Why would we have an article such as 110.14(C)(1)(a)(1-4) when terminal ratings are usually dual listed at 60c/75c? Who uses column 60c in table 310.16 for ampacities 14-1/oo? I understand using the 90c column for derating, but are the editors possibly considering older equipment still in use that may have only been listed for 60c at that time? I may not be clear in stating this, but hopefully someone can expound. Have manufacturers made 90c terminal lugs yet?
terminal ratings
- Thread starter rihtnow
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ramsy
Roger Ruhle dba NoFixNoPay
- Location
- LA basin, CA
- Occupation
- Service Electrician 2020 NEC
I believe the enclosure listing is your bottleneck. See the paragraph numbered as 3. in this Online UL certifications directory below.
http://database.ul.com/cgi-bin/XYV/...n=versionless&parent_id=1073985569&sequence=1
60?C remains Underwriter Laboratory (UL) default operating temperature for enclosure / panel / outlets not specifically or legibly listed otherwise. While breakers & terminals may be listed for 75?C, enclosures have very strict requirements, before components (breakers) operating over 60?C can be mounted together. (ie) the entire equipment food chain must be marked suitable for 75?C.
http://database.ul.com/cgi-bin/XYV/...n=versionless&parent_id=1073985569&sequence=1
60?C remains Underwriter Laboratory (UL) default operating temperature for enclosure / panel / outlets not specifically or legibly listed otherwise. While breakers & terminals may be listed for 75?C, enclosures have very strict requirements, before components (breakers) operating over 60?C can be mounted together. (ie) the entire equipment food chain must be marked suitable for 75?C.
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- Location
- Massachusetts
I have been told that many of the cheap HVAC pull out disconnects are still only rated 60 C.
I don't see the NEC removing that section unless manufactures stop making 60 C equipment.
Also for what it's worth when running NM you must always use the 60 C rating regardless of the equipment rating.
I don't see the NEC removing that section unless manufactures stop making 60 C equipment.
Also for what it's worth when running NM you must always use the 60 C rating regardless of the equipment rating.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I have yet to see a 60 degree rated new piece of equipment. Not saying that that don't exist as Bob mentioned.
- Location
- Massachusetts
I have not seen any either, Websparky had pointed out in another thread that some of the cheap pull outs are 60 C rated but I have no first hand experiance with those.
As a side note it is my inderstanding that in testing breakers with terminals with rated cable the cable also acts as a heat sink as it removes some heat from the breaker. As I recall there must be a minimum of 4' of wire attached to the terminals when condicting these tests.
In addition, the only place where 90degC cable is addressed when applying breakers is with 100% rated breakers. Said breakers must be installed in enclosures or applications where they have been approves for 100% as will as using 90degC rated cable. But the cable still must be applied at 75deg C.
In addition, the only place where 90degC cable is addressed when applying breakers is with 100% rated breakers. Said breakers must be installed in enclosures or applications where they have been approves for 100% as will as using 90degC rated cable. But the cable still must be applied at 75deg C.
RayS
Senior Member
- Location
- Cincinnati
I think it wise to start with the 60deg. C rating, and only "resort" to the higher temp ampacity if needed to shrink to a specific size or budget. I just hate to think of the wiring as a heater...
Now, I do know that often the calc's are for a theoretical max load that the run may never see for any length of time, but a little extra copper goes a long way in the life of the installation for reduced I2R losses, better voltage hold up under load, and extra capacity for future loads.
Now, I do know that often the calc's are for a theoretical max load that the run may never see for any length of time, but a little extra copper goes a long way in the life of the installation for reduced I2R losses, better voltage hold up under load, and extra capacity for future loads.
BAHTAH
Senior Member
- Location
- United States
Terminal Ratings
Terminal Ratings
I am not where I can get my hands on my UL Green Book but if I remember correctly the 60/75 deg c rating for circuit breakers is based on the use of circuit breakers within a panelboard where the breakers are group mounted being 60-deg c because of the heating effects of the other breakers in the same enclosure. The 75-deg c rating is applied when the breaker is mounted in a separate enclosure with no other breakers.
Grant
Terminal Ratings
I am not where I can get my hands on my UL Green Book but if I remember correctly the 60/75 deg c rating for circuit breakers is based on the use of circuit breakers within a panelboard where the breakers are group mounted being 60-deg c because of the heating effects of the other breakers in the same enclosure. The 75-deg c rating is applied when the breaker is mounted in a separate enclosure with no other breakers.
Grant
Bob NH
Senior Member
- Location
- The "Live Free or Die" State
Bigger Wire Saves Money
Bigger Wire Saves Money
For sustained industrial operations, there doesn't seem to be any economic benefit to using the smaller wire that would be permitted by higher temperature. If you have sustained load, there is probably a saving in using the larger wire.
I did a calculation #6 and #4 copper with a 60 amp load, using the resistance values of Table 9 on page 70-636 of the 2005 code.
The difference is 0.18 Ohm per 1000 ft (0.49 - 0.31). At 60 amps, the power loss is 0.648 Watt per ft = 0.648 kWHr per 1000 hours.
Now if the cost of #4 is $0.20 per ft greater than #6, and another $0.20 for installation for a total of $0.40 per ft; and if power is $0.10 per kWHr, then the additional cost of installed wire would be paid off in about 6200 hours of operation.
Paying off the added capital cost in 6200 hours is a pretty good return on investment for a power-intensive industrial process.
Bigger Wire Saves Money
For sustained industrial operations, there doesn't seem to be any economic benefit to using the smaller wire that would be permitted by higher temperature. If you have sustained load, there is probably a saving in using the larger wire.
I did a calculation #6 and #4 copper with a 60 amp load, using the resistance values of Table 9 on page 70-636 of the 2005 code.
The difference is 0.18 Ohm per 1000 ft (0.49 - 0.31). At 60 amps, the power loss is 0.648 Watt per ft = 0.648 kWHr per 1000 hours.
Now if the cost of #4 is $0.20 per ft greater than #6, and another $0.20 for installation for a total of $0.40 per ft; and if power is $0.10 per kWHr, then the additional cost of installed wire would be paid off in about 6200 hours of operation.
Paying off the added capital cost in 6200 hours is a pretty good return on investment for a power-intensive industrial process.
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