Wery well said Gary, the service drop and service lateral serve to limit the
AFC,
I did not mention that large switch gear has to have With Stand Current rating
also which means if subject to a short and the AFC the gear shall not distruct
from the mechanical forces generated by the magnetic fields. In the case I
mentioned the busbars were ripped from their mounts and the cabinets were
pulled into the mess. ( ever see welding cables snap together when a high
current passes?
From: Gary Willett <[email protected]>
To: [email protected]
Sent: Monday, October 3, 2011 3:32 PM
Subject: Re: [RE-wrenches] interrupting current calculations used to determine
the interrupting of the AC equipment.
James:
I believe your PE is referring to the short circuit current
calculations of 110.10, and the 110.24 marking requirements for
AFC (Available Fault Current). The utility company should be able
to give you the AFC at the secondary of their transformer, or
better yet - at the service equipment.
The short circuit current rating of the utilization equipment, and
the AIC (Available Interrupting Current) rating of the OCPD in the
utilization equipment, must exceed the AFC.
Regards,
Gary Willett, PE
>
>From:[email protected]
>[mailto:[email protected]] On Behalf Of James Rudolph
>Sent: Monday, October 03, 2011 1:54 PM
>To: RE-wrenches
>Subject: [RE-wrenches] interrupting current calculations used to determine the
>interrupting of the AC equipment.
>
>Dearest Wenches,
>
> I received an e-mail from PE reviewing one of our projects
to build, and this is what they wrote-
>
>No interrupting current calculations were included. It is
suggested the utility company be consulted for available at
the service entrance and these values be used to determine
the interrupting of the AC equipment.
>
>Does any one out there have experience dealing with this
issue, or have the ability to shed some light on this subject.
>
>Many thanks in advance,
>
>--
>James B Rudolph
>NABCEP Certified PV Installer
>
>
>
>
>_______________________________________________
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