Number of appliances on one radial line

Presumably on a 20A MCB?


It does seem slightly mean, but I suspect it's unlikely to give problems in reality. Normally there a fair bit of diversity between kitchen appliances. I presume the boiling water tap is the 13A variety and will only be heating either when the tap is on or occasionally at other times to top up the heat in a stored tank. A dishwasher and washing machine will usually only take full power during the relatively short water heating part of the cycle. A conventional tumble dryer might well take a decent load (10A perhaps) for an extended time - hopefully a modern condensing mode dryer (usually what's in combined washer/dryers these day I think) should take rather less. I suspect the coffee machine would be drawing current for only a matter of a few minutes in an hour on average (and probably a lot less than 13A even then).


A 20A circuit doesn't have an absolute limit of 20A - 20A is what it can supply indefinitely - both the cable and MCB/fuse will be quite happy to supply more for short durations (say 30A for perhaps 10 or 20 minutes - that sort of thing) - so there's little risk if several appliances do occasionally happen to switch on at the same time.


A more conventional arrangement might be a 32A ring circuit (wired with two 20A cables) - but is (as is often the case) it's not well balanced, you can still have a a large proportion of the kitchen appliances' current going through a single 20A cable - and likewise actual problems are rare to non-existent.


If you had an entire kitchen/utility on there - perhaps including an electric oven or two - as well as many more sockets and perhaps separate washer and dryer, I might be more inclined to ask for an upgrade to a 32A circuit. But as stands it's less clear cut. If it were my house I would have put in a 32A radial as a minimum - but then my other half does keep throwing the phase 'never knowingly under-engineered' at me. Ultimately if the builder is working for you, they should be doing things to your satisfaction.


   - Andy.

If it is a new circuit, I cannot see any good reason not to use 4 mm² cable on a 32 A breaker. This assumes that the cable is not hidden deep in insulation in a stud wall, etc.

A bit mean, I reused the original 4 mm’ish imperial cooker circuit at home with a B32 MCB to supply a TV, microwave, washing machine, dishwasher coffee machine, kettle and a couple of spare sockets with USB charging.


Given that we have a 60 amp main fuse that circuit can take half the available capacity for the whole house, even if we had a 100 amp main fuse it would be a third of the available capacity for the whole house, so no need to get too carried away with it and have multiple circuits.


I bought a datalogger and it only records current above 10 amps and it barely recorded usage above that in an entire week when I tried it out at home, the dishwasher and washing machine rarely go above 10 amps even when running at the same time.

 I tried it out at home, the dishwasher and washing machine rarely go above 10 amps even when running at the same time.


Now that's what you call multitasking Andy!


Regards


BAD on Friday pm

A 20 amp circuit is almost certainly fine for the loads as described, I would however consider a 32 amp circuit to be better practice so as to allow for any extra appliances that may be added in future.

Thanks for all the advice guys.  Something related... builder has said he’s going to use the existing 10mm cable to power double oven (5.2kw) and induction hob (7.2kw) on a 45A mcd, is that ok?

Yes, provided again that the cable is not in insulation in a stud wall; and allowing for a little diversity, which we keep debating in here.

Again thanks for the professional opinions.  I’m sure I should just trust them but I just don’t want the job needing to be done twice!

BOG STANDARD answer.

without derating a 13KW load for a traditional cooker on a 6.0 T & E cable is ok for a traditional cooker (oven, hob, grill) on a 32A MCB or a 30A rewireable fuse and if you add a socket for a kettle you`d deduct 5 amps from the 13KW (not the fuse or MCB rating) so you are still within.


For a normal domestic circuit based on two adults and 2.4 children.

Of course an industrial kitchen with lotsa usage takes more thinking about.

So unless the manufacturer actually states other things then the two things in combo don`t add up excessively more than one traditional old fashioned cooker but in your case housed in two units not one unit.