Max zs on double pole mcb

[crotley32]

I am filling out test sheets and have a merlin gerin D32 C60 HD double.pole mcb. The rating on the mcb says 415V feeding 2 feeds to a canalis busbar.

BS7671 States max zs for D32 0.4 secs is 0.34. Is this just for single pole MCB?
I have also check my max zs value
from manufacture stating 0.51.

The reading I got at the furtheast light fitting at the tap off of Busbar was 0.47.

So question been do i go with bs7671 or manufacturing result??

 

[The Ghost]

What is a canalis busbar ?

 

[Risteard]

What is a canalis busbar ?

It's busbar trunking made by Schneider.

 

[The Ghost]

Oh hang on just found out. Ah yes it comes back to me now we had that in the place I trained in. All around the building.

 

[TJ Anderson]

I am filling out test sheets and have a merlin gerin D32 C60 HD double.pole mcb. The rating on the mcb says 415V feeding 2 feeds to a canalis busbar.

BS7671 States max zs for D32 0.4 secs is 0.34. Is this just for single pole MCB?
I have also check my max zs value
from manufacture stating 0.51.

The reading I got at the furtheast light fitting at the tap off of Busbar was 0.47.

So question been do i go with bs7671 or manufacturing result??

It's the same Zs. Does not matter if it is single or double pole. It is still a BS EN60898 D32 MCB.

Look again regarding Zs for a D Type curve MCB. Think what disconnection time are you looking for with that particular circuit type......

 

[Strima]

I'd be using the manufacturers information. The C60 range covers two standards, both 60898 and 60947, BS7671 only recognises 60898.

 

[TJ Anderson]

Come on chaps ..... its a distribution circuit. That canalis busbar has fused tap offs, it's not a final circuit. Only 5 second disconnection required. 0.68ohms max Zs for D32. You recorded 0.47ohms. Satisfactory disconnection achieved. It complies!!

 

[crotley32]

If what your saying is correct then wouldn't the max zs be whatever size fuse is in the tap off plug and not the distribution fuse?

 

[Toneyz]

So what is the Zs at the end of the busbar trunking?

 

[crotley32]

See Original post 0.47 ohms.
I have been told the distribution mcbs are to be chamged to C types to meet max Zs. As some of these tap offs are the ones without fuses in

 

[TJ Anderson]

The distribution circuit Zs would be taken at the supply terminal to the Canalis End Connectors.

As you are only looking for 5s disconnect then it is actually the same maxZs in BS7671 for both 60898 C&D type MCB's as the regs only separates values for D types.

The MCB protection is protecting the cable supplying the Canalis and meeting ADS.

Changing the type wont help you with unfused tap offs and reduced conductor sizes. Thats very irregular for lighting to be infused of a busbar. If there are unfused tap offs then you would need to confirm that they are also suitably protected against bith overload and fault currents. Overload protection may well not be required due to loads being determined so can be omitted. You would then need to work out if reduced size cables would disconnect under fault condition a) in time, b) before they exceed 70C.
Does raise some Q's anyway.....
How many taps off plugs is there? Can you not put fused ones in? Are the light fittings designed for 32A protection.....I doubt it...