On 2009-10-01, SteveB wrote:
FACTS:

I need to run about 190' from breaker box to my shop. I have a double pole
breaker on a 200 (+ or -) v. that says 30 on each leg.

In the shop, I will be running a SP175+ 220v MIG Lincoln welder rated at 22
amps, but that only when cranked fully open. Most of the stuff is half
that. I will be running about four shop lights, radio, and a power tool or
two at any given time. My electrician buddy has suggested IIRC a #6 wire.

Does this sound adequate? Do I get the bundled wire, or use the separate
strands? How much voltage drop on that far? Is #6 marginal, or should I
slightly oversize?

Mike (my electrician) will put the right thing, but I just wanted to start
shopping and getting prices together. BTW, does anyone know what #6 copper
solid strand goes for now? There would be just about a 200' run.

I did get about 800' of 2.5" underground conduit for free, so that helped.

Steve



Steve, a more relevant question is, what is the highest current you
think you might need in the future?

As of now, I know that I need 100 amps to my garage, from time to
time. This is mostly when I run the three phase plasma cutter that
runs off my phase converter, and at times my compressor kicks in.

So, try to think of the highest POSSIBLE current that you need and
provide cabling for that.

Voltage drop is not some sort of mysterious concept, available only to
the initiated. It is equal to the resistance per foot of cable
(available in tables, see attached below), multiplied by total number
of feet (twice the distance to your shop), multiplied by your
projected current.

The table below shows ohms/1000 ft, so you need to divide that number
by 1000 to get ohms per foot.

You need to have this table for future reference, so save it

Example:

100 amps
190 ft distance
6 gauge cable

Voltage Drop = 0.3951/1000*(190*2)*100 = 15 volts.

Example:

100 amps
190 ft distance
4 gauge cable

Voltage Drop = 0.2485/1000*(190*2)*100 = 9.44 volts.

Example:

100 amps
190 ft distance
2 gauge cable

Voltage Drop = 0.1563/1000*(190*2)*100 = 5.39 volts.

As far as heat losses are concerned, a cable would produce
(amps*voltage drop) watts of wasted power that would be converted to
heat. For your 6 gauge cable, it will be 15*100 or 1,500 watts. 1,500
watts means 8 watts per linear foot of your conduit. It is kind of
warm, but would be unlikely to get you in trouble. For a 4 gauge
cable, it will be about 5 watts per foot of conduit. For 2 gauge, it
will be less than 3 watts per foot.

i

AWG Wire Table for BARE COPPER Wire Compiled by a program written by Fr. Tom McGahee

Compiled by Fr. Tom McGahee
Permission granted to copy freely so long as credit line above is included

AWG = American Wire Gauge size
Dia-mils = Diameter in mils (1 mil = .001 inch)
TPI = Turns Per Inch (Ignoring thickness of unknown insulation)
Dia-mm = Diameter in millimeters (For comparison with non-USA coilers)
Circ-mils = Circular Mils. (circular mils = diameter in mils squared)
Ohms/Kft = Ohms Per 1,000 Feet
Ft/Ohm = Feet Per Ohm
Ft/Lb = Feet Per Pound
Ohms/Lb = Ohms Per Pound
Lb/Kft = Pounds Per 1,000 Feet
NormAmps = Normal Average Amp Capacity based on 500 circular mils per Amp
MaxAmps = Maximum recommended Average Amp Capacity in Open Air based on 438.489 circular mils per Amp

Actual Amp capacity of a wire depends on form factor and method of cooling!
MaxAmps assumes free flow of air around wire. Do NOT exceed this maximum without cooling!
Wire wrapped in a coil or without any form of cooling may over-heat at MaxAmps!
Many factors govern the ACTUAL Max Amps you can pass through a wire continuously. Be careful!



AWG Dia-mils TPI Dia-mm Circ-mils Ohms/Kft Ft/Ohm Ft/Lb Ohms/Lb Lb/Kft NormAmps MaxAmps

0000 459.99 2.1740 11.684 211592 0.0490 20402 1.5613 0.0001 640.48 423.18 482.55
000 409.63 2.4412 10.405 167800 0.0618 16180 1.9688 0.0001 507.93 335.60 382.68
00 364.79 2.7413 9.2657 133072 0.0779 12831 2.4826 0.0002 402.80 266.14 303.48

AWG Dia-mils TPI Dia-mm Circ-mils Ohms/Kft Ft/Ohm Ft/Lb Ohms/Lb Lb/Kft NormAmps MaxAmps

0 324.85 3.0783 8.2513 105531 0.0983 10175 3.1305 0.0003 319.44 211.06 240.67
1 289.29 3.4567 7.3480 83690 0.1239 8069.5 3.9475 0.0005 253.33 167.38 190.86
2 257.62 3.8817 6.5436 66369 0.1563 6399.4 4.9777 0.0008 200.90 132.74 151.36
3 229.42 4.3588 5.8272 52633 0.1970 5075.0 6.2767 0.0012 159.32 105.27 120.03
4 204.30 4.8947 5.1893 41740 0.2485 4024.7 7.9148 0.0020 126.35 83.480 95.190
5 181.94 5.4964 4.6212 33101 0.3133 3191.7 9.9804 0.0031 100.20 66.203 75.489
6 162.02 6.1721 4.1153 26251 0.3951 2531.1 12.585 0.0050 79.460 52.501 59.866
7 144.28 6.9308 3.6648 20818 0.4982 2007.3 15.869 0.0079 63.014 41.635 47.476
8 128.49 7.7828 3.2636 16509 0.6282 1591.8 20.011 0.0126 49.973 33.018 37.650
9 114.42 8.7396 2.9063 13092 0.7921 1262.4 25.233 0.0200 39.630 26.185 29.858

AWG Dia-mils TPI Dia-mm Circ-mils Ohms/Kft Ft/Ohm Ft/Lb Ohms/Lb Lb/Kft NormAmps MaxAmps

10 101.90 9.8140 2.5881 10383 0.9989 1001.1 31.819 0.0318 31.428 20.765 23.678
11 90.741 11.020 2.3048 8233.9 1.2596 793.93 40.122 0.0505 24.924 16.468 18.778
12 80.807 12.375 2.0525 6529.8 1.5883 629.61 50.593 0.0804 19.765 13.060 14.892
13 71.961 13.896 1.8278 5178.3 2.0028 499.31 63.797 0.1278 15.675 10.357 11.810
14 64.083 15.605 1.6277 4106.6 2.5255 395.97 80.447 0.2031 12.431 8.2132 9.3654
15 57.067 17.523 1.4495 3256.7 3.1845 314.02 101.44 0.3230 9.8579 6.5134 7.4271
16 50.820 19.677 1.2908 2582.7 4.0156 249.03 127.91 0.5136 7.8177 5.1654 5.8900
17 45.257 22.096 1.1495 2048.2 5.0636 197.49 161.30 0.8167 6.1997 4.0963 4.6709
18 40.302 24.813 1.0237 1624.3 6.3851 156.62 203.39 1.2986 4.9166 3.2485 3.7042
19 35.890 27.863 0.9116 1288.1 8.0514 124.20 256.47 2.0648 3.8991 2.5762 2.9376

AWG Dia-mils TPI Dia-mm Circ-mils Ohms/Kft Ft/Ohm Ft/Lb Ohms/Lb Lb/Kft NormAmps MaxAmps

20 31.961 31.288 0.8118 1021.5 10.153 98.496 323.41 3.2832 3.0921 2.0430 2.3296
21 28.462 35.134 0.7229 810.10 12.802 78.111 407.81 5.2205 2.4521 1.6202 1.8475
22 25.346 39.453 0.6438 642.44 16.143 61.945 514.23 8.3009 1.9446 1.2849 1.4651
23 22.572 44.304 0.5733 509.48 20.356 49.125 648.44 13.199 1.5422 1.0190 1.1619
24 20.101 49.750 0.5106 404.03 25.669 38.958 817.66 20.987 1.2230 0.8081 0.9214
25 17.900 55.866 0.4547 320.41 32.368 30.895 1031.1 33.371 0.9699 0.6408 0.7307
26 15.940 62.733 0.4049 254.10 40.815 24.501 1300.1 53.061 0.7692 0.5082 0.5795
27 14.195 70.445 0.3606 201.51 51.467 19.430 1639.4 84.371 0.6100 0.4030 0.4596
28 12.641 79.105 0.3211 159.80 64.898 15.409 2067.3 134.15 0.4837 0.3196 0.3644
29 11.257 88.830 0.2859 126.73 81.835 12.220 2606.8 213.31 0.3836 0.2535 0.2890

AWG Dia-mils TPI Dia-mm Circ-mils Ohms/Kft Ft/Ohm Ft/Lb Ohms/Lb Lb/Kft NormAmps MaxAmps

30 10.025 99.750 0.2546 100.50 103.19 9.6906 3287.1 339.18 0.3042 0.2010 0.2292
31 8.9276 112.01 0.2268 79.702 130.12 7.6850 4145.0 539.32 0.2413 0.1594 0.1818
32 7.9503 125.78 0.2019 63.207 164.08 6.0945 5226.7 857.55 0.1913 0.1264 0.1441
33 7.0799 141.24 0.1798 50.125 206.90 4.8332 6590.8 1363.6 0.1517 0.1003 0.1143
34 6.3048 158.61 0.1601 39.751 260.90 3.8329 8310.8 2168.1 0.1203 0.0795 0.0907
35 5.6146 178.11 0.1426 31.524 328.99 3.0396 10480 3447.5 0.0954 0.0630 0.0719
36 5.0000 200.00 0.1270 25.000 414.85 2.4105 13215 5481.7 0.0757 0.0500 0.0570
37 4.4526 224.59 0.1131 19.826 523.11 1.9116 16663 8716.2 0.0600 0.0397 0.0452
38 3.9652 252.20 0.1007 15.723 659.63 1.5160 21012 13859 0.0476 0.0314 0.0359
39 3.5311 283.20 0.0897 12.469 831.78 1.2022 26496 22037 0.0377 0.0249 0.0284

AWG Dia-mils TPI Dia-mm Circ-mils Ohms/Kft Ft/Ohm Ft/Lb Ohms/Lb Lb/Kft NormAmps MaxAmps

40 3.1445 318.01 0.0799 9.8880 1048.9 0.9534 33410 35040 0.0299 0.0198 0.0226





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