[RE-wrenches] interrupting current calculations used to determine the interrupting of the AC equipment.

[Darryl Thayer]

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 <gary at icarussolarservices.com>
To: re-wrenches at lists.re-wrenches.org
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:re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] 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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