sizing feeder

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GThomas23

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I working on a single family home with a 120/240V 600A Main Lug I-Line Panel. I have 4 200A breaker in the panel. My 42C main lug panels are about 100 feet away. What size feeder conductor can I run? (copper) & Can I use table 310.15 (B)(6) for this application?
G. Thomas
 
Feeders size

Feeders size

I am working on a single family home, with a 120/240V 600A service. I have a Main lug I-Line Panel with 4 200A Breakers. My 42C main lug panels are about 100 feet away. Can I use Table 310.15 (B) (6) to size my feeder conductors?
G.Thomas
 
No.

Table 310.15 (B) (6) can only be used for feeders that carry 100% of the dwelling units load.

You will have to size from T310.16 and very likely the 60C column.
 
If you are permitted to use 310.15.B.6 to size the service conductors, can you not use the same size for the feeders from a combination service entrance device to a panelboard based on "The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors." I understand how a sub-panel must be wired using SE for a smaller ampacity than the main. Please help me to understand. This code change will cause many discussions in the field.
 
Yes - you can.... 3/0 al, noalox, and a torque wrench.... Or 2/0 copper, depending on the taste of the salad you'll be coughing up for 4 runs at a 100' - wait 600a single family? Use 310.16 just because they can afford it!
 
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Historically inspectors in this area have allowed you to use 310.15(B)(6) in this type application, however, since each individual feeder is not carrying the entire load, I beleive a case could be made to require 310.16.
 
Historically, in this area, inspectors have alowed 310.15(B)(6) to be used in similar situations, (such as (2) 200 amp panels) however, I don't believe there is any doubt that Bob is correct in it being a violation. With the new 60 deg. requirement on SE, I can imagine the practice (of allowing) will diminish more so.
 
How come in 310.15 (6) It said for application of this section, the main power feeder shall be the feeder(s) between the main disconect and the lighting and appliance branch-circuit panelboards(s). I am quoting the 2005 NEC.
Thanks
G.Thomas
 
thanks, I don't think 3/0 AL is correct, thats only good for 175A in Table 310.15(B)(6) But 4/0 AL and 2/0) copper is being done by most contractor and All inspector are passing it based on this table.
This is from the 2005 NEC. I understand 08 has made a change.
G.Thomas
 
G.Thomas, welcome to the forum. :)

I do have to ask you not to start duplicate threads that does not help get a 'better answer' all it does is make things more confusing to those that want to help you out.

As you already had responses to both threads I have merged them into one.
 
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GThomas23 said:
How come in 310.15 (6) It said for application of this section, the main power feeder shall be the feeder(s) between the main disconect and the lighting and appliance branch-circuit panelboards(s). I am quoting the 2005 NEC.
Thanks
G.Thomas
Click to expand...

It could be used to size a feeder to a lighting and appliance branch-circuit panelboards that is used for 100% of the dwellings power.

For instance, say you had a meter main disconnect outside, now you have to run a feeder inside to the panel. That feeder could be sized per T310.15(B)(6) as that panel carries 100% of the load, the feeder would be a "Main Power Feeder" However, if you ran a feeder from that panel onto a second panel you would have to use 310.16.

The reason for this is load diversity, the NEC knows that the load diversity for the entire dwelling unit will be such that T310.15(B)(6) can be used. Once you start breaking the load up all bets are off as to how that new panel carrying only part of the load will be loaded.
 
jimman said:
If you are permitted to use 310.15.B.6 to size the service conductors, can you not use the same size for the feeders from a combination service entrance device to a panelboard based on "The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors."
Click to expand...

Yes and no, if you had a 200 amp service with service conductors based on T310.15(B)(6) and then you ran multiple 200 amp sub panels from the 200 amp service panels then "The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors." would come into play.

However, in this case we have a 600 amp service supplying multiple 200 amp subpanels.
 
e57 said:
Yes - you can.... 3/0 al, noalox, and a torque wrench.... Or 2/0 copper, depending on the taste of the salad you'll be coughing up for 4 runs at a 100' - wait 600a single family? Use 310.16 just because they can afford it!
Click to expand...

In this case '200 amp sub panels supplied by a 600 amp service panel' the conductor size from the 600 panel to the 200s would have to be at least

3/0 copper or 4/0 AL @ 75 C (Pipe and wire, or MC)

OR

4/0 copper or 300 AL @ 75 C (SER) (Edit; this should have been 60 C)

Don't forget that under the 2008 NEC SER would have to be used at 60C.


Noalox is optional. :grin:
 
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GThomas23 said:
I working on a single family home with a 120/240V 600A Main Lug I-Line Panel. I have 4 200A breaker in the panel. My 42C main lug panels are about 100 feet away. What size feeder conductor can I run? (copper) & Can I use table 310.15 (B)(6) for this application?
G. Thomas
Click to expand...

310.16 for 2008 new construction. (In this case)
 
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augie47 said:
Historically inspectors in this area have allowed you to use 310.15(B)(6) in this type application, however, since each individual feeder is not carrying the entire load, I believe a case could be made to require 310.16.
Click to expand...
Augie
310.15(B)(6) says
For application of this section, the main power feeder shall be the FEEDER(S) between thew main disconnect and the lighting and appliance branch circuit PANELBOARD(S) NEC 2005
Click to expand...
This seems to allow more than one feeder and panel to carry the entire dwelling load. NEC 2008 eliminates this
application
 
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GT,
normally the rules that apply are based on the date you bought the permit. If you buy a permit while '02 is being enforced, then the job is inspected per '02 rules, even if '05 or '08 is adopted.
May not be the case in your area, but it is in most I've seen.
That help any ??
 
Permit cycle

Permit cycle

augie47 said:
GT,
normally the rules that apply are based on the date you bought the permit. If you buy a permit while '02 is being enforced, then the job is inspected per '02 rules, even if '05 or '08 is adopted.
May not be the case in your area, but it is in most I've seen.
That help any ??
Click to expand...

Be aware that generally there is a set time limit statuate by an AHJ.
 
bob said:
Augie
310.15(B)(6) says
This seems to allow more than one feeder and panel to carry the entire dwelling load. NEC 2008 eliminates this
application
Click to expand...

Bob, there are those that agree with you, that was why the wording was changed but the IMO the actual requirements remain the same. I can provide CMP statements to that effect.

Under the 2005 NEC as it was written it said 'the main power feeder'.

Any feeder that does not supply all the dwelling units load can not be 'the main feeder'.
 
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