Oven & Hob Wiring, Part P etc.

[RealPolitik]

Thanks again.

I don't have Part P in front of me, but there's a lot of contradictory information on the internet. For example, diyfaq.org.uk says:

"In general, ANY cable which is less than 50mm below the wall surface AND is NOT mechanically protected as defined by the IEE Regulations... MUST HAVE a 30mA non timed delayed RCD protecting that circuit, in addition to all other requirements."

More reading required.

 

[echoes]

Thanks again.

I don't have Part P in front of me, but there's a lot of contradictory information on the internet. For example, diyfaq.org.uk says:

"In general, ANY cable which is less than 50mm below the wall surface AND is NOT mechanically protected as defined by the IEE Regulations... MUST HAVE a 30mA non timed delayed RCD protecting that circuit, in addition to all other requirements."

More reading required.

Well, in general, that's true, but that depth applies to cables in walls, not clipped to the surface or in trunking.

The OSG says (paraphrased because I can't be a***ed typing out the lot):

RCDs are required:
(i) where the earth fault loop impedance is too high ... e.g. TT system
(ii) for domestic socket-outlet circuits
(iii) locations containg bath /shower
(iv) ... mobile equipment <= 32A outdoors
*(v) for cables without earthed metallic covering installed in walls or partitions at a depth of less than 50mm and not protected by earthed steel conduit or similar
(vi) ... walls or partitions with metal parts ...

*Cables on the surface do not require RCD protection.

Specific labelled sockets not requiring RCDs as per (ii) to (iv) do not require RCD protection.

* My bold

Out of interest, did the electrician say why an RCD was needed?

 

[RealPolitik]

Most helpful.

The RCD was apparently required because it was a new circuit and regulations required an RCD on all new circuits.

 

[ban-all-sheds]

But that's just it - they don't.

 

[RealPolitik]

Another electrician, needs RCD because stuck on a surface is less than 50mm deep in it.

His price was reasonable despite, so he's got the job.

 

[ban-all-sheds]

And what do you get when you pay peanuts?

This person (I won't falsely call him an electrician) is ignorant and incompetent beyond belief. You've got someone with below average reading and comprehension skills and below average intelligence who is utterly incapable of thinking and truly understanding the type of work he is fraudulently charging you to do and which you delusionally think he is capable of doing.

Best of luck - you're going to need it.

 

[echoes]

"Cables on the surface do not require RCD protection."

I can see how that might be open to interpretation...













...by a c**k.


We tried, OP!

 

[RealPolitik]

And what do you get when you pay peanuts?

This person (I won't falsely call him an electrician) is ignorant and incompetent beyond belief. You've got someone with below average reading and comprehension skills and below average intelligence who is utterly incapable of thinking and truly understanding the type of work he is fraudulently charging you to do and which you delusionally think he is capable of doing.

Best of luck - you're going to need it.

Wow - what a chippy response.

His work has been recommended, it's a very simple job for which I need a certificate, it's a fair price and I simply do not have the time to wait around for another four electricians to tell me I need something I don't because they either can't or won't correctly interpret the rules.

You seem to forget that most tradesmen possibly aren't the best-equipped to interpret rules, most are out to make as much as they can and a fair proportion don't really care about their trade.

Your average electrician/plumber/carpenter/decorator is unlikely to even know about sites like this, let alone post on them so don't assume the knowledge here is in any way representative.

It's nothing to do with being delusional, it's to do with being pragmatic.

 

[ban-all-sheds]

I simply do not have the time to wait around for another four electricians to tell me I need something I don't because they either can't or won't correctly interpret the rules.

You don't get it, which is quite understandable if you don't have a copy of the regulations to look at.

There is no "interpretation" involved. The relevant regulations are 522.6.6 & 522.6.7.

522.6.6 begins "A cable concealed in a wall or partition at a depth of less than 50mm from a surface of the wall or partition shall:
(i)... or
(ii)... or
(iii)... or
(iv)... or
(v)..."

522.6.7 begins "Where 522.6.6 applies...." and is the one which calls for an RCD if the wiring is not going to be under the supervision of a skilled or instructed person if certain of the (i), (ii) etc are the ones chosen to deal with a cable concealed in a wall or partition at a depth of less than 50mm from a surface of the wall or partition.


But a cable on the surface of a wall is not affected by the regulation, because it is not concealed.


522.6.6 clearly does not say

"A cable not concealed in a wall or partition at a depth of more than 50mm from a surface of the wall or partition shall:
(i)... or
(ii)... or
(iii)... or
(iv)... or
(v)..."

The purpose of those 2 regulations is to reduce and mitigate the risks of someone drilling or nailing etc into a cable which he cannot see because it is concealed in a wall or partition and which is at a shallow enough depth (<50mm) to make it likely that a drill or a nail etc would reach it.

So you have got an "electrician" who obviously just does not understand the purpose of the regulations he is "using" and who equally obviously just cannot read and understand perfectly clear, perfectly simple, and perfectly unambiguous English.

Recommended or not, you have got an "electrician" who cannot read or understand the Wiring Regulations.

Good luck.

 

[ajrobb]

Check the oven's installation instructions. Do they say that the oven must be protected against current over 16A? You might be able to use the existing 13A socket for the oven or you might need a separate radial. You might NOT be able to share a single 45A cooker point for oven and hob. You probably need to spend a small fortune to upgrade the electrics. It's not as easy as slot-in cookers.

Personally, I think the fashion for a separate hob over a built-in oven is daft. If it's arranged like a cooker, I'd have a cooker. I'm planning a new galley kitchen in a refurbishment and I have to go with separate hob over oven because that is what fashion dictates. I wouldn't do that in my own kitchen. Put the oven at counter height on the other side of the kitchen by all means. (rant over)

Is it OK to run a concealed CU (16A and 32A) from the switched side of a 45A cooker point?

 

[echoes]

Check the oven's installation instructions. Do they say that the oven must be protected against current over 16A? You might be able to use the existing 13A socket for the oven or you might need a separate radial. You might NOT be able to share a single 45A cooker point for oven and hob. You probably need to spend a small fortune to upgrade the electrics. It's not as easy as slot-in cookers.

Maunfacturer's instructions could be adhered to by using a plug+socket or fuse-only FCU between the CCU and the oven. The CCU switch will satisfy requirement for double pole isolation.

Is it OK to run a concealed CU (16A and 32A) from the switched side of a 45A cooker point?

Don't see why not. Or take 6mm2/10mm2 to a dual outlet or a double back box with outlet + FCU/socket.

 

[ajrobb]

Is it OK to run a concealed CU (16A and 32A) from the switched side of a 45A cooker point?

Don't see why not.

Something like
http://www.screwfix.com/prods/95875...K-Consumer-Units/MK-2W-4-Module-Consumer-Unit
with just a couple of MCBs (no isolator or RCD, as these would be provided by the cooker point and main CU respectively).

 

[RealPolitik]

Back to the original question - the CU had a dedicated supply to an immersion heater (just removed). It's 6mm cable and is switched via the kitchen (big cable into the switch, big cable out up to the old water tank), right where the oven is going.

Could I use this cable run for the oven and hob (assuming it's big enough)?

 

[ban-all-sheds]

Firstly, what happened to the trustworthy electrician who will be doing the work and from whom you need a certificate? Why isn't he deciding if that cable can be used?

Secondly it's very unlikely that 6mm² cable would have been used for an immersion heater. They're usually around 3kW max. What's the rating of the MCB?

Are you sure it's a cable with L&N conductors with a csa of 6mm², and not a 2.5mm² cable which is

a) much more likely for an immersion heater
b) about 6mm across.... //www.diynot.com/wiki/electrics:flatpvccables

 

[ajrobb]

Take yourself to a DIY store and look at their cables. Immersion heater cables are usually 2.5mm² single strand conductors (but the cable drums are often mislabelled 2.5mm). Cables for cookers often have 7 strand conductors.