I would usually go underground for this....never have done it overhead. Doing a 200A meter combo upgrade. Relocating meter from house to detached garage and GC wants to do 100A subfeed back to house as an overhead feed. Its about 30-40 ft through backyard to subpanel location. Do I go w/ #4 THHN or should I get some kind of triplx for this. At 40' will I need a pole between to maintain clearance??
Overhead subfeed
- Thread starter sparky76
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The first thing that comes to my mind is 310.15(B)(6)
For dwelling units, conductors as listed in 310.15(B)(6), shall be permited as 120/240-volt , 3-wire, single phase service-entrances conductors, service lateral conductors, and feeder conductors THAT SERVE AS THE MAIN POWER FEEDER TO A DWELLING UNIT and are in a raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder(s) between the main disconect and the lighting and appliance branch circuit panelboard.
I see too many times #4 THWN run for 100a or #2/0 TWWN run for 200a 3 phase pannels in my area.
With a 100a feerder you would meet the requirements of 225.6(A)(1) - #8 copper or #6AL unless supported by a messenger wire. Myself I would still use a messenger wire.
Quote:
At 40' will I need a pole between to maintain clearance??
That would depend on the drop heights and what your spanning. I would guess at least 1 side needs to be higher than 1 story.
Depending on your grounding situation you would need triplex or quadplex. Myself I like to uses an equipment grounding conductor even if there is no other metalic paths between structures. Reason is it's still safe if they create a metalic path later.
Based off 2002 NEC as I don't have the other versions with me.
For dwelling units, conductors as listed in 310.15(B)(6), shall be permited as 120/240-volt , 3-wire, single phase service-entrances conductors, service lateral conductors, and feeder conductors THAT SERVE AS THE MAIN POWER FEEDER TO A DWELLING UNIT and are in a raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder(s) between the main disconect and the lighting and appliance branch circuit panelboard.
I see too many times #4 THWN run for 100a or #2/0 TWWN run for 200a 3 phase pannels in my area.
With a 100a feerder you would meet the requirements of 225.6(A)(1) - #8 copper or #6AL unless supported by a messenger wire. Myself I would still use a messenger wire.
Quote:
At 40' will I need a pole between to maintain clearance??
That would depend on the drop heights and what your spanning. I would guess at least 1 side needs to be higher than 1 story.
Depending on your grounding situation you would need triplex or quadplex. Myself I like to uses an equipment grounding conductor even if there is no other metalic paths between structures. Reason is it's still safe if they create a metalic path later.
Based off 2002 NEC as I don't have the other versions with me.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I don't believe T.310.15(B)(6) can be used in this situation since it does not carry the entire load of the service. You need to use T. 310.16
No you cannot use #4 nor can you use THHN. You must use a 4 conductor cable that is suitable for this install if you are under the 2008 code. I would read art. 250.32(B) of whatever code you are using.
tryinghard
Senior Member
- Location
- California
Make sure your 100A feeder is correctly sized for the calculated load of the house. THHN is not sunlight compatible, you’ll need quad-plex aerial and it’s usually aluminum for weight, the neutral cannot common with the equipment grounding on your sub feed this would be a violation(250.24(5) & 250.142(B)). The span distance is up to you but a compliant overhead feed I believe must be 10’+ above grade (you should verify this with NEC; see 225.18), I don’t think your span needs a pole if you obtain the height as long as your risers are compatible.
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Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
Dennis, that article specifically mentions feeders too.
My comments:
a. IMHO, 310.16 for your conductors {310.15(B0(6) is at best debatable}
b. conductors must be sunlight resistant
c. in this area AL ACSR is normally used due to messanger..(if ASCSR is used those conductords must terminate outside at the drop)
d. Address 250.32 depending on your Code Cycle and other varibles (in 2008 you must have a EGC)
e. Address 250.32 as far as your gounding electrodes at the residence.
a. IMHO, 310.16 for your conductors {310.15(B0(6) is at best debatable}
b. conductors must be sunlight resistant
c. in this area AL ACSR is normally used due to messanger..(if ASCSR is used those conductords must terminate outside at the drop)
d. Address 250.32 depending on your Code Cycle and other varibles (in 2008 you must have a EGC)
e. Address 250.32 as far as your gounding electrodes at the residence.
310.15(B)(6)
...... and feeder conductors THAT SERVE AS THE MAIN POWER FEEDER TO A DWELLING UNIT..... For application of this section, the main power feeder(s) between the main disconect and the lighting and appliance branch circuit panelboard.
Being the feeder is going to a detached garage and not a dwelling unit 310.15(B)(6) would not apply IMO.
I would guess that the intent of the feeder statement in that section is for when you have a situation such as a disconect on the meter or 1 disconect for a multi family meter bank.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
JohnJ0906
Senior Member
- Location
- Baltimore, MD
"....and feeder conductors that serve as the main power feeder to each dwelling unit....."
No mention of entire service load.
310.15(B)(6) applys, as long as that 100 amp feeder carries the entire house load.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I sit corrected.
I gave up too easily. :smile:
JohnJ0906 said:
Art. 310.15(B)(6) states this:
Would you not consider the garage whether remote or not to be associated with the dwelling unit? I would thus I will recant and state that T. 310.15(B)(6) is not applicable.
In my post (#6) I stated "debatable", but, personally I agree with you.
The garage is "associated" and 310.15(B)(6) is not applicable.
Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
It is the main feeder between the main disconnect and the panelboard and that dwelling panelboard does contain all the branch circuits, feeders, etc that serve that dwelling unit.
I might be all wrong on this but, doesn't table 310.20 apply to the portion of conductor that is in free air then after the splices to the others conductors( in the conduits or cables) then 310.16 would apply.
as far as the 40 ft. span, I don't see a need for a lift pole as long a the anchoring points on the strucure a properly installed.
as far as the 40 ft. span, I don't see a need for a lift pole as long a the anchoring points on the strucure a properly installed.
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