You are watching: How many current carrying conductors are allowed in a conduit before derating
How many 12 ga circuits have the right to I download in 1/2" EMT?How numerous 12 ga circuits can I download in 3/4" EMT?Many thanks!Bill
Bill,See this thread:http://forum.lennythewonderdog.net/showthread.php?t=81969 This thread likewise answers the question about the usual neutrals. It"s a long thread, but well precious it considering the concerns you room asking. I understand *I* learned a lot from it.
Early in the tread, it says I can use 12 thhn conductors in 3/4"Is this correct?How about how plenty of thhn conductors in 1/2"?Has thhn replaced thw?Thanks.Bill
You deserve to install 16 THHN #12 awg in 3/4" EMT and 9 THHN #12"s in 1/2" EMT as to conduit to fill of 40%. You cannot exceed this 40 % in EMT because that over 2 wires. If you download 4 to 6 dimension 12 awg THHN existing carrying conductors in 1/2" EMT then you should derate to 80% using the 90 C pillar of table 310.16. So the 30 amp #12 is now 24 amp rated. 7 come 9 #12 THHN conductors you have to derate 70% so friend are currently rated at 21 amps for the size and also insulation rated conductor. You i do not know install much more than 9 THHN #12 awg current carrying conductors in 1/2" EMT for this reason you space finished in ~ this point. THHN/THWN is the an ext common insulation used today vs the THW
Roger i think you have actually it only partially correct. The beginning point for deration is not 20 amps because that this application. You can use approximately 9 before you are below the 20 amp threshold.
My question had three parts:1.How plenty of 12 ga conductors have the right to be offered in 1/2" EMT with a 20 amp breaker?2. " " " 3/4" EMT?3. Walk thhn have actually a better rating enabling for much more conductors?ThanksBill
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Joed: correct deration for this application would be calculated from the 90 degree column so would begin at 30 amps no 20 amps mine mistake. I have actually edited the post. Girlfriend must additionally consider approximately temp factors of 310.16 before derating for number of wires in conduit. 1.) 9 THHN #12 awg present carrying conductors prior to you drop listed below 20 amp rating. 2.) tho is 9 THHN"s before downsizing the breaker come 15 amps you have the right to fill the conduit to 40% of its overcome sectional area if end 2 wires for this reason you might put a best of 16 THHN #12"s in 3/4 EMT. 40% equates to .213sq.in. Because that 3/4 EMT. One #12 THHN is .0133sq.in. Therefore 16 x .0133sq.in. Is .2128sq.in. Nice much precisely .213 or 40% of the cross sectional area the 3/4 EMT. If you put over ripe wires approximately 16 wires then the ampacity derates native a beginning point the 30 amps to 15 amps. 3.) THHN is rated at 90 C (194 F) yet I am utilizing it right here for deration purposes. Numerous factors enter into the really temp. Pillar from table 310.16 for which ampacity is calculated. Counts on the temp. Rating the the machine you are connecting to, whether its a motor, that type of information.THW is rated a 75C together opposed come THHN at 90C for this reason the starting point because that #12 THW would be 25 AMPS for deration purposes for conduit ~ considering the approximately temp factors. The cross sectional area is also greater because that THW 보다 THHN (.0260sq.in vs .0133sq.in.) for this reason the number of wires in the conduit will be much less for THW vs THHN regarding the end 2 wires 40% fill restriction.Example: You have a #8 THW conductor in a conduit in addition to 5 others because that a complete of 6 present carrying conductors. The ambient temp because that the installation is 50 C. In the 75 C columnn that 310.16. The correction element for this approximately is .75. The ampacity because that 75 C #8 THW is 50 amps. So .75 times 50 is 37.5 amps. Currently you must think about the deration early out to number of wires in a conduit. In this instance the deration percent would certainly be 80% for 6 wires in a conduit. Therefore 37.5 times .80 is 30 amps. Then take into consideration 110.14 if your conductor is much less than 1 awg and also compare your final ampacity come the 60 level column of 310.16 and chose the smaller sized of the two due to termination restrictions. In this instance 30 amps is the last ampacity rating because that an #8 awg THW conductor in conduit with five other conductors.Having funny yet?