Kitchen Wiring

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polarity

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Hi All

Good to be back after an electrical "vacation" putting in windows and knocking down walls!

Now preparing for fitting our new kitchen and doing the same electrically as I did with the bathroom (in an earlier thread), ie installing it and getting it inspected at 1st and 2nd fix then tested - this time by the LABC's people as they never did sort out the grey area of a qualified electrician signing off the bathroom (despite that being exactly what LABC do when you pay them...).

So as before please, I would welcome any input in case there is some rule/best practice I am inadvertently breaking, or might not have accounted for also, have a couple of questions...

So ...(NB this is a bungalow with NO access to most of the roof space and solid floors)

Two Ring Mains already feed the kitchen.

Ring Main #2 drops down the kitchen wall (buried) in a corner to an existing double socket above existing units. A new kitchen cabinet will be placed above it so I will replace the socket with an under cabinet unit one like this http://www.tlc-direct.co.uk/Products/KS104.html.

The next existing socket on RM #2 comes down the wall on the other side of the kitchen, so I intend to isolate between the two and extend the ring by going down the wall from the cabinet skt into the service void behind the units and clip it to a batten about 600mm from the floor, where it will run horizontally, until the next new socket at which point it comes up, under the spashback and services the socket, comes back down and carries on doing this until it reaches the RM#2 socket mentioned.

For integrated appliances I will run the ring through a surface mounted, switched, socket on the inside of the kitchen units on the 18mm thick backs and bring the moulded plug in through a hole. I have read a lot of discussion on this method (this for a start http://www.talk.electricianforum.co.uk/showthread.php?t=1594 ) but it seems to be very common practice and sensible in terms of access/aesthetics.

RM #1 is a similar set up with a socket in another part of the kitchen, but the next socket on RM#1 (again coming down the wall) is not in a good place - if I remove it and just carry on the cable down to the void, I lose the safe zone above so have to rip out the plasterboard and mechanically protect its cable, so instead was thinking to cut it out of the ring with a JB before the wall drop (one bit of the loft I can get too!) and extend the ring out and back from the first RM#1 socket.

Both RMs are on RCBOs

The electric double oven (5.7KW) and induction hob (7.2KW) are going in on two 6mm radials/32A breakers, again coming in from overhead - but not yet installed

Q - these cables will travel a short distance chased into the wall above a tall cupboard, not in a safe zone (unless I install plates which could be done). If not in a safe zone what mechanical protection do I need, can I use any available earth for it, and would they then need an RCD each?

These cables will travel on the same batten and up to two cooker isolators switches before splitting off to their respective loads.

Q All plumbing will be in plastic/push fit, it's 5m+ to the nearest (bonded) copper pipe - what if any, are the bonding considerations?

Sure there will be a few more Q's!

Thanks all!

Polarity

Kitch elect (Large).jpg

 
The RM stuff sounds ok, will the JB be in the attic and will it be visible/accessible for maintenance if not you may want to use one of these

Are you able to do a picture for the cooker cables like you did for the RM's so we can see your route? Would putting the cooker isolator in the cupboard you mention going over create a safe zone? Not ideal to have it in a cupboard but as long as it is within 2m of the appliance and accessible it would be ok.

 
Why two radials for the oven and hob? A single 32A/6mm cooker radial is good for up to 15kW. With diversity your total cooking load comes in at 24A. IMO you're wasting cable, accessories and time.

I would urge you to find a route that goes through the safe zones. if you cannot then 3mm steel is the level of protection you need. And put a note on the CU - some kitchen fitter is going to try and drill through it to fit a new cabinet in a couple of decades time! You should earth it to the same circuti it's protecting, preferably. Otherwise another note on the CU.

The copper pipe is already bonded, you say. Leave it as it is.

For RM1 mod, use crimps or a maintenance free jb.

 
Good point Ian, thanks, - yes it would be accessible but I will use an Ashley JB or Wago's anyway (BTW are push-fits in a chocbox acceptable as maint. free boxes?). Pic attached (with single 6mm)

Good thought PC, I did not think about the diversity calc, as there are 2 x 6mm already run that I managed to fish out and re-route. Having said that If I can get away with one and a single isolator that would be much better - I would like to make the isolator not visible but within 2m so it would have to be between the oven and hob - any suggestions from the pic?.

To create a safe zone I can put a plate above the tall cupboard out of sight, much easier.

Thanks

Kitch elect 6mm.jpg

 
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