One for Steptoe ETC

[Nicky Tesla]

"Im not sure, try checking stuff out for yourself sometimes."

I did check it out Steptoe, in the Snags and Solutions for earthing and bonding.

Snag 28........Quote. Electrical contractors sometimes provide earthing and bonding to the metallic grid of a suspendd ceiling when it is not necessary.

In practice, unless there are very exeptional circumstances, The conductive parts of a suspended ceiling will be neither exposed-conductive parts or extraneous -conductive-parts. Consequently, in normal circumstances, suspended ceilings need neither be earthed nor equipotentially bonded.

It is written Pray

 

[batty]

"Im not sure, try checking stuff out for yourself sometimes."I did check it out Steptoe, in the Snags and Solutions for earthing and bonding.

Snag 28........Quote. Electrical contractors sometimes provide earthing and bonding to the metallic grid of a suspendd ceiling when it is not necessary.

In practice, unless there are very exeptional circumstances, The conductive parts of a suspended ceiling will be neither exposed-conductive parts or extraneous -conductive-parts. Consequently, in normal circumstances, suspended ceilings need neither be earthed nor equipotentially bonded.

It is written Pray

I would agree with this but if you have an installation that has wires draped across it which was done in the past it may be an idea to bond it. But if its done correctly there should be no need to bond it.

 

[Andy™]

the cables should be DI. in which case, even if it was in metallic trunking, there would be no requirement bond required

 

[Doc Hudson]

Would that be from one of these snags books Nicky, If yes, for the benefit of other members, would you recommend them as helpful books?

Doc H.

http://www.amazon.co.uk/s/ref=nb_sb_ss_i_0_6?url=search-alias%3Daps&field-keywords=snags+and+solutions&sprefix=SNAGS+

 

[tom1]

Would that be from one of these snags books Nicky, If yes, for the benefit of other members, would you recommend them as helpful books?Doc H.

http://www.amazon.co.uk/s/ref=nb_sb_ss_i_0_6?url=search-alias%3Daps&field-keywords=snags+and+solutions&sprefix=SNAGS+

i was just going to start a thread on that. are you in my head :Welcome: .

no thats not good back on with my foil hat to keep you out my head.

there are 2 snag books i have seen and of course the part p doc.

can anyone recomend any, or does osg cover the same?

 

[Nicky Tesla]

it was ok for a quick read, telling you a lot of stuff you already know, but then there are some things you didnot as per the above quote but at least suspected, but now at least confirmed. But as with a lot of these books, once youve read them youve read them. So borrow one if you can

.........no youre not avin mine get your own

 

[wozz]

when i worked on commercial installations during my apprenticeship grids were always earthed by a bit of 4mm bolted to them from a local click box.

My thoughts on this were, can you effectively earth a large grid? even if you bond the long lengths and not the T bars is the grid still effectively bonded across the other side of the room considering the amount of joints and such like?

the grid is not a exposed conductive part by they can in direct contact with exposed conductive parts, will some people therefore they need to be earthed?

i always thought the earthing of these was a bit pointless considering we never earthed the masses of ductwork running through the buildings (although it may be earthed through the motors, this was never tested).

obviously i never questioned this as i was only a apprentice and if i did i would get the answer 'this is the ways we always do it'.

 

[Nicky Tesla]

John Whitfield does a great book, but it seems to have a lot of silly little mistakes in it, like referring to the wrong diagram and stuff, so takes a bit of deciphering at times.

The old yellow one, was better written. It really helped to get my brain working.

The "Practical guide to inspection , testing and certification of electrical installations" by Christopher kitcher looked good at first with loads of practical photos, but it didnot go any were near far enough, so ended up being a total waste of time and money.

 

[Nicky Tesla]

when i worked on commercial installations during my apprenticeship grids were always earthed by a bit of 4mm bolted to them from a local click box. My thoughts on this were, can you effectively earth a large grid? even if you bond the long lengths and not the T bars is the grid still effectively bonded across the other side of the room considering the amount of joints and such like?

the grid is not a exposed conductive part by they can in direct contact with exposed conductive parts, will some people therefore they need to be earthed?

i always thought the earthing of these was a bit pointless considering we never earthed the masses of ductwork running through the buildings (although it may be earthed through the motors, this was never tested).

obviously i never questioned this as i was only a apprentice and if i did i would get the answer 'this is the ways we always do it'.

Yes i totally agree, How can all the grid be bonded properly as per regs with 10mm cable. Just poss earth it to the local lighting cct thats it maybe? with 4mm. But I have seen post office leckys ROMEC fitting 10mm bonding.

 

[steptoe]

"Im not sure, try checking stuff out for yourself sometimes."I did check it out Steptoe, in the Snags and Solutions for earthing and bonding.

Snag 28........Quote. Electrical contractors sometimes provide earthing and bonding to the metallic grid of a suspendd ceiling when it is not necessary.

In practice, unless there are very exeptional circumstances, The conductive parts of a suspended ceiling will be neither exposed-conductive parts or extraneous -conductive-parts. Consequently, in normal circumstances, suspended ceilings need neither be earthed nor equipotentially bonded.

It is written Pray

just remind me again who publishes/prints/distrubites(whatever it is) that book.

I am only here to give my opinions as to what I recommend be done to ensure a safe and legal installation,

I dont make the rules,

EAWR do.

no one else.

if the suspended ceiling is being used to support cables(and Im sure we have all been somewhere where it has,) then it could even be arguable classed as an exposed conductive part.

either way, I will bond it, perhaps as has been pointed only from a local circuit, but I still bond it.

 

[Andy™]

and potentially introduce a potential that would never have existed

 

[steptoe]

[quote name='Andy

 

[Lurch]

lets not bother earthing trunking either then, after all, it only holds the cables.

I think you missed the point there. Yes trunking is generally earthed whether it contains singles or twin and earth etc... However, it doesn't always require it, and not everthing metallic with a double insulated cable on\near\through it requires bonding.

 

[spinlondon]

Is the bonding of containment done in 10mm

 

[SteveH37]

I have seen both earthed and unearthed grids, some in 10mm and others in 4mm but generally feel that the amount of parallel paths created by direct contact with the light fitting (usually recessed mods in my case) offers sufficient earthing arrangement. Feel sorry for the spark who fell though, perhaps if he was on a platform of sorts would have only fell a couple of feet.

 

[Lurch]

I have heard of a situation, where a light fitting was incorrectly wired by an apprantice, and the grid became live. The sparky who climbed a ladder to sort out the non-working light fitting got a shock and fell off his ladder breaking his leg. If the grid had been earthed, then the protective device should have operated.

But that's one of those situations where it shouldn;t have been live in the first place. Either the wiring should have been checked before it was made live or the apprentice shouldn;t have been allowed to wire it up. It's like the 'lets earth metal windows because a window cleaner got a belt from a live cable that was shoved through one', the cable shouldn't really have been stuck through the window in that situation and if it was it should have been done properly, so the fix is just patching the problem, not fixing the cause.

It's another one of those 'solutions to a problem that should never have never existed'. Do you work for the IEE or NIC?

 

[Andy™]

lets not bother earthing trunking either then, after all, it only holds the cables.

im really starting to doubt if your competent enough to do electrical work.

 

[steptoe]

[quote name='Andy

 

[binky]

The book referred to also recommends that all cables above suspended ceilings are strung from cateneary wires, with short lengths of cable direct to light fittings, ergo grid is not extraneous. However most lazy? (time poor) electricians throw cable across grid therefore grid is extraneous cos it holds cables. My only concern is howmany bonds you need to get a good bond to entire grid. 1 in total, 1 at each light point, 1 at each line?? On the one occasion I've been involved with a new grid install, I used trunking / conduit to provide extra insulation between grid and cable, and used flex cos the insulation is thicker than FTE just in case it snagged a sharp edge.

 

[Andy™]

just because something holds a cable doesnt mean its extraneous.

take a metallic class II light fitting - even though its DI and not designed to have an earth, would you still earth it 'because its metallic and has a wire in it'?