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04-16-2012, 03:51 PM
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#1
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Member
Join Date: Sep 2011
Location: SC
Posts: 39
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RTU circuit
I have a rtu mca 100 amps, can I pull 3 #2, #8 grd. and 2 #12 thhn (for recp.) in 1 1/4 " emt? We are under 2008 code.
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04-16-2012, 03:52 PM
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#2
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Member
Join Date: Sep 2011
Location: SC
Posts: 39
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voltage is 208
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04-16-2012, 03:54 PM
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#3
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Senior Member
Join Date: Nov 2010
Location: New England
Posts: 23,768
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Quote:
Originally Posted by papa
I have a rtu mca 100 amps, can I pull 3 #2, #8 grd. and 2 #12 thhn (for recp.) in 1 1/4 " emt? We are under 2008 code.
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The two 12 AWG extra current carrying conductors kills the ampacity of the feeder, but assuming 2 copper you will make it.
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04-16-2012, 04:00 PM
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#4
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Master Electrican
Join Date: Jun 2011
Location: West Texas
Posts: 612
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Quote:
Originally Posted by BBQ
The two 12 AWG extra current carrying conductors kills the ampacity of the feeder, but assuming 2 copper you will make it.
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What happened to people doing a few calculations on their own, don't make it so easy on them.
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The Following User Says Thank You to sstlouis03 For This Useful Post:
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04-16-2012, 04:02 PM
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#5
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Member
Join Date: Sep 2011
Location: SC
Posts: 39
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Yes its copper, that would leave me at 104 amps on the 2 AWG after derating is that correct?
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04-16-2012, 04:04 PM
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#6
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Member
Join Date: Sep 2011
Location: SC
Posts: 39
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Quote:
Originally Posted by sstlouis03
What happened to people doing a few calculations on their own, don't make it so easy on them.
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I did my own calculatons , just getting a second opinion.
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04-16-2012, 04:06 PM
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#7
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Senior Member
Join Date: Nov 2010
Location: New England
Posts: 23,768
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Quote:
Originally Posted by papa
Yes its copper, that would leave me at 104 amps on the 2 AWG after derating is that correct?
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Yes, that was what I came up with.
Of course I am assuming this run is inside the building and not on the roof in the sun.
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04-16-2012, 04:08 PM
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#8
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Electrical Simpleton
Join Date: Nov 2011
Location: Ohio
Posts: 927
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Will 250.122(B) have an affect on this install?
Pete
__________________
Confidence is the feeling you have before you understand the situation.
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04-16-2012, 04:14 PM
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#9
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Member
Join Date: Sep 2011
Location: SC
Posts: 39
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Quote:
Originally Posted by Pete m.
Will 250.122(B) have an affect on this install?
Pete
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I don't see why it would since I did not have to increase the size of the ungrounded conductors.
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04-16-2012, 04:16 PM
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#10
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Member
Join Date: Sep 2011
Location: SC
Posts: 39
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Quote:
Originally Posted by BBQ
Yes, that was what I came up with.
Of course I am assuming this run is inside the building and not on the roof in the sun.
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Yes its inside .
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04-16-2012, 04:18 PM
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#11
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Electrical Simpleton
Join Date: Nov 2011
Location: Ohio
Posts: 927
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Assuming your terminations are good for 75 degrees #3 copper would have sufficed based on 100 being the MCA.
Pete
__________________
Confidence is the feeling you have before you understand the situation.
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The Following User Says Thank You to Pete m. For This Useful Post:
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04-16-2012, 04:23 PM
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#12
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Member
Join Date: Sep 2011
Location: SC
Posts: 39
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Quote:
Originally Posted by Pete m.
Assuming your terminations are good for 75 degrees #3 copper would have sufficed based on 100 being the MCA.
Pete
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Sorry your right , Thanks 
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04-16-2012, 04:34 PM
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#13
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Electrical Simpleton
Join Date: Nov 2011
Location: Ohio
Posts: 927
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Quote:
Originally Posted by papa
Sorry your right , Thanks |
Not a problem... just didnt want to see you get hit on inspection. 
Pete
__________________
Confidence is the feeling you have before you understand the situation.
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04-16-2012, 04:37 PM
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#14
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Good at being Evil
Join Date: Mar 2010
Location: Long Island,NY & Poconos
Posts: 11,064
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The two #12s shouldn't count as they will only carry current while the unit is being serviced.
__________________
All these liberal laws has turned me into a right wingnut..
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04-16-2012, 04:41 PM
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#15
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Senior Member
Join Date: Jan 2007
Location: Dayton Ohio
Posts: 1,573
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Quote:
Originally Posted by BBQ
The two 12 AWG extra current carrying conductors kills the ampacity of the feeder, but assuming 2 copper you will make it.
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True, it might be easier to just pick up the 120v close and feed unit seperatly.
__________________
I'm just hoping to not end up on Electricmanscotts signature line.
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04-16-2012, 05:03 PM
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#16
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Master Electrican
Join Date: Jun 2011
Location: West Texas
Posts: 612
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How does 110.14 (c) play into this. It seems to me like he should be using #1.
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04-16-2012, 05:11 PM
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#17
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Senior Member
Join Date: Nov 2010
Location: New England
Posts: 23,768
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Quote:
Originally Posted by Shockdoc
The two #12s shouldn't count as they will only carry current while the unit is being serviced.
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Well if you interlocked them so only one circuit at a time could be used ....
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04-16-2012, 09:45 PM
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#18
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Should be working
Join Date: Apr 2011
Location: California
Posts: 3,791
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Ahhh..... Got it , but Pete isn't considering the #12's ?
Last edited by dronai; 04-16-2012 at 10:34 PM.
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04-16-2012, 09:50 PM
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#19
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Chief Electron Relocator
Join Date: Sep 2007
Location: Cornpatch USA
Posts: 31,246
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Quote:
Originally Posted by sstlouis03
What happened to people doing a few calculations on their own, don't make it so easy on them.
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What happened to English? 
__________________
In winter, why do we try to keep the house as warm as it was in summer when we complained about the heat?
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04-17-2012, 08:50 AM
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#20
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Master Electrican
Join Date: Jun 2011
Location: West Texas
Posts: 612
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Quote:
Originally Posted by 480sparky
What happened to English? |
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