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