Emergency power passes through normal power switchboard

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Frederick Cox

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A normal-power 480V switchboard originally direct-fed a 600 amp transformer load. An emergency power source was later introduced to feed this transformer, via a properly-installed 600/3 ATS. However, the original feeder cable was intercepted in the switchboard and extended to the ATS as the normal-source feed, and the load feeder out of the ATS (now = emergency power) re-entered the switchboard where it was spliced into the original transformer feeder. Thus, emergency power is running through the normal-power switchboard. Workmanship and materials appear good; just the decision to do it this way is in question.

Is it sufficient to wrap the emergency cable with Scotch 77 fire tape and affix tags & labels describing the external emergency power source? Or must these emergency cables be completely removed from the switchboard? Thank you!
 
The load does include emergency loads so yes - article 700 would apply. I'm not familiar with it. Is there a chapter-and-verse that forbids sharing an enclosure?
 
700.9. But you need to be certain that the loads are those covered by 700. Many people refer to all loads that have backup power as emergency. But 701 and 702 cover other standby loads and aren't as stringent as 700.
 
Frederick Cox said:
The load does include emergency loads so yes - article 700 would apply. I'm not familiar with it. Is there a chapter-and-verse that forbids sharing an enclosure?
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If there are true emergency loads on this panel (emergency egress lighting that doesn't have battery backup, for example) along with non-emergency loads, then you have antoher problem.

An ATS that feeds emergency loads is not allowed to also supply other loads.
 
I agree that it is a violation, and that the feeder from the load side of the ATS is not allowed to travel through the normal switchboard on its way to the transformer. But I will another consideration to, well, to consider. You have a three pole ATS, meaning it does not switch the neutral. Indeed there isn't a neutral to switch. Thus, the source of backup power will not be a separately derived system. That alters the way the EGC connections need to be made, and alters the way the generator (or other source) needs to have its neutral point grounded. I would, at least, look into how this was wired up.
 
This is an old system containing a mix of emergency, Code-required standby and optional standby loads - all served by this single feeder. I believe the presence of emergency loads (egress lighting, etc.) raises the separation requirements of this feeder to Article 700 level, but I can't find the section that stipulates that emergency feeders cannot share an enclosure with normal feeders.
 
Frederick Cox said:
This is an old system containing a mix of emergency, Code-required standby and optional standby loads - all served by this single feeder. I believe the presence of emergency loads (egress lighting, etc.) raises the separation requirements of this feeder to Article 700 level, but I can't find the section that stipulates that emergency feeders cannot share an enclosure with normal feeders.
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700.9(B) in the 2008 Code.

Also, 700.6(D) and 700.15 for seperation of loads.

Steve
 
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