Generator disconnecting means

[brentp]

Need some help here.

I've got a hospital with (3) gensets in parrallel. The design does not call for disconnecting means at the generators. I'm trying to get my ducks in a row for a conversation with the engineer, who says it is not required.

I can't get past 445.18(2) which nixes any exception for the disconnecting means in this circumstance.

Does anyone know of a code rule that does not require disconnecting means at the generators?

Brent

 

[JES2727]

Brent,
I was recently asked to quote a small job that involved removing an existing output breaker ( because it was faulty ). I had the same concerns as you. I went nuts trying to figure it out, but no one here - or anywhere else - could tell me that the disconnecting is required at the generator.
Here's the thread: http://forums.mikeholt.com/showthread.php?t=112758

 

[benaround]

Need some help here.

I've got a hospital with (3) gensets in parrallel. The design does not call for disconnecting means at the generators. I'm trying to get my ducks in a row for a conversation with the engineer, who says it is not required.

I can't get past 445.18(2) which nixes any exception for the disconnecting means in this circumstance.

Does anyone know of a code rule that does not require disconnecting means at the generators?

Brent

Brent,

445.18(2) does not nix the disconnect, it allows it for parallel operation,IMO. It allows no disc. at the gen set.

 

[Pierre C Belarge]

Sometimes when we read the NEC, it is difficult to understand just what the wording actually means. I believe the section requiring the disconnecting means for generators is one of those. 445.18

Here is a clip I took from a CSE magazine article, by Michael Kirchner, Sales Training Manager, Generac Power Systems - 4.1.09


"
Is a disconnect required on the generator? NEC 445.18 shows a preference for the generator to be equipped with a disconnecting means but allows the disconnect?typically the generator breaker?to be removed, provided that the generator can be readily shut down and that it does not operate in parallel. So, even though the NEC allows the generator to be provided without an output breaker, standard industry practice is to include this disconnect.
Is another disconnect required at the point of building entrance, in addition to the generator breaker? The market implementation of this requirement seems to be split?half of the market requires an additional disconnect and half of the market does not. Because the cabling from the generator is a feeder, NEC 225.31 requires a disconnect at the point of building entry unless exempted in another part of the code. Enter the local interpretation of the requirements for an outdoor-housed generator set?NEC 700.12(B)(6), 701.11(B)(5), and 702.11?which state: ?When an outdoor housed generator set is equipped with a readily accessible disconnect means located within sight of the building or structure supplied, an additional disconnecting means shall not be required.?
The issue here is what needs to be visible from the building. If your answer is the generator, then an additional disconnect generally isn?t required. But if the answer is the generator disconnect, then an additional disconnect typically be required (most generator breakers are not visible from the building)."

 

[ceb58]

On gen, sets I install the ruling from the DOI inspectors is a disconnect is requried at the building whether on the outside where the feeders enter the transfer switch or inside next to the switch. Their justification is even if you can see the gen. set a cover would have to be removed or opened to access the breaker thus making it non readily accessible. They also are sticklers for labeling as to exact location of the gen. disconnect.

 

[Twoskinsoneman]

On gen, sets I install the ruling from the DOI inspectors is a disconnect is requried at the building whether on the outside where the feeders enter the transfer switch or inside next to the switch. Their justification is even if you can see the gen. set a cover would have to be removed or opened to access the breaker thus making it non readily accessible. They also are sticklers for labeling as to exact location of the gen. disconnect.

How does having to open a panel make the breaker non readily accessible?
I've never seen a genset that you need any tools to get to the break just a pull-open panel like a panelboard/cabinet cover door....

 

[ceb58]

How does having to open a panel make the breaker non readily accessible?
I've never seen a genset that you need any tools to get to the break just a pull-open panel like a panelboard/cabinet cover door....

The newer genrac 25-35kw have a side panel that you must have a square head wrench to open the cover. then you must set the cover to the side. The larger units have doors but are lockable. Their thing is some one may not have a key or not know where the tool is located to access the breaker. There bottom line is if they cannot see the breaker,with the gen. set in a normal condition, then a disconnect is requried.

 

[Goroon]

The design does not call for disconnecting means at the generators

The design does not call for disconnecting means at the generators

Our generators are treated as Services, IE 701 and 702 send you to

225.36 Suitable for Service Equipment. that sends you to...

225.32 Location. The disconnecting means shall be installed either inside or outside of the.....

No Outside Access other than Lock and key or behind Generator Door/Panel.

 

[brian john]

I assume these generators are running in parallel and there is a CB with OCP in the paralleling gear for each generator?

 

[brentp]

You are correct Brian John, the conductors land on ocp's in the p-gear. The install is indoors in a room adjacent to the paralleling gear. Conductors are run underground. The ocp should comply with 240.21(B)(5)... outside taps of unlimited length.

I am still hung up on 445.18..."Generators SHALL BE EQUIPPED with disconnect(s)...". The exception to remove the requirement for the disconnects would mean I have to comply with 445.18(1) AND (2). I can't comply with 445,18(2) as the gensets are in parallel.

From Pierre's post:
"Is a disconnect required on the generator? NEC 445.18 shows a preference for the generator to be equipped with a disconnecting means but allows the disconnect?typically the generator breaker?to be removed, provided that the generator can be readily shut down AND IT DOES NOT OPERATE IN PARALLEL. So, even though the NEC allows the generator to be provided without an output breaker, standard industry practice is to include this disconnect."

I haven't found anything in the 700's to make me think I can call these gensets a service. Still thinking the conductors are feeders.

Thanks for the replies so far, but I still need some help wrapping my brain around this one. I'm just used to seeing generators supplied with breakers. This is a new one for me.

Brent

BTW, I posted this once but don't know what happened to it. If this is a repeat, I apologize.