Generator Disconnect at Transfer Switch

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I'm installing a 20 KW generator in a residential application. The generator will be located inside a detached garage with a 100 amp main breaker on the machine. The transfer switch will be located in the house about 100 feet away. Are there any requirements for a disconnect where the generator feed enters the house? The feed will enter the house underground in the same room as the transfer switch.
 

ceb58

Senior Member
Location
Raeford, NC
I'm installing a 20 KW generator in a residential application. The generator will be located inside a detached garage with a 100 amp main breaker on the machine. The transfer switch will be located in the house about 100 feet away. Are there any requirements for a disconnect where the generator feed enters the house? The feed will enter the house underground in the same room as the transfer switch.

First, have you checked the codes to see if you can install the generator indoors? Is it rated to be installed indoors? If it can be done, Generac has came out with a listing on the generator breaker that complies with 225.36. But with what you are proposing I think you need to consider 225.32
 

rlundsrud

Senior Member
Location
chicago, il, USA
I don't see why that would be any different than a generator installed outside since it has a disconnect at the generator itself. So I would say no, you wouldn't need one. I would also make sure that you have a floating neutral at the generator if you are using a two pole transfer switch. I am sure you are aware of this, but I would thought I would mention it anyway.
 

Smart $

Esteemed Member
Location
Ohio
I agree with the points presented by ceb58.

IMO, if the genset was installed outside and next to the house, you'd not need an additional disconnect at the house. However, being 100' away from the house AND inside another building on top of that, I'd say you'd need a disconnect at the house, preferably at or near the same location as the service disconnect. Say there's a fire in the house and first responders want to disconnect power... how will they know when they kill normal power there's a genset that's going to kick in???
 

rlundsrud

Senior Member
Location
chicago, il, USA
I agree with the points presented by ceb58.

IMO, if the genset was installed outside and next to the house, you'd not need an additional disconnect at the house. However, being 100' away from the house AND inside another building on top of that, I'd say you'd need a disconnect at the house, preferably at or near the same location as the service disconnect. Say there's a fire in the house and first responders want to disconnect power... how will they know when they kill normal power there's a genset that's going to kick in???

Yes, you are correct, I humbly admit my mistake. Given that I can see where it would just make sense regardless of code requirements, although it is required by code.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I am generally in agreement with the others. NEC 702.11 in '08, and 702.12 in '14 seem to allow the generator disconenct to meet the requirements of Art 225 if the generator is in sight and the disconnect is readily accessible.

As a side note, the "readily accdssible" term has caused some controversy locally.
What if you need a key to access the generator disconnect ?
 

ceb58

Senior Member
Location
Raeford, NC
Say there's a fire in the house and first responders want to disconnect power... how will they know when they kill normal power there's a genset that's going to kick in???

Because the OP is going to comply with 702.7
702.7 Signs.
(A) Standby.
A sign shall be placed at the service-entrance
equipment that indicates the type and location of on-site optional
standby power sources. A sign shall not be required for
individual unit equipment for standby illumination.

Isn't he :?:?:happyyes:
 

Joe Villani

Senior Member
First, have you checked the codes to see if you can install the generator indoors? Is it rated to be installed indoors? If it can be done, Generac has came out with a listing on the generator breaker that complies with 225.36. But with what you are proposing I think you need to consider 225.32

Ceb58

When did Generac come out with the listing complying with 225.36?

Got a link to it?

Thanks,

Joe Villani
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Ceb58

When did Generac come out with the listing complying with 225.36?

Got a link to it?

Thanks,

Joe Villani

Did that part of the requirement not drop out of the '11 or '14 Code ?
(don't have my books handy this a.m.)
 

Joe Villani

Senior Member
Did that part of the requirement not drop out of the '11 or '14 Code ?
(don't have my books handy this a.m.)

Still on the 08 here so I haven't really looked into the 14 in great detail.

But looking at the 14 the wording was added. Thanks!

That makes things a bit easier as the 08 rule wasn't really enforced around here anyway.
 

ceb58

Senior Member
Location
Raeford, NC
Did that part of the requirement not drop out of the '11 or '14 Code ?
(don't have my books handy this a.m.)

It did not drop from the 11 not sure about 14 since we haven't gone under it yet. My argument for having to comply with 225.36 was on another forum. Some one, and I am searching for who, posted that they worked for Generac and that due to conflicts about the requirement they had the breaker on the generator listed to comply with "service rated" and you could get a decal from them stating that it was "suitable for service equipment". I am trying to find the documentation that backs it up because as we all know you can get a decal to say anything. With out the documentation it is worthless.
 
I am generally in agreement with the others. NEC 702.11 in '08, and 702.12 in '14 seem to allow the generator disconenct to meet the requirements of Art 225 if the generator is in sight and the disconnect is readily accessible.

As a side note, the "readily accdssible" term has caused some controversy locally.
What if you need a key to access the generator disconnect ?

NEC 702.12 is titled "Outdoor Generator Sets" The Generator I am installing will be out of sight and inside a detached garage, so I don't see where that would apply. The Generator is approved for an inside installation. Also the garage could be locked. NEC 225.31 and 225.32 pretty much mandate that a disconnect at the house would be required.
Thanks for the input especially about the "Service Rated Breaker"
 

stevebea

Senior Member
Location
Southeastern PA
I'm installing a 20 KW generator in a residential application. The generator will be located inside a detached garage with a 100 amp main breaker on the machine. The transfer switch will be located in the house about 100 feet away. Are there any requirements for a disconnect where the generator feed enters the house? The feed will enter the house underground in the same room as the transfer switch.

Could you give us a make and model on this generator ? Thanks.
 
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