2008 NEC and art. 702.5 capacity & rating - Electrician Talk - Professional Electrical Contractors Forum

holtjgh1128 · 03-29-2010, 07:39 AM

Good day, could anyone indicate what is the proper way to calculate the proper size standby generator? Also how you calculate the deals with the maximun available short current at its terminals.
How to deal with motor loads on A/C units with high LRA?
thanks

raider1 · 03-29-2010, 10:34 AM

Welcome to the forum.

I would suggest that you ask each of those questions in a separate thread as they each could require quite a bit of explanation.

As for how to size a standby generator, what type of transfer switch are you going to use, automatic or manual? The answer makes a great deal of difference.

Chris

holtjgh1128 · 03-29-2010, 02:42 PM

thanks for the response. I install all sizes and wanted to see how others view the new 2008 section of 702.5

thanks

raider1 · 03-29-2010, 04:57 PM

I view it very simply, if you install an automatic transfer switch then you have 2 options for sizing the generator.

1. Size the generator for the full load to be transferred by the transfer switch.

2. Provide a load management system that sheds unnecessary loads and size the generator for the managed load.

Also 702.5(A) requires that optional standby system equipment be suitable for the maximum available short circuit current at its terminals.

Chris