Estimating Shop Power Needs

Phil Dwyer

Phil Dwyer

Joined
Feb 28, 2006
Messages
3,494
Hi Guys,

The high school where I teach is moving. I've got to fit into considerably less space. On the upside, I'll have a 330 SF enclosed room this time along with a small 140SF outside pad (once I make it with my students). I'm not sure how I'll fit 15 students into 470 sq feet along with forges, work benches, etc, but we'll figure something out.

Anyway, I've got to get power usage requirements figured out for the site folks to work with. I've read most of the labels on the various pieces of equipment, but am stumped on a few things.

  • I can't figure out the draw on stuff I got them off eBay: a GE Motors K-3 180VDC motor (model 5CD123PEQ01B) to be controlled by a KBP1-240D Penta Drive.

    And for someday maybe...
  • What's the likely draw of a small lathe?
  • What's the likely draw of a small mill?
Thanks friends! All the best, Phil
 
A small lathe or a small mill can draw something like ten amps of 220. However, I suggest sizing your wire for more than enough ampacity because start up amps on a lathe can be pretty high, and voltage drop on small wire could starve a lathe on start up.

Also, think about a HT furnace, which might be 4000 watt = 20 amps 220. I ran 60 amps 220 to my little work shop, but sized the wire where it could handle 80 amps for reduced voltage drop over the run.
 
Once you have the power to the work shop, it is sent to a sub panel where you divvy out the power to the lights, wall outlets and machines with several different circuits with their own breakers. You may want the lights split between two circuits so they can't all go out at once. You will want 20 amps 115 on the wall outlets etc.
 
Do either of the items in question have the horsepower rating on the nameplate? The closest model document I could find on the Penta Drive suggests a maximum load of 2.0 HP at 180 VDC. If this is accurate then the max load would be 15 Amps at 240 VAC. You should then size the load circuit for 240 VAC and 20Amps. This is all dependent however, on the true horse power rating of the drive and motor.
 
Anyone who has wired a shop will tell you the rule:
Figure all the power you think you will need....and double it.

For the setup you describe, I would put in a 300 amp box with two thirty amp 120V circuits, three twenty amp 240V circuits, the inside lighting will be on two 20 amp 120V, outside lighting 20 amp GFI 120V, inside wall receptacles on two 20 amp 120V, outside receptacle on 20 amp GFI 120V, and five 20 amp 120V circuits. ( I know that will add up to 400 amps, but all circuits will not be on and at full draw at one time)

Make sure there are lots of wall receptacles and overhead lighting. Try and run dedicated circuits to the main equipment ( good for safety).

Stacy
 
I agree with Stacy. If you can afford it buy a 300 amp service and service feed. That way as you find the need you can add on to the system. If you have any plans at all for using a number of 220 feeds at one time you will need it.
Think of it this way if you only go with a 200 amp panel and then you see the need down the line you have to add or upgrade a panel, plus the sevice feed into the shop. Having enough power in a shop is kind of like having too much storage space. The initial cost may be more then you want to pay but the upgrade later will be even more expensive because of rewiring, adding another panel, and the additional service feed!
 
My lathe (LeBlond Regal 15C5) needs a 30 amp 220 feed (5 HP single phase 220 motor, the lathe was custom built to run on single phase instead of 3 phase so it could run on household power, 3 phase is expensive)
you are in a unique situation where you are doing the shop as a classrom, that means multiple tools running at once. I would set up at LEAST 200 amp service, more is better. I would put in a 30 amp 220 and a 20 amp 220 on each wall. Every 4 feet you should have a 20 amp 110 quad box at 4 feet off the ground. You should put 20 amp duplexes in the cieling on a 4 foot grid to cut down on cords on the floor and bench space. Flourescent lights should ring the outside wall with a grid of flourescents on the cieling for even shadowless glare free lighting. Divide your power up so that you have as many independent circuits as possible. Maybe 2 200 amp breakerboxes depending on your expected parallel usage.

More power is better:D

-Page
 
Just another vote for more power. Labor cost the same so you just have an increase cost for material. More than worth it in the long run.

My mill is on a 15 amps 120V but of course it's only a 1HP motor. More than enough for a small Southbend 9" and the kind of work I do.

Pad
 
I am running 20 amp for the 110V recepticals in my shop. Everything runs on 110VAC and have had no problems. When I first set up the shop I had only one 110VAC 15 amp. It worked okay if I only used one machine at a time, but the big problem was the surge on start, up for the grinder and dust collections systems. I upgraded the wiring to accomodate 20 amp fuses at the pannel, and its been working fine all these years.
 
personally I think if you are using 200 amps balls to the wall all the time you'll want to leave the schools wallet with the electric company :D :D

if you have questions about a motor that you can't Identify have a electrician test the draw of it in use..

I have a 600 amp welder and didn't know what I would use for consumption with it, when I set it up..
I got the largest drag rod that I'd possibly use and had the line checked as I was using it. it was at 50 amp so I put in a 60 amp breaker for it.. it's never tripped in the 25 years since..
 
Phil, hope all is well. To help 1 hp is 746 watts, or at 120 volts that 6.2 amps. Your typical wall circuit is 20 amps. Are you running new wire to a seperate box off the school service. The service drops have more than enough power to meet your needs the critical step is from the box to the wall.

Either way figure 1-2 hp for all you want to run, if you will have multiple tools operating you need to figure your amperage from there.
 
When doing the planning, it isn't so much the actual draw as it is the number of circuits that you plan for. Making dedicated circuits for each major piece of equipment is the way to go. Most shops will only draw 50-70 amps at any one time, but there will be those occasions when the Paragon is running, and the forge is running, and both grinders, and.........well, you see how the draw can occasionally get up there pretty high. In a good size shop, just the lights and always on things (clocks, computers,fans, etc.) may draw 30+ amps.
Stacy
 
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