Pipe Fill

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I calculated 209, but that was based on TFF which, as I recall is same dimension as MTW, ....but as wbalsam1 says "wait on the correct answer"
 
I'm just a lowly inspector, for the correct answer we need someone far more intelligent. Perhaps a "Educator/adjunct professor Codes Division" :D
 
please provide more information about the discrete input signals (voltage/amps/number of active conductors at one time)
 
ptonsparky said:
My homegrown spreadsheet says 118 #14thhns (my minimum size) so it has to be more than that.
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you're jumping the gun on this one because the largest #18 is .0145 in./sq RHW and your #14 THHN is .0097 in./sq. So the #18 is actually a larger diameter than the #14 meaning less #18's RHW in this same pipe than #14 THHN's
 
ptonsparky said:
My homegrown spreadsheet says 118 #14thhns (my minimum size) so it has to be more than that.
Click to expand...

good point.. I dug deeper....not being worth a hoot at mil vs cir ml math, I did find at Southwire, the OD of 18 MTW is almost the same as 16 TFFN
and Table 5 gives us an area of .0072 for 16 TFFN
2" Sch 80 allows 1.150 in? for over 2 conductors 1.150/,0072 is 159

someone well versed in math can take the southwire data of 109 mils diameter for 18 MTW and get a more exact answer, but in round figures 159 is good.
aftually installing that many might be a bear, but thats approximately whats allowed.
 
billsnuff said:
http://www.kuramo.co.jp/catalog_e/fa/kr_mtw.pdf
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for me this link doesn't help because in Table 310.13(A) it lists MTW conductors and tell you that for sizes 22-12 the thickness of the insulation is.76 mm or 30 mils and your link which lists #18 as .75 mm/sq. I guess I can't help but wonder if one of these is a typo because they sound too similar but one of them is saying .76mm and the other .75 mm/sq. Why would the code list the thickness of the insulation and not the area of the MTW conductors. This bothers me. If the link is correct that #18 is .75 mm/sq and a 2" pvc sched. 80 is 742 mm/sq for 40% fill then you could put 989 of these #18's in this pipe. Sounds like an awfull lot of conductors doesn't it.

Also if you use the smallest #18 listed in table 9 which is 1.67mm/sq you can use 442 #18 KF. So the link must be a typo when it lists it as .75 mm/sq. It should probably mean .75mm insulation thickness just as the code says in table 9.
 
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after finding the area in mm/sq of #18 MTW to be 5.639 mm/sq assuming I did it right using table 8 conductor properties which is conductors without insulation 1 strand or 7 strand. I used 7 strand as all #18's I deal with are always stranded (however I don't know how many strands they usually have). I used the overall diameter to be 1.16 mm and adding .76 mm twice (thickness of insulation for MTW found in 310.13(A)) and getting 2.68mm for the diameter of a #18 MTW conductor. Then using PI=3.14 and multiplying it by the radius (which is half of the diameter) squared.

So the radius is 2.68 / 2 = 1.34.

And 1.34 x 1.34 = 1.7956

And 1.7956 x PI = 5.639

So 5.639 mm/sq is the area of a #18 MTW

divide that into 742 which is the 40% fill in mm/sq for a 2" PVC sched. 80 and I get 131 conductors allowed in the pipe.
 
Bluezebra, see what you have done ?:D

pick a number, any number :D

before we drive each other crazy..how many wires are you planning to install ??
 
#18 MTW, 16-strand on 2" sch. 80 PVC

#18 MTW, 16-strand on 2" sch. 80 PVC

#18 MTW - O.D. = 0.113" = 2.9464 mm
Wire area = (Pi X dia^2)/ 4 = 6.818 mm2
2" PVC, Sch. 80-I.D. = 1.939" = 49.2506 mm
Inside area of 2" PVC = 1905.079 mm2
40% of conduit area = 0.4 X 1905.079 = 762.03 mm2
no. of wires = 762.03/6.818 = 111.76; say 112 wires
 
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