New installation. Four 'uplighters' each equipped with a G24-D2 bulb:

http://www.saving-light-bulbs.co.uk/...c#.URAFaB002So

Simple lighting circuit two way switched, sourced from the same breaker as
other light circuits on that floor. Within two weeks the RCD for that bit of
the installation has tripped five times when the lights are turned off. RCD
was new, has been tested for trip point and time. Circuit (and whole
installation) has been tested using up to date, in cal, certified 17th Ed
equipment. Needless to say I cannot get it to trip on demand. Seems (but
only an impression) to happen when lights have been on for a while).

Presumably there must be an imbalance on switch off sometimes causing this,
but why not every time? Any one experienced anything like this, or has
suggestions what may be happening? Back EMF surge from the ballasts or
something? - I'm puzzled and so is my sparks.

AWEM

On Mon, 4 Feb 2013 19:12:43 -0000, Andrew Mawson wrote:

Simple lighting circuit two way switched, sourced from the same breaker
as other light circuits on that floor.

New installation shouldn't be a borrowed neutral and I'd expect that to
reliably trip not just "random" and after two weeks. The latter maybe due
to other kit sharing the same MCB appearing and being a bit leaky though.
So there is less headroom in the RCD for extra leakage.

Faulty uplighter? Connect only one and work through them one by one.

--
Cheers
Dave.

Andrew Mawson wrote:
New installation. Four 'uplighters' each equipped with a G24-D2 bulb:

http://www.saving-light-bulbs.co.uk/...c#.URAFaB002So

Simple lighting circuit two way switched, sourced from the same
breaker as other light circuits on that floor. Within two weeks the
RCD for that bit of the installation has tripped five times when the
lights are turned off. RCD was new, has been tested for trip point
and time. Circuit (and whole installation) has been tested using up
to date, in cal, certified 17th Ed equipment. Needless to say I
cannot get it to trip on demand. Seems (but only an impression) to
happen when lights have been on for a while).
Presumably there must be an imbalance on switch off sometimes causing
this, but why not every time? Any one experienced anything like this,
or has suggestions what may be happening? Back EMF surge from the
ballasts or something? - I'm puzzled and so is my sparks.


The first thing I do with a problem like that (assuming you have not got
immediate access again to the test gear) is to stick on a 500W load to see
what happens.

--
Adam

"ARW" wrote in message ...

Andrew Mawson wrote:
New installation. Four 'uplighters' each equipped with a G24-D2 bulb:

http://www.saving-light-bulbs.co.uk/...c#.URAFaB002So

Simple lighting circuit two way switched, sourced from the same
breaker as other light circuits on that floor. Within two weeks the
RCD for that bit of the installation has tripped five times when the
lights are turned off. RCD was new, has been tested for trip point
and time. Circuit (and whole installation) has been tested using up
to date, in cal, certified 17th Ed equipment. Needless to say I
cannot get it to trip on demand. Seems (but only an impression) to
happen when lights have been on for a while).
Presumably there must be an imbalance on switch off sometimes causing
this, but why not every time? Any one experienced anything like this,
or has suggestions what may be happening? Back EMF surge from the
ballasts or something? - I'm puzzled and so is my sparks.


The first thing I do with a problem like that (assuming you have not got
immediate access again to the test gear) is to stick on a 500W load to see
what happens.

As in "tune for minimum smoke" I suppose!

AWEM

Sounds like back emf to me, though have to say, it is not a common thing to
occur. I suppose if you judged it just as the max voltage was on the
ballast, then the back surge would be greatest.

Brian

--
From the Sofa of Brian Gaff Reply address is active
"Andrew Mawson" wrote in message
...
New installation. Four 'uplighters' each equipped with a G24-D2 bulb:

http://www.saving-light-bulbs.co.uk/...c#.URAFaB002So

Simple lighting circuit two way switched, sourced from the same breaker as
other light circuits on that floor. Within two weeks the RCD for that bit
of the installation has tripped five times when the lights are turned off.
RCD was new, has been tested for trip point and time. Circuit (and whole
installation) has been tested using up to date, in cal, certified 17th Ed
equipment. Needless to say I cannot get it to trip on demand. Seems (but
only an impression) to happen when lights have been on for a while).

Presumably there must be an imbalance on switch off sometimes causing
this, but why not every time? Any one experienced anything like this, or
has suggestions what may be happening? Back EMF surge from the ballasts or
something? - I'm puzzled and so is my sparks.

AWEM

On Monday, February 4, 2013 7:12:43 PM UTC, Andrew Mawson wrote:
New installation. Four 'uplighters' each equipped with a G24-D2 bulb:
http://www.saving-light-bulbs.co.uk/...c#.URAFaB002So
Simple lighting circuit two way switched, sourced from the same breaker as
other light circuits on that floor. Within two weeks the RCD for that bit of
the installation has tripped five times when the lights are turned off. RCD
was new, has been tested for trip point and time. Circuit (and whole
installation) has been tested using up to date, in cal, certified 17th Ed
equipment. Needless to say I cannot get it to trip on demand. Seems (but
only an impression) to happen when lights have been on for a while).
Presumably there must be an imbalance on switch off sometimes causing this,
but why not every time? Any one experienced anything like this, or has
suggestions what may be happening? Back EMF surge from the ballasts or
something? - I'm puzzled and so is my sparks.
AWEM


When the switch is opened, it can arc momentarily. The resulting hf causes much increased current through the usual capacitance to earth.

Options: fit a snubber to the switch, or reduce the total load on the rcd.


NT