Is there a practical way of providing earth leakage protection for a
group of machines fed from a 3 phase distribution board?
My workshop tenant has asked the question as he has someone working on a
*bench space* basis and doesn't want to be sued by a widow.
I have several modernish three phase distribution boxes here on the farm all
by Wylex. I simply removed the main breaker and replaced it with a
compatible three phase RCD one. Conventionally workshop machine are on 100mA
rcd trips but I feel happier with all mine at 30mA, particularly as several
machines have a standard 13a double socket on them powered from phase 1. To
date not had any nuisance trips. Single phase distribution is from a
separate box, also with a 30mA trip.
If your distribution boards will not accept an RCD main switch for some
reason, just intercept the three phase feed, and bring it via a three gang
box with an rcd mounted in it.
Umm... I assumed there would be a problem with starter coils being
across only two phases or even phase neutral. Local inspection lighting
The other unknown is DC injection braking on circular saws.
On Wed, 16 May 2012 21:45:24 +0100, Tim Lamb wrote:
Thinking about it logically provided all the current that is going
into the lines is also all coming back on "safe" lines, all is well.
It's when you don't get it all back that you assume it's going to
ground, possibly via someone, so you trip the power.
This implies that you monitor the three phases and the associated
neutral. How you actually do that I haven't a clue and in delta
connected kit there isn't a neutral to monitor, I think. I know
enough about three phase to know I'm dangerous...
It should not matter... the sense coil is round all phases and neutral.
As long as the vector sum adds up to zero, then it can assume all is
well. Only when some current returns via a path that does not include
the RCD does it trip.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.