Tap rules off a service entrance

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dummycheck

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Working on a project where I have a few interesting situations at play and hoping to get some guidance. I'm looking to add load to an existing service entrance.

Existing conditions are 480V 800A service entrance, main lug only, (5) disconnects existing. The AHJ has agreed to grandfather us in to the having the 'six disconnect rule' and allow us to add another disconnect.

The problem is that the breaker size we want to install will not fit within the existing enclosure. So we're looking at tapping off the service entrance bus and installing a separate enclosure disconnect switch adjacent to the service entrance enclosure. We might be able to get it within 10 ft, but it could be tight. I think I would consider this "grouped" with the other disconnects, although I guess that'll be up to the AHJ.

The question I have is that the tap rules don't really talk about tapping off a service entrance, but it doesn't seem like this is a "shall not" type of situation. Do you think this will be allowed under the NEC? What things to I need to consider here?
 
I am not sure if it is compliant to tap the bus but you could tap the service conductors. I would definitely check with the authority having jurisdiction about how far a disconnect can be and still be considered grouped. The nec is silent on that
 
Dennis Alwon said:
I am not sure if it is compliant to tap the bus but you could tap the service conductors. I would definitely check with the authority having jurisdiction about how far a disconnect can be and still be considered grouped. The nec is silent on that
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Wouldn't the bus in this case technically be an extension of the service conductors?
 
dummycheck said:
Wouldn't the bus in this case technically be an extension of the service conductors?
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Yes but unless the manufacturer allows tapping the bus then you are modifying equipment. It may be just fine and that may be the norm for large equipment but I don't know. I am sure someone here will jump in.
 
10ft is irrelevant because it's service entrance conductors and not taps. (Unless there's some Article 705 aspect you haven't mentioned.)

If the existing service equipment doesn't have documented provisions for taps then you could either get it field listed or tap the conductors ahead of the busbars.
 
dummycheck said:
The question I have is that the tap rules don't really talk about tapping off a service entrance, but it doesn't seem like this is a "shall not" type of situation. Do you think this will be allowed under the NEC? What things to I need to consider here?
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The tap rules in 240.21 are for feeders, not for service conductors.
 
As others have stated there is no tap rule applicable so you're left with how far will the AHJ allow the new service conductors to be run within the building. Some might accept 10' some might not. They could be run in a raceway and encased in concrete for unlimited length.
 
Alright, thanks for the responses. So if I'm understanding this correctly, tap rules do not apply to service conductors. In this case I would be extending the service. This will essentially be up to the AHJ as to what they will allow. Is that correct?
 
dummycheck said:
Alright, thanks for the responses. So if I'm understanding this correctly, tap rules do not apply to service conductors. In this case I would be extending the service. This will essentially be up to the AHJ as to what they will allow. Is that correct?
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If the equipment is outside there should be no major restrictions. If it's inside you have the 230.70(A)(1) requirement that the disconnect be 'nearest the entrance' so that's up to AHJ interpretation. The farther you go the thinner the ice you're on.
 
jaggedben said:
If it's inside you have the 230.70(A)(1) requirement that the disconnect be 'nearest the entrance' so that's up to AHJ interpretation
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Well, the existing service entrance is inside a warehouse-type of space pretty much in the middle of the building, not exactly 'nearest the entrance'... lots of grey area here, I'm going to schedule a meeting to talk with the AHJ.
 
dummycheck said:
Well, the existing service entrance is inside a warehouse-type of space pretty much in the middle of the building, not exactly 'nearest the entrance'... lots of grey area here, I'm going to schedule a meeting to talk with the AHJ.
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Underground conductors are often not 'inside' the building until they make an entrance by poking through the slab.
 
dummycheck said:
Well, the existing service entrance is inside a warehouse-type of space pretty much in the middle of the building, not exactly 'nearest the entrance'... lots of grey area here, I'm going to schedule a meeting to talk with the AHJ.
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Note that there are indeed service tap rules, but they aren't called that. These rules would be covered under 230.40 and it's exceptions, and 230.70-72. and just a little correction, note that the two through six rule did not go away, but they do have to be in separate enclosures now.

There is nothing wrong with adding a sixth disconnect next to the existing five. Tapping a bus bar in a switchboard or panel board can be a little tricky depending on how picky the inspector is. Some will let you replace or add lugs as necessary, some will want a UL field evaluation of any changes to the distribution equipment, or written approval that the manufacturer approves the changes. To that and you could look to see if the manufacturer offers any subfeed lugs feed through lugs or lugs with different configurations that meet your needs. I have bolted new lugs on busbar joints and had the inspector be okay with it but you never know.
 
dummycheck said:
Alright, thanks for the responses. So if I'm understanding this correctly, tap rules do not apply to service conductors. In this case I would be extending the service. This will essentially be up to the AHJ as to what they will allow. Is that correct?
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Is it a PV (solar) system interconnection, by any chance? Depending on the code cycle there are specific rules for supply side connected PV conductor length from the point of interconnection to its fused disconnect. These rules will go away in the 2023 NEC, though.
 
Alright, to close the loop on this, I had a meeting with the AHJ today and they didn't have any concerns with tapping off the bus. They just wanted to make sure that the termination matched the existing rating. I'll try to update if anything changes.
 
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