Commercial sub mains exceed max zs of mccbs

[davesparks]

Are the 125A mccbs set at full or have they been adjusted down to a more sensible level?

 

[jackhammerJIM]

Are the 125A mccbs set at full or have they been adjusted down to a more sensible level?

Hi Dave this type is not adjustable

 

[jackhammerJIM]

This statement to me gives the impression is all okay and maybe it is as fault protection is provided but the issue of selectivity is not clearly addressed. There is no selectivity between x and the supply protective device y whereby fault protection is provided by y. Or something along those lines.

I have commented on the poor discrimination between devices and made them aware of the inconvenience a fault may cause .

cheers lads thanks for your input ....

 

[westward10]

Selectivity these days

 

[jackhammerJIM]

Selectivity these days

person receiving the report won't under stand either term

 

[arashabb]

Hi Guys,
in an installation with one main Distribution board and several submain-DBs, do when you measure Zdb on a submain-DB incomer? and do we need to verify the Zdb value with the up stream protection device?( for example, a 125A, MCCB on the MDB outgoing). If yes, how can I get the max Zs values for MCCBs ?

 

[westward10]

Hi Guys,
in an installation with one main Distribution board and several submain-DBs, do when you measure Zdb on a submain-DB incomer? and do we need to verify the Zdb value with the up stream protection device?( for example, a 125A, MCCB on the MDB outgoing). If yes, how can I get the max Zs values for MCCBs ?

Hello Arashabb this is an old thread so you need to create a new one.