×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Air v Moulded Case

Air v Moulded Case

Air v Moulded Case

(OP)
We have to get an incoming device for a board.

Normally it’s easy, 1kA and down get MCCB, 2kA and up get ACB but this one is 1.6kA and ACB and MCCB will both deal with the load current and fault levels.

Anybody got a view on other things I should consider in making my choice?

RE: Air v Moulded Case

MCCBs in series will not fully coordinate.  If selectivity is important, you will need a power circuit breaker w/o instantaneous trip.

Power circuit breakers are maintainable, MCCBs are not.  

Obviously the MCCB will be much less expensive.  

RE: Air v Moulded Case

ACB will allow use of a definite-minimum-time protection scheme to ensure coordination with downstream breakers. On a high fault level system this is invaluable because an MCCB will trip instantaneously to clear a fault while the ACB will hold in. Thus an ACB is a good choice for an incomer to a board with multiple outgoing circuits protected by MCCBs where a fault on one load must not cause loss of the whole board.

----------------------------------
  Sometimes I only open my mouth to swap feet...

RE: Air v Moulded Case

please do not cross post

RE: Air v Moulded Case

rbulsara,

That's a bit harsh!

Quote (from other thread):

thinking about it this would be better over in the switchgear & boards forum so if a passing mod would care to delete this I'd appreciate it

The other thread has been flagged for deletion.

----------------------------------
  Sometimes I only open my mouth to swap feet...

RE: Air v Moulded Case

OK:)

RE: Air v Moulded Case

except I had posted a reply there..

RE: Air v Moulded Case

here it is: (as other post was not yet deleted):

its not as simple..

Items to consider and evaluate are:

Cost
application
degree of reliability required
maintainability required ( ACB are maintainable)
electrically operation required or not
Plug in, bolt-on, drawout, stationary- what is important to you
Short circuit ratings- switchboard or switchgear?
Short time ratings- for coordination purposes
ACB have more flexibilty to help coordination
Size of equipment (space )

RE: Air v Moulded Case

(OP)
I’d thought of the coordination aspect and passed my thoughts on to the consultant.

His suggestion is a 1600 mccb incomer with dummy trip unit (so basically a switch only) and relying on the upstream device at the transformer for protection. The board will have two 800A switchfuses as outgoing devices.

My initial suggestion was ACB incomer and MCCB outgoing but, as always, cost is an issue

At the end of the day, he’s got to be happy paying for it but I’ve got to be happy building it

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources