Replacing 6 Gang Light Switch -Crabtree to MK

[ian283]

HI There,

Replacing 6 Gang Crabtree with MK model

I am a confident person when it comes to following instructions and replacing switches but this one has me stumped.

The Crabtree Has L1 L2 and L3 with some link cables between some of these. One of the switches has developed a fault and shorts out the MCB when thrown so I am replacing the entire switch.

I have a new MK one with me but the holes are different. With 6 Common and L1 and L2's. Is there a straight forward logic with these or should I leave to a Qualified Spark? If so what would be a fair price to replace this?

Thanks in advance for any constructive advice and or input

 

[Mighty Quinn]

HI There,

Replacing 6 Gang Crabtree with MK model

I am a confident person when it comes to following instructions and replacing switches but this one has me stumped.

The Crabtree Has L1 L2 and L3 with some link cables between some of these. One of the switches has developed a fault and shorts out the MCB when thrown so I am replacing the entire switch.

I have a new MK one with me but the holes are different. With 6 Common and L1 and L2's. Is there a straight forward logic with these or should I leave to a Qualified Spark? If so what would be a fair price to replace this?

Thanks in advance for any constructive advice and or input

At a guess, the L1 on the original switch will be on it's own, which would correspond with the common on the MK one.

 

[ian283]

At a guess, the L1 on the original switch will be on it's own, which would correspond with the common on the MK one.

There are three cables coming into the switch and all three end up in different L1's with some linking off to L3 and L2's!

 

[Spark123]

I'd be suprised if it is the switch at fault causing the MCB to trip, not a lot to go wrong. Is it a metal one or similar?
The L1 on the old switch will correspond to Com, L2 to L1 and L3 to L2.

 

[jj4091]

Beat me to it, I was just going to ask if it was definately the switch, it would be very unusual.

 

[bernardgreen]

Is the switch that causes the trip part of a two way ( two switches controlling one light ) or is it switching a flourecent light fitting ?

Has the switch worked previouslywithout causing any problems.

 

[ian283]

I'd be suprised if it is the switch at fault causing the MCB to trip, not a lot to go wrong. Is it a metal one or similar?
The L1 on the old switch will correspond to Com, L2 to L1 and L3 to L2.

Hi Spark123

I thought that at first - when I kept resetting the MCB and throwing the switch it kept blowing. On one throw of the switch it felt stiff and I had to 'force' the throw. It was then that I thought the switch may be faulty and the easiest thing was to change the switch to elimainte that as a potential problem. If the fault was still there after replacing that I was then going to check the unit it powers [a fan unit and light combined] It worked fine from when we bought the house in mid december until New Years Eve.

To answer it is a std plastic faced unit

 

[Spark123]

Chances are the switch will not be at fault, the contacts are probably broken now as it sound like it has been in effect closed under short circuit conditions, so a new switch will be in order anyway. The problem lies with the fact that the new switch will probably do exactly the same thing unless you rectify the underlying problem first. Is it a shower light or or one of those large ceiling fans?

 

[ian283]

Is the switch that causes the trip part of a two way ( two switches controlling one light ) or is it switching a flourecent light fitting ?

Has the switch worked previouslywithout causing any problems.

Hi bernardgreen.

The switch has worked. I don't think it is part of a two way circuit. It powers a fan/light in a conservatory. I have not located another light switch fro this yet!!. Although there are some switches in the house that I have not been able to identify what they do. There are a number of other two way circuits that are run from this six gang. IE outside light.

 

[ian283]

Chances are the switch will not be at fault, the contacts are probably broken now as it sound like it has been in effect closed under short circuit conditions, so a new switch will be in order anyway. The problem lies with the fact that the new switch will probably do exactly the same thing unless you rectify the underlying problem first. Is it a shower light or or one of those large ceiling fans?

A ceiling fan with a light cluster under.

 

[Spark123]

If you turn the eleccy off, take the light down and with your multimeter check the resistance across the input to the light unit (L-E, L-N, N-E) what does it measure? The problem is likely either a faulty fan unit or the cable supplying it has become damaged.

 

[Steve]

In answer to the OP's original question, L1 L2 and L3 on the old switch correspond to COM L1 and L2 respectively on the new switch. Wire it exactly the same as before - theres only one way to wire it and if you mess it up, you'll never forgive yourself!!!

But fix the problem first!

 

[RF Lighting]

The switch which is 'faulty'. Label which wire goes where, and disconnect them both from the switch. put them both into a piece of strip connector, and see if the MCB will stay on.

This will show for sure if the switch is at fault.

If you fit your new switch and the fault still exists, then you risk welding the contacts on your new switch.

Would it not have been easier to get a replacement crabtree module, rather than having to replace the entire grid switch?

 

[plugwash]

he didn't say it was a grid switch.

you can get 6 gang switches as one unit that fits a normal double box you know (unlike the grid switches which are somewhat bulkier).

 

[RF Lighting]

I'm certain I read grid somewhere. I must be losing the plot.