Romex size

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2008 White Book
This category covers Types NM-B and NMC-B nonmetallic-sheathed
cable, rated 600 V, intended for use in accordance with Article 334 of
ANSI/NFPA 70, ??National Electrical Code?? (NEC), and Listed in copper
sizes 14 to 2 AWG inclusive and aluminum or copper-clad aluminum​
sizes 12 to 2 AWG inclusive.


See also 334.104
 
Interestingly enough is that SE cable comes in sizes up to 4/0 copper. One of our supplies is now selling 250MCM aluminum SER. They said that it is good for the 200 amp panels when the se cable is rated 60C and not the total load of the panel. I disagree with them on that. 300 mcm would be needed with a load not greater than 190 amps.
 
Dennis Alwon said:
Interestingly enough is that SE cable comes in sizes up to 4/0 copper. One of our supplies is now selling 250MCM aluminum SER. They said that it is good for the 200 amp panels when the se cable is rated 60C and not the total load of the panel. I disagree with them on that. 300 mcm would be needed with a load not greater than 190 amps.
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Any reason you cant use 4/0 Al for 200amps??
Was looking at 75 degree column..............
 
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I'm with ya, I use 4/0 ser Alum. for 200 amp panels all the time in residential as its cost effective and easy to install in retro jobs. Just mount a disco either at the meter or inside to meet the AHJ rules. I throw some no-ox on the terminals and she's ready for use.
 
jrannis said:
Any reason you cant use 4/0 Al for 200amps??
Was looking at 75 degree column..............
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When you all start using the 08 NEC you will see that Se cable is rated at 60C when used as a feeder. Unless it carries the entire load of the dwelling then you cannot use 310.15(B)(6)
 
I am trying to help an AC friend who is in a jam to try and get 15 kw heat to a split system. Its a messed up job on a new house that his company did not install. They ran 10-2 to try run a 7.5 kw air handler. No it did not work but somehow got passed. He will have very little space and in an attic so conduit just not happening. I told him i wasn't sure if or where he could get romex #4
 
Jim W in Tampa said:
I am trying to help an AC friend who is in a jam to try and get 15 kw heat to a split system. Its a messed up job on a new house that his company did not install. They ran 10-2 to try run a 7.5 kw air handler. No it did not work but somehow got passed. He will have very little space and in an attic so conduit just not happening. I told him i wasn't sure if or where he could get romex #4
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Why would you need #4. #6 would be adequate for 7.5kw. With 125% it calculates to about 40 amps. Then you need to add the blower motor which should not be that much. #6 is good for many 10Kw units.
 
Dennis Alwon said:
Why would you need #4. #6 would be adequate for 7.5kw. With 125% it calculates to about 40 amps. Then you need to add the blower motor which should not be that much. #6 is good for many 10Kw units.
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The 7.5 kw is too small for 3,000 sq feet. He is thinking 10 or 15 kw. Talked to him half hour ago and think he can talk the guy into changing unit to a heat pump and keep the 10-2 romex. In the long term he will save money. This is Tampa so a heat pump works great. Almost never below 30 and then only for a few hours. Real shame that the guy got ripped off to start with. When he called me he was after advice and i was not sure if #4 could even be had in romex. Fixing to go check by code book but even #4 not likely handle 15 kw.
This is just a friend helping a friend. Nothing in it for me. Always nice to have a friend in the AC buisness when you own a nightclub.
 
lmchenry said:
Dennis, where in the 08 does it specify 60 degree?
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Article 338.10 (B)(4)(a) . In the 2005 the article read "excluding 334.80". Those words have been omitted from the '08

This mean that 334.80 shall apply to SE cable.

334.80 said:
The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The ampacity shall be in accordance with the 60?C (140?F) conductor temperature rating
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Jim W in Tampa said:
#6 is good for 55 amps. I will suggest it and 10 kw. #2 would be needed if he wants 15kw ,that would be fun to fish into a panel.
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#6 does not always work for 10kw. I have seen some 10 kw units that have a mca of 56 amps. Usually a 10kw unit is not really 10 kw. The elements are often 9.6kw or 9.8 but when you add in the blower it can be over 55 amps.
 
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