why 2 sircuit breaker in series

[ashraf_s_y]

first at all i am using one of the systems at follow
NFPA 20 code
in the code, the control panel should have two circuit breaker, one for isolation and the other for any short circuit
i want the technical reason of butting two circuit breacker specially thy are in series directly, if one trip the other will be useless.
and why we can't install one circuit breacker has the same feathers for both of them.
please in form me.
and i want to thank u for your support.
thanks

 

[bob]

Re: why 2 sircuit breaker in series

The breaker in the source panel will provide short ckt protection. The breaker at the load is installed so that anyone working there can de-energize the equipment. If the first breaker is close by it can do both jobs per the NEC.

[ April 17, 2005, 11:28 PM: Message edited by: bob ]

 

[kiloamp7]

Re: why 2 sircuit breaker in series

You say NFPA 20. Well that's fire pump requirements.

Controllers for fire pumps have to meet all kinds of special requirements.
Most of those requirements make sense. You best be careful if you go messing with 'em.