Current Draw, How Much

[a1gutterman]

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&#8217]Mark V[/U]

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

Hi Dusty,

It looks like you are being quite thorough. Some of your results can explain why, even though a Mark V will work on a 15 amp circuit, it will work better on a 20 amp circuit. At a minimum, for those owners that do knot have the option of a 20 amp circuit, a person should knot be sharing the 15 amp circuit with any other "appliance" while using the Mark V on it. Are you doing more research, or are these the final results?

[dusty]

The only other test that I had planned was to record the changes in voltage, if there are any, when the Mark V blogs down.

Since the current changes, unless the resistance/reactance changes, the voltage must change.

However, if you have any specific questions that might be answered with this setup, I would be glad to do the test. Just tell me what you need to know.

[a1gutterman]

The only other test that I had planned was to record the changes in voltage, if there are any, when the Mark V blogs down.

Since the current changes, unless the resistance/reluctance changes, the voltage must change.

However, if you have any specific questions that might be answered with this setup, I would be glad to do the test. Just tell me what you need to know.

Thanks for offering, but no, I do knot have any quetions, except: What conclusions do you draw from this?

[dusty]

Current Draw, How Much

I started this thread with a purpose in mind and a purpose has been served. But the effort does not conclude with the results that I had expected. I have a pretty good background doing this sort of testing in the electrical fields so I thought I knew what to expect. I was wrong – grossly over confident to say the least.

I have always understood and agreed that when you operate the Mark V from a poor power distribution system that it would not perform as well as it could. I have always been confident that the power available in my shop was all that would ever be needed for the Mark V.

I have a dedicated 12gauge, 20 amp circuit available to power the Mark V. I occasionally take the Mark V to areas where the distribution system is not quite as robust. My Mark V funstions satisfactorily in all of these conditions.

When I saw the current fluctuations (demands) that I have previously reported, I decided that I needed to perform one more set of tests. I needed to operate in an environment where the current available was greater than what it is in my shop.

I have a 120 vac, 60 amp service line available to me. It is a drop that I had put in so that I could put ground power to my RV when it is parked in the driveway.

I moved the Mark V to a location where I could utilize that abundance of power. Following is a chart that shows my observations. One column shows the voltage changes that occurred at the outlet where the Mark V is normally plugged in. The other shows the same data only the Mark V is plugged into a 60 amp source.

I DO NOT RECOMMEND THAT ANYTHING GREATER THAN A 20 AMP SERVICE BE USED FOR THE MARK V but I do conclude, with no doubt in my own mind, that many of the blogging down problems that we read about can be resolved by simply making sure that the primary power source is adequate (120vac, 20 amp breaker, and 12 gauge wire) as a minimum. Less than that will result in poorer performance from your Mark V.


Unloaded................ 120-121 ....................... 121.4

Startup..................... 89 ............................... 101.2

Run Speed.............. 115-116....................... 118.19-118.35

Loaded................... 113-115......................... 118-119

Heavily Loaded....... 107,103,89................... 112 (some slowing but no bog down)

Using a heavier gauge wire, as I did, tends to reduce the line voltage drop and therefore results in better performance. However, doing this may be a code violation and more importantly a safety issue. I do not know enough about this to comment further.

I am concerned that making available a more abundant source of current so that you can allow your Mark V to labor harder and longer without popping a breaker could do serious damage to the Mark V motor. This is the only reason why I recommended using nothing greater than a 20 amp breaker.

[JPG]

It would be interesting(enlightening) to observe the current draw when loaded and when near bogging with the 20A AND 60A sources. I anticipate(guess) the currents would be less with the 60A source. Not sure exactly how the ss motor will react. I presume since the bogging down does not occur as readily with the higher voltage when loaded and when connected to the 60A source that more power is going to mechanical effort rather than increasing the temperazture of AZ!

[Ed in Tampa]

Current Draw, How Much
Using a heavier gauge wire, as I did, tends to reduce the line voltage drop and therefore results in better performance. However, doing this may be a code violation and more importantly a safety issue. I do not know enough about this to comment further.

I am concerned that making available a more abundant source of current so that you can allow your Mark V to labor harder and longer without popping a breaker could do serious damage to the Mark V motor. This is the only reason why I recommended using nothing greater than a 20 amp breaker.

Dusty
I concur putting a Shopsmith on circuit with a breaker larger than 20 amps is asking to destroy the Shopsmith. In fact I'm not real sure it is a good idea using a breaker bigger than 15 amps.

However the circuit itself should be at least 12 guage wire. I think I'm safe in saying (code wise) in most places you can use a smaller breaker with larger gauge wire but not vice versa.

I think the ideal situation for most would be a 12 guage circuit with a 15 amp breaker. You should have all the power you need but if for some reason there is a current draw that will damage the SS the breaker will blow before the SS fries.

Personally if I ever have to wire a new circuit for the my SS I will probably pop for 10 guage wire (to miminize line voltage drop). I also have a 10 gauge extension cord which I use if I ever have to run my SS off an extension.

I'm a big believer in the damage to motors caused by running motors on circuits with more than a few percent voltage drops.

[JPG]

. . .

I'm a big believer in the damage to motors caused by running motors on circuits with more than a few percent voltage drops.

Which IS a reason to believe that a 60A(due to decreased voltage drop) source IS better! However the load(MOTOR) is NOT being protected by the 60A breaker.

Using wire LARGER than the minimum size for a given breaker IS required on long runs where the voltage drop would be excessive with 'minimum' sized wire. IMHO I see no difference between long run requirement and our need for our SSs!

The best way to wire a 'shop' is to run a feeder from the 'main' breaker panel to a feeder panel in the shop using very large conductors. This feeder panel would contain all the breakers for all branch circuits in the shop. This minimizes the length of smaller conductors to within the shop area. Should a breaker trip, it is far more convenient to walk across the room to reset it!

Part of my thinking re 60A is better depends on my presumption that the CURRENTS for various load/voltage drop conditions as done by dusty are LOWER for the 60A setup.

[dusty]

.....Part of my thinking re 60A is better depends on my presumption that the CURRENTS for various load/voltage drop conditions as done by dusty are LOWER for the 60A setup.

I did not do the current test while using the 60amp source but it is safe to conclude that the current is proportionately less.

I say that simply because the voltage drops (which I did record) are a function of current drawn and the resistance of the line. The primary source voltage (measured at the breaker) did not drop. The resistance of the line was less because part of it was much larger gauge wire thus the decrease in line loss. When the current demand did go up (start up current as an example) the voltage decreased by a lesser amount because the line resistance was less.

We must keep in mind the fact that just because there is a 60 amp source available does not mean that a good motor will draw anymore than it would with a 30 amp source available.

[a1gutterman]

Hi Dusty,

I appreciated your efforts and I am glad to see that you have joined those of us that think a 20 amp circuit is best (although knot required). I agree completely with your conclusions as quoted:

I DO NOT RECOMMEND THAT ANYTHING GREATER THAN A 20 AMP SERVICE BE USED FOR THE MARK V but I do conclude, with no doubt in my own mind, that many of the blogging down problems that we read about can be resolved by simply making sure that the primary power source is adequate (120vac, 20 amp breaker, and 12 gauge wire) as a minimum. Less than that will result in poorer performance from your Mark V.

In regards to your quote;

Using a heavier gauge wire, as I did, tends to reduce the line voltage drop and therefore results in better performance. However, doing this may be a code violation and more importantly a safety issue. I do not know enough about this to comment further.

I do know that in the state of Washington, you can always use larger wire then required in any circuit. I.e., 12ga wire with a 15 amp breaker, and Ed in Tampa's idea of wiring with 10ga wire and a 15 amp breaker is also allowed. I can knot think of a single reason why that wood be a code violation any where. It might be difficult to get the 10ga wire secured to the receptacles though, and it is darn near impossible to use 10ga wire with those receptacles that you just slip the wire into the holes. But since that style of receptacle is knot intended (or built to handle) a 30amp circuit, they have done that on purpose.

Thank you again for your efforts, as you have documented the info that allows others to make an educated decision on how to supply electricity to their own Mark V's!

[a1gutterman]

...The best way to wire a 'shop' is to run a feeder from the 'main' breaker panel to a feeder panel in the shop using very large conductors. This feeder panel would contain all the breakers for all branch circuits in the shop. This minimizes the length of smaller conductors to within the shop area. Should a breaker trip, it is far more convenient to walk across the room to reset it!...

That is exactly how I wired the shop in my first home. I had bought a house that had an attached 2 car carport and converted it to a 2 car garage that also served as my shop. I had previously replaced the old electric hot water tank with a gas one, and was no longer using the 10ga cable for anything. When I converted the carport, the location of the hot water tank allowed me to use the no-longer-utilized 10ga wire to supply my shop with power. I used a sub panel with a single 15 amp circuit (for overhead lighting) and two 20 amp circiuts (one for each side of the shop). It worked great! When I designed and built my new home, I brought the power right to the shop, so that is where the breaker panel is located.