Disconnect Required for Standby Generator?

[richwaskowitz]

On a 20 kW pad-mounted optional standby generator project for a commercial building, the customer wants to mount the 200 amp automatic transfer switch inside the building for security and maintenance reasosns. It will not be the service disconnect as I am only supplying power to one sub-panel for the IT room. I am not clear as to whether I will need to provide a disconnecting means at the generator outside or not.

Is a disconnecting means required outside?

 

[jumper]

Not sure. This says you got to have one, but not where.

445.18 Disconnecting Means Required for Generators.
Generators shall be equipped with disconnect(s), lockable
in the open position, by means of which the generator and
all protective devices and control apparatus are able to be
disconnected entirely from the circuits supplied by the generator
except where both of the following conditions apply:
(1) The driving means for the generator can be readily shut
down.
(2) The generator is not arranged to operate in parallel with
another generator or other source of voltage.

 

[augie47]

My take:
225.30 allows the feeder.
225.32 allows the disconnect to be outside or inside at the point of
entrance of the conductors.
702.11 Provides requirements to omit the disconnect in 225.32

 

[jap]

702.11 Indicates "Readily Available" and "Within Sight".

If the Generator has a Factory installed Disconnecting Means but it is inside of the Generator Housing,,,,, is it still considered "Within Sight"?

I say no.

You can see the generator but not the disconnecting means.

I also do not understand this rule.

Is it for emergency personell or what?
If the disconnect is "In Sight" of the building,,,, but all of the equipment likely to need servicing is on the inside anyway,,, what difference does it make?

What if the disconnecting means was on the outside of the Generator Housing but on the side of the generator that you couldnt see from the building?

I still say It's not "Within Sight".

I may be all wet on this one though.

 

[qcroanoke]

702.11 Provides requirements to omit the disconnect in 225.32

Gus it has been argued here before that the breaker inside a outdoor generator enclosure is not readily accessible because the doors can be locked and it was also argued that the generator output breaker was not suitable for service equipment required by 225.32.

 

[augie47]

Gus it has been argued here before that the breaker inside a outdoor generator enclosure is not readily accessible because the doors can be locked and it was also argued that the generator output breaker was not suitable for service equipment required by 225.32.

and I agree.... I may have missed it, but I did not see where the OP indicated where the generator breaker was located and I was simply trying to bring attention to 702.11 IF it is applicable.

 

[ceb58]

Not only will you have to supply a gen. disconnect per 225.32. A disconnect is required for the utility before the ATS.

 

[richwaskowitz]

Xfer switch has a utility disconnect included

Xfer switch has a utility disconnect included

I am not sure what we are trying to isolate from what here. The utility source of power which feeds the transfer switch originates at the building's main panelboard at a 200 amp fused, lockable disconnect cube. That would kill power to the xfer switch. The generator has a circuit breaker at its control panel AND no one has to leave it running to work on any energized components or wiring if they don't want to.

In this application, the gen transfer switch will not be the service disconnect. The generator will only be tied into one feeder which supplies power to a specific sub-panel. The transfer switch is on the inside of the exterior wall (right next to the service disconnect and panelboard) and the generator is located outside a few feet from that same wall. One will not be able to see the generator from the transfer switch. I cannot tell from the literature if the utility breaker is lockable or not, but if it is UL listed. for service equipment, would it not have to be lockable?

According to the manufacturer's installation manual "This transfer switch is suitable for use as service equipment" and "consists of a transfer mechanism, utility disconnect circuit breaker, control relays, fuses, terminal strip......".

So....did I just answer my own question (no additional disconnect would be required) or is another disconnect required outdoors for some reason I just don't see yet?

 

[ceb58]

The utility source of power which feeds the transfer switch originates at the building's main panelboard at a 200 amp fused, lockable disconnect cube. That would kill power to the xfer swit

"This transfer switch is suitable for use as service equipment" and "consists of a transfer mechanism, utility disconnect circuit breaker, control relays, fuses, terminal strip......".

Now we have more info.
Then no you will not need a utility disconnect, you all ready have it twice.

The generator has a circuit breaker at its control panel AND no one has to leave it running to work on any energized components or wiring if they don't want to.

What about working in the ATS? "no one has to leave it running" just doesn't fly.
The feeders from the gen. to the ATS fall under Art.225. So you must comply with 225.32.

 

[RUWired]

The feeders from the gen. to the ATS fall under Art.225. So you must comply with 225.32.

That doesn't seem to match the requirements of 702.11. 225.32 says the disconnect can be inside or outside, 702.11 says it has to be outside.

Rick

 

[jap]

So now it seems we're back to, does the Output Breaker on the Generator qualify as a Disconnect and if its inside the Generator Enclosure,is it considered "Readily Accessible" and "Within Sight".

 

[ceb58]

That doesn't seem to match the requirements of 702.11. 225.32 says the disconnect can be inside or outside, 702.11 says it has to be outside.

Rick

This is the same wording just new # for 2011

702.12 Outdoor Generator Sets​

[/QUOTE]Where an outdoor housed generator set is equipped with a readily accessible disconnecting means located within sight of the building or structure supplied, an additional disconnecting means shall not be required where ungrounded conductors serve or pass through the building or structure. The disconnecting means shall meet the requirements of 225.36.

Look at the last of 702.11. It then takes you to 225.36

225.36 Suitable for Service Equipment.​

The disconnecting means specified in 225.31 shall be suitable for use as​

service equipment.

Then you must look at 225.31

225.31 Disconnecting Means.​

Means shall be provided for disconnecting all ungrounded conductors that supply or​

pass through the building or structure.

Which is now followed by 225.32. Unless you order a gen. set with a service rated disconnect the breaker on a gen. doesn't meet 225.36. Then if it is behind a cover you get into the accessible and with in sight rules.

​

 

[RUWired]

225.31 Disconnecting Means.​

​

Means shall be provided for disconnecting all ungrounded conductors that supply or​

pass through the building or structure.

Which is now followed by 225.32. Unless you order a gen. set with a service rated disconnect the breaker on a gen. doesn't meet 225.36. Then if it is behind a cover you get into the accessible and with in sight rules.
​

I am saying the disconnect required can only be located in the genset enclosure if it qualifies or outdoors. 225.32 doesn't play into the requirements of 702.11 reference to 225.36. 702.11 is already saying it has to be within site of the building. Rick

 

[ceb58]

I am saying the disconnect required can only be located in the genset enclosure if it qualifies or outdoors. 225.32 doesn't play into the requirements of 702.11 reference to 225.36. 702.11 is already saying it has to be within site of the building. Rick

If the disconnect that is built into the gen. complies with 225.36 and is within sight and accessible then that is where it stops. No other disconnect for the gen. is required is what 702.11 is saying,period end of sentence.
But if it doesn't comply with 225.36 the rules of art.225 for outside feeders must be met which include 225.32. So the disconnect can be located outside or inside at the closest point of entry.

 

[RUWired]

If the disconnect that is built into the gen. complies with 225.36 and is within sight and accessible then that is where it stops. No other disconnect for the gen. is required is what 702.11 is saying,period end of sentence.
But if it doesn't comply with 225.36 the rules of art.225 for outside feeders must be met which include 225.32. So the disconnect can be located outside or inside at the closest point of entry.

Why would 702.11 be so adamant about being readily accessible and within site and then allow a disconnect to be located in a possibly locked building in a locked room.

 

[ceb58]

Why would 702.11 be so adamant about being readily accessible and within site and then allow a disconnect to be located in a possibly locked building in a locked room.

Rick, the only thing 702.11 allows is if the disconnect on the generator complies with 225.36, being service rated, and is with in sight and accessible then that's all that is needed. But if it doesn't then we must follow 225.31 & 32

 

[shortcircuit2]

OK, I just read through this thread and the 702.11 (now 702.12 of the 2011 NEC) requirement is that the disconnect SHALL be "suitable for use as service equipment" under 225.36

So, if the disconnect is suitable for use as service equipment, then it would have provisions for a bonding connection from the neutral bar to the disconnect enclosure.

Is this bond required to be made in this disconnect?

 

[Hendrix]

So now it seems we're back to, does the Output Breaker on the Generator qualify as a Disconnect and if its inside the Generator Enclosure,is it considered "Readily Accessible" and "Within Sight".

The Generator enclosure is not service rated. You need to go to a service rated disconnect inside or outside the building. If it is outside it must be in sight.

 

[Hendrix]

OK, I just read through this thread and the 702.11 (now 702.12 of the 2011 NEC) requirement is that the disconnect SHALL be "suitable for use as service equipment" under 225.36

So, if the disconnect is suitable for use as service equipment, then it would have provisions for a bonding connection from the neutral bar to the disconnect enclosure.

Is this bond required to be made in this disconnect?

Only if it is a seperatly derived system.

 

[EZ Generator Switch]

Generator switch CB Readily accessible

Generator switch CB Readily accessible

Why would any inspector not consider the breaker "Readily Accessible" located on the side of a generator? Think about this before you answer...Main panel in a house has a door covering the breakers...its readily accessible...but we place a door on a generator and its not the same? I think the OHJ should want to see the door as you approuch it not hide it around the back of the generator....it's just common sense. I would think that anyone having the skills & knowledge ...article 100 qualified person... If you have the skill & knowledge you should know there is a breaker behind that door just like on the panel.
There is no doubt in my mind the generator companies placed that breaker there as a means of service disconnect..not because they had some extra breakers laying around
IMO...I think AC units should have the same disconnect mounted with in the unit just like the generator has.