On Fri, 18 Nov 2016 12:57:48 -0000 (UTC), Tim+ wrote:

Jack Lawson wrote:


Earlier this week I bought from Homebase a mitre saw:
http://www.homebase.co.uk/en/homebas...s-2125u-389395

I had read reviews and seemed to fit my needs perfectly.
Got it home - and tested it. I found that when I started the saw, it tripped
my RCD on the supply. Tested it further - sometimes it tripped - sometimes
not. This was on initial start-up with no load.
Took it back - got a replacement.
The new one is just the same. About 1 in 10 of start-ups the RCD will trip.
The saw seems perfect for my needs - very accurate mitres and 90 degree cuts
are spot on - I think I will live with what for me is a minor problem - but
thought I'd just share.


Is it definitely a RCD tripping and not just a MCB?


Excellent - it is in fact a MK (ELECTRIC) 5916S Thermal Magnetic Circuit
Breaker, SENTRY Series, 240 VAC, 16 A, 1 Pole, DIN Rail

I now realise that there is just one RCD in the box - and it was in fact not
that which was tripping - I should have looked properly. It was the fact that
it tripped sometimes - not others - which confused me. The start-up current of
the motor must be round about the tripping current of the device - and nothing
to do with RCD nuisance tripping!!! (Since I made my post I had been reading
up about RCDs and have seen that they *can* trip when there is no earth-leakage
- known as nuisance tripping.)


Many thanks - problem solved.