Old Light Switch Box too small for modern switch plate

[Barryx]

Hi,

I am rewiring a lighting circuit. The existing one is 1930s in steel conduit. The boxes are smaller than modern ones and have no earth point, but I can remedy this. They have special lugs which grip the sides of the box when tightened by the usual screws on the front of the plate. The only problem is that modern plates have mounting holes slightly too far apart.

Is there a conversion kit available?

Is there a modular system that can be made to fit?

Thank you in anticipation,

Barry

 

[ban-all-sheds]

Replace the boxes with modern standard ones.

I assume that you'll be installing a cable cpc, not hoping to re-use the conduit system for this?

 

[Barryx]

Thank you for your reply.

It would be a major job, inc replastering to change them. I don't know how to get the boxes out without removing the conduit. I intend to put twin & earth in the existing conduit. Surely that's ok, except for the box problem?

 

[Chri5]

Barry could you post a picture ?

If not could you give fuller details:-

From what you've mentioned the conduit is connected to the existing box, is this via a beezer box

or does the conduit simply terminate on a metal box via a bush or lock ring ?

A messy alternative might be to provide a surface plastic back box and with the use of long screws have this fixed to the existing flush box screw points.

As BAS mentions the correct method would be to replace the existing undersized boxes, but I appreciate that certain amounts of decor and fabric damage would add to the work.

 

[Chri5]

You could try a old established electrical wholesaler, I'm almost certain that you could (once apon a time ) get metal brackets that converted the old back box to the new size.

A carp drawing, but hopefully you get the idea

 

[oldman2]

1930's conduit is going to be old slip jointed stuff isnt it?

As said pics would be nice

 

[Barryx]

...Thanks again to every one. I'll photograph it when the batteries in my camera are charged. I can't tell how it's jointed without hacking away the plaster, but yes, the conduit terminates in the box directly somehow. It has no fixing points! The method of fixing was a special bracket on each side with a serrated edge which gripped the inner wall of the box when the screws were tightened from the front. There was no earth connection via wire. I can tap M3.5 holes into the box for an earth and to attach an adapter, but it's not ideal. I'm afraid of wrecking the wall trying to extract it

Barry

 

[Spark123]

If there is adequate metal i.e. in a box like Chris's picture above then you can drill a hole and tap it so a machine screw can be used to earth it. You may struggle with twin and earth in a proper conduit system.

 

[Click-Sure]

I've worked on places where everything is wired in steel conduit, as the customer didn't want any new sockets or light switching I chose to pull out the old VIR and pull in nice new PVC singles (not stripped out of T&E!). I ensured the conduit was earthed (within acceptable limits) all the way, and thankfully it was, but decided not to use it as the CPC and pulled in a G/Y to do that job.

I certainally wouldn't try to use T&E, even if you can get one down there without damaging it, two will be very difficult as it they will bind up together. Conduit singles are not only slimmer overall but are less likely to bind up together.

Other than a few tricky bends, not a bad job to do.

 

[ban-all-sheds]

Conduit singles are not only slimmer overall but are less likely to bind up together.

Handy stuff.

 

[Spark123]

Yellow 77

 

[oldman2]

Washing up liquid was the lube of choice on a council house rewire contract I was on many years ago

 

[17thman]

that yellow 77 pulling lubricant, would it work on a saturday night?

 

[JohnD]

It's described as "IDEAL — Wire Pulling" so I guess you can do that whenever you want.

 

[Barryx]

Hi guys,

I have finally managed to upload the pictures. As you can see, I managed to pull a T&E through.