2/0 for 200 amp service

[FlComm]

I'm getting ready to install a 22kw Generator with200 amp ATS & service. The ATS will be directly beside the service disconnect so my length from the disconnect to the ATS is less than 5' in length.

Will 2/0 copper THHN suffice for this due to the short distance or do I need to bump up to 3/0.

 

[david luchini]

3/0. (2/0 can't be protected at 200A.)

 

[Dennis Alwon]

Is this residential?

 

[FlComm]

YES. RESIDENTIAL APPLICATION

 

[infinity]

YES. RESIDENTIAL APPLICATION

Then the 83% rule may apply.

 

[FlComm]

3/0. (2/0 can't be protected at 200A.)

My thought was that since the generator would not be supplying 100% of the loads in the house that the rating could be adjusted by the 83% of service rating per 310.15(b)(7).

 

[FlComm]

Then the 83% rule may apply.

So I can apply the 83% rule and be safe with a 2/0 copper.

I appreciate it guys.

 

[david luchini]

My thought was that since the generator would not be supplying 100% of the loads in the house that the rating could be adjusted by the 83% of service rating per 310.15(b)(7).

I'm not sure I understand your setup. You have an ATS being supplied directly from the service disconnect, but its NOT supplying 100% of the loads in the house?

 

[infinity]

I'm not sure I understand your setup. You have an ATS being supplied directly from the service disconnect, but its NOT supplying 100% of the loads in the house?

I'm not clear on it either that's why I said the 83% rule may apply.

 

[McLintock]

I'm getting ready to install a 22kw Generator with200 amp ATS & service. The ATS will be directly beside the service disconnect so my length from the disconnect to the ATS is less than 5' in length.

Will 2/0 copper THHN suffice for this due to the short distance or do I need to bump up to 3/0.

So, is the service not going though the ATS?, the length does not matter at all. Why not run 4/0 AL to the ATS?


“ shoot low boys their riding shetland ponies”

 

[FlComm]

I'm not sure I understand your setup. You have an ATS being supplied directly from the service disconnect, but its NOT supplying 100% of the loads in the house?

Correct. I'm going to use the load shedding smart modules from Generac to lockout particular circuits when on generator as the KW I would need to supply 100% of circuits puts me into a commercial model.

My setup is identical to the one shown here https://forums.mikeholt.com/threads...erac-installation.2551970/page-2#post-2560465

 

[Beaches EE]

If you are asking about the conductors from the ATS to the generator, what is the calculated load on the genny after loads are shed? What size conductors run from the meter to the main?

 

[FlComm]

If you are asking about the conductors from the ATS to the generator, what is the calculated load on the genny after loads are shed? What size conductors run from the meter to the main?

The final location of the gen is not yet determined so I can't even start to calculate that, unfortunately. Right now we are installing the ATS with the gen to follow.
If I recall they are 4/0 to the main from the meter but not positive.

 

[Beaches EE]

I would match the SE conductors to be safe and to allow for expansion of the generator's capacity to service the full load of the structure. The difference between 2/0 and 3/0 CU is minimal. I don't have the tables handy but I believe you will be fine with 2" conduit either way..

 

[FlComm]

I would match the SE conductors to be safe and to allow for expansion of the generator's capacity to service the full load of the structure. The difference between 2/0 and 3/0 CU is minimal. I don't have the tables handy but I believe you will be fine with 2" conduit either way..

Based on the opinions here It would make sense. I had some 2/0 remnants I've been keeping, no idea why, and thought I might finally have a use for them. I corrected my earlier post as my notes show the mains as 4/0 but either way, its so short that cost is mostly irrelevant.
Better safe than sorry I suppose.

 

[Another C10]

310.15(b)(7).

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.

 

[texie]

I'm getting ready to install a 22kw Generator with200 amp ATS & service. The ATS will be directly beside the service disconnect so my length from the disconnect to the ATS is less than 5' in length.

Will 2/0 copper THHN suffice for this due to the short distance or do I need to bump up to 3/0.

If this is residential then you can use the 83% rule from the main disconnect to the ATS and on the load side of the ATS. Your load shedding is irrelevant to this. The conductors from the genset to the ATS are sized to the genset.

 

[Dennis Alwon]

If this is residential then you can use the 83% rule from the main disconnect to the ATS and on the load side of the ATS. Your load shedding is irrelevant to this. The conductors from the genset to the ATS are sized to the genset.

Yes but the generator must be rated for the calculated load of the dwelling if you don't shed some loads. If he has 125 amps or more load on the home then he has to shed loads or have a generator rated for the load. Isn't that correct?

 

[texie]

Yes but the generator must be rated for the calculated load of the dwelling if you don't shed some loads. If he has 125 amps or more load on the home then he has to shed loads or have a generator rated for the load. Isn't that correct?

Yes, but he said he has load shedding for when operating on the genset. I was just pointing out that this has nothing to do with using the 83% rule.

 

[augie47]

Agree. With loads shed modules present it's difficult to make the case for "entire house feeder" so, IMO, 2/0 would not be acceptable.