PIR on garage

graham123 · Mar 10, 2012

Completed a pir on a small block of garages. An old rewirable fuse board, with one lighting circuit and one radial socket circuit. one light and socket in each garage. The owner wants the garages up to spec his words. Now ive offered to change the distribution board. The wiring is singles in metal conduit which runs into an asbestos celing. My question is if i change the board do i have to pull an earth cable to each point?. Or is it still acceptalbe to use conduit as earth?.

needasparks · Mar 10, 2012

Would have thought due to possible corrosion the conduit would not be relied on. Even if it reads good today, in 12 months it could go.

mogga · Mar 10, 2012

If its one socket and one light for the cost and future hastle imo it would be better to PVC tubing it as for the "A" roof so long as its not broken,rubbed then it MAY be ok altho id try n get hold of some sort of sealing paint on like the asbestos contractors use and spray it OR put it in the contract that Asbestos should be sealed before you start the job

Edd · Mar 10, 2012

graham123 said:
My question is if i change the board do i have to pull an earth cable to each point?. Or is it still acceptalbe to use conduit as earth?.

The direct answer is the conduit earth is fine as long as you get a good R2 reading (not Earth loop) it must be done on low ohms. (earth loop will show good through rusty joints). if this tests out then its fine.
but as others have said, it may be worth rewireing, but you dont need too.

needasparks · Mar 10, 2012

Edd said:
The direct answer is the conduit earth is fine as long as you get a good R2 reading (not Earth loop) it must be done on low ohms. (earth loop will show good through rusty joints). if this tests out then its fine.
but as others have said, it may be worth rewireing, but you dont need too.

I would agree normally if this was an inside install but the OP says this is outside garages which are more at risk to corrosion.

telectrix · Mar 10, 2012

think he meant thy're outside garages, but the conduit is inside. as long as it's not corroded and as Edd said give good R2 readings, it's fine to re-use.

needasparks · Mar 10, 2012

Mmmm, Just my take really.
Its a pass on the pir for sure if good readings but just IMO if i was putting an EIC on it and upgrading i would like to think it would last longer than pack of biscuits for the sake of a cpc, its all got to come apart to test anyway for a socket and light.
I think alot depends on its current condition really having just an asbestos roof cunjures damp walls in my head and an insulated board would be easier to make off with cpc's if he does get the job.