De-rating

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AZsparky

AZsparky

Senior Member
Location
Scottsdale, AZ
Hi all: I need to move a residential electrical service out from under a covered patio per the POCO. We are upgrading to a 200 amp overhead service from a 60. Anyway, the new service drop to the 200 amp all-in-one will be about 16 feet from the old service. So, I'm setting an 18x18x4 3R j-box at the old service and surface piping 2" EMT over to bring the branch circuits over. Do I need to de-rate and upsize all the cables in that conduit to meet NEC? Thanks in advance. This will be City of Phoenix inspected.
 
Dennis Alwon

Dennis Alwon

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Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Are you pulling cables in the conduit on the outside of the building? It needs to be UF. Yes you must derate as you would for any install with 3 or more CCC in the conduit.
 
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Glennsparky

Member
Location
Casselberry, FL USA (near Orlando)
Instead of a j-box at the old location how about a main lug panel with feed through lugs? Pretty inexpensive and no splices. Old circuits terminate in breakers and the service cables go in one end and out the other. Or, instead of an all-in-one, just a meter base at the new location. The new panel at the old location would then need a main breaker for the disconnect and still need feed through lugs.
 
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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
It might be more cost effective to replace the existing panel with a new panel and just run 4 wires from a main CB at the new service point instead of the all in one idea.
 
AZsparky

AZsparky

Senior Member
Location
Scottsdale, AZ
Sorry, I meant pulling THHN individual conductors in the 2" conduit. Also, I'm kind of locked in to an all in one at the new metering location. According to a pre-con meeting with the POCO, they originally OK'ed the position right next to where the old service is. Then they called me after a few days and said it wouldn't be accepted there. In the meantime, I had hung the all in one, drillled the roof, installed the new 2-1/2" riser and associated new bracing on the roof. So, it's kind of a cluster now. The POCO is willing to pay me half of the re-location costs, so they knew their guy mis-directed me. But again, since I need to pipe over about 16' with 2" EMT to connect the j-box at the old service location, does the NEC require me to de-rate? Any more info needed to advise? THANKS...
 
kwired

kwired

Electron manager
Location
NE Nebraska
AZsparky said:
Sorry, I meant pulling THHN individual conductors in the 2" conduit. Also, I'm kind of locked in to an all in one at the new metering location. According to a pre-con meeting with the POCO, they originally OK'ed the position right next to where the old service is. Then they called me after a few days and said it wouldn't be accepted there. In the meantime, I had hung the all in one, drillled the roof, installed the new 2-1/2" riser and associated new bracing on the roof. So, it's kind of a cluster now. The POCO is willing to pay me half of the re-location costs, so they knew their guy mis-directed me. But again, since I need to pipe over about 16' with 2" EMT to connect the j-box at the old service location, does the NEC require me to de-rate? Any more info needed to advise? THANKS...
Click to expand...
Yes, read 310.15(B)(3), while at it read the rest of 310.15 - some other things in there may apply to your installation.
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
AZsparky said:
But again, since I need to pipe over about 16' with 2" EMT to connect the j-box at the old service location, does the NEC require me to de-rate? Any more info needed to advise? THANKS...
Click to expand...

Yes derating will apply to those conductors in the 16' of raceway. There are many variables, first thing you need to figure out is how many current carrying conductors will be in the raceway.
 
aftershock

aftershock

Senior Member
Location
Memphis, TN
AZsparky said:
Sorry, I meant pulling THHN individual conductors in the 2" conduit. Also, I'm kind of locked in to an all in one at the new metering location. According to a pre-con meeting with the POCO, they originally OK'ed the position right next to where the old service is. Then they called me after a few days and said it wouldn't be accepted there. In the meantime, I had hung the all in one, drillled the roof, installed the new 2-1/2" riser and associated new bracing on the roof. So, it's kind of a cluster now. The POCO is willing to pay me half of the re-location costs, so they knew their guy mis-directed me. But again, since I need to pipe over about 16' with 2" EMT to connect the j-box at the old service location, does the NEC require me to de-rate? Any more info needed to advise? THANKS...
Click to expand...

Why not set a 60 amp sub panel where the original was and feed it from the meter panel combo?
 
AZsparky

AZsparky

Senior Member
Location
Scottsdale, AZ
Doesn't look good right now..

Doesn't look good right now..

There is a 2" EMT raceway joining old panel location to new is 22' long. OK, so at the old service panel location, I have (7) 20 amp 120 volt circuits, (1) 60 amp 220 volt circuit (A/C), (1) 50 amp 120 volt circuit (range), (1) 60 amp sub panel feeder, and (2) 15 amp 120 volt circuits. Located in Phoenix, so looks like ambient temp probably precludes me from using this 2" EMT raceway. Please tell me differently.....
 
F

fmtjfw

Senior Member
Location
Fairmont, WV, USA
AZsparky said:
Sorry, I meant pulling THHN individual conductors in the 2" conduit. Also, I'm kind of locked in to an all in one at the new metering location. According to a pre-con meeting with the POCO, they originally OK'ed the position right next to where the old service is. Then they called me after a few days and said it wouldn't be accepted there. In the meantime, I had hung the all in one, drillled the roof, installed the new 2-1/2" riser and associated new bracing on the roof. So, it's kind of a cluster now. The POCO is willing to pay me half of the re-location costs, so they knew their guy mis-directed me. But again, since I need to pipe over about 16' with 2" EMT to connect the j-box at the old service location, does the NEC require me to de-rate? Any more info needed to advise? THANKS...
Click to expand...

THWN
 
Smart $

Smart $

Esteemed Member
Location
Ohio
AZsparky said:
There is a 2" EMT raceway joining old panel location to new is 22' long. OK, so at the old service panel location, I have (7) 20 amp 120 volt circuits, (1) 60 amp 220 volt circuit (A/C), (1) 50 amp 120 volt circuit (range), (1) 60 amp sub panel feeder, and (2) 15 amp 120 volt circuits. Located in Phoenix, so looks like ambient temp probably precludes me from using this 2" EMT raceway. Please tell me differently.....
Click to expand...
Number of current-carrying conductors (ccc) adjustment will impact you more than ambient correction. But that's irrelevant since they are compounded. If all circuits are 2 ccc, that's 45%, while ambient is 82%... both amount to 36.9%. So your probably looking at #8 for the 15A circuits, #6 for 20A's, 3/0 for 50A, and 2/0 for 60A's. I'm not going to do the fill calculation for you, but my hunch is the 2" won't have enough room. If you made your 20A and 15A circuits MWBC's you would "gain" 5% on ccc derating, but it probably won't help.
 
kwired

kwired

Electron manager
Location
NE Nebraska
Eliminate the 2 inch and run multiple smaller raceways, if you keep each raceway limited to 9 current carrying conductors max you usually will not run into situation of needing to increase conductor size until ambient temp deration is necessary then it may still make you increase conductor sizes, but you are probably only looking at one size up instead of multiple sizes up.
 
P

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
AZsparky said:
Hi all: I need to move a residential electrical service out from under a covered patio per the POCO. We are upgrading to a 200 amp overhead service from a 60. Anyway, the new service drop to the 200 amp all-in-one will be about 16 feet from the old service. So, I'm setting an 18x18x4 3R j-box at the old service and surface piping 2" EMT over to bring the branch circuits over. Do I need to de-rate and upsize all the cables in that conduit to meet NEC? Thanks in advance. This will be City of Phoenix inspected.
Click to expand...

why not just leave the old panel board in place and run a single feed to it.
 
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