Extension Cord Question

[tubamonster]

I have a 3450 rpm 3/4 hp electric motor that came from a pool pump. The cord on it is only about 2 feet long. I am planning on using this motor to build a belt grinder, and I will need a 25 foot extension cord because their are only a 3 electrical outlets in my garage. The cord on the motor is 12/3. Because it is a pool pump, it says do not use an extension cord. I figure using an extension cord shouldn't be a big deal considering it will be nowhere near water and plugged into a GFCI outlet.

My question is do I need a 10/3 extension cord or will a 12/3 extension cord do just fine? I'm on a serious budget and cannot afford to spend a few extra dollars for a 10/3 extension cord if it isn't absolutely necessary.

 

[metaleltr]

12/3 should be fine, chances are the wires in your walls are also 12 gauge

 

[malibu101]

I agree that a 12 gauge cord will be fine.
You are probably plugging it into a circuit that is protected by a 15 or 20 amp breaker. Right?

For this application I would certainly use no smaller than 12 but I can't see a real reason to go larger than 12 either.

 

[Falcon67]

12 gage will be fine. I built my building with a 1 1/2 HP compressor on the end of a 50' 12-3 cord.

 

[larry_g]

I have a 3450 rpm 3/4 hp electric motor that came from a pool pump. The cord on it is only about 2 feet long. I am planning on using this motor to build a belt grinder,

As others have said 12 ga should be fine. However pay attention to the grinder in operation as it is easy to overload the motor and put it to max current and beyond. If your using it hard enough to slow down the motor then back off a bit.

lg
no neat sig line

 

[RECox286]

Unsure of the reason for the warning about using an extension cord for the original

purpose of the motor, but since it is usually an outside application, I should think

that the use of an extension cord puts more connections in the circuit.


More connections to become corroded, and cause more resistance/heat, more

resistance, equals a burnt up cord or motor. (guessing but seems logical)

Since most people are unaware that extension cords come in different gages, I

might also expect to find a piece of 16-2 cord inbetween the receptacle and the

motor ! We do see anything and everything out in the field, do we not ?

Uncle Bob

 

[rodm1]

The warning is for people like my Mom that use a 16ga extension cord to run the refrigerator and everything else! The wiring in your home is not much different then an extension cord just sized properly.

You should only buy 14ga or 12ga extension cords any ways.

 

[theoldwizard1]

Unsure of the reason for the warning about using an extension cord for the original purpose of the motor, but since it is usually an outside application, I should think that the use of an extension cord puts more connections in the circuit.

More likely the manufacturer did not want to see some one trying to run it off the end of a 100' 16/2 cord !

 

[tubamonster]

Thanks for the replies. I already figure 16 gauge wasn't a good idea. I'll be getting a 25 ft 12 gauge cord.

 

[Kevin C]

Assuming the motor draws 9 amps ( 70% efficiency, 100% loading) the voltage drop on a 25 foot, 16 gauge extension cord would be about 1.8% or 2.2 volts.

A 14 gauge gets you a 1.4 volt drop. 12 gauge .9 volts... 10 gauge .5 volts.

Also, this application should be intermittent duty VS a pump that can be used continuously.

With a 16 gauge cord, so instead of 120 volts you get 117.8.

I dont see any issue using a 16 gauge extension cord.

 

[rodm1]

The problem with under sizing your extension cord is you are making it a fusible link instead of the breaker being the week link.

 

[Alchymist]

Y'alll check it out for youselves!

http://home.mchsi.com/~gweidner/extension-cords.pdf

 

[Kevin C]

The problem with under sizing your extension cord is you are making it a fusible link instead of the breaker being the week link.

This is based on ? Are you saying that a 16 gauge cord will burn out before it clears a short on a 20 amp circuit?

The one second fusing current of 16 gauge wire is 377 amps. At 32 ms the fusing current is 2100 amps. I know that will trip my 20 amp breakers.

 

[theoldwizard1]

Y'alll check it out for youselves!

http://home.mchsi.com/~gweidner/extension-cords.pdf

The real difference between S and SJ cord is the voltage rating. S is rated for 600V and SJ is rated for 300V. The insulation on an SJ cord is thinner, meaning that 100' of that cord is easier to carry !