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View bungy's profile

electric for shop

by bungy
posted 11-19-2009 05:34 PM


30 replies so far

View rustedknuckles's profile

rustedknuckles

160 posts in 2437 days


#1 posted 11-19-2009 05:39 PM

you need to add up your amp usage, lights, heat air con., etc., things you would normally run while in there then see if you have enough left to run the tool with the greatest draw. I have a one man hobby shop that I ran two 100 amp entrances to. Did I need that much? Probably not but I don’t have any power issues.

-- Dave- New Brunswick

View GMman's profile

GMman

3902 posts in 2383 days


#2 posted 11-19-2009 05:54 PM

All depend on the tools you’re going to use.
200 amps is large for a shop unless you have very large tools or some that runs on 220 volts
I have pretty well all the tools you need in a shop and I run on 60 amps.

View pete79's profile

pete79

154 posts in 1826 days


#3 posted 11-19-2009 06:05 PM

I run my garage on 15 amps. It’s WAY too low, but I only blow the fuse (yes, i’m still on fuses) if I run the shop vac, table saw, lights, and space heater all at the same time. This method stinks, so I just turn off the heater when i’m cutting. I’d have to imagine that with another 35 amps it would be fine, but like the others said – depends on what you’re running.

-- Life is a one lap race.

View GFYS's profile

GFYS

711 posts in 2156 days


#4 posted 11-19-2009 06:09 PM

Just because an appliance uses 220 volts does not mean it requires more amps.
The average modern HOUSE uses less than 100 amps.
I doubt a “hobby shop” would require more than 50 amps but…it depends on what your hobby is.

View GMman's profile

GMman

3902 posts in 2383 days


#5 posted 11-19-2009 07:59 PM

mics-54 that you are right re: 220 volt all depends on your tools and other appliances heaters, airconditioners etc.
Like I said I run on 60 amps 220 volt it is just like having 120 amps 110 volts.

pete79 you must change a lot of fuses and they are not cheap.

View GFYS's profile

GFYS

711 posts in 2156 days


#6 posted 11-19-2009 08:02 PM

not exactly…a 60 amp 220 breaker supplies 60 amps per leg or 120 amps total.
Oh you are right I misread it.

View reggiek's profile

reggiek

2240 posts in 1956 days


#7 posted 11-19-2009 08:18 PM

I wired my shop with a 50 amp load – for two reasons….I had a spare 50 amp breaker and the largest amperage I could carry on the 10 guage wire I had was 50…. To date I haven’t had any issues with popping breakers….or with any wires getting hot….I have run 2 – 220 tools (TS and Planer), the dust collector @110 and the shop lights all at the same time without any noticeable effect…not even a noticeable dimming when the TS kicks on.

-- Woodworking.....My small slice of heaven!

View a1Jim's profile

a1Jim

112295 posts in 2263 days


#8 posted 11-19-2009 08:26 PM

My take on it is ,it’s just like clamps you can’t have enough. I have a separate 200 amp service to my shop with about 100 (110) outlets on about 14 circuits and 12 (220) outlets on separate circuits and sometimes I wish I had more.

-- http://artisticwoodstudio.com Custom furniture

View LesB's profile

LesB

1069 posts in 2129 days


#9 posted 11-19-2009 08:42 PM

I think you are find for a “hobby” shop. Try not to run more than two large machine at a time and unless you are using electric heat there will be no problems. Be sure your wiring from the panel to the outlets is also up to the load you will put on it. I would suggest #10 wire all around but #12 will work on the 120v outlets. Be sure you follow the code and you should get a permit because if you do have a fire your insurance company may not pay should they become aware of wiring installed with out a permit.

Fortunately my shop is similar to a1Jim’s except it should have added more 240v outlets. I have had to add a couple using surface mounted cables )-;

-- Les B, Oregon

View pete79's profile

pete79

154 posts in 1826 days


#10 posted 11-19-2009 08:43 PM

Yep – I keep a box of fuses. The other night i had to change it 3 times!!! Stinks getting stuck in the garage with the door closed and all the lights off trying to find your way out.

-- Life is a one lap race.

View BlankMan's profile

BlankMan

1487 posts in 2038 days


#11 posted 11-19-2009 08:46 PM

I have a 60A Load Center dedicate to my workshop, it’s plenty because a max of 3 things, typically 2, are running at one time. That’s the cyclone and a machine, table saw or RAS or jointer etc. The 3rd thing kicks in if the air compressor is on. So if the TS, cyclone, and AC are running I’d be pulling 35A but that’s at rated for the TS, realistically I’m pulling about 25-28A so that’s my worst case. Plus a few amps for lighting which is a on it’s own circuit so I don’t lose the lights if something pops a breaker (which has yet to happen except for the new air compressor which is a whole other story).

So, for the 8 circuits in the Load Center I have one for lighting, one for the AC, one for the outlets in half the workshop another for the outlets in the other half of the workshop, then two 220V breakers. I divided up the two 220V breakers this way: Circuit 1&2 Cyclone 1-1/2HP & Jointer 1-1/2HP, circuit 3&4 20A Table Saw 3HP, Radial Arm Saw 1-1/2HP, Mill/Drill 2HP, & 180A MIG Welder. So the circuits are balanced and I never overload a single circuit.

Proper planning, efficiently balancing the circuits so some can handle two or more things at once negates the need for the brute force 200A approach for the single user. If this is a shop with multiple people running different machines at the same time that then changes the equation.

-- -Curt, Milwaukee, WI

View LesB's profile

LesB

1069 posts in 2129 days


#12 posted 11-19-2009 09:18 PM

Hey Pete. Yu need to add one of those automatic emergency exit lights (battery back up) that come on then the power fails (-;

-- Les B, Oregon

View rustedknuckles's profile

rustedknuckles

160 posts in 2437 days


#13 posted 11-19-2009 09:32 PM

Why hasn’t any one said it yet, in the words of Tim the Tool Man Taylor..”More Power” At the most I’d have 2 people in my shop, dust collection running, a 220 heater, a 110 heater, lights, and two big tools, (not us, I actually mean tools) I don’t even see a dimming of the lights, I figure it doesn’t cost me anything extra to have it so why not go with 200 amps….just me.

-- Dave- New Brunswick

View pete79's profile

pete79

154 posts in 1826 days


#14 posted 11-19-2009 09:41 PM

Les – I need a lot more than that – haha.

In all seriousness…if you’re just a hobbyist and generally working alone in a small space with only 1-2 tools running at a time, maybe some form of dust collection, and some lights – I would think 50amp would be fine. Heck I’ve managed on 15 amp – now that’s sad.

-- Life is a one lap race.

View Rick  Dennington's profile

Rick Dennington

3467 posts in 1880 days


#15 posted 11-19-2009 09:42 PM

I’m with Jim—the more clamps I get, the more power I need!!!!! lol.

Rustedknuckles: You had me for a moment—I thought you were bragging, or awlfully proud!! lol.

-- " I started with nothing, and I've still got most of it left".......

View GFYS's profile

GFYS

711 posts in 2156 days


#16 posted 11-19-2009 09:43 PM

I’ve built entire houses on a 20 amp circuit

View reggiek's profile

reggiek

2240 posts in 1956 days


#17 posted 11-19-2009 09:53 PM

I just noticed that my post did not have the last 2 lines I put in….well here goes:

I believe that Topamaxsurvivor is/or was a sparky. You might want to PM him and get his take (if he doesn’t see or post on this blog). He would definitelly give you the code take on this.

-- Woodworking.....My small slice of heaven!

View sIKE's profile

sIKE

1271 posts in 2439 days


#18 posted 11-19-2009 11:09 PM

When someone asks this question, I always recommend that they go out to the Orange box and go to the electrical section and pick up the book Wiring Simplified. It explains things very well.

The basic answer is add up the expected amperage of everything that will be running at once and you should plan for 10% over that to account for sudden surges.

AKA TS/Dust Collector/Air Conditioner/Air Compressor

Make sure you use the largest tools for the math part. If you have a bench top saw and a bad boy battleship sized Jointer …use the Jointer and account for the AMPs used on both legs.

Hope this helps.

-- //FC - Round Rock, TX - "Experience is what you get just after you need it"

View GMman's profile

GMman

3902 posts in 2383 days


#19 posted 11-20-2009 12:54 AM

mics-54 I believe you because building a house you’re using mostly one tool at one time and maybe a couple light which doesn’t take muck power that is way different hat working in a shop.
I still say that 60 to 100 amps is enough.
I have 35 years of electrical work.
My house is fairly large and I only have 125 amps entrance which also feeds my shop.

View TopamaxSurvivor's profile

TopamaxSurvivor

14849 posts in 2361 days


#20 posted 11-20-2009 06:29 AM

Pete, you should be using slo-blo 15 amp fuses for motors.

Joe, my Sq D motor calculator says to use 60 amp breaker for the 5 hp saw. It draws 28 amps at full load. If you run dust collector at the same time, you are probably marginal at 50 amps.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View BlankMan's profile

BlankMan

1487 posts in 2038 days


#21 posted 11-20-2009 06:57 AM

Hey Topa, I just went through an ordeal with my new Porter-Cable air compressor. It’s got a 15FLA (110V) Marathon motor Code J, when it tried to recharge it kept popping the 20A Square D breaker and it is the only thing on that breaker. So I replaced the breaker thinking it might be weak. No joy.

So I contacted Porter-Cable, Square D, Bussmann, and Marathon. PC was of no help, “take it the service center”. Square D after a bunch of prodding told me that a 40A breaker was required. Bussmann and Marathon got me on the right track. I finally determined that the locked rotor current on that motor was 129A, this was confirmed by Marathon. And when the compressor tries to restart with 100psi head pressure it may draw close to that, hence the 20A breaker popping.

What I finally did was put in a 30A breaker and wire it with 10ga to a fuse holder and put in a Type T 15A fuse. It popped. So did the second one. So I tried a 20A Type T fuse, that is working. Bussmann got back to me and based on the motor nameplate said I needed a 19A Type T fuse so the 20A fuse was ok.

When I told Marathon that Square D recommended the 40A breaker and would that then protect the motor, they backed out of helping any further at that point. But I sure wasn’t’ going to put in a 50A 110v outlet to handle that 40A breaker Square D recommended.

Does that jive with your calculator? There is no HP on the nameplate but if it’s efficiency is 80% I figure it’s 1.93.

-- -Curt, Milwaukee, WI

View TopamaxSurvivor's profile

TopamaxSurvivor

14849 posts in 2361 days


#22 posted 11-20-2009 07:17 AM

15 amps at 120 is about 1 hp motor. If you are going to try to start a motor at locked rotor current, you definitely need a heavy duty over current device ;-)) and you might even hear the conductors rattling against the walls of a metallic conduit!! Slow blow fusses are normally a little smaller than non-adjustable trip breakers in that type of situation.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View BlankMan's profile

BlankMan

1487 posts in 2038 days


#23 posted 11-20-2009 07:58 AM

Huh?

746 watts per HP, that’s 6.8 amps at 110V, is 1 HP at 100% efficiency. That’s why I used 80% efficiency, what most good motors are. So 1 HP at 80% efficiency is 932 watts, 8.4 amps at 110V. 15 amps at 110V producing 1 HP would mean the motor’s efficiency is only 45%. Maybe a Taiwanese motor but I would hope Marathon is better then that.

I got this from the engineer at Marathon I was dealing with:

For reference…
At 230V, 8amps equals about 2.0HP. Every +/- 4amps is going to be another HP.
So 10.0A would be about a 2.5HP motor.

So that would seem to say that 16 amps at 110V would be a 2HP motor. Half the voltage double the current.

So 4 amps per HP at 230V, 8 amps per HP at 110V. That indicates an 84% efficiency factor. He might have used those numbers because that’s the efficiency of their motors.

-- -Curt, Milwaukee, WI

View bungy's profile

bungy

24 posts in 2070 days


#24 posted 11-20-2009 05:58 PM

thanks for the info.

View rep's profile

rep

95 posts in 1795 days


#25 posted 11-20-2009 07:44 PM

Don’t forget to include room for future expansion and tool upgrades.

-- rick

View TopamaxSurvivor's profile

TopamaxSurvivor

14849 posts in 2361 days


#26 posted 11-21-2009 03:05 AM

Curt, All I can say is I have wondered the same thing for 40 years. As soon as I was told 746 watts = 1 hp, I had to calculate it on the next motor I hooked up. I was way, way off. I have asked a few engineers years ago, but never got a reasonable answer. I am using the code amp figure for 1 hp. The code tends to be on the high side, most motors come in a little under what they require to be provided for a motor circuit. I suppose the newer energy efficient motors might be a bit closer but I haven’t hooked any of them up for years. I’m mostly doing control work these days.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View BlankMan's profile

BlankMan

1487 posts in 2038 days


#27 posted 11-21-2009 11:15 PM

Topa, that’s why I use the 80% efficiency fator. No motor is 100% efficient and converts all the current to work. Sometimes you can get the efficiency of the motor from the manufacturer, the reputable ones, but not so much from the Taiwanese ones because they tend to be low.

I took apart a Taiwanese motor one time, the ones that have the nice black case with the cooling fins, they look impressive. What I found inside amounted to a washing machine motor. Not the nice round stator fitted to the housing and a full lenght rotor. A fricking square washing machine motor…

-- -Curt, Milwaukee, WI

View TopamaxSurvivor's profile

TopamaxSurvivor

14849 posts in 2361 days


#28 posted 11-21-2009 11:42 PM

I always wonder about the overseas junk without the proper NEMA labels. We (in the USA) started accepting the foreign motor starters about 25 yrs ago. They amount to what a NEMA control relay would be in terms of serviceability, longevity and the contact size. The NEMA stuff would last for millions of operations in normal rated use. Now, the normal cheapie junk lasts a 100,000 operations and you throw it a way. It doesn’t matter for the hobbyist, but for industrial use, it is garbage.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View BlankMan's profile

BlankMan

1487 posts in 2038 days


#29 posted 11-22-2009 05:05 AM

bungy, didn’t mean to hijack the thread I hope at least you found the info useful.

topa, I’ve got a horse and a half Taiwanese motor sitting on the floor in my basement never used. It came on my milling machne, it was supposed to come with a 2HP Marathon motor. When I pointed that out to Enco they sent me the 2HP Marthon and told me to keep the horse and half. They didn’t even want it back. Shows what they are worth. It was cheaper for them to let me keep it then pay for shipping it back.

If I get some time maybe I’ll open the horse and a half up and see what’s inside, and take some pictures if it too is a washing machine motor. Might be informative to some and explain why the Taiwanese stuff is cheaper, you’re not getting quality.

That’s why all my machines have Americen made motors, Baldor, Marathon, or Leeson. Marathon and Leeson happen to be in Wisconsin and I like to support local compnies also. Taking the Made in America one step further.

-- -Curt, Milwaukee, WI

View TopamaxSurvivor's profile

TopamaxSurvivor

14849 posts in 2361 days


#30 posted 11-22-2009 05:20 AM

I hope they keep making them, They may be the last Americans making anything?? Most of the old American companies outsourced and became garbage importers :-(( Look how far Boeing is behind on the 787. They won’t admit it, but global partners are not producing air worthy parts.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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