Ask The Trades - Print Page

Ask The Trades
https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> earthing ? https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1090322505 Message started by jaja on Jul 20^th, 2004, 12:21pm

Title: earthing ?
Post by jaja on Jul 20^th, 2004, 12:21pm

Cheers for all the advice on DB thread. Very helpful!

One more ? for you guys. Im currently looking for an office to rent and think ive found one, but it's quite old ( nice and cheap)! but had a sparky look at the electrics , and he tells me that the system is a bit dated! The main problem is that it has no separate earths to circuits and DB's. everything is earthed through the existing metal works, conduits etc..

sparky tells me that it's not necessarily illegal but wasn't completely sure!He said he wouldn't be able to test it properly, and he recommended some works. My question is, is it illegal or against building regulations in this day and age to work in a building which is earthed just via metal work or not. and should i take on the office, considering that i will have a few people working for me! i dont want to put anyone in danger and i dont wanna end up in court

Title: Re: earthing ?
Post by scotspark on Jul 20^th, 2004, 2:47pm

you can still use conduit and trunking as your eartg with just flying leads of back boxes. well up here in scotland anyway!! would always prefer to run seperate earth myself but can't see any reason why if your sparky has appropriate test gear he can't test the installation to see if earth is ok.

if he finds any problems you can then go to landlord as they must have buildings in sound condition if they r letting them out

Title: Re: earthing ?
Post by L.Spark on Jul 20^th, 2004, 3:45pm

well ive no idea why he can't test it, there are severl tests for checking the earthing trough metalwork, and yes it's normal to earth trough conduit and trunking, if it's dont properly tho, it's not somthing I would be overly concerned or not, however it must be connected to earth at some point and it would be essential to check the cables at this point were correctly sized, refer the electrician to this if he comes back to you.

Title: Re: earthing ?
Post by jaja on Jul 20^th, 2004, 4:54pm

So what your saying is that it's not against regulations to use metal work as earth. And as long as the system tests out ok then theres no need to install separate earths to the existing circuits?

Correct me if im wrong.

Title: Re: earthing ?
Post by Lectrician on Jul 20^th, 2004, 5:01pm

Yep, no probs. Get the Zs on the ccts tested, but i would think it would be ok.

Title: Re: earthing ?
Post by jaja on Jul 20^th, 2004, 5:24pm

wrote on Jul 20^th, 2004, 5:01pm:

Yep, no probs. �Get the Zs on the ccts tested, but i would think it would be ok.

Zs CCTS??????????????????? :-[

Title: Re: earthing ?
Post by Lectrician on Jul 20^th, 2004, 5:36pm

Checks to ensure that the earth at the end of the circuits is suitable (and low enough) to operate fuses/mcb's that our protecting the circuit in the event of a fault.

Conduit can rust at joints, and joints can loosen, so it is important to undertake Zs at the furthest point of the conduit. (a 25amp test is recommended.)

Title: Re: earthing ?
Post by L.Spark on Jul 20^th, 2004, 8:48pm

don't forget this is the diy section :)

Title: Re: earthing ?
Post by scotspark on Jul 20^th, 2004, 9:17pm

yes but these are basic tests his sparky should know how to do.

have no idea why he would say he can't test to see if earhing is ok

Title: Re: earthing ?
Post by L.Spark on Jul 20^th, 2004, 9:33pm

same scot ::)

Title: Re: earthing ?
Post by Beanzy on Jul 22^nd, 2004, 6:49pm

Only thing for spark to worry about is testing conduit if building in use or fire hazards stored near conduit. He should ideally do 'flash' insulation tests on it and it can cause problems if not done correctly. A crappy joint in the conduit may arc so you have to monitor it properly that's all really. If he's work his salt he'll be able to do it.

Title: Re: earthing ?
Post by ChubbyPhaseWire on Jul 22^nd, 2004, 9:13pm

Where metallic enclosures have been used as the protective
conductors, e.g. conduit, trunking, steel-wire armouring etc the
following procedure should be followed:
(i) inspect the enclosure along its length for soundness of
construction
(ii) perform the standard ohmmeter test using the appropriate test
method described above.
Instrument: Use a low-resistance ohmmeter for this test.

Title: Re: earthing ?
Post by rabbit_rabbit on Jul 22^nd, 2004, 9:29pm

Chubby!! Ya elusive character.

Ya DEAD right about the fire hazard bit. My lecturer (2391) relays a story where tests were being done on some old conduit in a flour mill (before the days where flour mills are treated same as Petro-chemical Fuel Hazards).

Anyway, out with the Megger and tests the conduit. There was one Hell of a bang in the loft as the flour dust exploded (sparks from rusty old conduit due to 500v insulation tester). The entire buidling was gutted by fire.

RR

Title: Re: earthing ?
Post by scotspark on Jul 22^nd, 2004, 10:49pm

unfortunately I doubt you will be able to visually check all of the conduit without ripping up floors n cielings.

check as much as you can tho

Title: Re: earthing ?
Post by L.Spark on Jul 22^nd, 2004, 11:49pm

have to have the proper steel conduit for stuff like that where fire risk,explosion etc

Title: Re: earthing ?
Post by Lectrician on Jul 23^rd, 2004, 7:39am

Solid drawn conduit for explosive atmos.

Title: Re: earthing ?
Post by L.Spark on Jul 23^rd, 2004, 1:04pm

damn ur good! :D

Title: Re: earthing ?
Post by supersparky on Jul 23^rd, 2004, 5:07pm

wrote on Jul 23^rd, 2004, 1:04pm:

damn ur good! :D

lectrician, we wont need toilet paper soon ;)

lol

ss

Title: Re: earthing ?
Post by Lectrician on Jul 23^rd, 2004, 5:31pm

That joke just wont 'click' ???

Title: Re: earthing ?
Post by supersparky on Jul 23^rd, 2004, 6:07pm

wrote on Jul 23^rd, 2004, 1:04pm:

damn ur good! :D

i beleve the correct expression is 'Licking ass'

lol

ss

Title: Re: earthing ?
Post by Lectrician on Jul 23^rd, 2004, 6:17pm

I wasnt looking for something so simple :-)

How rude :-[ ;D

Title: Re: earthing ?
Post by Beanzy on Jul 23^rd, 2004, 10:56pm

wrote on Jul 22^nd, 2004, 9:13pm:

That covers the continuity but you have to do insulation resistance to earth conductors and between live conductors. That's the one where real care has to be taken with testing. don't want to 'Megger' the shop cat or the boss won't pay. �;)

Title: Re: earthing ?
Post by L.Spark on Jul 23^rd, 2004, 11:10pm

some people have no respect! ::)