Just a quick follow-up on the form of the control switch used for each
feed off the radial. Are there any regs about this concerning what
the switch implies about the underlying electrics? In other words, is
it against the regs to use (if you were stupid) a cooker-type switch
when the supply to that is actually off a standard ring circuit? If
the switch also had a three-pin plug outlet then someone might assume
they are safe to power their hefty cooker or hairdryer off that. My
reason for asking is to determine whether the control switches for
both feeds off my cooker radial can/should be cooker-type switches, to
indicate that both are fed from a cooker radial, or would this imply
that both have dedicated radials behind them? Or does it not matter?
I guess any electrician would be able to tell with a little detective
work, but I'm thinking more of Aunt Mable here. Forgive my use of
inappropriate terminology.

Thanks.

Michael Brewer

wrote in message ...
In uk.d-i-y, Michael Brewer wrote:
Can you not have a separate switch for each; one on one side of the kitchen
near the mwave/oven, the other on the other side near the oven, both from
the same radial circuit? Forgive my complete ignorance if this is the most
idiotic suggestion ever made on this newsgroup !

Coming back to a related aspect of my original post, is it at all possible
to power the single oven (3.6kW; 15A) off the ring circuit? I'm guessing
the "diversity" calculation I've read about only applies to estimating the
likely max load for a number of separate ring loads, but for the oven "max
15A" really does mean that it's going to draw 15A when you have it on the
most power-intensive mode?

If you try news.google.com's archive, you'll see a fine old ding-dong on
more or less this exact subject about three weeks ago. Roughly summarising
and applying to your enquiry: first, it would not be best practice to run
your single oven off the kitchen ring. Even if you have a ring dedicated
to the kitchen, it's prolly got two or three heavy loads on it (dishwash,
washmosh, tumblebumble) and a few more intermittent 1-2kW loads (toaster,
kettle). "Preloading" that ring with an oven (when it's on and its
thermostat is calling for heat, it's pulling the 15A specified) is not
the best of ideas. (I put it no more strongly than that: depending on how
your particular household runs, it could be anything from definitely
stupid (say there's 6 of you, serious amounts of cooking and washing
going on espepercially at particular times of day) to entirely fine
(one or two members, appliances used lightly and rarely at the same time,
etc.) But on balance, and allowing for future occupants, it's distinctly
better to use a dedicated higher-current circuit (or two) for your
electric cooking needs. Diversity, as the Regs, On-Site Guide, decent
books and so on all stress, is a "what's sensible in practice" notion which
needs to be applied with relevant knowledge of how the circuit's going
to be used in practice, and in the absence of detailed usage knowledge
one should err on the side of caution.

Your existing radial would be a good and proper circuit to feed both
appliances. I'm rather assuming the single oven is a built-in job
which really truly will be used as a conventional oven quite often, pulling
its rated 3.6kW: this makes powering it off a 13A plug and socket less
than a brilliant idea (13A plugs aren't that great for continual loads
at their full rating). Depending on the physical layout of your kitchen,
it's OK to have either a single place where separate isolators (switches)
for each appliance are located, or to have the isolators closer to each
appliance. There's a requirement that these isolators be within 2m of
the appliance they control.

In your case, you can provide the isolation for each appliance using
any of: 20A double-pole switches (with neon indicators if you like),
cooker-control switches (usually rated at 45A, and possibly physically
bigger than you want), or fused-connection-units with a 13A fuse: but
these last are kinda marginal, with the 13A fuse rating telling you
they're specced for a nominal 3.12kW. If you use a decent brand (MK,
Crabtree) they should be just fine, especially as your appliances won't
be pulling their full rated power most of the time (as their thermostats
cut in and out, etc.), but I wouldn't use that no-brand cheapie you found
at the bottom of the bargain bin ;-)

The argument we had a few weeks back were about the guage of cable you
could use for the final leg of the feed once you've split the radial
into two for the two appliances. After some marginally ill-tempered
discussion, we more or less agreed that 2.5mmsq is OK in most cases,
4mmsq would avoid doubt for any split-level use, and 6mmsq preserves
maximum flexibility for either of the exit positions being usable in
future for a single all-in hefty-cooker. (Balanced against the thicker
sizes is the awkwardness of working with them: you want nice deep back
boxes (47mm) if possible, though 4mmsq isn't too much of a pain). It
also depends *critically* on how your radial's laid out: if the two
isolators are daisy-chained, i.e. a single cable runs first to one
of them, with the first appliance connected to the load terminals, while
a second cable runs from the incoming-mains side of the first to
the incoming-mains terminals of the second isolator, *only* that second
cable can be reduced in size from the radial feed, since the first
one is supplying both appliances.

Hope that helps - Stefek
though your
The argument we had was all about the thickness of