Shopsmith Forums

How much current does your Mark V draw?

There has repeatedly been a lot of discussion about current requirements, breakers and wire size for Mark V installations. However, no one has reported any empirical data about the voltage/current requirements of a Mark V.

I wonder if anyone has ever taken the time to measure the current.

I discovered today that I had an old Simpson Multimeter that could measure that current so I did. Now I am even more curious about that information.

Using a real kludge hookup I measured steady run current at a bit less than 8 amperes. This current did not change as a run the speed up and down. I did not load the motor because I could not safely do that and monitor the meter at the same time. The max AC current capability the meter is 30 amperes. At start up and for a very, very short period of time the needle was defected to almost maximum (30 amperes).

SO WHAT.

Well, I have always suspected that much was being said about needing 20 ampere breakers and #12 wire that can not be substantiated.

I shall be doing more testing and will report my observations when I have them done. You can then do as you see fit with that data.

If you had a video camera, you could record the multimeter while running various load tests safely. You'd have to provide verbal cues as to what you were doing to load the ShopSmith.

That sounds like an interesting project, Dusty! I hope that you are able to get us some results. As far as actual requirements, SS printed in my owners manual, on page A-3, that for the Mark V (highlights are mine),

The wall receptacle and wires in the circuit must be rated for at least 15 amps.

Of course that leaves open the use of 20 amp circuits, even though they are knot, strictly speaking, required. As I have reported in another thread, I have used 15 amp circuits to operate my Mark V. It has been my experience, that when operating on a 15 amp circuit, the draw from the Mark V creates issues, such as lights dimming, which of course is explained by the nearly 30 amp spikes that you mention.

Dusty
Once again your right the Shopsmith doesn't require 20 amp circuit. That is a fact. That fact is proven by the fact they have a UL certification. To get a UL approval the tested device (110 AC voltage) must be able to run on a normal 15 amp circuit.

That said the bigger the guage of wire the less voltage drop the circuit will experience. Hence a 12 guage circuit will have less voltage drop than the same length 14 guage circuit. The closer to 110 volts the Shopsmith motor sees the lower the amperage it will draw and the less heat will be generated. Heat is power wasted!

While I have no empirical data to prove what I say, my experience with my SS has convinced me my SS works better being on a total 12 guage circuit.
By total I mean my circuit from the breaker to the receptacle is 12 guage as is the line cord (plug to SS motor).
To me the difference was night and day. The biggest change I saw was when I changed my line cord to a 12 guage wire, however that was to be expect since my shop was alread 12guage wired.

I really don't remember if the breaker I used was 20 amp or a 15 amp (I suspect it is a 20 amp but I will look tomorrow).

Before I collect all of the data on current draw, I would appreciate some feedback on Mark V power cord characteristics.

What I would like to know is what resistance does every one see when measuring the resistance looking into the Mark V with the power switch turned on.

To do this, you must have a Volt/Ohm meter. Then you simply UNPLUG your Mark V and after turning the Mark V switch to the on position measure the resistance as seen across the two prongs of the AC plug.

This resistance includes that of the power cord, internal headstock wiring, the start winding, contacts through the centrifugal switch and the on/off switch.

Mine measures .82 ohms on the Mark V and .80 ohms on the Crafters Station.

Also, I have a 15' extension cord that occasionally gets into the setup. It measures .39 ohms round trip (ie approximately .2 ohms on each conductor).

I would like to say thank you for your inputs in advance.

A fellow at work showed me a device he picked up at an electronics store in Indy. It's made by P3 International (http://www.p3international.com) called the Kill A Watt. It cost $20. It displays 8 units of measure: Volts, Amps, Watts, KWH, Frequency (Hz), Volt Amps (VA), Power Factor (PF), and elapsed time. He used to check the how much power our servers were drawing.

Sincerely,

Ron

1 1/8 HP Goldie 230v with original linecord(plug changed to 230v). 3.1 Ω.
I assume rewiring windings from series to parallel(230v to 115v) would result in a reading approximately half that(the linecord resistance is a constant).

3/4 HP Power Station 115v with linecord of unknown origin. 1.3 Ω.

I know this looks suspicious, but that IS what they measured.

Will measure no load run current when I locate my clampon meter.

1 1/8 HP Goldie 247v 3.6A (no load). === 7.2A @ 123.5v?

3/4 HP Power Station 122.5v 8.8A (no load)

In an effort to ascertain just how much current capacity our shops need, I have compiled the following information for some items of equipment in my shop.

This information is nothing more than that. It is data collected in only one shop and should be taken to be nothing more than that.

Dust Collector

The DC3300 draws nearly 25 amperes at start up and then after only a couple seconds settles in to run at 8.0 amperes. Closing off or opening the three portals seems to have no effect.

I was surprised at the amount of current drawn by this device.

Florescent Lights

My ceiling hung florescent lights (six tubes) draw .9 amps after a short start up time when they draw .2 amperes.

Worksharp

When I first turn on the Worksharp (sharpening station) it draws 1.7 ampers. And then settles in at 1.4 amperes.

Crafters Station

The Crafter’s Station exhibits characteristics almost identical to the Mark V. It is a power hog for about 2 seconds (at statrup) demanding 26-26 amperes and then it settles in at 8.0 amperes I was surprised to learn that current demand does not change as a function of speed. Don’t confuse this with loading.

Mark V

I collected data on the Mark V in two differebt configurations. I did one test with the Mark V plugged into a 15’ extension cord (14ga) and the other without the extension cord.

With the extension cord, the momentary (about 2 sec) startup demand current is just a bit below 30 amperes. Once the Mark V reaches run speed, the current draw settles at 8.0 amperes. Starting up at low speed is slightly different than starting up at high speed. There is a slight difference in the duration of time when the machine draws that extra “startup current”. With the machine set at saw speed, the peak draw lasts for about 3 seconds.

Without the extension cord, the momentary (about 3 sec) startup demand current is still 30 amperes. Once the Mark V reaches run speed, the current settles in at 7.5 amperes.

While ripping ½” and ¾” stock, the current draw increases to between 8.5 and 9.0 amperes.

While “attempting” to rip a piece of 2” alder, the Mark V was laboring. I had to back off to keep from stalling the motor. I saw current draws as high as 20 amperes. I did achieve a clean cut but had some burning (on the piece against the fence). The cutoff was not discolored and the cut is clean. I was using a heavily used blade but one that is still reasonably sharp.

If I had not backed off when the Mark V labored, I could easily have tripped the 15 amp breaker that I was operating on. I normally operate on a circuit that has a 20amp breaker.

All but two of my power feeds throughout the house/shop are via 12 gauge wire. EXCEPT When the house was being built, I initiated a change order to sheet rock the garage. When they did that, they also put in two outlets and a ceiling light that were done using 15 ampere breakers and 14 gauge wire. If I had realized, that would have been changed.

I believe that if I did not have time-delay breakers, the startups currents could be high enough and long enough in duration to trip the breakers

dusty wrote:Before I collect all of the data on current draw, I would appreciate some feedback on Mark V power cord characteristics.

What I would like to know is what resistance does every one see when measuring the resistance looking into the Mark V with the power switch turned on.

To do this, you must have a Volt/Ohm meter. Then you simply UNPLUG your Mark V and after turning the Mark V switch to the on position measure the resistance as seen across the two prongs of the AC plug.

This resistance includes that of the power cord, internal headstock wiring, the start winding, contacts through the centrifugal switch and the on/off switch.

Mine measures .82 ohms on the Mark V and .80 ohms on the Crafters Station.

Also, I have a 15' extension cord that occasionally gets into the setup. It measures .39 ohms round trip (ie approximately .2 ohms on each conductor).

I would like to say thank you for your inputs in advance.

Sorry Dusty, I have no working ohm meter at this time.