GFPE Fused Disconnect

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charlie b

charlie b

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I am doing a QC review for a new high rise building. The main switchboard is shown with fused disconnects (incoming main and all feeders). Same for the emergency switchboard. Two questions:
  1. Since the service is 4000 amps at 480V, article 240.13 requires Ground Fault Protection for Equipment (GFPE) for the main building disconnecting means. Can that be achieved with a fused disconnect?
  2. Backup generator feeds a four section vertical switchboard. The four sections feed a fire pump, another fire pump, an NEC 700 ATS, and an NEC 701 ATS. The 700 ATS feeds the emergency switchboard, which has a fused disconnect as its main OCPD. They are showing it with GFPE. Is that needed?

My answers are, in order, "I don't know and I can't understand how," and "No." What say ye?
 
iwire said:
Not standard fused disconnects by but bolted pressure switches with a GFP accessory that can trip the switch.
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A.k.a. "Pringle switch". Instead of the standard knife switch mechanism, a bolted pressure switch has a spring charged mechanism that, like a circuit breaker, can be triggered to release and open the switch. So you can add a shunt trip coil to that, wired to a GFP relay.
161015287632__65176.1423866931.220.290.jpg

Here's one with the charge handle in a different position to be clear.
830598.jpg
 
iwire said:
Yeah, easier to say for sure.

Kind a Band Aid vs Adhesive Bandage kind of thing.
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Well "Pringle" was a brand name OF a Bolted Pressure Switch. Most of the major players offer a BPS option, only the Eaton one is technically a "Pringle". When Cutler Hammer bought Pringle years ago, they kept the name as their trade name of a BPS, because it was so widely known by that name. Ironically now, a lot of people have never heard of a Pringle Switch, I get blank stares when I mention it to anyone under 30 now and I have to go through this explanation over and over.

Actually, most of them have ever heard of a Bolted Pressure Switch either... One guy thought I was talking about a disconnect switch in an explosion proof enclosure when I used that term!
 
Well in one installation of a BPS I saw that a nameplate has been glued to it stating that it was "Main Boiled Pressure Switch" :?
 
OK. Thanks for the information. Now, does anyone wish to offer an opinion on my second question?
 
GE calls theirs a high pressure contact switch. I was told years ago that it was a trademark issue.
 
charlie b said:
OK. Thanks for the information. Now, does anyone wish to offer an opinion on my second question?
Click to expand...

The GFP on the emergency distribution main would be optional. But it would then require all the downstream feeders to to be GFP as well to achieve coordination. See 700.27 and 700.28.
 
dkidd said:
GE calls theirs a high pressure contact switch. I was told years ago that it was a trademark issue.
Click to expand...

GE used a mechanism with butt style contacts, ones like you would find in a circuit breaker. Most other manufacturers use a mechanism that effectively, if not literally, bolted the switch blades closed.
Some of the big names were Pringle (later bought by Cutler Hammer), Barkelew 'Bolt-Loc' (bought by Square D in the 70s), and Boltswitch (still independent).
 
Jraef said:
A.k.a. "Pringle switch". Instead of the standard knife switch mechanism, a bolted pressure switch has a spring charged mechanism that, like a circuit breaker, can be triggered to release and open the switch. So you can add a shunt trip coil to that, wired to a GFP relay.
View attachment 16321

Here's one with the charge handle in a different position to be clear.
View attachment 16322
Click to expand...

What would the interputing rating be of one of those?
 
mbrooke said:
What would the interputing rating be of one of those?
Click to expand...
The switch mechanism is rated for load break at the switch ampacity. Since the GF trip is never going to pickup at more than 1200A, that works.

In the event of massive instantaneous fault the thinking is that the fuses will clear prior to switch operation so the switch contacts will not be responsible for breaking that load, and that's how they get away with rating it at the fuse AIC.
 
big john said:
The switch mechanism is rated for load break at the switch ampacity. Since the GF trip is never going to pickup at more than 1200A, that works.

In the event of massive instantaneous fault the thinking is that the fuses will clear prior to switch operation so the switch contacts will not be responsible for breaking that load, and that's how they get away with rating it at the fuse AIC.
Click to expand...

Makes sense now, thanks :) As is shouldn't the GFP have a slight delay?
 
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