25 ft tap rule

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Peter Furrow

We’re not born humble, we’re born to be humbled
Location
Cape canaveral Fl
Occupation
Electrical contractor
A question came up regarding an installation and “tap rules”
article 240.21 B(2).
The apartment owner on the third floor wanted a Tesla charger. Polaris taps would be installed at the meter center after the 150 A main for the apartment. The number six copper feeder wire would be tapped off of the 2\0 Al going to the 3rd floor apt. That tesla feeder is only 4 feet so It wouldn’t be a violation. It transitions to a branch circuit and goes 50 feet to the charger and still will not be a violation. Correct?
However, Now that the feeder has been tapped for the third-floor indoor apartment panel and it’s 70 feet away this would violate the 25 foot tap rule. Correct?
My thought is that the violation is not so much the Tesla charger tap but the third-floor indoor panel has now become a tap and it’s over 70 feet
 

Peter Furrow

We’re not born humble, we’re born to be humbled
Location
Cape canaveral Fl
Occupation
Electrical contractor
A question came up regarding an installation and “tap rules”
article 240.21 B(2).
The apartment owner on the third floor wanted a Tesla charger. Polaris taps would be installed at the meter center after the 150 A main for the apartment. The number six copper feeder wire would be tapped off of the 2\0 Al going to the 3rd floor apt. That tesla feeder is only 4 feet so It wouldn’t be a violation. It transitions to a branch circuit and goes 50 feet to the charger and still will not be a violation. Correct?
However, Now that the feeder has been tapped for the third-floor indoor apartment panel and it’s 70 feet away this would violate the 25 foot tap rule. Correct?
My thought is that the violation is not so much the Tesla charger tap but the third-floor indoor panel has now become a tap and it’s over 70 feet

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winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
So it isn't a tap if it is protected at its ampacity. However the ampacity of 2/0 is less than 150A, thus the issue.

If the 2/0 carries the full load of a residence, it is kosher protected with a 150A breaker. But once the tap for the charger is added, then the 2/0 is clearly not carrying the full load.

If you have 2/0 service conductors then no feeder need be larger than 2/0, and you have that few feet of 2/0 which is carrying the full load of the residence, but I think you end up with a technical violation in a situation that is perfectly safe.

Jon
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
petersonra: good point.

I amend my statement: a feeder is not a 'tap' if it is considered protected by OCPD at its supply end.

2/0 AL with a calculated load of <= 135A is considered protected by a 150A OCPD, and thus not a tap.

2/0 AL carrying the entire load of a residence with a calculated load of <=150A is considered protected by a 150A OCPD, and thus not a tap.

If the calculated load of the apartment is > 135A, or the calculated load of the apartment plus the charger is > 150A, then the installation is not acceptable.

-Jon
 

Peter Furrow

We’re not born humble, we’re born to be humbled
Location
Cape canaveral Fl
Occupation
Electrical contractor
petersonra: good point.

I amend my statement: a feeder is not a 'tap' if it is considered protected by OCPD at its supply end.

2/0 AL with a calculated load of
2/0 AL carrying the entire load of a residence with a calculated load of
If the calculated load of the apartment is > 135A, or the calculated load of the apartment plus the charger is > 150A, then the installation is not acceptable.

-Jon

So I have to calculate the load to determine if it’s acceptable. But as it stands , the feeders to the apartment panel do not fall under the 25 foot tap rule. Even though there is a Polaris tap on those panel feeders to provide power to the Tesla charger It still does not fall under the tap rule of 25 feet. At tap rule with only apply to the Tesla charger. That’s my take away from your comment. Correct me if I’m wrong


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winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
So I have to calculate the load to determine if it’s acceptable. But as it stands , the feeders to the apartment panel do not fall under the 25 foot tap rule. Even though there is a Polaris tap on those panel feeders to provide power to the Tesla charger It still does not fall under the tap rule of 25 feet. At tap rule with only apply to the Tesla charger. That’s my take away from your comment. Correct me if I’m wrong

That is my understanding.

You have a 'feeder'. The 2/0 Al is protected on its supply end by the 150A breaker.

The feeder to the Tesla charger breaker is a 'feeder tap' because it is protected on its _load_ end by the 60A breaker.

The fact that the 2/0 Al has been 'tapped' does not make it a 'feeder tap' because it remains a 2/0 Al.

You need to do the calculations to make sure 1) that the 2/0 Al is in fact properly loaded and protected and 2) that the 150A service is itself not overloaded.

-Jon
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
petersonra: good point.

I amend my statement: a feeder is not a 'tap' if it is considered protected by OCPD at its supply end.

2/0 AL with a calculated load of <= 135A is considered protected by a 150A OCPD, and thus not a tap.

2/0 AL carrying the entire load of a residence with a calculated load of <=150A 135A is considered protected by a 150A OCPD, and thus not a tap.

If the calculated load of the apartment is > 135A, or the calculated load of the apartment plus the charger is > 150A 135A, then the installation is not acceptable.

-Jon
fixed it. you can go up to the next highest rated CB but the ampacity of the conductors does not change.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
fixed it. you can go up to the next highest rated CB but the ampacity of the conductors does not change.

I am open to being corrected, but I really did mean 150A. If the article 220 load calculation for the total load of a residence is 150A or less, then the '83% rule' applies. This would permit 2/0 Al protected by a 150A breaker with a calculated load of anything up to 150A.

-Jon
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I am open to being corrected, but I really did mean 150A. If the article 220 load calculation for the total load of a residence is 150A or less, then the '83% rule' applies. This would permit 2/0 Al protected by a 150A breaker with a calculated load of anything up to 150A.

-Jon
good point
 

Eddie702

Licensed Electrician
Location
Western Massachusetts
Occupation
Electrician
I agree with @winnie

To meet code the existing feeder no longer carries the full load so they would have to be recalculated. But the easiest fix is to make the tap conductors the same ampacity as the existing feeder as mentioned above.

A good example of when common sense and the code do not coinside. I think most would agree that it would be perfectly safe with the #6 tap
 
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