The Inspector Calls - Part P

[TheScullster]

Hi all

For anyone interested, I had my first fix kitchen inspection this morning by our BC electrical guy.

Very amenable chap, happy to explain stuff 2 or 3 times for "a bear with very little brain" (sorry - hard day - needed to include Winny the Pooh quote to enable sanity to be maintained).

The good news: happy for me to continue with install to 16th Edition Regs and for brother-in-law to do testing (or at least guide me with the same). Looked at the main earth provision and was satisfied. Declared that supplementary bonding would not be required in the kitchen.

The bad news:

Maybe this is a misunderstanding on my part, but he wants the breaker sized on the total max connected load for oven and hob with no diversity considered. His take on diversity is that it is for whole house assessment only and should not be considered for individual mcb/cable sizing etc. This means that I will have to fit a 40A breaker to give 9600w (@ 240v) - which just about covers a hob (6.6Kw) and single oven (2.8Kw). As luck would have it SWMBO only wants a single oven, but I would have preferred a double.

Isolation of white goods - his rule is that free-standing under-worktop equipment can be isolated in an adjacent cupboard, but integrated appliances must have a separate visible isolator above the worktop. This means a lot of re-work for the oven supply isolator as this was intended to be at the back of an adjacent utility cupboard. Also integrated dishwasher will need supply re-work - this is currently a socket at the back of a cupboard.

Smaller items included: data cables (TV, telephone and alarm) need to be in trunking at points where they come within 50mm of power cables - something to do with the low insulation rating of the cable screening. Where a water pipe passes in front of electrical trunking he wants 50mm between trunking face and pipe face.

I have made provision for an outside socket isolated by a DP fused spur. I was considering fitting an RCD socket, but wasn't sure whether this would work. To ensure discrimination between this and the ring RCD, the socket RCD would need to be 10 or 15mA according to BC guy. Are these available as normal sockets and will they simply trip out frequently when used on garden equipment due to low rating?

He must have noticed the look of horror/dejection/impending suicide on my face when he mentioned the cooker feed etc. cos he was quite complimentary of the work standard in general. He will return once I have made the first fix changes.

Could have been worse I suppose, but I was hoping that the dirty stuff was done!

Going home soon to ponder the re-work method now.

Phil

[nimbusjunk]

[The Natural Philosopher]

I think he sounds a bit of a wanker frankly.

Make that a total wanker.

That sounds better. Mine are off rings which I really must fit with RCBOs' when I get...

I am not sure he has the regs aright. You should double check. My BCO pointed out that the regs insisted on guttering the roof. I pointed out wthat while the regs specified what sort of guttering was supposed to be used, they did not specify that guttering had to be used at all - e.g. on a thatched roof. Provided there was some means of keeping drop water clear of te walls and dealing with it at ground level..the regs are in fact staisfied.

I.e. its a dangerous game, but you can quote the book back if you are.

What the regs are MOSTLY are not a set of things you MUST do to achieve a certain structural or safety goal, they are more about a particular issue, followed by 'standard methods that will meet this requirement' BUT as long as you can meet the PURPOSE of the regs, you don't need to meet the letter of the suggested solutions.

Fr example, you need to be able to get out of an upstairs bedroom window in case of fire.. Or do you? Not sure but as I understand it if there is e.g a second exit to a second set of stairs, then you might argue..that alternative exists are in fact covered by that.

[ARWadsworth]

I AM interested as I have done a couple of Doncaster Councils Part P inspections.

Was it ever required?

He does not know as much as some posters on this newsgroup:-)

Again, he is wrong.

Indeed. Tables 7.6 and 7.7 of the OSG apply.

A little OTT if they are crossing each other

A 10mA socket may help, however I would not bother as it will not guarantee discrimination.

I would appeal against the cooker decision. The BC guy cannot overule the IEE rules on cookers.

I would ponder how to convince him that he is wrong with the cooker and the integrated appliances.

[Doctor Drivel]

Yep. Integrated appliance can be isolated in a cuboard in the kitchen. Look at all the designer kitchens, yiu no isolators I have seen 20A grid switches with 13A fuses in walk-in cuboard for all appliances - integrated or not. In fact a free standing plugged in appliance does not need an isolating switch at all AFAIK.

What if CAT 5 cable is used?

Yep. Not sure about CAT 5.

I would a split RDD CU. All circuits are on an RCD. Or RCBs all around.

[John Rumm]

Most of them are IME...

Alas he is wrong on this. I would be tempted to go back with a "could you clarify something for me" type of approach, so as not to be too confrontational. Then follow up with "Perhaps I misunderstood, but reading appendix 8 page 154 of the 16th edition of the OSG it says I should apply diversity to the circuit sizing"

If he still does not agree, then see if you can get him to agree to let you ask an electrician and be guided by his advice. (for which you have a handy cut out and keep posting from Adam elsewhere on this thread!)

FYI:

"The rating of the circuit is determined by the assessment of the current demand of the cooking appliance(s), and cooker control unit socket-outlet if any, in accordance with Table 1A of Appendix 1. A 30 or 32 A circuit is usually appropriate for household or similar cookers of rating up to 15 kW."

(same wording used in the 17th edition, section 8.4 page 160)

What he says makes sense for stuff that is wired into a FCU perhaps, but I can't really see a problem with a socket at the back of an adjacent cupboard.

There is no harm in having a lower rated trip on a garden socket, although this won't actually ensure discrimination. Any leakage over the threshold of both devices could trip either or both.

Also if the circuit already has 30mA RCD protection, then the requirements of BS7671 are met without any additional RCD.

Generally there ought not be much leakage on garden tools etc.

Mostly rework on the BCO's knowledge by the sounds of it ;-)

[ARWadsworth]

Well tables 7.6 and tables 7.7 of the OSG apply

Don't worry Nursie will see to it for you.

Would you fit that with a hacksaw?

[ARWadsworth]

The BCO may need the Iz and Id of the cooker supply cables inserting into one of his orifices. I'll happily supply the vocal parts if TheSkullster gives me the BCOs phone number.

They all seem to be class II or petrol powered these days.

[Doctor Drivel]

So Cat 5 is OK then?

[ARWadsworth]

As long as you keep it 50mm from mains cables then yes.

[Doctor Drivel]

Gosh! That is running in parallel. Whay about crossing a power cable with CAT 5?

[ARWadsworth]

Yes in parrallel. I would aim for a bigger gap.

If they cross there is not usually a problem. 50mm seems like a good gap.

[Hugo Nebula]

This chap sounds more like an electrician than a BCO. I certainly wouldn't have a clue on any of the issues mentioned.

[Tim Watts]

ARWadsworth ( [e-mail]) wibbled on Thursday 17 March

2011 20:31:

I must admit I don't worry too much with CAT5 used for ethernet. I've seen abominations under computer room floors with mains flex, armoured and CAT5 all mixed up in a right rats nest - same in the back of 19" racks too - 20 bits of mains flex and networking going up the side in a bundle. OK, your ISP or major bank datacenter do it nicer, but your average university does not always.

Thing about CAT5 is it is both balanced drive and the ends are isolated with transformers too - so you are very unlucky to get any intereference. And even if the odd power spike killed a packet, the higher protocol layers generally sort that out.

Technically CAT5 is not rated to 240V but to be honest, I reckon the sheath is actually good for a kV at least in any practical interpretation of reality - and if it comes into contact with bare 240V metal, you've got other problems anyway.

But Adam is stating the by-the-book way which is perfectly good to aspire to

- but sometimes it's not always possible to achieve without a lot of effort.

Cheers

Tim

[D.M.Chapman]

All kept nice and sperate - and then strapped together and run through the cable management arms to the server...

Mains power and UTP all tied together with velcro straps. Never had a problem - not really any option tbh.

Darren

[TheScullster]

"John Rumm" wrote

Thanks both John and Adam

Although I have researched a lot of this stuff before implementing (with invaluable help from both you, Adam and others here), I am not a "think on the feet" kind of guy unfortunately. So although I had done the sums including diversity etc I couldn't focus clearly enough to confront him confidently with my figures/approach.

Although it means significant re-work, I might concede the point about accessible isolation points for integrated items. From previous group discussions, this does seem to be a matter of individual preference/open to some interpretation

I will certainly go back on the cooker cable sizing and circuit rating though, as this did/does seem fairly clear in the OSG. The BCO referred to the green "Guide to the Regs" as his point of reference. I don't have a copy of this unfortunately, so cannot consult the appropriate reference to cooker cable sizing.

Phil

[TheScullster]

"ARWadsworth" wrote

Yes thanks Adam - I know you are interested from the help and advice you've given in the past.

I'm thinking about bonding of pipes and lugs on sinks.

Do you have a 16th edition reference to support this?

I'll try to put some diplomatic words together to support the use of diversity on the cooker circuit - it is not absolutely clear from the on-site guide, but does the reference to diversity and 30/32A circuit being good for 15Kw include the breaker rating? He seemed to want to start with the breaker and work backwards IYSWIM.

Thanks again Adam

Phil

[MuddyMike]

I like the idea of isolators for built in appliances and would automatically fit them. I would still use a 13amp socket at the back of the cupboard as well (if that is allowed) as most appliances come with a plug moulded onto the lead.

Mike

[Skipweasel]

That's the usual plan - switch above the counter, socket below.

[sm_jamieson]

My understanding is that the cooker needs a visible isolator above (standard cooker isolator) even if on a plug - not sure where I got that from. However, other build-ins are fine with just a socket that can be unplugged (unless they are hard-wired with no socket of course). In fact, an unswitched socket is really better, since you have to rely on the plug being removed, which is a better physical obstacle than just a switch.

Simon.