Classification of Busbar Trunking

[Mattman]

Hi all!

I was having a bit of a to do with a colleague of mine regarding busbar trunking.

We both agreed during our inspection that a busbar deserves it’s own test sheet as it is a method of distribution which each “tap off” denoting a separate circuit. However I argued that the ‘Zdb and ‘Ipf’ ’figure be taken from the farthest point of the bar as this will (hopefully) denote the highest reading for that distribution circuit.

He argued that the busbar itself IS the distribution board and thus the figure should be taken from the earliest point of the busbar (where it’s supply connects to)

Personally, I can see his point but there’s a considerable amount of potential impedance going unrecorded his way.

Thoughts?

 

[Risteard]

To me whilst it may be a distribution circuit it is in no sense a distribution board. So I would just list whatever circuit(s) are supplying the busbar trunking. Obviously make sure that the tap-offs are correctly fused etc., and that ADS will operate.

 

[Mattman]

To me whilst it may be a distribution circuit it is in no sense a distribution board. So I would just list whatever circuit(s) are supplying the busbar trunking. Obviously make sure that the tap-offs are correctly fused etc., and that ADS will operate.

Thanks for the reply!

So would you consider the tap-offs not to need recording? Similar to a plug on a socket circuit?

 

[Risteard]

Well the more I think of it I don't think there's any harm listing the tap-offs separately. (Apart from a lot of paperwork!)

The fact that there is a fuse in the busbar plugs could be argued to be the origin of a circuit.

Sorry for the contradiction between the two posts.

 

[Mattman]

Well the more I think of it I don't think there's any harm listing the tap-offs separately. (Apart from a lot of paperwork!)

The fact that there is a fuse in the busbar plugs could be argued to be the origin of a circuit.

Sorry for the contradiction between the two posts.

No problem, it’s a bit of an open one!

The way I see it is that the busbar is a circuit, not a distribution board - however due to the amount of sub-circuits it could warrant its own sheet. I believed that any recording for busbar circuit should be taken from the farthest point as this would be a true Zs for the circuit (and could be used as a subsequent Zdb for its own sheet).

His point was to take it from the first point because it was essentially a very long fuse board.

He’s got a point, but the busbar isn’t exactly the same size as one in a conventional distribution board and there is potential to gain impedance over those long runs.

It’s petty, I know, but a technicality that could do with addressing.

 

[westward10]

What type of busbar are we talking of.

 

[Ian1981]

As said it creates a lot more paperwork but I would list and record as much information as I could including the tap off points but they could be recorded as the ocpd for the distribution circuit / final circuits of which it supplies on the EIC or the EICR

 

[Mattman]

What type of busbar are we talking of.

Honestly, I’m not sure if it’s particulars.

It has 70 tap-off points, with each tap-off containing 3 inserts for BS88 fuses. They’re direct wired to the tap off as opposed to the ‘plug in’ tap-off that contains its own switchgear and is simply pushed into the terminals.

 

[westward10]

Needs discussing with the client. I have done this in factories and it is a royal pain in the a***. Have spent weeks in one factory as there were hundreds of them.

 

[davesparks]

This could be a case for customising a test results sheet to suit the installation.