Cooker installation

[Luvverboy]

I am moving and upgrading a hob/oven installation. The cable is currently 6mm and fused at 30A. The max connected load of the new appliances is
11.8KW = 11800/240 = 49A. Using diversity the rating is 10A + 30% of the remainder of the total connected load. Equals 10 + (30 * 39)/100 = 21.7A

Can i use both new appliances off the existing cable?
What is the best way to extend the length of the cable or should a whole new run be installed?

 

[Steve]

in general, its not a good idea to apply diversity to cooker installations, sinc there are times when all of the elements will be burning, despite cycling on thermostats.

For the figure of 21.7A, you can run it on the existing circuit, but i would be tempted (if it were my own house) to use a 45A MCB and 10mm² cable. This gives you plenty for the "christmas day scenario" when you have all the family round and all the hob rings and both ovens are on. Your choice.

If you are extending the circuit, best advice is to use a new piece of cable. And as you are ripping it out, why not upgrade to 10mm² at the same time?

 

[Luvverboy]

Thanks for the recommendation.

Running a new cable is going to require a lot of raising of floors as I suspect I cannot pull the new cable through with the old although it is worth a try. Perhaps I can find a new route.

Is it likely that I can change the 30A breaker to a 45A in the existing consumer unit?

 

[Steve]

Could you find another route for the cable? Just a suggestion: sometimes an obvious route is staring you right in the face. Dont try to pull the cable through if its an awkward run: you may end up damaging it.

Post a picture of your consumer unit, or find a model number and someone will be able to tell you if you can get 45A breakers. But dont fit a 45A without fitting new cable first - this needs 10mm².

By the way, i didnt notice your mistake earlier: UK voltage is 230V, not 240V. though it is allowed to vary between about 215 and 250V.

 

[Adam_151]

You considered SWA on the outside of the building?

 

[baldelectrician]

you could just run another 6mm, one for hob and one for oven, job sorted

 

[Luvverboy]

I have a run of around 3 metres under floor to pull through (about 6 rafters). I am going to give it a pull. If it moves easily I will pull through. If not I will consider taking up the floor (a real pain as it's a laminate floor).

The consumer unit is a Wylex 604 IVY. It is currently fitted with B6, B6, B16, B32, B32, B20 breakers. The unit is rated at 60A. It appears I was wrong in thinking the Cooker was on a 30A breaker.

I think upping the cable to 10mm² and the breaker to 45A or 50A is not going to work with this CU. I guess I either need an additional CU or replace the existing one.

I am considering getting the cable in place and then contracting an electrician to install the CU and certificate the system. Does this make sense?

 

[Steve]

I would find another route for the cable, will it not run under the base of the kitchen cabinets for example? Or in trunking along the top of the wall or on top of the wall cabinets? I wouldnt lift a nice laminate floor for anything! Would rather chase it into a wall!

http://www.tlc-direct.co.uk/Products/WY604.html does this look like yours? Could do with an upgrade, you just have plug in MCBs and no RCD protection. And the biggest breaker that board will take is a 40A, which would be ok, but not exactly robust for this application, and your fuse box sounds like its at its limit already.

Your suggestion sounds ok - route the cable yourself and get a spark to come an change the CU. Expect to pay about £300-400 for a decent job. Have him connect the other end of the cooker circuit too, including a cooker cable outlet behind the cooker location.

 

[plugwash]

<i>And the biggest breaker that board will take is a 40A</i>
not entirely true, the largest breaker wylex do for those units is indeed 40A. However GE do a range of breakers intended for use in wylex standard consumer units and they go all the way up to 45A under the name minitrip.

toolstation sell the ge minitrips and the bases to go with them http://www.toolstation.com/shop/Electrical/CircuitProtection/d190/sd2615

 

[Luvverboy]

Re Crafty1289. Yes that is the correct CU however the fuse cover has been cut so that the plug in MCB's will fit.

The £300 - £400 sounds a bit expensive if the CU is only around £100 however I agree an upgrade is probably the thing to do.

I am going to fit two cooker outlets, one each for hob and oven.

Still not certain about the cable run, I could possibly run it up into the loft to avoid the laminate which is a bit convoluted but but still cannot see an easy way of getting it back down and into the garage. I will keep thinking about that one.

Thanks for all the advice guys, this forum really works.

p.s. Are there any rules about where to chase cables into walls? Do all channels have to be vertical or can any angle be used?

 

[Steve]

in general, i think this is right: chased cables must run horizontally or vertically from any accessory (including blank plates for junction points or change of direction), and they may also run within 150mm of any ceiling and corner. I think thats it, just stated what i remember, there may be more permitted zones. Not sure if this is in "for reference"