cooker circuit

[pixielee9]

is it necessary to have an rcd supply for a cooker circuit

 

[PrenticeBoyofDerry]

It can be excluded, but would depend on the situation.
If the cooker circuit was installed prior to July 1st, 2008, then there was no requirement for it.
If after that date, then any cable buried less than 50mm in walls, that are not mechanically protected would require RCD protection, as would any newly installed socket. Cooker circuits are normally hardwired without a socket outlet but a cooker outlet, therefore it is the method that the cable is run, that would determine if RCD protection would be needed.

The 50mm rule, includes the reverse side of the wall. Taking note of that, there is also a building regulation that does not allow wall chases to exceed a 1/3rd of depth vertically and 1/6th horizontally of a single leaf/skin of the wall. So that does not include double skin or cavity walls. This is a structural regulation (Part A of Building regs)

 

[pixielee9]

It can be excluded, but would depend on the situation.
If the cooker circuit was installed prior to July 1st, 2008, then there was no requirement for it.
If after that date, then any cable buried less than 50mm in walls, that are not mechanically protected would require RCD protection, as would any newly installed socket. Cooker circuits are normally hardwired without a socket outlet but a cooker outlet, therefore it is the method that the cable is run, that would determine if RCD protection would be needed.

The 50mm rule, includes the reverse side of the wall. Taking note of that, there is also a building regulation that does not allow wall chases to exceed a 1/3rd of depth vertically and 1/6th horizontally of a single leaf/skin of the wall. So that does not include double skin or cavity walls. This is a structural regulation (Part A of Building regs)

 

[PrenticeBoyofDerry]

what?

 

[ban-all-sheds]

It can be excluded, but would depend on the situation.
If the cooker circuit was installed prior to July 1st, 2008, then there was no requirement for it.
If after that date, then any cable buried less than 50mm in walls, that are not mechanically protected would require RCD protection, as would any newly installed socket. Cooker circuits are normally hardwired without a socket outlet but a cooker outlet, therefore it is the method that the cable is run, that would determine if RCD protection would be needed.

The 50mm rule, includes the reverse side of the wall. Taking note of that, there is also a building regulation that does not allow wall chases to exceed a 1/3rd of depth vertically and 1/6th horizontally of a single leaf/skin of the wall. So that does not include double skin or cavity walls. This is a structural regulation (Part A of Building regs)

Yes, we know he did.

 

[ericmark]

is it necessary to have an rcd supply for a cooker circuit

No

It may be needed for other reasons, new circuits not surface and not wired with one of the permitted cables, for example, but keeping the answer to question asked answer is no.

 

[PrenticeBoyofDerry]

No

It may be needed for other reasons, new circuits not surface and not wired with one of the permitted cables, for example, but keeping the answer to question asked answer is no.

But the answer is not a simple one, as it could quite easily be necessary to require one.
So the answer depends on when and how the circuit was/is constructed.

For example:

I am having a cooker circuit installed, the cable is to be chased into the wall at a depth of about 15mm, to allow the twin and earth cable to be plastered over, there will be no additional protection, the specification on the appliance states it can be connected using a flexed cable with a 13A plug. Does this circuit require RCD protections?

So that answer would be different to:

I have just purchased a property, there is an electrical report/certificate, stating that a cooker circuit was installed in 2007, the twin and earth cable is buried in wall just below the plaster, the cable has no mechanical protection and there is also a socket outlet on the circuit. Does this require RCD protection?

 

[ban-all-sheds]

So, then...

is it necessary

Not necessarily.

Whoever is designing the circuit, and making that decision, should be aware of this information:

http://electrical.theiet.org/wiring-matters/54/-files/cables-in-walls.cfm?type=pdf
http://electrical.theiet.org/wiring-matters/54/-files/socket-outlets.cfm?type=pdf

Circuits cannot be competently designed by means of asking vague and incompletely specified questions on DIY advice sites.

 

[ericmark]

For example:

I am having a cooker circuit installed, the cable is to be chased into the wall at a depth of about 15mm, to allow the twin and earth cable to be plastered over

But where in the question was twin and earth refereed to? If one uses Ali-Tube which could be plastered over in the same way as twin and earth then RCD not required.

The question was simple, and the answer is simple it is "No".

There may be methods of install which would need a RCD, but that was not the question, there is one way where a RCD may be required, that is if the manufacturer stipulates it's use, even then with amendment 3 the blind following of manufacturers instructions has been removed.

 

[ban-all-sheds]

But where in the question was twin and earth refereed to? If one uses Ali-Tube which could be plastered over in the same way as twin and earth then RCD not required.

Circuits cannot be competently designed by means of asking vague and incompletely specified questions on DIY advice sites.

The question was simple, and the answer is simple it is "No".

No, the question was simplistic, and the correct answer is not "No". Examples of correct answers are "possibly", "not necessarily" and "it depends".

 

[PrenticeBoyofDerry]

But where in the question was twin and earth refereed to? If one uses Ali-Tube which could be plastered over in the same way as twin and earth then RCD not required.

The question was simple, and the answer is simple it is "No".

There may be methods of install which would need a RCD, but that was not the question, there is one way where a RCD may be required, that is if the manufacturer stipulates it's use, even then with amendment 3 the blind following of manufacturers instructions has been removed.

There was no mention of t&e, nor was there mention of ali-tube, swa or metallic plate or depth of cable or socket outlet connection at outlet or isolator. I gave a couple of many scenarios, that would offer differing answer to the question.

There are too many variables regarding method of installation, cable used, cable protection, accessories installed and date of work.

So it is impossible to give a simple answer of no, as my examples are evidence of.
You are offering misleading information.

 

[pixielee9]

Thank you for your replies regarding RCD protection for cooker supply. The reason I asked was that after having work done in the kitchen, the electricians seemed to think that it WAS necessary. So in the absence of a spare RCD way in the existing CU. they proceeded to provide one by hacking the live copper bus bar away and fitting an RCD in the gap provided.
They then had the nerve to write in the certificate RECOMMEND REPLACING CONSUMER UNIT.
Part P qualified ?

 

[EFLImpudence]

Well, assuming they were correct and an RCD was required because of the work they had done then all seems satisfactory.

You say "hacking" but (again) assuming they did it properly then that is how it is done.

Why are you upset about a recommendation; you don't have to follow it.


It's nothing to do with Part P which merely states, in so many words, work shall be done to ensure safety.
A Part P qualification does not exist.

 

[ericmark]

It would be very hard to say if you needed a RCD or not in what you now describe, it would seem likely you did, it is also hard to work out from your description if the work was within the rules.

In a factory I can get a box and install DIN rail and build a distribution unit, however where there is no skilled person in charge, the rules change, so in any normal house we need to use a type tested distribution unit called a consumer unit, these have a maximum current of 125 amp and are single phase, in real terms they are 100 amp. The consumer unit can only be modified as instructed by the manufacturer, so in the main all parts inside the consumer unit must be made by the same manufacturer even if they will fit, the manufacturer has not done the type testing with other manufacturers stuff inside them.

They do have options which include cutting buzz bars to varying lengths, and fitting fuse holders, MCBs, or RCBO's, even in some cases relays and door bell transformers, but in the main they have to all be from same manufacturer. In some cases we all know that other stuff will fit, however although it may be safe, it does not mean we can do it.

The problem for an electrician is he needs to issue a minor works or installation certificate for every job, and on that document he needs to sign it is safe, and list any rules broken, even when breaking the rules does not make the installation dangerous, we can write what we want here, but we are not signing those documents, and so it is down to the electrician as to what he does and how much he bends regulations.

One has to use some common sense, and also watch ones own back, so if fitting a RCD and in doing so one has for example used wrong manufacturer maybe as now a discontinued board, recommending changing the consumer unit would be a good move. However he should really explain why he has done it. We are not allowed to make a home uninhabitable, so not to connect the cooker breaks the rules and fitting wrong make of RCD breaks rules so he has to decide on which is the best option. He really can't win.

Reading between the lines he seems to have done the best he could, where he went wrong is maybe not explaining why he did it.

 

[PrenticeBoyofDerry]

Thank you for your replies regarding RCD protection for cooker supply. The reason I asked was that after having work done in the kitchen, the electricians seemed to think that it WAS necessary. So in the absence of a spare RCD way in the existing CU

As has already been posted, if the cooker circuit was altered/extend/relocated and the new cable was buried in the wall less than 50mm, without mechanical protection. Then RCD protection is required. The same applies if any socket outlets were newly installed.
If the circuit was not altered in any way, then probably a RCD was not required.

they proceeded to provide one by hacking the live copper bus bar away and fitting an RCD in the gap provided.

Again this has been already been touched on, if the busbar has been altered, it could be that the RCD fitted was not manufactured and type tested for the CU and could be consider a risk at worse and bad practise at best. But I would code this on an inspection.

They then had the nerve to write in the certificate RECOMMEND REPLACING CONSUMER UNIT.
Part P qualified ?

Well it is only a recommendation and as the wiring regulation now ask for non-combustible units/enclosures to be installed. Then that would be a common recommendation/observation.