# Electricital question

• posted

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.

Steve

• posted

Yesterday you were warning us about the arrival of the antichrist. Will this new power supply be used to electrocute him like they frequently do in the movies? If so, then #6 is definitely too small. Or are you planning to curry his favor by welding his lawnmower or something?

Wayne

• posted

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 tom snipped-for-privacy@sigmais.com 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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• posted

Kft =A0Ft/Ohm =A0 =A0Ft/Lb =A0 =A0 Ohms/Lb =A0 Lb/Kft =A0 =A0NormAmps =A0Ma= xAmps

=A01.5883 =A0 =A0629.61 =A0 =A050.593 =A0 =A00.0804 =A0 =A019.765 =A0 =A013= .060 =A0 =A014.892

Some of your table is good, but look closer at the normal and max amp values.

jsw

• posted

? Ohms/Lb ? Lb/Kft ? ?NormAmps ?MaxAmps

? ?0.0804 ? ?19.765 ? ?13.060 ? ?14.892

Those could be for long range power transmission

• posted

Ohms/Lb Lb/Kft NormAmps MaxAmps

0.0804 19.765 13.060 14.892
• posted

In NEC table 310-16, #6 copper wire is rated at ampacity of 55, 65, or

75 amps, depending on its type of insulation, so the wire is heavy enough to meet national code requirements when using a 30A breaker. As Igor or someone else mentioned, you could reduce heavy-load (100A) voltage drops by 5 to 10 volts by going to #4 or #2 wire.

What I think would make sense is 4-conductor aluminum wire (3 #2 Al, insulated, and 1 #4 Al ground wire), attached to a 100A breaker in an entrance service panel. #2 Al ampacity is slightly larger than #4 Cu ampacity, ie 75, 90, or 100 for the #2 Al and 70, 85, or 95 for the #4 Cu, again depending on type of insulation. #2 Al should cost somewhat less than #4 Cu. (Also see ebay # 180398856402, appears to be 300' 3-cdr #0000 Al, around \$1.58/ft when you count shipping.)

Bundled wire would be easier to pull but might cost a little more, and with heavy current it heats up a little more than not-bundled wire.

I think ebay prices (about \$2/foot for #6-3+ground; search for romex), even with shipping, will beat prices at (eg) Lowes or Home Depot, but haven't been able to make either of

or
reveal anything about wire heavier than #8, so that's just a guess. (When I bought about 90' of 3-cdr #2 Al and

1-cdr #4 Al at Lowes a few years ago, the price worked out better than ebay, due to sales, so it's worth going and looking.)

Use sweeps (big-radius ells) rather than the usual ells on turns, and it might make sense to pull the wire through any long straight sections and then slide the corner pieces near the ends onto the wire, unless you like using a half-ton winch to pull the wire.

• posted

...

These ampacity tables never say what the conditions are for "Normal Amps" and "Max Amps".

Romex in air? Raw wires in conduit? Buried? Transformer winding?

From the other responses, it's sounding like you're looking at 2 AWG.

Good Luck! Rich

• posted

James Waldby wrote in news:X7idnUE4t560kljXnZ2dnUVZ snipped-for-privacy@bresnan.com:

#6 copper is perfect for 30 or 40 amps at that distance. Go any bigger and you will likely have problems fitting it in the breaker you have.

Adequate I guess for what you have mentioned - so far. Personally I like to size home shops for 60 amps. That allows a buzz box welder or 5hp compressor motor to be used without trouble. There's nothing like finding a great deal on a tool and realizing you don't have enough juice to run it. #2 aluminum would be good for 60 amps at that distance, probably similar price to the #6 copper.

Use underground rated cable unles you are prepared to deal with pull boxes and conduit bending and assorted stuff to pipe everything from panel to panel. Cable lets you run through the house and bend easily as many times as you need to get into the conduit just before it goes underground. My charts show less than 3% drop on #6cu at 30 amps for that distance, that's pretty good.

Too big to be worth the effort, at nearly any price.

Cable is physically harder to pull - more weight and less flexible. Heat is irrelevent when the wire is upsized for distance like this and burried and never going to see continuous full load.

Get him to tell you what cable or wire to shop for. He will be familiar with your house and be best to advise which method to choose.

Romex isn't suitable for underground. Even if it is in conduit it needs to be a wet location rated cable or conductor to be in the ground.

• posted

I realize that, and only mentioned romex as a tag to find the \$2/foot auction for a representative price point. Unfortunately, insulation type letters like RHW, THW, THHW, and XHHW don't seem to be particularly useful for ebay searches.

• posted

The handbook says for a 2 % voltage drop over 200 ft. to use #4. So your electrician is about right with his suggestion of #6.

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.

Steve

• posted

60A may be plenty for a home shop woodworker, but is pretty feeble for a home shop metalworker. I ran a 125A sub panel for my shop, and can readily push it to near capacity (intermittent) if I'm doing heavy welding + shop lighting + shop A/C.
• posted

That #6 will have ~.5 ohms impedance /1000 ft or ~ .1 ohms for your

200' [Assumes single conductors) at 35 amps (more than you should ever draw with your breakers) you have 3.5 V drop on each leg, or 7 V total. If your Voltage is already down to 200V, that would give you only 193V at that load.

"SteveB" wrote:

jk

• posted

Forgot to include some pertinent information:

The most that will be used will PROBABLY be a Lincoln 175SP+, some lights, and hand tools, one at a time. And then in the winter, a 1,000-3,000 watt heater. I have a Lincoln SA 200 for any heavy welding, so doubt I'd ever hook up a buzz box. However, later, who knows?

Steve

• posted

I'd use stranded wire if you can get it. Likely that is all you can get.

My charts show for #6 it has a cir. mil of 26250 and a resistance of .395 ohms / 1000'.

E=I*R - 30a * .395 * 190/1000 = 2.2v or so at 30 amps. for #6 at 30 amps 190 feet.

Now for the facts - double it - since you have the hot wire to and back - even you run 220 - effective the same.

So for 30 amps you get 5v drop. for 22 - 22/30 * 5v ~ 3.5v

That assumes 68 degrees - warmer will be slightly higher voltage dr> FACTS:

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