Date : Wed, 02 Sep 2009 01:26:26 +0100
From : dm.hunt@... (David Hunt)
Subject: Leccy @ Acorn World '09
> > The power used by the device is a fraction of the peak demand when it is
> > initially powered (inrush current). For a (fully loaded) Beeb the
> current
> > pulse is 1.8A for 120ms dropping to 0.15A and for my Beeb Sony CRT
> monitor
> > it's around 5A for 850ms dropping to 1A. I think we will need to avoid a
> > situation where a lot of stuff gets turned on at the same time and if
> we're
> > looking at RCDs that people don't try and reset the trip with everything
> > still switched on, otherwise the current rush could trip the main
> breaker
> > for the room. I doubt if we'd be popular ;)
>
> > Dave
>
> Thanks for answering an issue I have with my electric on my sockets
> ring-main, which is 32A, after a power-cut, it always trips out!
>
> and I have to go round the house turning stuff off, to get it back on
> again,
> I suspect it's inrush current exceeding 32A!
>
> Umm! Maybe I need to get an up-rated one!
>
> Andrew
I'm no electrician, but I'd hazard a guess that you've got too many
appliances connected to a single ring main. Putting in a higher rated
breaker doesn't sound like a good idea... The breaker is there to protect
the wiring from causing a fire.
When I re-wired my old house (can't do that anymore!) the socket ring main
cable was rated for 45A continuous with a 32A breaker and a 10mA RCD, well
within the 90A continuous load the cable was rated to.
I split the downstairs into four separate zones with their own ring main and
the upstairs into two. Direct runs for the remainder e.g. boiler, cooker,
pump, shower etc.
My fridge/freezer has an inrush current of 17A for 120ms dropping down to 4A
in around 600ms, it doesn't take many appliances with these characteristics
to overload a trip. I agree. it's a pain having to go around and turn off
everything and then perform a selective soft-start. Probably best to ask a
friendly electrician, especially now they've actually got to be qualified.
Dave ;)