The customer wanted a CU just for the kitchen. So in goes the 16mm T&E for a CU in a kitchen cupboard that is quite a distance from the house CU and cutout.
I wish all customers could be so smart. Like he said "I'll probably have another new kitchen fitted with a diffent layout in 10 years time and the only room you will then have to make a mess in then is in the kitchen."
I used 16mm T&E to supply a small computer room. Quite a bugger to thread it anywhere, or bend it any way it isn't already bent. You can get 25mm T&E too...
;-)
Small computer room! Was this the power supply for Deep Thought?
You need to warm the 16mm up before you use it. I ran over 1000m of the stuff before Christmas in the cold. It just kept returning back to its coiled up position.
She looked the high maintainance type. I cannot see her using a kitchen though.
In message , ARWadsworth writes
Isn't this the Unwritten Rule of Kitchens? The more a kitchen costs, the less it is actually used ...
Smart? ... maybe for driving up the price of copper or lining the pockets of electricians :) Separate rings or even worse consumer units for individual rooms like kitchens are a pet hate of mine. In the vast majority of cases there is bugger all need for them unless you have a seat in the house of lords, a country house covering an acre or so and a commercial kitchen manned by full time staff.
The sparkies at work, accustomed to light work in an electronics factory, were most put out when I insisted on 16mil, 4-core, SWA for a UPS - and then wanted the 240V out in steel conduit. They wanted to move the UPS which, by the time of wiring, had 35 heavy-duty 12V batteries in it, rathet than try and bend the SWA to position.
Seperate rings for the kitchen are very common. And often the CU is in the kichen or next to it. In this case the guy is spending a little more now to save money in the future. He will be able to have everyone in to redo the kitchen without having to go into the rest of the house or lift up the wooden floors he is having fitted upstairs after this kitchen is done. The kitchen ceiling can be ripped down and replaced once everyone has done their work.
I usually install up/down/kitchen on a 3 bed house rewire/new build. Small 3 bed houses might get a kichen/rest of the house circuits.
The last kitchens I did predate 17th Edition. I install two rings, an RCD one for worktop and portable appliances, and a non-RCD one for some stationary/fixed appliances such as fridge, freezer, boiler, oven.
*in certain installation conditions* specifically reference method C, clipped direct to surface and ungrouped.
That is a slightly dangerous assumption - if the cable is grouped or running in less than idea conditions, the max current will be considerably less.
eg Ref method A, enclosed in thermally insulating wall etc it is 20A and in coduit in masonry it is 24A
If it is bunched with other circuits for any significant distance (more than
1/2m or so) it will be further derated.
Site conditions are very relevant and blanket generalisations are not really valid as you say.
I have 2 rings in my kitchen.
1 very short ring that has 2 heavy appliance FCU drops and 4 13A sockets in a location *highly likely* to have a combi microwave, toaster and kettle as well.I specifically ran both legs in such a way as to balance their lengths and tests with a clampmeter showed they were balanced all the way to a test load of around 40A.
The other ring takes a much wider path likely to be only used by lots of small appliances. That ring is shared with the bedroom that is the other side of one of the walls.
Where's the RCD going to reside? Unless you can make sure the 16mm T+E is more than 50mm from any surface?
You also need to ensure that taking a MCB in the kitchen CU through a fault won't also take out the MCB on feed for the 16mm cable, otherwise the whole exercise is pointless.
BICBW
ss
Buried in insulation means 4" or more all round, conditions that are usually not met.
Yes there are derating factors that can apply at times. But 2.5mm^2 cable can handle considerably in excess of its 17th edition ratings without harm in practice. There seem to be many that think 33A on a
32A circuit is dangerous, but normal working conditions include running at 45A for time limited periods only. Its not dangerous.NT
That may be true, but it is unwise IMHO to encourage designing to that assumption -
Indeed - provided the circuit is designed correctly, diversity applies and more importantly the circuit protective device will protect the cable ;-)
That should generally happen, as long as the feed cable has a higher current mcb/rcbo than 32A, i/t curves will generally result in discrimination.
I dont see why it would be.
NT
In the kitchen CU with RCBOs. The cable route is OK without RCD protection.
No. You are not wrong.
Of course fuses/MCBs sometimes seem to disagree with me with regards to discrimination. Old fuses are often not up to the job.
If your happy to argue with the good folks at the IET, be my guest.
Just because you can "get away" with anomolies does not mean one whould design to such. The design criteria of a 32A British ring is based on each leg being rated to 20A maximum. You can argue that in eceptional cases (such as the carefully balanced ring I installed) you can safely run the whole circuit at 40A forever, does not mean the rules are wrong. The rules are a general case where many variations are expected to occur and the conservative choice of 20A was presumably chosen as being on balance safe for most typical installations.
You can of course ignore the IET regs, and design something specific for a particular installation - but that's not something anyone can easily do (and defend).
The particular point I questioned that you made was an unqualified claim that 2.5mm2 was good for 27A - this is a public group with archiving, so I felt it reasonable to clarify that.
I dont think you've understood what I said
And fwliw, yes I can put a better case than Mr Lovegrove easily.
NT
16mm 4 core armoured is light work:-)
It would not be a good design if you did not try to cascade the devices.
In this case it is the feed for all of the kitchen, lights, cooker, sockets everthing.
Indeed, I visited one of the datacentres we have servers in yesterday, not been there for a few years and they've done some re-wiring since, two incoming SWA cables the size of drainpipes, the cable tray running above the racks is earthed using two 240mm^2 "singles".
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