No RCD = EICR fail ?

grumbler

Risteard said:

grumbler said:

Risteard said:

grumbler said:

Risteard said:

movilogo said:

markin said:

You don't want the fridge turning off for another device tripping so both would need replacing or rcbos used.

I won't mind  I lived in this house for decades without any issues and now just for letting I need to get EICR. So if just one RCD solves my problem then I'll go for that route. 

no-one can install one RCD for it.

Why can't it be one RCD?

For numerous reasons which I already outlined in a post above.

OK, hopefully I am the only one who cannot make sense of them.

But I am happy to clarify if you tell me which part(s) you don't understand.

OK, thanks.

* It doesn't mitigate the effects of a single fault causing loss of supply to the entire installation;

Does it have to? In my CU (mid. 90s) I have only one RCD  controlling the sockets and the shower. For the OP it can be kitchen ('cooker'), water heater and sockets.

* An RCD should not have cumulative Earth leakage exceeding 30% of its nominal rating - in the case of a 30mA device this is merely 9mA of leakage. It is unlikely that you could guarantee this across an entire electrical installation.

'unlikely' is less categorical than 'no-one can'. And if it's really the case, and the MCBs 5 and 4 aren't in use, I think there is place for one RCD and one RCBO in the CU.

Risteard

grumbler said:

Risteard said:

grumbler said:

Risteard said:

grumbler said:

Risteard said:

movilogo said:

markin said:

You don't want the fridge turning off for another device tripping so both would need replacing or rcbos used.

I won't mind  I lived in this house for decades without any issues and now just for letting I need to get EICR. So if just one RCD solves my problem then I'll go for that route. 

no-one can install one RCD for it.

Why can't it be one RCD?

For numerous reasons which I already outlined in a post above.

OK, hopefully I am the only one who cannot make sense of them.

But I am happy to clarify if you tell me which part(s) you don't understand.

OK, thanks.

* It doesn't mitigate the effects of a single fault causing loss of supply to the entire installation;

Does it have to? In my CU (mid. 90s) I have only one RCD  controlling the sockets and the shower. For the OP it can be kitchen ('cooker'), water heater and sockets.

* An RCD should not have cumulative Earth leakage exceeding 30% of its nominal rating - in the case of a 30mA device this is merely 9mA of leakage. It is unlikely that you could guarantee this across an entire electrical installation.

'unlikely' is less categorical than 'no-one can'. And if it's really the case, and the MCBs 5 and 4 aren't in use, I think there is place for one RCD and one RCBO in the CU.

Yes, it does have to. The consequences of the operation of any single protective device must be duly accounted for, and it is also required to avoid danger and minimise inconvenience in the event of a fault. It is further required that the possibility of unwanted tripping of an RCD due to excessive protective conductor currents not due to a fault be avoided. You must also take account of the hazards caused by the failure of a single circuit, e.g. a lighting circuit.

The use of RCBOs to protect individual final circuits in residential premises is also required to be considered, and the limiting of protective conductor currents to not more than 30% of the rated residual operating current of the RCD (I delta n) is also required.

I wasn't really being "less categorical" - it is essentially impossible to achieve this with one RCCB protecting an installation especially with the increase in electronic equipment; LED lighting; switch-mode power supplies etc.

Essentially the use of a single RCCB dated back to when these devices were very expensive. This is no longer the case. Nowadays even a dual RCCB setup is extremely difficult to justify as a design decision and as compliant with BS 7671:2018 (2022).

movilogo

So what is the answer for my original question?

1. Can I replace my main consumer unit with something like this? 
https://www.cef.co.uk/catalogue/products/4945937-10-way-dual-100a-type-a-rcd-high-integ-metal-clad-consumer-unit-with-10-x-mcbs
2. If answer is yes, then what would be a reasonable labour cost for an electrician to fit?
3. If answer is no, what do I need to pass EICR?

Thanx

Risteard

movilogo said:

So what is the answer for my original question?

1. Can I replace my main consumer unit with something like this? 
https://www.cef.co.uk/catalogue/products/4945937-10-way-dual-100a-type-a-rcd-high-integ-metal-clad-consumer-unit-with-10-x-mcbs
2. If answer is yes, then what would be a reasonable labour cost for an electrician to fit?
3. If answer is no, what do I need to pass EICR?

Thanx

As I mentioned all RCBOs would be the better option. I would leave it to the electrical contractor to source and supply the necessary equipment rather than randomly purchasing items.

An EICR does not "pass" or "fail". The installation will either be deemed to be in a "Satisfactory" condition to remain in service or "Unsatisfactory". The normal thing to do would be to have the inspection done - even though it may well be "Unsatisfactory" - and then upon receiving the Report to discuss what options there are for resolving those issues which led to it being classified as "Unsatisfactory". I think you're pulling the cart before the horse.

grumbler

1 - yes, you can. The question is whether this can solve the alleged problems.

My impression is that @Risteard is either incapable of explaining (most professors are the worst teaches) or deliberately overcomplicates everything.

Risteard said:

The consequences of the operation of any single protective device must be duly accounted for, and it is also required to avoid danger and minimise inconvenience in the event of a fault.

My understanding of this is that the problem is that your CU2 is connected not directly to the main switch, but to the 'cooker' MCB, i.e. you have MCBs connected sequentially. If so, then simply replacing your CU1 doesn't solve this problem as the cable between the CUs has to be protected by a MCB, not just by a RCD.

Risteard

grumbler said:

1 - yes, you can. The question is whether this can solve the alleged problems.

My impression is that @Risteard is either incapable of explaining (most professors are the worst teaches) or deliberately overcomplicates everything.

Risteard said:

The consequences of the operation of any single protective device must be duly accounted for, and it is also required to avoid danger and minimise inconvenience in the event of a fault.

My understanding of this is that the problem is that your CU2 is connected not directly to the main switch, but to the 'cooker' MCB, i.e. you have MCBs connected sequentially. If so, then simply replacing your CU1 doesn't solve this problem as the cable between the CUs has to be protected by a MCB, not just by a RCD.

Instead of being abrasive you should instead publicly state that you are not qualified or competent to give such advice, unlike me.

markin

movilogo said:

Actually he had not given me EICR. He said giving me an unsatisfactory EICR serves no purpose so he told me verbally and charged me his call out charges. 

When I used a lawn mower I used an extension cord from inside. I don't have sockets on outside wall.

If I need to upgrade to RCD how much would be a reasonable cost? 

Its presumed the downstairs rings are used that way and is why that ring needed RCD under the old regs (2007?), Now that RCD's and RCBO's are cheap they have to protect the idiot that drops a Toaster/tv/phone charger in the bath using an extension cord in the current regs

Risteard

markin said:

movilogo said:

Actually he had not given me EICR. He said giving me an unsatisfactory EICR serves no purpose so he told me verbally and charged me his call out charges. 

When I used a lawn mower I used an extension cord from inside. I don't have sockets on outside wall.

If I need to upgrade to RCD how much would be a reasonable cost? 

Its presumed the downstairs rings are used that way and is why that ring needed RCD under the old regs (2007?), Now that RCD's and RCBO's are cheap they have to protect the idiot that drops a Toaster/tv/phone charger in the bath using an extension cord in the current regs

Actually, socket-outlets which might reasonably be expected to supply equipment outside required RCD protection even under the 16th Edition of the IEE Wiring Regulations, long before 2007. The 17th Edition (2008) made this all socket-outlets essentially (and this has been further tightened after each Amendment and new Edition).

movilogo

There are standalone RCD plugs like this to mitigate this issue.
https://www.screwfix.com/p/masterplug-13a-fused-plug-through-active-rcd-adaptor/63731

BTW, there is an excellent YouTube video which explains all these in nice animation.

https://www.youtube.com/watch?v=W0_1xRqT8uU

grumbler

movilogo said:

There are standalone RCD plugs like this to mitigate this issue.
https://www.screwfix.com/p/masterplug-13a-fused-plug-through-active-rcd-adaptor/63731

  They do - IF they are used. Our regulators think that everything has to be fool-proof.