Generator Replacement / Article 700 / System Replacement

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cyriousn

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ME / CT
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EE & BIM
I'm working with a building owner that has an original electrical system from the 70s or 80s. They have a 1000A normal utility service and a somewhere along the way they installed a 60kW gen set that that powers emergency lighting, and optional standby loads. They want to replace the the generator set to be able to power the entire building based on their peak power demand over the past few years which was roughly 138kW. I'm using 125% of that load to figure they could probably go with a 175kW unit to cover their needs and they could just install a 1000A service entrance ATS to intercept the service feeders and swap over the grounding.

What I can't remember is if there is something in the code that will trigger an entire electrical system upgrade? Just installing the generator and ATS would not come close to meeting article 700 and selective coordination would not be met for sure. For some reason I thought this might be up to the local AHJ but I wasn't 100% sure. Any insight is much appreciated.
 
Article 700 and 702 loads have to be kept separate, so you would need 2 ATS's already which makes things more messy already.

Because it isn't a direct replacement for maintenance, most AHJ's would require compliance with current code for the system you touch, so emergency system(s) overcurrent devices (Article 700) shall be selectively coordinated with all supply-side overcurrent protective devices.

If you are on NEC-2017, you have lots of other things like 700.3(F) for maintenance switching for a backup
 
Yeah that's what I was afraid of. Sounds like it's going to cost them a lot of money to fix the problem that they have. Everything is mixed up in the same panels past the ATS. This is all stemming from wanting to add all of the air conditioning to the generator. Plus they have LP and going over the 125kW mark they will pay good money for the gen set.
 
You really need to talk to your local AHJ.

In at least one state; if it was to code once, it is still to code. In your case you would only need to coordinate new protective devices, you would ignore the existing ones.

However because you are changing the generator, they would require any new components and wiring meet the 700 and 702 separation, up to the point of the existing circuits. As Ron said, your emergency lighting would need its own transfer switch.
 
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