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DIY Forum >> Electrical Questions >> Earth bonding https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1105552866 Message started by JohnDavies on Jan 12th, 2005, 6:01pm |
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Title: Earth bonding Post by JohnDavies on Jan 12th, 2005, 6:01pm I will need to earth our gas and water supplies - at present there is just the one elderly dog eared 6mm earth lead from the Board terminal to the consumer unit. Gas is no problem. The water stop tap is at the rear of the building and due to concrete floors the easiest route means leading a cable up into the bathroom and down again. Is it o.k. to have a run of about 20 - 25 feet in 10mm? Is it o.k to earth to the earthing bar in the consumer unit or do I need a separate earthing terminal in line with the main one? . P.S. Before anyone says anything, this is all part of a job commenced before Jan 1st......... Thanks John Davies |
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Title: Re: Earth bonding Post by HandyMac on Jan 12th, 2005, 6:04pm I'll let one of the resident sparkies answer the question, but one thing that I was brought to book on previously was that "earthing" and "bonding" are two different things. I think what you are trying to do falls into the "bonding" camp :) Bonding is about equi-potential, making everything share the same potential. That may or may not be the same potential as earth. HM |
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Title: Re: Earth bonding Post by Lectrician on Jan 12th, 2005, 6:17pm No restricition on bonding conductor length. Ensure you bond within 600mm of the stop tap/gas meter, and before any tee's. Use 'Blue' clamps if in a damp environment, or ('green' if corrosive ;)) Upgrade your main earth to 16mm, and your mains tails to 25mm a tthe same time. Yes you can use the earth bar in the CU for the bonding. Many modern units have a few terminals labelled 'B'. What type of CU do you have at the moment?? |
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Title: Re: Earth bonding Post by ChubbyPhaseWire on Jan 12th, 2005, 6:27pm Lectrician Don't forget the 'P' Word ;) |
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Title: Re: Earth bonding Post by JohnDavies on Jan 12th, 2005, 6:29pm Thanks for this. C.U. is a Crabtree starbreaker. John |
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Title: Re: Earth bonding Post by Lectrician on Jan 12th, 2005, 6:31pm Not to bad a CU, and not too old. Does it incorporate an RCD for the sockets?? And as CPW is hinting........You must have all your works checked by building control, or work closely with an electrician registered with an approved body. Search 'PART P' an this site, or read any newspaper ;) ;D |
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Title: Re: Earth bonding Post by JohnDavies on Jan 12th, 2005, 7:26pm Re. my rewire. Yes, it has a RCD. As to Part P, as I said originally, the work was started before 1st. January, so I thought it came under the period of grace mentioned elsewhere on this forum - 30th. March, isn't it? It will in any case have to be checked in due course as (a) there will be a kitchen going up and as it wasn't started before 1st. Jan all the wiring for that will come under building control which as far as I can see will also mean having to test the exisiting installation (i.e. my rewire) for compliance with Building Standards. and (b) I will need it checked out anyway in due course as otherwise I could invalidate my house insurance if anything was wrong - or could be said to be wrong, for that matter. and (c) anyone can make errors - even a talented amateur like me - and I'd rather get it checked out for piece of mind....it cannot be worse that the horrible and lethal job it replaced - some of which was still rubber! Thanks, John D |
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Title: Re: Earth bonding Post by Lectrician on Jan 12th, 2005, 7:51pm You have your head screwed on, and have a fair few posts under your belt, so sorry if i sounded harsh ;) Is the RCD covering all the circuits in the CU, or is it a split load unit (Didnt think crabtree made a starbreaker splitload). If you are undertaking a rewire, and adding many circuits, a new CU would be a good idea. I am glad you are one of the sensible ones who will get his work checked over, and appreciates the need due to insurance etc. |
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Title: Re: Earth bonding Post by ChubbyPhaseWire on Jan 12th, 2005, 7:55pm Lectrician Don't forget the 'P' Word ;) Sorry Lec i meant PRACTICABLE lol 547-02-02 The main equipotential bonding connection to any gas, water or other service shall be made as near as practicable to the point of entry of that service into the premises. Where practicable the connection shall be made within 600 mm of the meter outlet union or at the point of entry to the building if the meter is external. |
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Title: Re: Earth bonding Post by JohnDavies on Jan 12th, 2005, 7:57pm Starbreaker is 100 amp spilt load, 63? (from memory) amp RCD. New unit last year. It is always fair to suggest getting work checked out, though with part P the further I get in my reading the less clear it is.... John Davies |
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Title: Re: Earth bonding Post by Lectrician on Jan 12th, 2005, 8:01pm LOL CPW....... Sorry..... Yup. If your rising main is chased into the wall until beneith the floor, with just the arm of the stop cock emerging from the wall, then bond where PRACTICABLE ;) In the 60/70's it was not uncommon for the rising main to appear in the WC downstairs, and the pipework and stopcock to be burried in the wall. I have bonded a few rising mains in the airing cupboard above the WC, or in the loft if it is a bungalow. Cheers CPW......but of course, the DIY-er dreaded PART-P still plays a role ;) And gas.....well....... If the meter is in a box outside, you can bond there, or at the point where it enters the building |
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Title: Re: Earth bonding Post by Lectrician on Jan 12th, 2005, 8:05pm I have not seen recent crabtree units, not a choice of mine. You are familiar with what needs to be protected by the RCD, and what is best left on the main switch side?? Part P will take a long time for people (including sparks and the council.....and government) to get used to. I am sure many ammendments will follow.... |
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Title: Re: Earth bonding Post by JohnDavies on Jan 13th, 2005, 2:41am I thought of something like this main switch side Cooker 40a Central heating 16a Ground floor lights 6 a Kitchen and utility lights (possibly) 6 a (or in with rest of ground floor - it's only a 3 bed house) First floor lights 6 a RCD side Garage 32 a - taken by 6 mm flat to separate wylex fusebox, with 16 a and 6 amp MCB for power and light respectively. I may need a different, less sensitive (type d, is it?) MCB at both ends to cope with my single phase welder. Kitchen and Utility power 32a(posh name for a washing machine and tumble drier in a very small cubby hole!) Ground floor power (dining room, hall, living room) 32 a First floor power 32a Loft 16a What do you think? Question - can the loft supply - a 16a radial - also supply a 1kw heater in bathroom and a 250w towel rail in the bathroom, or is this best included on the upstairs ring (which would make this a lot longer but still within limits). Thanks John |
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Title: Re: Earth bonding Post by L.Spark on Jan 13th, 2005, 4:05pm wrote on Jan 12th, 2005, 6:31pm:
Quote:
Can add just bonding if it's not there already without involving part-p Quote:
It can but it need's to have local isolation for the heater and towel rail, and all of these needs to be in the correct zones for the bathroom and suitibly constructed for the job. |
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Title: Re: Earth bonding Post by dingbat on Jan 13th, 2005, 7:46pm There is no actual maximum length for a main bonding conductor, but there is a maximum impedance of 0.05Ω between the extraneous conductive part (e.g. gas pipe) and the main earthing terminal. Assuming good contact at the BS951 clamp then this give a max length for 10mm2 of 27m at 20°C. (The same value applies to suppplementary bonding, which gives a max length for 4mm2 of around 10m... for those of you with humungous bathrooms! ;D) |
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Title: Re: Earth bonding Post by JerryD on Jan 13th, 2005, 11:11pm wrote on Jan 13th, 2005, 7:46pm:
So what if you use 2.5mm, you're down to maybe 6.5 metres? Hardly enough for many bathrooms trying to connect rad, basin, bath, wc, shower and the cpc's. Why are these maximum lengths not more known about. |
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Title: Re: Earth bonding Post by JohnDavies on Jan 13th, 2005, 11:22pm Thanks. Radiant is on its own pull switch - I thought a fused spur box coupled to the fire ( as at present) would be o.k., and a fused neon switch in the adjoining bedroom for the towel rail. John Davies |
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