In message ,
"dennis@home" wrote:


"Martin Angove" wrote in message
...

Taking the biggest potential loads there, you'd have to have the kettle,
microwave, WM and tumbler all operating at their maximum capacity
simultaneously even to reach 7.5kW. This is (IMO) unlikely unless you're
in the habit of starting the washing machine while the tumbler is
running then immediately deciding simultaneously to make a cup of tea
and microwave your TV dinner. Just the time taken to read the
instructions and unpack the TV dinner is likely to be enough to allow
the kettle to boil!

Well funny enough...

you take the washing out of the washer and put it in the dryer...
then you put the next load in....

Then you decide on a cuppa having just done the washing.
So you get the iron out and plug it in and then put the kettle on.

And you think it won't happen.....

Well, given what you have described, it won't. TD+WM+K adds up to 6kW or
so. Most irons are in the 500W to 1kW range and are thermostatically
controlled. At best you have described 7kW of load for maybe as much as
three or four minutes. 500W "in hand" to the nominal spec., and a lot
more to the real limit.

[...]

What is more likely is a bad connection causing overheating, and
this is likely to have worse effects on a radial where all the
circuit current might pass through that connection than on a ring
where there is going to be an alternative (hopefully good) path to
every other point.

Yes but with a radial you are likely to notice the problem with a ring the
appliances work fine and you don't notice the fault.

With a broken connection I'd agree, but I have seen many cases of
"loose" connections on radials which don't exhibit any obvious symptoms
unless you happen to dismantle the problem junction whereupon you spot
the blackened copper and bubbling PVC. Classic example recently was a
45A shower switch to an 8.5kW shower. As far as the people were
concerned, the shower had worked just fine with no problems at all until
a guest decided to use the 45A switch to switch off after having a
shower (the householders usually left it on). The switch jammed in the
off position (though indicating on) and they called me in. I found two
or three loose screws in the switch and obvious signs of sustained
overheating.

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... Not a computer nerd; merely a techno-weenie.