Had a short on a light fitting. Tripped the mcb & rcd.

Repaired fault and went to switch light on, to discover switch now "always on" and not turnable off?!?!

It now won't break elec. contact and won't latch in the "off" position, i.e.. it's no longer a switch..

Its a crabtree flat plate, screwless front 1gang 2 way light switch in brass.


The "switch" is attached to the metal backplate with one screw and a location tab at the other end.. presumably some sort of grid switch?

I've goggled various phrases to try and find something similar to try and just buy the "switch" bit as opposed to the whole bloody brass lightswitch at £10+.

Anyone got any clues please on where to get just a spare "switch" not the whole shooting match?

CHeers
Jim K

On Sun, 15 Dec 2013 14:20:02 -0800 (PST), Jim K
wrote:

Had a short on a light fitting. Tripped the mcb & rcd.

Repaired fault and went to switch light on, to discover switch now "always on" and not turnable off?!?!

It now won't break elec. contact and won't latch in the "off" position, i.e. it's no longer a switch..

Its a crabtree flat plate, screwless front 1gang 2 way light switch in brass.


The "switch" is attached to the metal backplate with one screw and a location tab at the other end.. presumably some sort of grid switch?

I've goggled various phrases to try and find something similar to try and just buy the "switch" bit as opposed to the whole bloody brass lightswitch at £10+.

Anyone got any clues please on where to get just a spare "switch" not the whole shooting match?

CHeers
Jim K




Surely you can dismantle the switch and force the welded contacts
apart?
--
Dave W

--- news://freenews.netfront.net/ - complaints: ---

Dave W

No apparent way in!

Moulded brown plastic with 3 terminals.

How come contacts welded with a 30ma rcd installed & working?

Jim K

On 15/12/2013 23:59, Jim K wrote:
Dave W

No apparent way in!

Moulded brown plastic with 3 terminals.

How come contacts welded with a 30ma rcd installed & working?


I think the tripped MCB might be a clue. RCDs often trip simultaneously.

On 15/12/2013 23:59, Jim K wrote:
Dave W

No apparent way in!

Moulded brown plastic with 3 terminals.

How come contacts welded with a 30ma rcd installed & working?

The fault was an overcurrent rather than an earth fault current. So the
RCD trip was probably just in response to the transient and a reflection
on the fact that its probably sensitised to the point of being close to
tripping due to the leakage normally present in the circuit.

So you would have had at least 30A through the switch briefly.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

"Jim K" wrote in message
...
Dave W

No apparent way in!

Moulded brown plastic with 3 terminals.

How come contacts welded with a 30ma rcd installed & working?

Jim K

The 30ma is the current to earth before it trips.
It probably tripped as a result of a transient ie not a "real" fault to
earth.
The actual damage was due to the short circuit & could have been 60-100a
for a few miliseconds.
A lot depends on what part of the cycle is happening at the instant the
fault occurs.

On Sun, 15 Dec 2013 15:59:20 -0800 (PST), Jim K wrote:

No apparent way in!

Even when the module is removed from the plate by taking out the
screw and disengaging the tab?

You may find that a cheaper plastic switch from the same maker has
the same module on the back.

--
Cheers
Dave.

"Jim K" wrote in message
...
Dave W

No apparent way in!

Moulded brown plastic with 3 terminals.

How come contacts welded with a 30ma rcd installed & working?

Well 30mA is (roughly) the minimum that will trip a RCD, the RCD does not
limit the current to 30mA in the event of a direct short. There was probably
6000A flowing when the RCD and MCB tripped.

Anything in here to help you?
http://www.electrium.co.uk/CrabtreeWADCP2010.pdf



--
Adam

On Monday, 16 December 2013 09:03:52 UTC, Dave Liquorice wrote:
On Sun, 15 Dec 2013 15:59:20 -0800 (PST), Jim K wrote:



No apparent way in!



Even when the module is removed from the plate by taking out the
screw and disengaging the tab?

nope.

You may find that a cheaper plastic switch from the same maker has
the same module on the back.

yup will try that when I get some tuits.

Cheers
Jim K

On Monday, 16 December 2013 18:45:11 UTC, wrote:
"Jim K" wrote in message

...

Dave W

No apparent way in!

Moulded brown plastic with 3 terminals.



How come contacts welded with a 30ma rcd installed & working?



Well 30mA is (roughly) the minimum that will trip a RCD, the RCD does not

limit the current to 30mA in the event of a direct short. There was probably

6000A flowing when the RCD and MCB tripped.



Anything in here to help you?
http://www.electrium.co.uk/CrabtreeWADCP2010.pdf

--

Adam

mmm lots of minutely different variations of Platinum Flat plate yokes and switches.... none of which appear to be what I have here :(

Cheers
Jim K

"Jim K" wrote in message
...
On Monday, 16 December 2013 18:45:11 UTC,
wrote:
"Jim K" wrote in message

...

Dave W

No apparent way in!

Moulded brown plastic with 3 terminals.



How come contacts welded with a 30ma rcd installed & working?



Well 30mA is (roughly) the minimum that will trip a RCD, the RCD does not

limit the current to 30mA in the event of a direct short. There was
probably

6000A flowing when the RCD and MCB tripped.



Anything in here to help you?
http://www.electrium.co.uk/CrabtreeWADCP2010.pdf

--

Adam

mmm lots of minutely different variations of Platinum Flat plate yokes and
switches.... none of which appear to be what I have here :(

No number on the one you have?



--
Adam

No number on the one you have?

--Adam

Placcy switch :- BS EN 60669 1M
10AX 250V

Yoke :- SERIES 7000
XV21434 102
CRABTREE ENGLAND

Tia
Jim K