*****DERATING*****

[iwire]

Re: *****DERATING*****

I do not think anyone forgot about 240.4(B), you forgot to tell us the actual load on the conductors.

240.4(B) will let you move up to the next OCPD.

BUT, the load on the conductors still has to be less then the conductors are rated for.

Example. If the ampacity of the conductors is 570 amps and the load is 550 amps you could use a 600 amp OCPD, but if the load is 580 amps you can not use the 570 amp conductors.

 

[steve66]

Re: *****DERATING*****

No need to yell gregsparky.

Since the person you work with says always use the 90 degree column, I would always go to that person for advice instead of trying to get advice from some internet forum.

I'll bet that person is always right.

Steve

 

[charlie b]

Re: *****DERATING*****

Originally posted by gregsparky: GENTLEMEN

There are ladies who also participate in this forum.

Also, please turn off the CAPS LOCK feature. It makes the text harder to read, and is considered impolite (i.e., as though you were SHOUTING at the reader).

MY OBJECT IS TO FIND OUT WHAT THE SMALLEST SIZE THHN/THWN CONDUCTOR I CAN INSTALL IN THAT SAME CONDUIT (PARALLELED) AND STILL FUSE IT AT 600 AMPS.

I stand by my previous answer. You can get 6 conductors at 400 MCM, and perhaps a #1 EGC, into a 3? EMT, and fuse the circuit at 600 amps. The two tricky parts are (1) This presumes you don?t need a neutral, and (2) You would have to manually calculate the area, if you need to add the EGC.

However, based on the revised wording of your question, I will add one other solution. A set of 6 300 MCM conductors in a 3? conduit is rated at 512 amps (80% x 2 x 320). If the load is less than 512 amps, you could fuse this at 600. Just out of curiosity, what is the calculated load that this set of conductors will be called upon to serve?

SOMEONE AT WORK TOLD ME THAT YOU ALWAYS USE THE 90C COLUMN FOR FINDING AMPERAGES FOR DERATING.

That is true. See 110.14(C).

 

[Guest]

Re: *****DERATING*****

Good point about keeping things gender-neutral.

Originally posted by charlie b:
<snip>Also, please turn off the CAPS LOCK feature. It makes the text harder to read, and is considered impolite (i.e., as though you were SHOUTING at the reader).<snip>

I'm not making excuses for the OP or meaning to be overly argumentative, but please keep in mind there may be a hidden reason why the OP chooses to use ALL CAPS. For instance, many trades dictate that all correspondence be in ALL CAPS. It can be hard to turn off the habit. Additionally, there are certain physical limitations that may make it difficult for someone to use the Shift-key in which case they find it better to stay ALL-CAPS vs. staying all lower-case.

Not trying to start a side issue here, just trying to give the OP the benefit of the doubt. In general it's best Netiquette to use upper & lower case, but it may not always be possible.

 

[sjaniga]

Re: *****DERATING*****

Gregsparky,

I'M ATTEMPTING TO GET 600 AMPS IN A SINGLE 3" EMT CONDUIT.

MY STORY ABOUT INSTALLING 6-400 KCML THHN/THWN'S IN A 3" EMT CONDUIT IS TRUE, IS LEGAL AND IS DONE.

There you have answered your own question and untill you give us more information I doubt that anyone on this forum will say that you can use anything smaller.

 

[frenchelectrican]

Re: *****DERATING*****

excuse me lady and guys ; i will like to rejoin the band wagon again and i did use my calcuater for the wire size and this person oringally asked us ( the fourm members ) to find the wire size to fit in the 3 inch EMT conduct and i came up with paralled 350 KCM or mcm ( your choice to call it ) that baised on without neutral conducter but add neutral conducter and grouding conducter also it will not fit into the 3 inch EMT. i did try that with my calcaucater with neutral and ground and it need at least 4 inch conducts or go with 5 inch conduct but IMO it will not really look very nice at all..

merci , marc

 

[gregsparky]

Re: *****DERATING*****

GOOD EVENING LADIES AND GENTLEMEN--
I'M NOT YELLING AND I'M NOT MAD. I'M NOT HANDICAPPED AND WHEN I SAID GENTLEMEN, AT THE TIME THAT'S ALL THERE WAS.
NO OFFENSE LADIES!
AND THE LOAD! THERE IS NO LOAD... WELL AT LEAST NOT YET. THE FEEDER IS TO A 600 AMP 3 PHASE 3 WIRE BUS DUCT.
I HOPE THIS CLEARS UP MORE OF THE CONFUSION. IF NOT, ASK ME MORE ?'s.

 

[Guest]

Re: *****DERATING*****

OK. I'll bite. Why do you use ALL CAPS?

PS: Online you don't know what sex people are. Even in real life Kevin, Mike, Chris, Don, etc. are gender neutral names.

../Wayne C.

[ October 08, 2003, 08:42 PM: Message edited by: awwt ]

 

[iwire]

Re: *****DERATING*****

OK your not mad or yelling, maybe you just do not know where the button is.

 

[gwz2]

Re: *****DERATING*****

Guessing that the terminal(s) at the OCPD will be rated for 75?C and using 2 condutors per phase, that 2 condutors per phase of 500 Kcmil THHN would have the ampacity of 608 amperes. 380A times 80 percent times 2 = 608 Amperes.

Allowing the EMT to be the EGC, 3.5" EMT would be the minimum size to contain 6 500 Kcmil THHN conductors.

This does not derate for any temperature factors that may be present.