Electrical queries
 

This is a 50 year old installation with existing vertical steel oval conduits to sockets plastered into the walls. The rubber(!) cable enters from above and there is a grommet inserted into each of the conduits to prevent damage to the cables.

Now if rewired with PVC sheathed cable, then
a) Can I re-use the steel conduit?
b) Where can I get suitable grommets? These are top hat shaped with central hole for the cable.
c) The recessed steel boxes do not have an earth connection. Can one be fitted or is it better to replace each box?

Many thanks.

Electrical queries
 

MisterP said the following on 24/06/2007 15:35:
This is a 50 year old installation with existing vertical steel oval
conduits to sockets plastered into the walls. The rubber(!) cable
enters from above and there is a grommet inserted into each of the
conduits to prevent damage to the cables.

Now if rewired with PVC sheathed cable, then
a) Can I re-use the steel conduit?

Yes.

b) Where can I get suitable grommets? These are top hat shaped with
central hole for the cable.

Never seen 'em for sale anywhere. I'm not saying you will not be able to
get them; someone might come along and prove me wrong...

Just be careful when pulling the new cables through (use the old cables
to pull the new ones in).

c) The recessed steel boxes do not have an earth connection. Can one
be fitted or is it better to replace each box?

Better to replace each box - not least because the shiny new screws
supplied with your new accessories will be metric and the screw holes in
your old boxes will be imperial...

Electrical queries
 

MisterP wrote:

This is a 50 year old installation with existing vertical steel oval
conduits to sockets plastered into the walls. The rubber(!) cable
enters from above and there is a grommet inserted into each of the
conduits to prevent damage to the cables.

Now if rewired with PVC sheathed cable, then
a) Can I re-use the steel conduit?

Yes - at least for switch drops. You may have difficulty getting
2x2.5mm^2 T&E through the socket runs, but then again it is possible
sometimes using the old cable to pull through the new. (strip the outer
insulation at the end of the old and new wires and firmly twist the
inners together before taping up. tape the second wire a couple of feet
back from the joint of the first and it will make pulling through a bit
simpler.

b) Where can I get suitable grommets? These are top hat shaped with
central hole for the cable.

Usually the existing ones stay put and remain serviceable.

c) The recessed steel boxes do not have an earth connection. Can one
be fitted or is it better to replace each box?

As long as they don't have two moveable screw holes then you can rely on
the screwed connection from the accessory to earth the box. Often older
installs like that will have odd sized backboxes, or wooden ones which
need replacing. Needless to say you probably want lots of sockets in
positions where there are currently none.



--
Cheers,

John.

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Electrical queries
 

John Rumm wrote:
MisterP wrote:

c) The recessed steel boxes do not have an earth connection. Can one
be fitted or is it better to replace each box?

As long as they don't have two moveable screw holes then you can rely on
the screwed connection from the accessory to earth the box.

Really? But modern backboxes typically don't have two moveable screw
holes, just one; and surely a modern box must always be earthed
separately?

David

Electrical queries
 

"Lobster" wrote in message
...
John Rumm wrote:
MisterP wrote:

c) The recessed steel boxes do not have an earth connection. Can
one
be fitted or is it better to replace each box?

As long as they don't have two moveable screw holes then you can
rely on
the screwed connection from the accessory to earth the box.

Really? But modern backboxes typically don't have two moveable
screw
holes, just one; and surely a modern box must always be earthed
separately?

David



Would it be legitimate to fix a crimped earth tag to the back box
using either a pop rivet or a self tapping screw ?

AWEM

Electrical queries
 

In article ,
MisterP writes:

This is a 50 year old installation with existing vertical steel oval
conduits to sockets plastered into the walls. The rubber(!) cable
enters from above and there is a grommet inserted into each of the
conduits to prevent damage to the cables.

Now if rewired with PVC sheathed cable, then
a) Can I re-use the steel conduit?
b) Where can I get suitable grommets? These are top hat shaped with
central hole for the cable.
c) The recessed steel boxes do not have an earth connection. Can one
be fitted or is it better to replace each box?

There's no requirement in the regs to earth back boxes unless
they are exposed. It's good practice of course, but I wouldn't
replace a back box just because it didn't have an earthing point.
It would be easier to drill a tiny hole for a self-tapping screw
if you really want to do this.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Electrical queries
 

Lobster wrote:
John Rumm wrote:
MisterP wrote:

c) The recessed steel boxes do not have an earth connection. Can one
be fitted or is it better to replace each box?

As long as they don't have two moveable screw holes then you can rely
on the screwed connection from the accessory to earth the box.

Really? But modern backboxes typically don't have two moveable screw
holes, just one; and surely a modern box must always be earthed separately?

It is preferable, but not actually a requirement, IIUC.

--
Cheers,

John.

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