310.15 (B) (7) Reduced Service Feeder - Page 5 - Electrician Talk - Professional Electrical Contractors Forum
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Old 02-11-2018, 06:18 PM   #81
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being in free air it can dissipate the heat very easily, jackets and raceways insulate the conductors like insulation in the walls of your house
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Old 02-11-2018, 06:22 PM   #82
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Quote:
Originally Posted by HackWork View Post
FWIW, around here they also use #2 for the hot conductors in the overhead line as well, not just the neutral. But that is only on newer lines, I have seen some old ones with #6's.
#2 aluminum #6 copper for 100A?
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Old 02-11-2018, 06:24 PM   #83
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lighterup

remember current rating is based on the temperature the conductor insulation can withstand, it is the weaker link and the wire operating temperature is based on the current and how easily the conductor assembly can get rid of the heat

and also remember to take into consideration your terminations temperature ratings which you cannot exceed(ESPECIALLY WITH ALUMINUM)

the tables read in current but they are based on temperature at that current with that insulation and situation, those tables are actually using a wire length as well
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Old 02-11-2018, 06:40 PM   #84
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Question:


what I'd like to know is , other then being in open air ,
how can that #2 messenger wire handle this type of load
thus why even worry about 4/0 AL?
table 310.5(B)(20) free air #2 aluminum is good for 106-123 amps depending on insulation (100 amp services?)

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Old 02-11-2018, 06:42 PM   #85
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#2 aluminum #6 copper for 100A?
Ya for POCO drop or laterals .,

Yes I have see it over here as well and it is very common over here too.

I have see alot of #2 al drop with 100 and 200 amp service and the POCO conductors have diffrent rating on their conductors.

#6 CU ? some area yuh but yes I have see #6 Al drops for 100 amp service and they handle it pretty good.

Now ya mention POCO cut off .,, in North America side the POCO is typically sized the OCPD way above the transfomer rating which I have it it often but here in my location they sized little more closer to the transfomer rating but yes it still above the transfomer due they can handle alot of overload for a quite a while.

If you ever see the service drop shorted out ? the resdentail drop or light commercal drops the service drop conductors will keep shorting until the transfomer OCPD drop out ( some case it did not kick out espcally with larger transfomer with light load ) but well loaded transfomer yes it can kick out quicker.
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Old 02-11-2018, 06:45 PM   #86
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I would say the bulk majority of electrical services I've done
in residential (3 wire Edison) 200 amp services. Tons of them.
of which most % of those I used 4/0 ALURD ...cut & dry

some of those 250cm or a few 350cm strictly cause
of compensating for very long distances on the secondaries.

I have not ever encountered any problems with this issue.

I do agree that the demand factor is a rough guess
cause we don not know what future loads will be brought into
the scenario after we are gone from the job.
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Old 02-11-2018, 06:46 PM   #87
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you sure the #6 al aren't for the old 60 amp services
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Old 02-11-2018, 06:47 PM   #88
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Quote:
Originally Posted by hd13 View Post
table 310.5(B)(20) free air #2 aluminum is good for 106-123 amps depending on insulation (100 amp services?)
also average ambient air temperauture

example here in Ohio vs Nevada? more than likely different
capabilities
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Old 02-11-2018, 06:48 PM   #89
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table 310.5(B)(20) free air #2 aluminum is good for 106-123 amps depending on insulation (100 amp services?)
I hate to tap on your shoulder but can ya clearify it little more on the table 310.5 ? which type of conductor insluationg and type what you are refering to .? The SE or SER or XLPE or others ?
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Old 02-11-2018, 06:50 PM   #90
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nevermind table 310.15(B)(21) does allow #6 al to 101 amps
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Old 02-11-2018, 06:50 PM   #91
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you sure the #6 al aren't for the old 60 amp services
If ya going from 60 to 100 amp service most case the POCO dont bother change the #6 service drop at all unless it was cracking bad or other type of damage show up on it.
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Old 02-11-2018, 06:51 PM   #92
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I hate to tap on your shoulder but can ya clearify it little more on the table 310.5 ? which type of conductor insluationg and type what you are refering to .? The SE or SER or XLPE or others ?
that's why i put the current range, i'm not talking about a specific insulation the range covers all of them in the table
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Old 02-11-2018, 06:54 PM   #93
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If ya going from 60 to 100 amp service most case the POCO dont bother change the #6 service drop at all unless it was cracking bad or other type of damage show up on it.
never-mind table 310.15(B)(21) does allow #6 al to 101 amps
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Old 02-11-2018, 06:55 PM   #94
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i'm needing to get off here, i'll check back in another day. thanks for not lynching me, i'm honestly just trying to help.
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Old 02-11-2018, 06:56 PM   #95
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that's why i put the current range, i'm not talking about a specific insulation the range covers all of them in the table
Fair enough on that.
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Old 02-11-2018, 06:58 PM   #96
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@hd13, I still don't understand what you're trying to explain. Can you say it in a different way?
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Old 02-11-2018, 07:03 PM   #97
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@hd13, I still don't understand what you're trying to explain. Can you say it in a different way?
yes, if your messing with me i'm gonna be mad. let me think for a minute. whats your understanding or what part do you think your not understanding?

please give me some feed back to see what your thinking on the subject
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Old 02-11-2018, 07:09 PM   #98
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310.15(B)(7) is not allowing you to use an ocpd(breaker/fuse) with a setting above the ampacity(given in 310.15 tables based on the particular situation(free air/raceway etc)) of the conductor used, just like you would size ocpd for a #6 branch circuit.


-you do your load calc
-your service must be big enough for load
-your conductors have to be big enough for the load
-your conductors must have ocpd protection for overload based on the tables alone. 310.15(B)(7) has nothing to do with this


-310.15(b)(7) allows you to use wires smaller than the ampacity of the service( but still large enough for load)

-ocpd setting is determined by the wire you use not the service size, the ocpd must have a setting that will limit the over-current on the conductors to there allowable ampacity


these code panel guys aren't complete dumbass'

burning houses down is bad for anyone that can be associated with it, including them

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Old 02-11-2018, 07:13 PM   #99
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table 310.5(B)(20) free air #2 aluminum is good for 106-123 amps depending on insulation (100 amp services?)
Utilities don’t use the NEC. You really need to step away and stop giving all this bad information.
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Old 02-11-2018, 07:18 PM   #100
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Utilities don’t use the NEC. You really need to step away and stop giving all this bad information.
the insulation burns off at the same temperature whether in a house or on the pocos pole
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