Adjustable breakers

brizospark · May 16, 2011

In the case of adjustable breakers which value goes in the column for protective device

i.e. if it a a 200a breaker and it has been tuned down to 180a?

DurhamSparky · May 16, 2011

i would put 180A but make a note that the unit is adjustable to 200A

Guest 004 · May 16, 2011

You will then have to look at the graph of that type of breaker in BS7671, to get Zs values

Engineer54 · May 16, 2011

As the 200A MCCB has been adjusted down to 180A that is the value to be taken. Are there any other adjustable parameters on this MCCB?? Always remember that adjustable MCCBs do not have a common trip value like MCB types. (B,C,D,) They are can be considered as ''one offs'' as there protection levels will vary according to the adjustment values being set on such breakers....

Guest123 · May 16, 2011

MrEnigma said:
You will then have to look at the graph of that type of breaker in BS7671, to get Zs values

If it is an MCCB to BS 60947-2, there are no max Zs values in BS 7671 for them. They can either be calculated or obtained from the manufacturer.

Guest 004 · May 16, 2011

or you can use Amtech

Guest 004 · May 16, 2011

Lenny said:
If it is an MCCB to BS 60947-2, there are no max Zs values in BS 7671 for them. They can either be calculated or obtained from the manufacturer.

yep stand corrected, you can get the graphs from the manufacturers