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John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:8

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reply to Clever_Proxy

Re: Turning off Power to a Building

Just a couple of things for people not used to seeing that kind of equipment...

-Those are fused disconnects rather than circuit breakers. They use bladed fuses and feed the distribution panels in the building where the 'normal' branch wiring circuits terminate.

- That kind of switchgear of that vintage can have covers that slide down when the screws are removed so it is imperative to be very careful when removing the covers that they do not slide down and severely injure your toes/feet (even through your boots), or that they do not fall into the gear unexpectedly.

- Most reasonably modern (last ~20 years) RTUs have phase-loss and reverse rotation protection devices in the control circuitry. Additionally, one more thing to look out for on building restarts after a prolonged outage is the sudden load of all the units being called at the same time on hot days, or even cold days when the system has electric supplemental/emergency heat. This can drive demand charges up if the units all come on at the same time. Again, most units have staggered on-delay timers to alleviate this problem during power outages of the normal kind (i.e., storm-related, etc) so it shouldn't be too much of an issue.

As was pointed out by others, reverse rotation can be an issue, so it would be best if someone contacts the power crew foreman prior to their beginning work to make sure that the crew addresses the phase sequence issues appropriately. Most utilities are aware of the issue, and endeavor to address it, but you never can be too sure unless you ask. Be polite and diplomatic, of course, when doing so.
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