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#90557 11/29/04 02:36 PM
Joined: Feb 2004
Posts: 494
M
Member
Hi,
If I use the 90 column of 310.16 do the terminal of the OCPD like a breaker have to be rated for AT least the same rating as that of the conductor?

What table do you use most for SE conductors?

I am sizing the conductors for a 200A Service for a commercial job. Can I use 2/0 copper that is from the 90Celcius column?

-regards

Mustang

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#90558 11/29/04 03:39 PM
Joined: Jan 2003
Posts: 4,391
I
Moderator
The only time you can use the 90 C column is to start your derating calculations.

You will need to use the 75 C column and 3/0 copper for a 200 amp commercial service.

If the calculated load is under 180 amps you could also use 4/0 AL.

Glad to see you stuck around. [Linked Image]

Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#90559 11/30/04 02:16 PM
Joined: Jul 2001
Posts: 599
J
JBD Offline
Member
There are no UL Listed overcurrent devices, of any type or manufacturer, that are rated for use with wire/cable sized using the 90C ampacity column.

#90560 11/30/04 02:20 PM
Joined: Feb 2004
Posts: 494
M
Member
Hi,
Thanks for the interesting replies. I was not aware that there were no equipment rated for 90 celcius.

Why is that?

-regards

Mustang

[This message has been edited by mustangelectric (edited 11-30-2004).]

#90561 11/30/04 02:52 PM
Joined: Jun 2002
Posts: 58
E
Member
You can only use the lowest common temp. rating, including terminations, per 110-14(C).
For instance, feeders would include OCPD temp rating at main switchboard/panel, conductor temp. rating, and temp. rating at lugs at subpanel. SWBD and panels are typically 75°C per the listing info on the panel covers, and THWN is 75°, so 75° can be used.
For branch circuits, the OCPD ratings are 75° or 60°, per what's printed on the device, the conductor rating (usually 75° for THWN), and the utilization device (usually 60°); so you usually have to use 60° for branch circuits.
I rarely ever see a combination of conductors and terminations that allow the use of 90°.


[This message has been edited by energy7 (edited 11-30-2004).]

#90562 11/30/04 05:23 PM
Joined: Nov 2000
Posts: 2,148
R
Member
Quote
I was not aware that there were no equipment rated for 90 celcius. Why is that?
What do you think your customers would say after they burnt their fingers on the electrical equipment that you installed? 90°C is 194°F. That will burn you.
Don

[This message has been edited by resqcapt19 (edited 11-30-2004).]


Don(resqcapt19)
#90563 11/30/04 07:20 PM
Joined: Feb 2004
Posts: 494
M
Member
Hi,
Thanks again for the replies. I realize that 90 c is a high temp but these types of conductors are designed for use in high temp areas are they not? Like on a boiler or furnace or nuclear reactor?

Where in the heck would you use these conductors? Where would you install conductors like these where they would be accessible to personnel?

I was thinking that this is the maximum allowable temperature of the conductor BEFORE overheating not normal operating temp.

Interesting.

-regards

#90564 11/30/04 07:33 PM
Joined: Sep 2004
Posts: 167
S
Member
The temperature rating of insulation is about heat generated by current flow as well as heat imposed upon the conductor by the surrounding ambient just as you said.
Some more examples:
Most luminaires require a specific insul temp.
Flourescents 90deg
Some incandescants with the bulb base up and wiring compartment on top - 90deg and higher
Romex is required to be 90deg conductor type because of the ambient.


Larry LeVoir
Inspector
City of Irvine, CA
#90565 12/01/04 08:07 AM
Joined: Jan 2004
Posts: 1,507
G
Member
The statment:
Quote
There are no UL Listed overcurrent devices, of any type or manufacturer, that are rated for use with wire/cable sized using the 90C ampacity column.
Needs to be qualified a little bit by saying for 600v or less. Once you get over 600v. there are terminals rated for 90 degree C and the 90 degree column in wiring tables is acceptable for termination.

[This message has been edited by George Little (edited 12-01-2004).]


George Little
#90566 12/01/04 10:36 AM
Joined: Jul 2001
Posts: 599
J
JBD Offline
Member
mea culpa

George, you are correct about the 600V. I swear I had edited my original post, but I geuss I remembered it wrong.


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