Motor quits

[cincinnati]

Here is a video to take care of your next question. Look at #3

http://www.shopsmithacademy.com/SS_Archives/SS111/SS111_Index.htm

[Ed in Tampa]

Ok, evidently the switch I got at the Home Depot was junk. I got a new Gardner-Bender DPST 20A 125VAC switch at Sears and now it works without shutting down, and starts every time. Yahoo!
The replacement cable I had put on it is a 14 gauge cable as is the 25' extension cord I have it plugged into. I was thinking I might need a 12 guage cable, but the 14 guage seems to be sufficient.

Thanks Rusty, Bill, and Bill.
My next question will be about lubricating this thing!

Ron309753
Believe me the 14 gauge isn't big enough. I had to replace my standard line cord and when I did I replaced it with a 12 gauge cord. The diffference was day and night. Before my SS ran perfectly and never blew a fuse but it would bog down at times. When I replaced the cord it acted like it had new life. I have done things on it that I know in the past would have bogged it down and yet it didn't bog at all. I'm totally sold on 12 gauge line cords in a dedicated service for the SS.
Ed

[a1gutterman]

Hi Ron309753,
Although using a 14 gauge power cord will work, it can heat up with prolonged use or frequent on and off changes. A 12 guage cord will not heat up and will help preserve your SS's other electrical components, like the motor and switch.:D

[BigSky]

Does using a heavier gauge power cord enable the motor to draw less current (thus less heat)?

[cowboyplus]

Does using a heavier gauge power cord enable the motor to draw less current (thus less heat)?

Yes.

A load (effective power) is the quantity of electricity, measured in amperes, multiplied by the electric pressure, measured as voltage available at the load, and is expressed in watts.

The motor rating is supplied by the manufacturer in watts. It is then typically simply split in two, divided by the average voltage and the result is the average amps (full load amps -- FLA).

Wire resistance affects the voltage first. A conductor will never supply the full voltage to the load as was available at the supply. When a conductor is undersized, either by gauge, loose connections, or by length [including the hard wiring from the breaker], the motor voltage is decreased. The load (motor) is however still requiring it's total amount of watts and the amperes increase proportionally and generate more heat.

There is a thermostatic overload protector inside the motor which trips on excessive heat and interrupts the flow of electricity until the temperature returns to a safe level.

This internal overload can also be a cause of premature shutdown either by being defective or it itself can be getting hot by excessive current draw, before the motor can physically be classified as hot.

Motor voltage needs to be measured at the motor (best with a full load) and the connections at the terminal block need to be verified solid (tight).
.

[Ron309753]

Ok, I'm convinced. A 12 guage power cable it is!

[BigSky]

I'm not convinced quite that easily. This is probably because I don't understand everything I think I know.

I have a book (from ACE Hardware) that tells me the resistance per foot of a piece of typical stranded copper 25' extension cord is .0405 ohms for 12 gauge and .0645 ohms for 14 gauge.

Actually, the booklet provides resistance per 1000' of cable; I calculated the resistance for a 25' length.

Assuming the Shopsmith is the load and it draws its full 15 amps, the voltage loss on the 14ga power cord would be .9675 volts ac (14.5125 watts) and the loss on a 12ga power cord would be .6072 volts ac (9.108 watts).

Does the 5.405 watts (.3603 volts ac) delta between the two cord sizes really make that big a difference.

I recently put a new 18' 14 gauge cord on my Shopsmith and it seems to be working fine. I replaced the cord because the connector was corruded (where it had arced) and the rubber insulation was becoming brittle.

Are you telling me that I screwed up and put on the wrong size wire and should do this over again?:confused:

[cowboyplus]

...

Are you telling me that I screwed up and put on the wrong size wire and should do this over again?:confused:

Not at all.

In our country, our electric voltage standard is 220 volts, split in half at the delivery point, resulting in the original 220 volt supply and two 110 volt supplies, by the introduction of a connection to the earth referred to as a neutral, to each supply. [This connection can (and frequently is) substandard at the utility delivery point, and results in as an example, a 135 volt supply offset on the other half as a 105 volt supply.]

Since the resistance with the carriers and extra demands on especially older installations, the utility voltage supply has increased over the years to a more common 240 volts and some localities will be as much as 260-280 volts in an effort to transport enough power to communities.

This increased voltage on a 15 amp motor will allow an example of a smaller conductor size being able to deliver the required power.

Your calculations are valid and your thought is based on having a near perfect supply of voltage delivered to the motor. When a voltage supply to your breaker box is substantial, you do need to add that delta to your calculation.

When you are getting a lower supply of voltage to begin with, it then is up to you to maximize and protect your investment.
.