310.16

Status
Not open for further replies.
D

dnj12345

Member
What is the correct way to read this table. How do you know which column to use. Thanks I've been getting a lot of different answers.
 
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.
 
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.
 
hardworkingstiff said:
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.
Click to expand...


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?
 
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.
 
infinity said:
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.
Click to expand...

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.
 
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 .
 
310.16

thanks guys sometimes the code book can be discouraging there is so much to know and many different scenarios
 
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.
 
Len said:
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.
Click to expand...

I have also heard this your statement from others. Is there any code reference NEC to clearly say what you are saying.

I really want clear for me this.
 
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.
 
Here's a good graphic on termination temperature ratings:

6_15_34_3_2.gif
 
Status
Not open for further replies.
Top