Legally Required Standby

[mshields]

To be sure, Legally Required Standby loads should be on a dedicated ATS so that a facility that needs it would have an Article 700, 701 and 702 ATS's. My question is this, is it mandated that Legally Required Standby have it's own ATS OR so long as the 702 ATS switches in 60 seconds albeit with a mix of 701 and 702 loads, could that be deemed acceptable?

 

[texie]

Yes as long as the 701 loads are supplied in compliance with 701 the 702 loads could be tagged on to the system. One area that comes to mind is selective coordination would be required.

 

[mshields]

Ah - good point - thanks

 

[d0nut]

I don't know that I would want the systems on the same ATS even if it is permitted by the NEC. Using the 2020 NEC for references, 701.2 states that the Legally Required Standby Systems loads are those that are specifically classed as such by a governmental agency having jurisdiction. While you do not have to keep the wiring separate from other systems, from a reliability standpoint, the fewer items you have on a branch the less items you have to cause issues on that branch.

If there is a legally required standby system, I would want to keep those loads separate from my other loads from a maintenance standpoint and to lower the risk of a system that isn't required causing an issue with my legally required systems.

 

[texie]

Ah - good point - thanks

I tend to agree with d0nut. If given the choice I would not do it just to keep things simple.

 

[mshields]

I would definitely always give its own ATS. I've run into a situation where that happens not to be the case. So I'm looking for the letter of the law. I think the biggest problem as was pointed out above would be 0.01 selectivity that IS required. That's tough to get to and if you have to get to it even for loads that don't need it, it's more likely than not, that you won't be able to get there. For 120 control circuits you'd probably need the Bussman fusible breaker panels and there is no way you want to ask your client to pay for those where they're not needed. Thanks for all the input.