Automatic generator installation

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crtemp

crtemp

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Wa state
I have a customer that wants a automatic generator installed. Just have a few quick questions.

I'm looking at the generator article in the 2008 nec. It says that the ampacity of the conductors must be 115% of the nameplate rating. This generator is rated at 65 amps. I guessing that means that I will need to run a conductor that can handle a minimum of 75 amps. I will most likely run a #2 SER. Will this be okay?

I also see that it says it will need a disconnect. Don't most automatic generators come with disconnects built in?
 

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crtemp said:
I have a customer that wants a automatic generator installed. Just have a few quick questions.

I'm looking at the generator article in the 2008 nec. It says that the ampacity of the conductors must be 115% of the nameplate rating. This generator is rated at 65 amps. I guessing that means that I will need to run a conductor that can handle a minimum of 75 amps. I will most likely run a #2 SER. Will this be okay?

I also see that it says it will need a disconnect. Don't most automatic generators come with disconnects built in?
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First the generator has a breaker installed so 445.13 (2011) is a moot point.
The argument has been that the feeders fall under Article 225. 225.36 states the disconnect must be suitable for service equipment and the breaker built into the generator did not comply with the code. Generac now states the breaker now meets the requirement and they can provide documentation. I, personally, have not seen this documentation so I am not sure if they have had the breaker listed by UL or some other NRTL or what they have done.
 
Check with your inspector, it seems to be a local thing.

Out of what must be 100+ automatic standby generators I have seen installed in my area, I have never seen one with a separate disconnect.

As for the conductors, size them for the breaker in the generator.
 
I agree. From the nameplate it appears the generator already has a 65 amp breaker so you conductors should have that ampacity. Note some generators call for a Cu conductor termination.
I am also in agreement with ceb58 on the 225.36 situation
 
augie47 said:
I agree. From the nameplate it appears the generator already has a 65 amp breaker so you conductors should have that ampacity. Note some generators call for a Cu conductor termination.
I am also in agreement with ceb58 on the 225.36 situation
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Isnt 225.36 for feeders for buildings or structures?
 
ceb58 said:
ARTICLE 225
Outside Branch Circuits and Feeders




That's how its looked at by the definitions. And if its installed out doors then the feeders fall under Article 225.
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Structure - that which is built or constructed.

That's pretty vague. That could mean virtually anything.

If the breakers on the generator aren't accepted as the disconnect and I have to install one, does it have to be within site of the generator? I don't think it says one way or the other.
 
The disconnect requirements in Article 225 are for branch circuits or feeders supplying a structure. The conductors running from the generator to the transfer switch are not supplying the generator. There is no logical reason to install a service disconnect switch at a generator since it will not serve any useful purpose. The power is coming from the generator not to the generator so the generator will still be energized with the switch off.
 
curt swartz said:
The disconnect requirements in Article 225 are for branch circuits or feeders supplying a structure. The conductors running from the generator to the transfer switch are not supplying the generator. There is no logical reason to install a service disconnect switch at a generator since it will not serve any useful purpose. The power is coming from the generator not to the generator so the generator will still be energized with the switch off.
Click to expand...

That makes sense
thank you
 
crtemp said:
Isnt 225.36 for feeders for buildings or structures?
Click to expand...

Yes, and you have a feeder from the generator supplying a separate building or structure.


HackElectric said:
A generator is a structure. Just like a pole is.


I didn't make this crap up :D:lol:
Click to expand...

And nether does the NEC, the definition is from the building codes.

The thing is, just because a definition does not agree with your preconceived ideas does not make it wrong. :p
 
With an automatic arrangement, if the 65A generator is going to serve the entire house service (not just a subpanel), then you need to think about load shedding extraneous loads above 65A
 
curt swartz said:
The disconnect requirements in Article 225 are for branch circuits or feeders supplying a structure. The conductors running from the generator to the transfer switch are not supplying the generator. There is no logical reason to install a service disconnect switch at a generator since it will not serve any useful purpose. The power is coming from the generator not to the generator so the generator will still be energized with the switch off.
Click to expand...
A valid point in most of the cases. But when the generator operates in parallel with utility and for a short on the generator, service disconnect switch at the generator may help avoid any untoward incident.
 
HackElectric said:
A generator is a structure. Just like a pole is.


I didn't make this crap up :D:lol:
Click to expand...

A pole is not scoped under chapter 4 NFPA 70 equipment for general use. I do not see a generator as being defined a structure. If housed in a structure that would be different. A pole is a structure not the equipment on a pole. IMO unless a generator is (mounted on a pole) or in a building it is equipment defined that way by NFPA 70
 
david said:
A pole is not scoped under chapter 4 NFPA 70 equipment for general use. I do not see a generator as being defined a structure. If housed in a structure that would be different. A pole is a structure not the equipment on a pole. IMO unless a generator is (mounted on a pole) or in a building it is equipment defined that way by NFPA 70
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Is a generator built or constructed?

In my opinion yes it is, that makes it a structure per the NEC definition.

It may well be equipment for general use but it is also a structure.
 
iwire said:
Is a generator built or constructed?

In my opinion yes it is, that makes it a structure per the NEC definition.

It may well be equipment for general use but it is also a structure.
Click to expand...

There are manufactured buildings, (structures) but a generator is manufactured equipment and UL listed that way. I really do not know what difference it makes though in this discussion since the disconnecting rules for gen. or rather buildings supplied by this equipment is addressed specifically in the NEC . It really does not make a difference if you call it a structure or not since the specific rules for generator disconnects trump the general rules .
 
ron said:
With an automatic arrangement, if the 65A generator is going to serve the entire house service (not just a subpanel), then you need to think about load shedding extraneous loads above 65A
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the house will have a 320 meter base with one 200 amp panel not on the generator and other 200 amp panel on generator. The panel that will be fed from the generator can have more than 65 amps on it correct? I have fed entire 200 amp panels before with a 30 amp generator and never had any issues
 
crtemp said:
the house will have a 320 meter base with one 200 amp panel not on the generator and other 200 amp panel on generator. The panel that will be fed from the generator can have more than 65 amps on it correct? I have fed entire 200 amp panels before with a 30 amp generator and never had any issues
Click to expand...

"No issues" does not make it Code compliant. If it's an automatic transfer switch, 702.5(B)(2) requires the calculated load can not exceed the generators capacity.
Automatic load shedding is one method to accomplish this.
 
crtemp said:
the house will have a 320 meter base with one 200 amp panel not on the generator and other 200 amp panel on generator. The panel that will be fed from the generator can have more than 65 amps on it correct? I have fed entire 200 amp panels before with a 30 amp generator and never had any issues
Click to expand...
With a manual transfer switch you can use any size generator with any size load. But for an automatic standby system, the generator has to be able to handle the load placed on it by the ATS.

First, you need to go by the generator's output, not the breaker's rating.

That generator is either 17kw on propane or 16kw on NG. That's 70a or 66A.

You need to do a load calc on that panel to make sure that it isn't above the rating of the generator. If it is, then you can either move loads to the other panel or load shed.

BTW, I am surprised that the generator only has a 65A breaker.
 
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