NEC 110.14 and 310.16

[JBUDA54]

Why is there a table for 75 deg C and 90 deg C for less than 100A in Table 310.16 if section 110.14 (c) (1) (a) restricts using anything other than the 60 deg C table?

 

[davidbeach]

1) It doesn't; 60[°] is for unless otherwise listed.

2) Even if you can't exceed the 60[°] rating you can start with 75[°] or 90[°] if/as appropriate when derating conductor ampacity.

 

[JBUDA54]

My engineering manager told me that UL testing does not go above 60 deg C terminations below 100A therefore anything rate 100 and below must use 60 deg column. Was I misled?

 

[davidbeach]

Lots of decent equipment has a 75[°] rating below 100A. Look at Square D, Eaton, GE, others and you will see that there are listings for 60[°] and 75[°]. If you are looking at the cheap junk used in residential construction then you probably won't find any 75[°] ratings.

 

[JBUDA54]

I think he is stating that most of UL testing has been with terminations listed for 60 deg c for less than 100A therefore use the conservative aproach... maybe...

 

[dpc]

Above 110 A UL REQUIRES the termination be rated for 75 deg C wire. At 110 A and below, it's optional.

So if you KNOW what equipment you are getting and you specify 75 deg C termination, you can use that. But remember, this has to apply at BOTH ENDS of the circuit.

The most conservative approach is to size using 60 deg C ampacity up through 110 A and then use 75 deg C above that.

 

[mcgyvr]

This is why we stopped using UL and have switched to ETL (Intertek). dpc's post is correct.

UL is loaded with people (idiots as I call them) who have no idea of the proper interpretation of the standards and go off their own guesses which in the end costs you as the customer more money because you have to fight UL on everything.

The last 2 projects I sent through UL ended up costing us twice as much as origionally quoted and that cost increase was due to use having to schedule extra meetings with their supervisors just to tell them the proper way to interpret the standards. Even though they admitted they were wrong we still had to pay for the time to meet and educate their reviewers. They get pretty nasty when you tell them you refuse to pay extra to educate them.

We just took another product through UL and they came back with 27 issues that they raised (none of which we agree with or are correct). We then took that same product (no changes at all) to ETL and it was listed without any issues.

 

[hp2spare]

The 310-16 rating of a 75 or 90 degree cable may be used to meet requirements other than 110-14C. For example, ambient temp derating can be applied to the actual cable temp rating ampacity and not the 60 degree rating.

Woody