The AM Forum

Howdy folks..

I'm busy building my new hamshack in the basement and it's time to start thinking about running some AC power lines from the breaker box. I need a 220v line to power the big solid state linear, which will draw about 25 amps at 220v. It's about 75 feet from the breaker box to the shack. Will 10/2 romex be a good choice or do I need to go with a more macho sized wire?. I know the bigger the wire, the less voltage drop but I don't want over kill..... wire is expensive these days!

Thanks.

#10 wire is good for 30 amps in residential wiring.  I would make sure it is 10/2 with ground or 10/3 if you are going to use it for 115 also.

75 feet is a long run I would do #8 for a 30 amp circuit. A long run for a 20 amp circuit I use #10. Not like it is that much higher. I see home depot wire prices have come down a bit. New NEC you need to run 4 conductors (3 plus ground) with a 4 prong socket.

      cm = (l I k)/ e      l is length ( both ways,  75 foot run = 150 feet), I is current, k is  14 for Cu, 17 for Al and e is the allowable voltage drop for the run.
The cm is circular mills...take the resultant , compare it to wire sizing table ( there is one in the Handbook) and pick the next highest AWG ..... 
     
      Its (almost always)  cheaper to go with stuff bigger than you think you'll need..... You could run a subpanel for the shack and have everything killed when you pull the big switch... ( run lights off the other panel and maybee a ckt for a clock and  807 cooler)

klc

Hi guys;

I'll go with #8 for the 220v amplifier circuit and a couple of #10 lines for the rest of the shack.

Whats with the 4 conductor wire and the 4 prong outlet? hot, neutral and 2 grounds?

75 of 4 cond #8, that's gonna be an expensive hunk of wire  :o

Should I specify oxygen free copper?  ;D ;D

 the 220 has 2 hots ......   Yes, get the 02 free and the cyrogenic treated also....

Forgive my ignorance.... single phase 220v.... hot#1 to neutral = 110v,  hot#2 to neutral = 110v, hot to hot = 220v, correct?...

neutral and ground are at the same potential, right?

Hi Glenn,

Red, Black:   240ac active legs

Wht:       neutral CT for the 120ac legs.

Green/bare:     "Earth" ground. (Chassis gnd of appliances and rigs)


red/blk:  240ac  out

black/wht   or  red/wht :  120ac out



The Earth ground and neutral may measure slightly different voltage potentials at times AWAY from the box - they are actually separate legs. The Earth ground is green or bare and all feed greens/bares get tied together at the main breaker box.

The Earth ground is what connects to the chassis of the rigs. Don't tie the neutral to the rig chassis', or tie it to the Earth ground away from the breaker box..  This is a lightning and safety precaution.  The Earth and neutral are tied together at the box but float when they come out to the various rooms.

In real practice I have seen variations of the above. But this is what was told to me from a guy who does this kind of work. Maybe someone else will have some more info.

T

You won't pass inspection if you use those colors and you will get zapped.  Black is hot, red is the second hot, white is neutral, green or bare is ground.  220V between black and red, 110V between black and white and 110V between red and white.  Just the opposite from electronics wiring where black is usually ground.   The hot leads connect to the brass colored screw(s), the white to the silver screw and the bare wire to the green screw.

That is correct.......white is NEVER hot if used as a feeder from the source.

You have two grounds so there is no current on the safety ground/ Yes they are connected at the panel. New stove and dryer sockets have 4 prongs 2 hot neutral and safety ground. White can be hot if you marke it with colored tape.
Say you run a 240 line for electric heat with 12-2 with ground. The white will be on one side of the 240 line. There is no center tap to the load yet a safety ground.
Tom Vu black is never a neutral in the AC world only DC.

" ...black is the color of death... "  1972  Mr. Williams, High Screwel electricity class....  

   "T"  has the correct dope ............   klc

Thanks for the heads up.  Funny, but I checked my own wiring and see I did it correctly - white neutral.

Before making the post above, I wanted to be sure and as luck would have it I pulled up an Austrailian 240AC standard on the web that uses black as neutral:  

http://www.accesscomms.com.au/reference/powerplug.htm

I corrected my post above to reflect the American standard..  ;D ;D

T

Ill remember that when I move over there....... ;D

Well Tom VK is on the bottom of the earth so they have to reverse the leads or go backwards

 ;D ;D ;D  hi hi FB, OM!

Thanks for the info guys. Now I know how to do it right!  ;)

I'll have to check the local code but I'm wondering about where the romex leaves the breaker box. It will be running through the garage external to the wall. Am I supposed to shove it through that gray plastic pipe?

You can use gray pipe which is very cheap. Outside rated wire is big bucks.
Home Depot has a good selection of clamps and fittings. I'm not sure about running multiple feeds through the pipe. This may require larger wire.

F.C. is correct on both counts.. UV proof wire is more 'spencive ; conductors in the gray electrical "pvc" get derated dependeng on various factors... If your going the pvc route, you may consider skipping the Romex and just run seperate conductors through... your going through 1/2 the work putting in the pvc ; why not just go fish???     klc

..... but is it ok to just nail bare romex up against the garage wall? (indoors) The only reason I'd be using the PVC is because I thought bare romex could only be used inside walls.

The bare wire is an idea, but since the garage part of the wire run is only 25 ft, I think it would be easier just to use romex inside the PVC for that short distance. The rest of the run will be in the ceiling and walls so I would have to go from indvidual wires to romex at the end of the garage.

Generall, "internal" wire should be covered. But you still have several options.

How are the walls constructed? Are they finished or are they open framed?..  Got a picture?....  If opened framed, drill through the studs, or run through the overhead. Fastening Romex to the surface might give your local inspector the hebejeebies.... If your going through the studs, try to drill through the middle of the stud. The inspectors worry that sheetrock nails(screws) will pierce the cable if mounted too close to the face of the stud. What your local jurisdiction finds acceptable may be an unknown untill the inspector shows up. Its usally better to follow the NEC code.....  A cup of coffee with the inspector before the work gets started may be helpfull to yall.  ( is that how you spell it?)

You have an option of using "Wiremolod" products. This is a kind of conduit/metalic cover for 'surface mount'. Run a Google on this stuff; you'll know what it is when you see it. It is worked  with a hacksaw, and the fittings are premade- no bending like with real emt. Personally, I think it looks unapealing, but thats just me... If your going the pvc, make sure you support the tub close to the ends, and every 3 studs or so in between ( I cant remember the code spec.)... 

Some more stuff ...I guess you have access to a Homley Depot... they do have quality lectrical stuff.. Buy a Romex stripper; they are cheep, save you lots of time and decrease your chance of cutting the cable conductors/insulation...  The UL ratings are Minimum ratings. Dont buy the  $0.49 switches, $0.99 recepticles, spend a few bucks and get the better stuff... that crap is a pain to work with and may fall apart whan you try to connect conductors to it ( really).....  I have a lot of respect for people in the Trades... As this little discussion illustrates,there is a lot more to construction than nailing up extension cords, or using garden hose for plumbing....    klc