2/0 for 200 amp service

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2/0 is compliant. 310.15(B)(7)(3) specifically says so. The mere fact that you remove load while running on generator does not disallow the use of 310.15.(B)(7) allowances.
The language that requires "supplying the entire load" in 310.15(B)(7)(1) is to prevent the use of the 83% rule when you have, say, 2 service disconnects with each carrying part of the service load. The feeders from each disconnect can not use the 83% rule but the service conductors or feeder conductors ahead of those disconnects could use the 83% rule as it carries the entire load. Dropping load as in load shedding has no effect on the rule.
 
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I'm not saying i makes sense.. I'm just giving my opinion on what it says, The (B)(7) exception is based on the diversity of the whole house and states:
For a feeder rated 100 through 400 amperes, the feeder conductors supplying the entire load associated with a one-family dwelling, or the feeder conductors supplying the entire load associated with an individual dwelling unit in a two-family or multifamily dwelling, shall be permitted to have an ampacity not less than 83 percent of the feeder rating
The generator does not fit that requirement.. The Code says what it says.
I enforce things weekly that I don't necessarily agree with so if I were called upon to inspect that install I would have to reject it. If n ot, the next question would be shed what percentage, etc.
 
augie47 said:
I'm not saying i makes sense.. I'm just giving my opinion on what it says, The (B)(7) exception is based on the diversity of the whole house and states:
For a feeder rated 100 through 400 amperes, the feeder conductors supplying the entire load associated with a one-family dwelling, or the feeder conductors supplying the entire load associated with an individual dwelling unit in a two-family or multifamily dwelling, shall be permitted to have an ampacity not less than 83 percent of the feeder rating
The generator does not fit that requirement.. The Code says what it says.
I enforce things weekly that I don't necessarily agree with so if I were called upon to inspect that install I would have to reject it. If n ot, the next question would be shed what percentage, etc.
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No, 310.15(B)7)(3) was put in just for these cases. For example, let's say you had a feed thru meter main with 8 spaces. You use 2 spaces to feed the A/C unit outside next to the service. Using your logic you are saying that you then will have to size the feeder to the panel in the house larger than the service conductors. 310.15(B)(7)(3) prevents that as the code recognizes that would be absurd just because you removed the A/C load from the feeder and end up with feeder bigger than the service conductors.
 
Isnt the key factor here the 200 Amp transfer switch, why provide a conductor larger than the breaker capability, its 5 ft. If the house draws 201 Amps the Transfer switch will trip.
 
Maybe I'm misunderstanding the arrangement, but even if the 83% rule does NOT apply to the genset, isn't the 2/0 fine because the genset is a lot smaller and presumably have something like a 100 or 125 am breaker? 2/0 fine when not on generator, and 2/0 still fine (even if can't apply 83%) because well within the capacity and breaker on the Genny?
 
texie said:
2/0 is compliant. 310.15(B)(7)(3) specifically says so
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I was or am still having trouble with this 310.15(B)(7)(3) I see it on my 2014 NEC but it is no where on my 2020 NEC,
The 2020 version goes from 310.15(B) 1-2 to 310.15 (C)1-4
I may be wrong ..
 
Another C10 said:
I 'm not seeing that 310.15 (b) (7) code in the 2020, I'll keep looking, you may be able to use 310.12, the feed is in a sense a utility, within its self.
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Article 310 was reorganized for the 2020 code. The langue in 310.12 in the 2020 was relocated from 310.15(B)(7) in the 2017 code. I don't believe there was any technical changes, but the formatting was changed.
 
It is my opinion that the conductors in question are feeder conductors covered by 310.15(B)(7)(3) in the 2017 code and 310.12(C) in the 2020 code. If the service entrance conductors are 2/0, the language in those sections permits the generator conductors to be 2/0.
 
With this being my first ATS install I'm curious to see what your thoughts are. Or what I might have screwed up :confused:

In the end, I went with a 3/0 copper between the service disconnect and ATS as well as from the ATS back to the SER feeding the house panel and #6 copper form the SD to the ATS. From the ATS I used #3 copper along with #8 ground.

The inside house panel will be getting replaced soon and with that, the SER will either be extended or replaced altogether to get rid of the Polaris units. Plus then I can go straight into the ATS from the soffit rather than the current routing which just does not look clean.

https://photos.app.goo.gl/tc1Six5sunfZvgRF8
 
IMO, the generator will never see the 2/0. Only the utility power will use the 2/0. The generator will only see/use the conductors run to it from the ATS. So the 2/0, IMO, would be fine since it does serve the entire load. When the entire load is not being served, then the conductors from the generator will be used and the 2/0 will not be in the picture.
 
FlComm said:
With this being my first ATS install I'm curious to see what your thoughts are. Or what I might have screwed up :confused:

In the end, I went with a 3/0 copper between the service disconnect and ATS as well as from the ATS back to the SER feeding the house panel and #6 copper form the SD to the ATS. From the ATS I used #3 copper along with #8 ground.

The inside house panel will be getting replaced soon and with that, the SER will either be extended or replaced altogether to get rid of the Polaris units. Plus then I can go straight into the ATS from the soffit rather than the current routing which just does not look clean.

https://photos.app.goo.gl/tc1Six5sunfZvgRF8
Click to expand...

Looks like a top notch install to me


“ shoot low boys their riding shetland ponies”
 
A few observations, in no particular order:

Isn't it a no-no to have the service conductors and feeder conductors in the same enclosure and/or raceway?

The neutral/ground bond strap in the panel should be removed, and the green jumper replaced in the ATS.

The generator-to-ATS feeder conductors need only be sized for the generator breaker, if I'm not mistaken.
 
Another C10 said:
I 'm not seeing that 310.15 (b) (7) code in the 2020, I'll keep looking, you may be able to use 310.12, the feed is in a sense a utility, within its self.
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Fl is under the 2014 NEC.

Roger
 
LarryFine said:
A few observations, in no particular order:

Isn't it a no-no to have the service conductors and feeder conductors in the same enclosure and/or raceway?

The neutral/ground bond strap in the panel should be removed, and the green jumper replaced in the ATS.

The generator-to-ATS feeder conductors need only be sized for the generator breaker, if I'm not mistaken.
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I can't speak to having them in the same raceway with certainty but a quick search does seem to indicate as much. I am planning to replace the SER soon so when I do they will be routed from the attic soffit directly to the ATS. Since it's not a direct safety issue ( no one will be in the panel except me) I'm going to let it ride for the next month or so until I do the replacement.
This does bring a question up though- When I do this my SE will now be outdoor (surface mount conduit from attic soffit on exterior of wall. NOT underground) so is there any issue with this application?

The Service panel also is my primary, first in line from the meter, service disconnect so the Neutral and ground should be tied together should they not? Therefore would that not make the ATS technically a subpanel and therefore have isolated ground & neutral?

The #3 I got from table 310 as well as this forum based on a 100 amp (generator breaker size) service at 75º. And it also is what Generac sells for the 22kw if you use their bundled wire. The run is roughly 25' from ATS to Gen.

Roger is correct that we are still under the 2014 code.

This is exactly why I posted so I appreciate all of the feedback. These forums are a gem for knowledge especially for us that don't do this every day.
 
FlComm said:
I can't speak to having them in the same raceway with certainty but a quick search does seem to indicate as much. I am planning to replace the SER soon so when I do they will be routed from the attic soffit directly to the ATS. Since it's not a direct safety issue ( no one will be in the panel except me) I'm going to let it ride for the next month or so until I do the replacement.
This does bring a question up though- When I do this my SE will now be outdoor (surface mount conduit from attic soffit on exterior of wall. NOT underground) so is there any issue with this application?

The Service panel also is my primary, first in line from the meter, service disconnect so the Neutral and ground should be tied together should they not? Therefore would that not make the ATS technically a subpanel and therefore have isolated ground & neutral?

The #3 I got from table 310 as well as this forum based on a 100 amp (generator breaker size) service at 75º. And it also is what Generac sells for the 22kw if you use their bundled wire. The run is roughly 25' from ATS to Gen.

Roger is correct that we are still under the 2014 code.

This is exactly why I posted so I appreciate all of the feedback. These forums are a gem for knowledge especially for us that don't do this every day.
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If I understand you correctly and the photos seem to look that way, you are feeding the ATS from the feed thru lugs in the main breaker panel and the loads within that panel are not on the generator. Do I have that correct? If that is the case , then yes, the existing main panel is still your serve disconnect and that is where the neutral/ground bond should be and it looks like you have it there. Then the ATS should not have a neutral/ground bond and it appears that is the way you have it.
If this is all true you do not have service conductors in the same race as they are feeders. Also, you did not need to use a service rated ATS as you didn't need the breaker it it the way you have it installed.
 
texie said:
If I understand you correctly and the photos seem to look that way, you are feeding the ATS from the feed thru lugs in the main breaker panel and the loads within that panel are not on the generator. Do I have that correct? If that is the case , then yes, the existing main panel is still your serve disconnect and that is where the neutral/ground bond should be and it looks like you have it there.
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Then I owe the OP an apology. I thought the entire service was routed through the ATS, not just the inside panel.

Then the ATS should not have a neutral/ground bond and it appears that is the way you have it.
If this is all true you do not have service conductors in the same race as they are feeders. Also, you did not need to use a service rated ATS as you didn't need the breaker it it the way you have it installed.
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Correct on the bonding, too. The original outside panel still the main, so the ATS is a sub just like the inside panel.

There is no problem having the redundant main, and I've found package pricing better with the service-rated ATS.
 
You are exactly correct Texie. None of the circuits in the main panel are generator supported and the house is fed off the feed thru lugs.

As Larry says the generator came with the service rated ATS at the same cost as the generator by itself so it was a no brainer.
 
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