Pete Posted November 1, 2018 Share Posted November 1, 2018 Can anyone please tell me the diameter of the incoming mains cable to the main fuse. I have the red 38mm ducting required by my local electric board into the house and I have been informed the incoming mains cable is 35mm diameter which seems a little tight to pass through and round the sweeping bend underground. My electrics are being connected on Monday and I am a little concerned I may have to dig down to ensure the duct is as straight as possible. Link to comment Share on other sites More sharing options...
joe90 Posted November 1, 2018 Share Posted November 1, 2018 Gosh, mine is about 15mm to 20mm from memory. Link to comment Share on other sites More sharing options...
recoveringbuilder Posted November 1, 2018 Share Posted November 1, 2018 Ours was just put in yesterday through the duct it’s about the diameter of your middle finger went in no problem with the pull rope we had through Link to comment Share on other sites More sharing options...
Pete Posted November 1, 2018 Author Share Posted November 1, 2018 I thought it was about that size and then this gives an allowance to pull through easily enough. Fingers crossed I think. Thanks Link to comment Share on other sites More sharing options...
ProDave Posted November 1, 2018 Share Posted November 1, 2018 I am surprised they specified ducting as small as 38mm. but you should be okay. The usual incoming supply cable is a concentric cable, and it seems to pass thtough a 25mm conduit without problem. Link to comment Share on other sites More sharing options...
Ed Davies Posted November 1, 2018 Share Posted November 1, 2018 Just measured the incoming cable on the house I'm renting with calipers: 13.8 mm diameter. 100 amp main fuse, single phase but overhead directly off the transformer pole. Link to comment Share on other sites More sharing options...
Pete Posted November 1, 2018 Author Share Posted November 1, 2018 I am relaxing more with these responses. I have had enough with heart failure today. The guy doing the sign off ready for Monday told me I had used the wrong ducting this afternoon when he looked at the pics I sent him on the phone. As my mind was computing having to dig it all up and do it all again he informed me he had made some calls and they would allow it. I had used red 117mm ducting in a 50m roll instead of the short red ducting in 3 metres lengths which is what he expected me to have used. I explained it was not very clear in the specification and he said do not worry about we have allowed it. Hence me now worrying about the smaller ducting pipe. Life of a self builder eh @recoveringacademic (Ian) Link to comment Share on other sites More sharing options...
Mr Punter Posted November 1, 2018 Share Posted November 1, 2018 It is more likely 35mm2 cable that being the area of the conductor. Your ducting is fine. The cable diameter is about 15mm including the sheathing. 1 Link to comment Share on other sites More sharing options...
Pete Posted November 1, 2018 Author Share Posted November 1, 2018 I now what it is like to win the lottery. Thanks everyone Link to comment Share on other sites More sharing options...
Mr Punter Posted November 1, 2018 Share Posted November 1, 2018 The actual conductor diameter is less than 7mm, which always seems quite small to feed a 100 amp supply, but I guess the DNO have played this game before... Link to comment Share on other sites More sharing options...
Jeremy Harris Posted November 1, 2018 Share Posted November 1, 2018 13 minutes ago, Mr Punter said: The actual conductor diameter is less than 7mm, which always seems quite small to feed a 100 amp supply, but I guess the DNO have played this game before... Indeed the DNO use a completely different set of rules; the "100 A" capacity incoming cable is protected by a fuse that's between 500 A and 800 A at the local transformer, something that would never be allowed in house wiring. I've heard tales of the aluminium core in concentric incoming cables burning back under fault conditions without blowing the transformer supply-side fuse, too. It's another good reason not to accidentally dig through an incoming LV cable... Link to comment Share on other sites More sharing options...
Pete Posted November 9, 2018 Author Share Posted November 9, 2018 (edited) Cable in and as people said it is the size of your finger. Edited November 9, 2018 by Pete error Link to comment Share on other sites More sharing options...
Pete Posted November 9, 2018 Author Share Posted November 9, 2018 Had to dig the holes for the 3 phase cable to domestic cable joints the other day for the pre site inspection. ( We had laid the ducting and back filled it as it was a working drive so had to dig the connection holes before they would sign it off ready for the cable to be pulled through). I then had to send photos of the holes to the pre site inspection engineer so we could move forward. I then received a phone call to say we had used the wrong ducting even though I had taken loads of pictures when we did the initial laying and sent them to the office staff to put on record. My heart sunk and all I could think of was having to dig it up and relay it. He then said do not worry I have managed to get it passed but you should have used the rigid 3 metre socketed lengths and not the 50m red twin wall that you have used.I then said all it said on my instructions was use red ducting he said yes, the rigid stuff. As it turned out the cable puller's said they prefer my ducting and it is a lot easier to work with. Link to comment Share on other sites More sharing options...
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