B or C type breakers?

[sjm]

Hi guys having a brain fade moment.

Any reason why I can't use C type RCBO's instaed of B?
Doing a CU change at a Nursing home and been quoted for C type, currently they're B type.

Board is 3 phase but all breakers are single phase.


Thanks in advance.
Steve.

 

[telectrix]

as long as the Zs is low enough to meet disconnection times. the max. Zs for C type is 1/2 that for a B type of the same rating.

 

[sjm]

It's a TT system and will have an upfront type S 100ma RCD.

 

[telectrix]

so the RCD side of the RCBO is used for fault protection. assuming a 30mA RCBO, then your max. Zs is 1667. it's fine.

 

[sjm]

That's what I thought, just having one of those moments.

Thanks telectrix

 

[Farmelectrics]

Am I right in saying b type are more sensitive more chance of nusiance tripping tend to install mainly c type myself

 

[High Tower]

No, they are more susceptible to tripping under inrush/ start up current, nothing to do with sensitivity, in most domestic cases B type should be used. And anywhere that c type is used great attention should be placed on measured ZS value. Unless as has been said, you are employing a RCD, then it matters less

 

[High Tower]

B type = domestic / standard circuits
C type = light commercial, inductive loads, inductive lighting such as loads of flouresents/ mods, etc
D type= heavy commercial/ industrial such as bigger motors/ commercial welding equipment
MCCB = are used in initial distribution and really big loads !!

Anything bigger and your into the realm of HV and ACB's etc and that's the speciality of maniacs like Tony!!