Tap Rule

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CurtLeeN

Member
Location
Rockwall, Texas
Hello, I’m just curious of the tap rule when it comes tofeeding multiple a/c disconnects out of a gutter off of one overcurrentprotection device. There will be a main 200a outdoor panel, We will be feedingone size equivalent to handle (7) 1 ½ ton a/c condensers. Each condenserrequires a 240v 1phase 15amp mocp, so what is the calculation on wire size tohandle (7) a/c units…. Wire will be running up the outside of the building, LBinto the building above attic space and run 60ft out the underside soffit ofroof line and down to a gutter. Then tapped to feed (7) individual 30a a/cDisconnects. So the question is, what is the tape rule for the SE cable in thegutter to each disconnect? Also, being that it only needs 15a to the disconnect........Will I need fusible disconnects for these knowing that the disconnect 30a and the breaker feeding these 7 units will 2 pole 100a or somethings?
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
If you're tapping a feeder then you need an OCPD at the end of the tap conductors. Also you probably cannot use SE cable for tap conductors.
 

MasterTheNEC

CEO and President of Electrical Code Academy, Inc.
Location
McKinney, Texas
Occupation
CEO
Greetings CurtLeeN,

First, I am not aware of anything would prohibit you from using Type SE-R in your configuration to the wirewayitself as long as you meet all the rules associated with Article 338. You do have to keep in mind that Type SE Cable does have some ampacity limitations and so on that are found in 338.10(B) to be aware of so I suggest you review them well prior to undertaking this task. However, as infinity states, the issue of the tap conductors would not permit Type SE from being used based on 240.21(B)(1)(3) so at that point you would have to transition.

In regards to the basics of proximity you describe I would assume (assuming always gets me in trouble) that the 10 tap rule under 240.21(B)

240.21(B)(1) Taps Not over 3 m (10 ft) Long. If the length of the tap conductors does not exceed 3 m (10 ft) and the tap conductors comply with all of the following:


(1) The ampacity of the tap conductors is
a. Not less than the combined calculated loads on the circuits supplied by the tap conductors, and
b. Not less than the rating of the equipment containing an overcurrent device(s) supplied by the tap conductors or not less than the rating of the overcurrent protective device at the termination of the tap conductors.


Exception to b: Where listed equipment, such as a surge protective device(s) [SPD(s)], is provided with specific instructions on minimum conductor sizing, the ampacity of the tap conductors supplying that equipment shall be permitted to be determined based on the manufacturer’s instructions.


(2) The tap conductors do not extend beyond the switchboard, switchgear, panelboard, disconnecting means, or control devices they supply.


(3) Except at the point of connection to the feeder, the tap conductors are enclosed in a raceway, which extends from the tap to the enclosure of an enclosed switchboard, switchgear, a panelboard, or control devices, or to the back of an open switchboard.


(4) For field installations, if the tap conductors leave the enclosure or vault in which the tap is made, the ampacity of the tap conductors is not less than one-tenth of the
rating of the overcurrent device protecting the feeder conductors."

Now, consider all those items that are in "BOLD" and "UNDERLINED" in your quest. Once you establish all that then look at 440.22(B)(1) and the math should become very clear at that point based on the information you actually know about each unit.
 

CurtLeeN

Member
Location
Rockwall, Texas
Correction: It will be a branch circuit tap

Correction: It will be a branch circuit tap

The SE-R cable will feed out of a 200a Main breaker panel off of a branch circuit breaker, It is over 25ft long up and through an attic and back down to a Gutter where the taps will be made. Out of the gutter and taps will feed 7 - 1 1/2 mini split a/c units that only require a 2 pole 15 amp breaker. So I will install 7 - 30 amp disconnects below the gutter, then to each individual a/c unit. the inspector is asking me to check my tap rule on this but after reading over the NEC, I don't see anything wrong with what I plan on doing.




Greetings CurtLeeN,

First, I am not aware of anything would prohibit you from using Type SE-R in your configuration to the wirewayitself as long as you meet all the rules associated with Article 338. You do have to keep in mind that Type SE Cable does have some ampacity limitations and so on that are found in 338.10(B) to be aware of so I suggest you review them well prior to undertaking this task. However, as infinity states, the issue of the tap conductors would not permit Type SE from being used based on 240.21(B)(1)(3) so at that point you would have to transition.

In regards to the basics of proximity you describe I would assume (assuming always gets me in trouble) that the 10 tap rule under 240.21(B)

240.21(B)(1) Taps Not over 3 m (10 ft) Long. If the length of the tap conductors does not exceed 3 m (10 ft) and the tap conductors comply with all of the following:


(1) The ampacity of the tap conductors is
a. Not less than the combined calculated loads on the circuits supplied by the tap conductors, and
b. Not less than the rating of the equipment containing an overcurrent device(s) supplied by the tap conductors or not less than the rating of the overcurrent protective device at the termination of the tap conductors.


Exception to b: Where listed equipment, such as a surge protective device(s) [SPD(s)], is provided with specific instructions on minimum conductor sizing, the ampacity of the tap conductors supplying that equipment shall be permitted to be determined based on the manufacturer’s instructions.


(2) The tap conductors do not extend beyond the switchboard, switchgear, panelboard, disconnecting means, or control devices they supply.


(3) Except at the point of connection to the feeder, the tap conductors are enclosed in a raceway, which extends from the tap to the enclosure of an enclosed switchboard, switchgear, a panelboard, or control devices, or to the back of an open switchboard.


(4) For field installations, if the tap conductors leave the enclosure or vault in which the tap is made, the ampacity of the tap conductors is not less than one-tenth of the
rating of the overcurrent device protecting the feeder conductors."

Now, consider all those items that are in "BOLD" and "UNDERLINED" in your quest. Once you establish all that then look at 440.22(B)(1) and the math should become very clear at that point based on the information you actually know about each unit.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
You need to comply with either the 10' tap rule or the 25' tap rule. The use of SE cable as you've described is prohibited.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
The SE-R cable will feed out of a 200a Main breaker panel off of a branch circuit breaker, It is over 25ft long up and through an attic and back down to a Gutter where the taps will be made. Out of the gutter and taps will feed 7 - 1 1/2 mini split a/c units that only require a 2 pole 15 amp breaker. So I will install 7 - 30 amp disconnects below the gutter, then to each individual a/c unit. the inspector is asking me to check my tap rule on this but after reading over the NEC, I don't see anything wrong with what I plan on doing.
I don't see why you can't use SE cable; you don't need SER unless you need a neutral.

Also, if the units are grouped, you can use a sub-panel instead of separate disconnects. That would save a lot of labor.
 

MasterTheNEC

CEO and President of Electrical Code Academy, Inc.
Location
McKinney, Texas
Occupation
CEO
You need to comply with either the 10' tap rule or the 25' tap rule. The use of SE cable as you've described is prohibited.
It is for the taps....where is it prohibited for the supply to the wireway?


Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 

CurtLeeN

Member
Location
Rockwall, Texas
True, that is what I thought to use just regular SE and a sub panel would work but it will still be a lot of trouble to feed out of the sub-panel and feed 7 a/c units all grouped in the same area. Either way, but after reading...it says nothing about feeding a SE into a gutter and tap off to feed several units. The inspector just wanted me to check the tap rule and confirm it with him that it's totally fine what i'm doing. These are going to a 15 unit apartment building, 7 units on one side grouped and 8 units on the other side. They are removing the old chiller system and installing these mini-split units. I have another issue on the apt building, There is a 200a breaker/breaker enclosure on the service feeding into a gutter on the inside of the wall and tapped to 4 - #2 Aluminum SE wires. Each #2 AL is feeding (1) apt unit, then lugged out of that one and feeding the apt unit below, then back up the attic and back down to feed the other 2 apt units. So basically 4 apt units feeding off of one #2 AL SE cable. All apt units have gas water heater, gas range, and everything else gas, It has just one laundry room for the whole apt complex. Each apt unit only has a 100a ML panel with 3 breakers in it (2-20a and 1-15a for the igniter on the AH (blower). Now with the mini-splits, the AH (blower) will now have a 5Kw heat strip that requires a 2 pole 30a that will take place of the Sp 15amp breaker. So the inspector wants to show him the Load calculation for the #2 AL SE to handle the 4 new 30amp 5Kw strips. So what is the way to prove the load calculation to him?






I don't see why you can't use SE cable; you don't need SER unless you need a neutral.

Also, if the units are grouped, you can use a sub-panel instead of separate disconnects. That would save a lot of labor.
 

MasterTheNEC

CEO and President of Electrical Code Academy, Inc.
Location
McKinney, Texas
Occupation
CEO
That wont be a problem, I'll use the proper wiring such as romex but just depending on what size I will need to handle 7 - 15amp a/c units.
Umm....Type NM-B is not permitted outside .

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 

MasterTheNEC

CEO and President of Electrical Code Academy, Inc.
Location
McKinney, Texas
Occupation
CEO
True, that is what I thought to use just regular SE and a sub panel would work but it will still be a lot of trouble to feed out of the sub-panel and feed 7 a/c units all grouped in the same area. Either way, but after reading...it says nothing about feeding a SE into a gutter and tap off to feed several units. The inspector just wanted me to check the tap rule and confirm it with him that it's totally fine what i'm doing. These are going to a 15 unit apartment building, 7 units on one side grouped and 8 units on the other side. They are removing the old chiller system and installing these mini-split units. I have another issue on the apt building, There is a 200a breaker/breaker enclosure on the service feeding into a gutter on the inside of the wall and tapped to 4 - #2 Aluminum SE wires. Each #2 AL is feeding (1) apt unit, then lugged out of that one and feeding the apt unit below, then back up the attic and back down to feed the other 2 apt units. So basically 4 apt units feeding off of one #2 AL SE cable. All apt units have gas water heater, gas range, and everything else gas, It has just one laundry room for the whole apt complex. Each apt unit only has a 100a ML panel with 3 breakers in it (2-20a and 1-15a for the igniter on the AH (blower). Now with the mini-splits, the AH (blower) will now have a 5Kw heat strip that requires a 2 pole 30a that will take place of the Sp 15amp breaker. So the inspector wants to show him the Load calculation for the #2 AL SE to handle the 4 new 30amp 5Kw strips. So what is the way to prove the load calculation to him?
That's why i said SE-R i guess, it a panel option is involved. However, as Larry said if no Grounded (neutral) is needed then SE-U would work and now that I think back not sure why I said SE-R...lol....but you get the drift.

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 

MasterTheNEC

CEO and President of Electrical Code Academy, Inc.
Location
McKinney, Texas
Occupation
CEO
Paul,

The NM-B will be sleeved in a EMT conduit up the building, through an LB and across the attic until it drops through the soffit....also sleeved in EMT coming back down.
Sleeve it or not won't work if the EMT is outside....not compliant.

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 

CurtLeeN

Member
Location
Rockwall, Texas
Solve This

Solve This

Lets say I use SE-U cable out of the 200a MB Nema 3R panel, Come out with 2 - 100a 2 pole breaker feeding each side to a 100a sub panel on the brick wall. then I can feed each unit with a 2 pole 15a breaker. Will this be fine to do, just according to the inspectors liking.
 

MasterTheNEC

CEO and President of Electrical Code Academy, Inc.
Location
McKinney, Texas
Occupation
CEO
Lets say I use SE-U cable out of the 200a MB Nema 3R panel, Come out with 2 - 100a 2 pole breaker feeding each side to a 100a sub panel on the brick wall. then I can feed each unit with a 2 pole 15a breaker. Will this be fine to do, just according to the inspectors liking.
In that plan SE-U is not gonna work for you, well it will but... i can see the debates now...run SE-R and save the drama of panel listings.

But of course if no grounded conductor is needed....then dismiss it as you don't need to run what's not required.

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 
Last edited:

CurtLeeN

Member
Location
Rockwall, Texas
Gotcha! So what is the easiest calculation to make sure (1) #2 AL SE (existing) feeding 4 apt units will handle replacing a 15a Sp breaker (igniter) to 30a 2p breaker for the 5kw heat strip? Keep in mind there are only 2 - 20a Sp breakers feeding general lighting and plugs in a 520sq ft apt unit.



In that plan SE-U is not gonna work for you....well i can see the debates now...run SE-R and save the drama of panel listings.

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 

MasterTheNEC

CEO and President of Electrical Code Academy, Inc.
Location
McKinney, Texas
Occupation
CEO
Gotcha! So what is the easiest calculation to make sure (1) #2 AL SE (existing) feeding 4 apt units will handle replacing a 15a Sp breaker (igniter) to 30a 2p breaker for the 5kw heat strip? Keep in mind there are only 2 - 20a Sp breakers feeding general lighting and plugs in a 520sq ft apt unit.
I did happen to edit my response because clearly in your case no grounded conductor is needed so running SE-R is pointless so SE-U would work. However, just remember the branch circuits to each AC unit can't be Type NM-B outside regardless of being sleeved in anything.

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 

CurtLeeN

Member
Location
Rockwall, Texas
No, I was going to run Sealtite with #12 thhn wire but as for the load calculations, how should I figure that?



I did happen to edit my response because clearly in your case no grounded conductor is needed so running SE-R is pointless so SE-U would work. However, just remember the branch circuits to each AC unit can't be Type NM-B outside regardless of being sleeved in anything.

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I think that I misread the setup the OP seems to indicate that he wants to feed the discos with SE cable. For tap conductors the conductors need to be in a raceway not a cable.
 
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