Bonding basket/tray on a fire alarm installation??

[devonsparky]

Just wondered how you guys interpret the regs on bonding dedicated basket/tray for a fire alarm installation. As it only contains ELV is there any need ? It plays no part of the LV electrical system (230v / 400v) so doesn't have any potential to become live at dangerous voltages.

Be interested to hear some views and more importantly some clarification from the BGB !!

Cheers

 

[Deleted member 26818]

You have to consider whether the tray/basket is either an exposed conductive part, or an extraneous conductive part.
If it's one, then it requires earthing, if it's the other it requires bonding, if neither, then it doesn't require either earthing or bonding.

 

[devonsparky]

Well, it's not an exposed conductive part because there is no basic insulation to fail and introduce 230/400.

Extraneous ? Not the way I see it. There is no earth potential as the basket/tray is on the wall and the metal conduits to break glass drops are coming out of the top of the break glass at 2 meters in length.

When you have some guy onsite who looks after sub-contractors telling you that all metal work needs to be earthed/bonded, you start to doubt yourself and want to get reassurance from here!! ha ha

 

[telectrix]

i tend to agree. no need to earth/bond.

 

[Engineer54]

When you have some guy onsite who looks after sub-contractors telling you that all metal work needs to be earthed/bonded, you start to doubt yourself and want to get reassurance from here!! ha ha

If this job your working on is a spec'd contract project then it doesn't matter what you or anyone else here thinks, you MUST follow the specification instructions.

As it happens, this project has basically the very same specification, in that ALL electrical metallic containment systems shall be referenced to the buildings earthing system... Who knows what that basket/traywork maybe used to carry in the future!! lol!!!

 

[devonsparky]

Well, this is in a factory environment where we have to install fire alarm specific basket/tray away from all other services so no 230/400 services will ever be allowed near it. The guy wants to be the big man with a fuzzy understanding of the regs and I want to be able to walk in on Monday and say with confidence that unless you can show me why it needs bonding/earthing then we won't be doing it.
It is not asked for in the specification ............. the only reason is that the guy thinks everything that is metal needs to be earthed/bonded !

 

[telectrix]

so nail his steel toe-cap boots to the floor.

 

[Engineer54]

Well, this is in a factory environment where we have to install fire alarm specific basket/tray away from all other services so no 230/400 services will ever be allowed near it. The guy wants to be the big man with a fuzzy understanding of the regs and I want to be able to walk in on Monday and say with confidence that unless you can show me why it needs bonding/earthing then we won't be doing it.
It is not asked for in the specification ............. the only reason is that the guy thinks everything that is metal needs to be earthed/bonded !

If you go in on Monday morning laying down an ultimatum, you better make sure your on solid ground!! The factory could well have a policy of earth referencing all metallic electrical containment systems.... And remember, many industrial installations are subject to other more stringent regulations than BS7671...

 

[topquark]

So assuming this is 24V alarm, he wants to have the possibility of the tray having a 230V potential on it in the event of a fault ??????? hmmm!!

 

[devonsparky]

If the pompous git stood still long enough I would !

I will tell him that I don't believe it needs bonding/earthing ! For a change I will look forward to a Monday morning.

 

[devonsparky]

There is no has no policy (Have checked that one)

His only argument is that its 'in the regs' that all metal work needs to be earthed/bonded. Nothing more sinister.

We all like to have reassurance ............ I'm an approved electrician / qualifying superviser so have some back up but it's always good to chat with you lot as you're all good for info and good with the banter!

 

[Deleted member 26818]

Get him to show you these Regs.

 

[trev]

Do an IR on the basket/tray against the MET while he's standing watching mate

 

[telectrix]

that ought to confuse him. (the jobsworth, not the OP)

 

[Guitarist]

Some people just like to big themselves up. Had it many times over the years as I'm sure most people have. You could always play it clever by being respectful of his decision, but wanting him to sign this ...

I, ............., do hereby accept full responsibility for any damage/injury which occurs following the bonding of ...........
I understand that .......... has recommended that this equipment not be bonded.


Signed ................

 

[Moses]

So assuming this is 24V alarm, he wants to have the possibility of the tray having a 230V potential on it in the event of a fault ??????? hmmm!!

I agree that in case of a fault the tray will become live, if not bonded.

If bonded then, ADS will ensure that it is safe in case of fault.

So i would bond it.

but you are the supervisor, Mr sparky from Devon, its your decision.

 

[telectrix]

how can it become "live" if it's only carrying 24volts?

 

[benji]

Whats it going to cost to bond it to earth compared with some dick on your back all the time

 

[Engineer54]

how can it become "live" if it's only carrying 24volts?

Doesn't have to be the cables ON the basket that could make the basket live!! Seen some pretty unlikely scenario's over the years, where the so-called impossible became possible, very quickly!! lol!!!

 

[Moses]

how can it become "live" if it's only carrying 24volts?

How can anyone drive a nail in to a cable berried in-line with a socket/switch.

Tel accidents happen. A fault is not designed, its an electrical accident.

People do funny/strange things.

The tray may not become live from the 24V cables in it, but then it could, if the PSU in the panel went faulty and introduced mains on to the detector loop.

Else, some one could leave a trunking cover lying across the mains and fire trunking, a fault on the mains trunking will leave both live???