I was told I needed a service rated disconnect for a portable generator. I believe it is correct for use on the fixed in place standby units, but for the portable. 225.31 was the reference given, 225.36 says it must be service rated. How do we get from 702 to 225 with a portable generator. I see Reliance sells a PB30 with a 30 amp breaker in it that's service rated, so maybe theres something to this. Never heard that before.
Portable generator required to have service rated disconnect?
- Thread starter nrp3
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ceb58
Senior Member
- Location
- Raeford, NC
I would agree that Art.225 wouldn't effect a portable unit. I think Art.590 would apply to a portable such as 590.4
(E) Disconnecting Means.
Suitable disconnecting switchesor plug connectors shall be installed to permit the disconnectionof all ungrounded conductors of each temporary circuit.Multiwire branch circuits shall be provided with a means todisconnect simultaneously all ungrounded conductors at thepower outlet or panelboard where the branch circuit originated.
Identified handle ties shall be permittedYou also have this but it doesn't apply to disconnecting
702.11 Portable Generator Grounding.(A) Separately Derived System.
Where a portable optionalstandby source is used as a separately derived system, itshall be grounded to a grounding electrode in accordancewith 250.30.
(B) Nonseparately Derived System.
Where a portable optionalstandby source is used as a nonseparately derived system,the equipment grounding conductor shall be bonded to
the system grounding electrode.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
That says nothing about being rated for use as service equipment.
If the generator has a circuit breaker or a receptacle (usually they have both on portables), then this requirement is alread fulfilled for temporary installations.
Is the generator in/on/ immediately adjacent to the building served?
225.31 is part of 225 Part II: More Than One Building or Other Structure
If there is not more than one building or other structure involved I would ask for a different code section that is in violation as it is not this section.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Lets back up a little farther and look at 702.11. (2008 NEC)
Does not mention portable generators.
702.11 requires a disconnecting means that meets requirements of 225.36.
225.36 talks about the disconnect required in 225.31. How does 225.31 come into play with a generator? It seems 702.11 should refer us to 225.31 and not 225.36. Or better yet why couldn't they just put the requirement for it to be suitable for service equipment right in 702.11 if that is the intention? (looks like 2011 is exactly the same except 702.11 is now 702.12)
Does not mention portable generators.
702.11 requires a disconnecting means that meets requirements of 225.36.
225.36 talks about the disconnect required in 225.31. How does 225.31 come into play with a generator? It seems 702.11 should refer us to 225.31 and not 225.36. Or better yet why couldn't they just put the requirement for it to be suitable for service equipment right in 702.11 if that is the intention? (looks like 2011 is exactly the same except 702.11 is now 702.12)
jwelectric
Senior Member
- Location
- North Carolina
The question is what is this generator and how is it being applied.
If it is being used as temporary power (not connected to the premises wiring) then it is a stand-alone power source and 590 would apply.
If this generator is being used as an optional standby generator (connected to the premises wiring) then the whole of 702 will apply including a disconnect that is suitable as service equipment
If it is being used as temporary power (not connected to the premises wiring) then it is a stand-alone power source and 590 would apply.
If this generator is being used as an optional standby generator (connected to the premises wiring) then the whole of 702 will apply including a disconnect that is suitable as service equipment
goldstar
Senior Member
- Location
- New Jersey
- Occupation
- Electrical Contractor
The Reliance PB-30 is a 30A-120/240 V power inlet box :
http://www.reliancecontrols.com/ProductDetail.aspx?PB30
If you plan to transfer selected circuits you'll have to use one of the packaged 6 or 10 circuit manual transfer switch units shown in this link :
http://www.reliancecontrols.com/Documents/S1204TE.pdf
If you plan to transfer the entire service then you'll have to use one of the complete breaker transfer panels shown in the same link. These panels have a main breaker and are service rated.
Just so we're all on the same page, we are talking about a portable - temporary - manual transfer system are we not ?
http://www.reliancecontrols.com/ProductDetail.aspx?PB30
If you plan to transfer selected circuits you'll have to use one of the packaged 6 or 10 circuit manual transfer switch units shown in this link :
http://www.reliancecontrols.com/Documents/S1204TE.pdf
If you plan to transfer the entire service then you'll have to use one of the complete breaker transfer panels shown in the same link. These panels have a main breaker and are service rated.
Just so we're all on the same page, we are talking about a portable - temporary - manual transfer system are we not ?
jwelectric
Senior Member
- Location
- North Carolina
It doesn?t mean anything as how the generator is fastened in place or not fastened in place type of enclosure or the lack of an enclosure.
What 702 address is Optional Standby Systems.
Should this portable generator be connected to the premises wiring as an Optional Standby System it must comply with the entire Article 702 which will include the disconnect that is suitable as service equipment.
It doesn?t matter the size of the generator or if it can be picked up and carried off by someone. Once the generator is connected to the building it becomes part of the premises wiring and is subject to the provisions of the NEC in its entirety. See Article 100 for definition of premises wiring to clarify that even temporary wiring is included.
In the 2002 cycle there was no mention of any type of a disconnecting means at all in 702. The 2005 cycle stated that if the generator had a means to disconnect then no other disconnect was required.
2005 702.11 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.
During the 2008 cycle the disconnect was mandated to be suitable as service equipment.
2008 702.11 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.
What 702 address is Optional Standby Systems.
Should this portable generator be connected to the premises wiring as an Optional Standby System it must comply with the entire Article 702 which will include the disconnect that is suitable as service equipment.
It doesn?t matter the size of the generator or if it can be picked up and carried off by someone. Once the generator is connected to the building it becomes part of the premises wiring and is subject to the provisions of the NEC in its entirety. See Article 100 for definition of premises wiring to clarify that even temporary wiring is included.
In the 2002 cycle there was no mention of any type of a disconnecting means at all in 702. The 2005 cycle stated that if the generator had a means to disconnect then no other disconnect was required.
2005 702.11 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.
During the 2008 cycle the disconnect was mandated to be suitable as service equipment.
2008 702.11 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.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Any idea why they send you to 225.36 which sends you to 225.31 which really has nothing to do with standby generators. Why can't they just put the requirement in 702 someplace, or at least reference 702.11 (or 702.12 in 2011) in 225.36?
jwelectric
Senior Member
- Location
- North Carolina
What does one call those conductors that are leaving one place (the generator) and ending up at another (the building)?
They don?t fit the definition of branch circuit conductors, The circuit conductors between the final overcurrent device????.
They don?t fit the definition of service conductors, The conductors from the service point to the service disconnecting means. Service Point. The point of connection between the facilities of the serving utility and the premises wiring. They are not from the serving utility.
I believe they are feeders. Feeder. All circuit conductors between the service equipment, the source of a separately derived system, or other power supply source and the final branch-circuit overcurrent device.
The generator in most cases will be outside and guess which article address feeders and branch circuits that is outside? Article 225 Outside Branch Circuits and Feeders
The generator did not grow there; it was constructed by some manufacture somewhere and therefore falls under Part II of 225. Buildings or Other Structures Supplied by a Feeder(s) or Branch Circuit(s)
This is the reason why it is in 702 to let us know that these feeders that are outside and supply another structure other than the one where they originate must comply with 225.36 when reaching that remote structure.
This generator that is being connected to the premises wiring as an optional standby system must comply with 702. It is here that we find the requirements for installing this standby system. Article 225 is only about feeders and branch circuits installed outside. It is possible to build a room somewhere in the building to house the generator and then 225.36 would not apply. That is the reason why 702 is not referenced in 225.36.
It is too late to get a proposal in for the next code cycle but remember it for the next code cycle in you feel a need for it to be mentioned in Part II of 225
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
I understand what you are saying but why does the generator have to be a separate structure? I understand it can be a separate structure. What if whatever mounting support / pad / whatever the generator is located on is in fact a part of the building it is serving? What if there is a roof over the generator and it is attached to the building served?
How many air conditioners or heat pumps are not attached to the building they serve other than via the refrigerant lines and the electric supply? Should they be called separate buildings or structures and supplied according to 225?
Yes the end result often will be same but it would come from 225 and not 210.
jwelectric
Senior Member
- Location
- North Carolina
With an air conditioner or heat pump the ?branch circuit? is coming out of the building supplying the appliance which is part of the building or connected to the air handler.
The generator is supplying the building through ?feeders.? The circuit is coming from the generator supplying the building it is the building that is the remote or second structure.
- Location
- Massachusetts
I agree with Mike on this point.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
I do not disagree with that one bit. Except the last sentence. Why does the generator have to be a separate structure? Where does the NEC tell us it is? If the generator is not located in, on, or immediately adjacent to the building then I have no problem saying it definately is a separate structure. Otherwise it is not really defined.
It is no more or less connected to the building than an AC or heat pump most cases. True it is supplying power instead of using it.
If NEC wants the disconnect rated for service equipment that is fine with me. Why do they have to send you on a wild goose chase to get the point across? How does one go from 702.11 to 225.31? 702.11 sends you to 225.36. 225.36 mentions the disconnect in 225.31 must be rated as service equipment. How did we ever get to 225.31 from 702.11 to make 225.36 mean anything for a 702 application?
You can read between the lines and assume they want the disconnect service rated. If you read what is actually written it does not make any sense. If in 702 it would just say that the generator is to be treated as a separate building or structure that would be another way to clear it up. No where does it say it is a separate structure, you have to read between the lines to come to that conclusion.
jwelectric
Senior Member
- Location
- North Carolina
Okay for the sake of this discussion I will agree with you simply to address the issue with a different way of looking at the situation. When I leave the generator with the feeders that it supplies what is the other end connected to? Could it be a separate building? Look at the building being supplied as the separate building and the confusion goes away.
I would say this is a big difference unless you would agree that the service entrance conductors are the same as the conductors supplying an AC unit
Through the reference in 225.36 If the disconnect on the generator is suitable as service equipment and is within sight and visible then no other disconnect is needed.
In my opinion nothing is hidden and no reading between the lines are needed.
Just as a side note look up UL FTCN in the White Book. We will leave this to another thread.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
It can be a separate building. It can also be same building the generator is located inside of.
The conductors supplied by a generator are not service conductors.
225.36 just says "The disconnecting means specified in 225.31 shall be suitable for use as service equipment."
Nothing in 702 ever required the disconnect mentioned in 225.31. You kind of have to assume they mean you need the disconnect mentioned in 225.31. 225.36 modifies a section we were never directed to in any way.
I have no problem with that.
I think the idea of a portable generator as a structure is a bit of a stretch. However, I buy into the idea that its in 702 and I didn't see any real exemptions or distinctions made therefore subject to the rules. Assuming its conductors are feeders thereby bringing it into 225 makes sense. Not well written for sure. Be nice if all these things were written into 702 and it would be a whole lot easier to follow.
Any of the generators have an internal disconnect that is service rated?
Any of the generators have an internal disconnect that is service rated?
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