swa earthing

[normspanners]

But the resistance of the steel conduit was to high to blow the 30a fuse wire. The main earth cable was passing roughly 20a directly through to the incoming steel water pipe, turning it into a huge heating element.

I have used that method for unfreezing pipe work that was solid, outside in fresh air at minus 15, my mums kitchen was an add on to main house and had been knocked down to extend the kitchen , the day before a surprise 10 day freeze snap kicked in on a friday, There was one wall left standing with the copper main running along it and as I tried heated it with hot air gun and moving along it just refroze I was on a hideing to nothing, so hit on idea of using a stick welder and jumper leads with proper earth straps one lead at one end on stop cock the other lead at the tap end turn welder on and it nicely heated the whole of the copper pipe thawing it out universally keeping the tap open, once the water started running, it was away, then could insulate pipe work, on the Monday the next week when i could get some heat trace to put in insulation , that at least gave her water to rest of the house.

That brings back memories I had to seal the kitchen door with tank tape, that door had now become the outside door! and the snow and rain had been drifted against it, there was 5" thick of solid ice, I had to chisel off the kitchen floor boards with a bolster chisel to open the door !!

 

[Ton-up]

But if you put your hands under one cold tap at the far end of the building you could feel something but the biggest clue was steaming hot water straight out of all the cold taps.
After a few hours testing we found a screw in a socket box had eventually squashed the insulation and made a short direct to earth. But the resistance of the steel conduit was to high to blow the 30a fuse wire. The main earth cable was passing roughly 20a directly through to the incoming steel water pipe, turning it into a huge heating element.

Had this at my parents house about 35 years ago - Hot water at cold taps! After Dad looked everywhere foe a water problem, he realised it was electrical, and traced it to the electric hob earthed to the cold water!
Lesson there I think!

 

[brightspark]

what generally used to happen was u would earth the system of a lead water pipe further out the garden it would be connected at the street in plastic mains . if the pipe was in sandy soil it wouldn't conduct a good earth . if an appliance got a fault to earth it wouldn't blow the fuse but would heat the water up in the cold water pipe for 4 or 5 meters I've seen damp walls and all the pipes in a house live along with all the electrical appliances and giving mild shocks good job there wasn't a gas service in the house that had a good ground

 

[WorkshopChris]

All shows how far we have move on nowadays with the sensitivity rcd,s. Although they are so common now it's about time more manufactures realised there is place for time delay and rcd rated at other than 30ma. Only seem to be special order items with a price to match.

 

[brightspark]

100 ma freely available just a bit more expensive there mainly used on tt systems back at source to protect cable. and 30 ma further down the line time delay tent to be ordered in

 

[normspanners]

100 ma freely available just a bit more expensive there mainly used on tt systems back at source to protect cable. and 30 ma further down the line time delay tent to be ordered in

Exactly the way I have done my garage wiring totally separate TT system direct off main isolator into 100ma then 100amp mcb swa earthed at source but not at workshop, thats got seperate earth rod at workshop to save transporting any earth fault to either the house or garage. The house runs totally on seperate rcbos.

 

[WorkshopChris]

Exactly the way I have done my garage wiring totally separate TT system direct off main isolator into 100ma then 100amp mcb swa earthed at source but not at workshop seperate earth rod at workshop to save transporting any earth fault to either the house or garage. The house runs totally on seperate rcbos.

That's what was originally suggested for our set up but as outbuildings are linked with cat 5 network, cctv and alarm etc decided to link all earth's direct back to main to avoid any potential differences to sensitive electronics.

 

[rosinante]

I have seen an earth system that spec,d 70mm csa earth from 1 building to another 500m way thru ducting the first and last few metres were 70mm. the bit in the middle was 6 mm
Chris

 

[Robotstar5]

I have seen an earth system that spec,d 70mm csa earth from 1 building to another 500m way thru ducting the first and last few metres were 70mm. the bit in the middle was 6 mm
Chris

Be interesting to see the Zs reading for that

 

[WorkshopChris]

Be interesting to see the Zs reading for that

6mm is roughly 3 ohms per km compared to about 0.25ohms for the 70mm thats going to be a huge difference. Wonder if someone had a good weekend with the 500m of 70mm in scrap.

 

[rosinante]

Oh yes, it wasn't our firm though, the knowledge was uncomfortable enough,dont like being associated with jobs that have been bodged before.
Chris