcd, surely you would need to have an rcbo? if there was an rcd installed rated at 40A 30mA, then the rcd would not be rated to support an overload because the upstream main switch would be say, 100A?

 

[malcolmsanford]

yos malcolm, it was done through a henley block and an earth block for the earth upgrade 10 to 16mm so what you are saying is link the new board through the old board via a fuse which will be 5 second disconnection time and then you isolate everything via the old boards main switch.

No i'm saying the new board should have a double pole device as in regulation 537.1.4 for isolation at the origin of the installation. As that new CU is obviously a seperate installation within the house and should have a means of double pole isolation.

 

[malcolmsanford]

where there are seperate boards i can see that they will have their own means of isolation of supply, but the kind of arrangement i had in mind is where someone has literally attached a 2 way enclosure to the wall next to the old cu and wired in the protective device to the old rewireable boards' rails.
Yes though I would not class that as good practice. If you had a 25mm set of tails in that switch, then it would be nice a cozy, and could stretch reg 526.1. A better way in my mind to do that is feed the enclosure with the new protection devices off of a spare way in the CU, and if none are available then henly block the tails.
i've seen showers done this way twice, and that prompted my initial enquiry.
my question about the rcbo was based on the requirement for an rcd not to be a main switch. i.e, in the above arrangement where there is not an existing rcd, surely you would need to have an rcbo? if there was an rcd installed rated at 40A 30mA, then the rcd would not be rated to support an overload because the upstream main switch would be say, 100A?

On your scenario you would need either a combination of RCD/MCB or a RCBO as the RCD alone would not be giving you overload protection,