Generator ATS Question

[Bill Annett]

Hi, I hope that you will understand this. I have never seen anything like this before.

A contractor is installing a generator ( as per Electrical engineered Drawings ) that will pick up some of the load of a 10 story building..

The generator is 175KW with 600 Amp over current protection. They have 3 - 125 amp automatic transfer switches, each goes to a 125 Amp panel. When power is lost the generator comes on. When the generator comes on it does not feed the panels, it feed a 600 Amp emergency panel which has 3 - 125 amp breakers that feeds the 3 panels. The only time that the 600 amp panel is energized is when the generator is on.

What do you think of that design? Do you feel that it meets the 2008 NEC. I feel that it does not meet the requirements of 700.5A . I feel that they need a 600 Amp automatic transfer switch ( which is the full load of the generator ) which would feed the 600 amp Emergency panel.

Any help would be appreciated.

Thanks, Bill

 

[augie47]

As long as the three 125 amp panels supply all then loads required to be connected to the generator, I see no problem.

 

[don_resqcapt19]

I don't see any issues either.

 

[Bill Annett]

Thank for the information. To tell you the truth I had no idea if it met code. The electrical contractor and I never seen any thing like that before. Have either of you seen it done that way before? The electrical contractor put in a request for information but have not heard back yet.

Thanks again for the information.

Bill

 

[augie47]

Sounds like it might be a good way to satisfy the requirement at a reduced price.

 

[jim dungar]

Sounds like it might be a good way to satisfy the requirement at a reduced price.

This was an extremely common installation method until the 2008 NEC changes dealing with separation of emergency circuits (e.g. 700.9(B)) versus legally required and option ones (701.10, and 702.9).

 

[augie47]

This was an extremely common installation method until the 2008 NEC changes dealing with separation of emergency circuits (e.g. 700.9(B)) versus legally required and option ones (701.10, and 702.9).

I may be overlooking something, but as long as the wiring was separated, would the install not be Code compliant ?

 

[hillbilly1]

I've had to do that before, where the customer leased the entire building, but it had 6 meters on half the building, and 5 meters on the other half. They did not want to consolidate all of the meters because they might sublet one of the suites later. Used two 1.2 meg generators,and two gears to feed 6, and 5 four pole transfer switches. Also seen the same thing done on a parking deck later on.

 

[jim dungar]

I may be overlooking something, but as long as the wiring was separated, would the install not be Code compliant ?

How do you keep the wiring separated when there is a common wireway in the panel?

 

[augie47]

How do you keep the wiring separated when there is a common wireway in the panel?

Afraid I don't understand.
As I read (or mis-read) 700.9 the two (or three) emergency circuits can share the wireway.
Where do you see the violation ?
(not challenging your knowledge, just trying to learn)

 

[hillbilly1]

Being that this is an existing building, the generator is probably used as an optional standby system, not a emergency system, even though the OP has called it an emergency panel (quite a common misclassification)

 

[jim dungar]

... the generator is probably used as an optional standby system, not a emergency system, even though the OP has called it an emergency panel (quite a common misclassification)

Yeppers.:thumbsup:

 

[Bill Annett]

I would like to thank every one for the information. I have been in the electrical field since I was a junior in High school. That has been over 35 years ago. I keep learning more and more from this site. I am glad for this site and it?s members. Thanks Again