310.16
- Thread starter dnj12345
- Start date
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- Location
- New Jersey
- Occupation
- Journeyman Electrician
It depends on the wiring method, the conductor insulation and the temperature ratings of the connections. For NM cable you would use the 60? C column. For THHN in conduit you would almost always use the 75? C column.
hardworkingstiff
Senior Member
- Location
- Wilmington, NC
If you give some examples of what you are trying to understand you can get more specific responses.
What Rob said is exactly correct. What Rob didn't mention is that you can use the 90c column when you are derating conductors but the final ampacity calculation cannot exceed the column that your terminations or wiring methods restrict you to.
What Rob said is exactly correct. What Rob didn't mention is that you can use the 90c column when you are derating conductors but the final ampacity calculation cannot exceed the column that your terminations or wiring methods restrict you to.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Lou is correct. The question is simple but there variables are vast (wiring method, derating, temperature corrections, terminations, etc.) Do you have a specific application?
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
As Infinity pointed there are a lot of variables and I will add that I was confused about location.
Notice that THHW and XHHW are in both the 75 degree and 90 degree column. It is because it depends whether it is used in a wet or dry location See T310.13.
Also a lot of the smaller single strand wire we pull has 2 designations, THHN/THWN. Again it depends on location. The THHN makes it 90 degrees for dry locations and the THWN makes it 75 degrees for wet locations.
Augie was nice and explained it to me. Hope this helps also.
Notice that THHW and XHHW are in both the 75 degree and 90 degree column. It is because it depends whether it is used in a wet or dry location See T310.13.
Also a lot of the smaller single strand wire we pull has 2 designations, THHN/THWN. Again it depends on location. The THHN makes it 90 degrees for dry locations and the THWN makes it 75 degrees for wet locations.
Augie was nice and explained it to me. Hope this helps also.
Volta
Senior Member
- Location
- Columbus, Ohio
Those ratings are very important. As Rob said, 75? C is usually ok, but you need to verify that the device you are connecting to is rated that high. Looking at a Leviton catalouge, some common duplexes (5362, BR20, or CR20) are designed for 60? C max continuous, and many switches for 65? C.
The rule 110.14(C)(1) requires us consider wire smaller than 1/0 at 60? C unless the termination devices are marked otherwise.
So 75? C may usually work, but it is your responsibility to show that when using small wires.
Buck Parrish
Senior Member
- Location
- NC & IN
So you could use #4 copper THHN on a 90 amp breaker?
This may be a good replacement for the old method #2 AL was being used for in Resi. To feed all the branch circuits at the inside sub panel .
This may be a good replacement for the old method #2 AL was being used for in Resi. To feed all the branch circuits at the inside sub panel .
hardworkingstiff
Senior Member
- Location
- Wilmington, NC
As long as the calculated load is =< 85-amps. If the load is higher than 85-amps then you would not have a NEC compliant installation.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Maybe, depends on the load. The sum of cont. x 125% + non cont. must not be > than 85 amps, and all your terminations must be rated 75C.
macmikeman
Senior Member
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- Planet macmikeman
Good replacement only if you completely ignore the cost portion of the equation......
Hameedulla-Ekhlas
Senior Member
- Location
- AFG
These columns just specify the current carrying capacity based on temperature and insulation type.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
HE, I believe location, wet or dry, applies also.
Volta
Senior Member
- Location
- Columbus, Ohio
It sure takes some getting used to.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
It sure takes some getting used to.
Oh yeah!!!!!
Len
Senior Member
- Location
- Bucks County
table
table
if you are under 100amps and under #4 then you use 60deg column, if you are over those specs then 75deg. column. but their is alot more to that table.
table
if you are under 100amps and under #4 then you use 60deg column, if you are over those specs then 75deg. column. but their is alot more to that table.
Hameedulla-Ekhlas
Senior Member
- Location
- AFG
I think the statement would be an old rule of thumb based on 110.14(C)(1).
It seems to me it would keep one out of trouble, but it is probably considerably outdated with most circuit breakers and equipment rated > 30 amps accepting 75? terminations.
It seems to me it would keep one out of trouble, but it is probably considerably outdated with most circuit breakers and equipment rated > 30 amps accepting 75? terminations.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Here's a good graphic on termination temperature ratings:
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