I wanted to start a discussion on code compliance of utilizing 3 Pole transfer switches with non switched neutrals on a 480 V system. If a fire pump is included in the design most manufacturers do not include neutrals making the system non separately derived. Another engineer came to me with this problem and I suggested pulling a neutral through the fire pump transfer switch so that there are no mixed transfer switches. However the other issue that I am concerned about in this design ( that’s already installed) is application of ground fault detection as the generator is 480v and has a 1200 A circuit breaker
Prior to this discussion, this article should be helpful. https://www.csemag.com/articles/choosing-between-3-pole-and-4-pole-transfer-switches/
Here is a better version of that article. https://www.google.com/url?sa=t&source=web&rct=j&url=https://resources.kohler.com/power/kohler/industrial/pdf/3_Pole_ATS_White_Paper.pdf&ved=2ahUKEwjz4u-4w97mAhWPQc0KHXevDzoQFjABegQIBhAB&usg=AOvVaw0Jv3qU5jQfEkwZABJgQY35
You may also find this Q&A helpful. https://www.neca-neis.org/code-question-of-the-day/code-question/cqd-8-29-2017
These articles are certainly informative! Problem is Mike Pincus does not clarify if using 3 pole transfer switches with a ground fault detection set up violates 700.6 D ( I think it does) Also NEIS indicates fire pump transfer switch and 4 pole switches neutral transfer switches my situation involves fire pump transfer switch and 3 pole bussed neutral
I’m trying to find out if there is a code compliant way to employ ground fault detection on the emergency source on a system with hard bussed neutrals
Oh sorry I think the articles provided some great background info... more asking the entire forum
It could be argued that the ground fault protection at the normal source would provide compliance with 700.31 if using 3 pole transfer switches in lieu of ground fault detection?
I believe that when working with 700.6(D) that the GF Detection at the generator would not function properly under the emergency power and leaves 700.6(D) if indeed part of an emergency system not in compliance.
I believe 700.6(D) and 700.31 are two different beasts. They are only interrelated when the GFP is not provided due to automatic disconnection means. However, if no automatic means are provided the alarm and indication is still mandatory in 700.6(D). 700.31 is just saying automatic disconnection is not required.