Discuss PME head , builder forgot earth cable , 100amp 3phase supply , 10 bedroom house , 10 bedroom house in the The Welcome Forum area at ElectriciansForums.net
My GN8 lists 4x35mm swa cable as having 78mm of steel, which is close but no banana. It may be your particular cable has more steel or a better conductivity than average, so it might be worth checking with manufacturer's data for that specific cable?
1) I agree with the early post - never trust a third party with this aspect of the installation. It doesn't matter how good we are as installers if the supply is f****d.
2) I'd be inclined (if there really is no possibility of adding an additional Main earth to take advantage of the PME conditions available) to do as Westward10 suggests.
3) If, however the ferret/ terrier/apprentice can be trained to do their duty and get the extra cable installed then surely 16mmsq.csa isn't big enough anyway?
It seems you may be able to get away with using the armouring as your earth conductor, however I don't mean to put doubt (or possibly more doubt) but if the outer plastic sheath has any damage (from sharp stones) moisture may get in and over time and rust, so the conductivity will be reduced. Did the builder lay the cable in a bed of sand, or just back fill with what they dug out?
No doubt, but, as said previously, with such a job, which is obviously important and could have a major affect on future work, I wouldn't be taking any chances. Get the job spot on...dig?
I once came across a 95mm 4 core SWA (installed 2007) where which was ran underground in a duct from a substation, ran downhill to a building. Where it was glanded into the section board was completely corroded as were the SWA armouring strands, could only presume the outer insulation was damaged during installing in the duct, and water has got in, and wicked its way out of the gland...luckily there was a separate earth cable installed.
If your cable was running through another building to the new one, then there's no chance of corrosion to the armour, however as it's ran underground and was installed by builders, who may not have took precautions to prevent damage to the cable.....
we are saying that the swa won't meet the required csa in copper for bonding
and that obviously not running in the cable that i can not say on its condition which puts even more doubt on the above
I would take an educated quess at the SWA being XLPE and not pvc/pvc...I can't remember the last time I had pvc/pvc swa from a whole salers. Regardless of being XLPE or PVC it's not adequate for bonding if you follow the guidance provided to us.....so it amazes me the NICEIC have given you a blanket statement saying it's adequate.
Once installed a 50mm 4c, OK for 6 months and then blew.... water through an indentation caused by builders digging machine. water and copper shrapnel blew back through the centre of the cable to the supply fused switch. Wet through and messy. Must have been bubbling a while and probably providing underground heating for the cobbled drive.
The way I see it is the builder sorts his fudge and slaps in a 16mm green and yellow or you make the far end TT. Being a new build you have the opportunity to build a little earth nest if the ground work isn't done...Could you clamp on to some rebar if traditional construction?
Agree which is why I asked what exactly he asked the Brains Trust.
Reply to PME head , builder forgot earth cable , 100amp 3phase supply , 10 bedroom house , 10 bedroom house in the The Welcome Forum area at ElectriciansForums.net
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) but if the outer plastic sheath has any damage (from sharp stones) moisture may get in and over time and rust, so the conductivity will be reduced. Did the builder lay the cable in a bed of sand, or just back fill with what they dug out?
