Proper cable for table saw

[rvcoaster]

this is interesting:

i have recently installed a subpanel in my detached garage. i ran #4 wire from the main panel in the house to the garage. i installed 6 20A circuits on four walls and ran 2 lighting circuits, 1 50A 220V circuit, a garage door circuit, furnace/outdoor lighting circuit. so far it all works great!

i am still deep in the build phase, right now i am working on the walls.

anyway i noticed yesterday that i had an issue with my tablesaw. up until yesterday i have had the TS close enough to the wall that i plugged it directly into the wall. TS is a 10" delta contractor, not a direct drive but a very heavy saw. when i have the TS plugged into the wall (12/2 romex) it starts up in around 1.5 seconds. i had it pulled away from the wall yesterday and had to use an extension cord, so i picked a decent 12/3 50' cable. plugged into this cable the TS starts slow and sounds like its working hard until it comes up to speed, takes maybe 3.5 seconds to fully start.

i'm not really seeing how 50' of 12/3 could cause enough drop to cause this issue. in any case, when the shop is done i wont have the TS located close enough to a wall to plug in directly, so i will need a cable. if 12/3 is causing issue, what cable can i use instead?

 

[theoldwizard1]

They do make 10/3 "portable cordage" (that is the industry terminology) as well as 10/3 extension cords. Not cheap ! Shop eBay. Some places will cut to order. Sometimes it is just cheaper to cut the female end off and use the rest as you power cord (that is what I did on a portable compressor).

All cordage should have lettering on the outside that indicates what the cord is made of and it intended use.

A short lesson in cord type

S - Service (standard) up to 600V
SJ - Service Junior up to 300V

E - Thermoplastic elastomer
T - Thermoplastic Insulation
(no letter implies thermoset "rubber" which is more flexible in cold weather)

O - Oil resistant outer insulation
00 - Oil resistant inner and outer insulation

W - Weather resistant (outdoor usage)

 

[Provincial]

Rule #1 on heavy draw power tools: Keep the length of the electrical cord to a minimum. Rule #2 on heavy draw power tools: Use the biggest wire size practical.

Your saw draws many times the rated amps while starting. A 12 gauge extension cord is OK for the running load, but it is limiting the amps on start up. Every extra foot of cord is choking the current flow during start up. A 10 gauge cord will help, but keep it as short as possible. theoldwizard1 has good advice. In additon to ebay, shop your local Habitat for Humanity Restore and look for an old heavy-duty extension cord to repurpose as a hard-wired cord for your saw. Often a contractor will donate a cord that has a repairable problem or which will work if shortened. Nowdays OSHA wants to see factory ends on extension cords, so perfectly repairable cords are tossed.

 

[Aceman]

Can you convert the saw to 240 volt?

 

[rvcoaster]

i do have quite a bit of SO, but its all 12 and 14 gauge. i havent figured out where the TS is going to live yet but i imagine at any location the total length of an extension cable would be around 10' to 20'

and yeah, it runs fine once its spinning but the start up struggles with the 50' cable. i imagine i may have similar issues with my air compressor and DC when i get to that point although they can likely live next to a wall.

 

[rvcoaster]

Can you convert the saw to 240 volt?

i actually dont know. i saved the instructions so it may be possible but i would have to look.

 

[Motofixxer]

I will echo what's been stated already

Can you convert the saw to 240 volt?

Also a good idea, my Tablesaw runs much smoother and more powerful running on 240v since I switched it.

 

[rwreuter]

this tool will have a name plate rating on it....that will tell you what is needed to operate it effectively.

can you locate it and tell us what is says....i think we will be better able to help you out.

 

[Greatbear]

Be careful of certain extension cords. A friend of mine had a 50' 12/3 cord he got from some fly-by-night tool sale. Nice heavy looking thing, with a triple tap on the end. When trying to use air compressors, miter saws, shop vacs or other high amperage stuff the power was down and the cord got quite hot. Come to find out this thick, beefy cord marked as being 12ga was at best 18ga internally.

He chopped it up and chucked it.

 

[bjcouche]

Also, you should try more than 1 cord of the same size and length. That 12awg cord you've been using for years may have a common problem. Often times the last foot or two near the ends get's broken and frayed internally to the cable from flexing over the years. Ever notice that an extension cable or large appliance cable is warmer near the ends than in the center? Your cable may be going bad and the table saw has exposed the problem. The last couple feet at each end might only be equivalent to 18awg while the rest is 12awg.. Try another extension cord before you rewire your saw or garage.
That said, a 12awg cord should be fine for a the saw itself, but if I were to be running it often on a 50' extension cord, I'd spring for the 10awg extension cord. The big box home stores even sell them, but they are pricey. I've noticed a difference in operation of my electric chain saw between 50 and 150fet of 12awg cord, so size does matter.

Brian

 

[Motofixxer]

so size does matter.

Yep, sure does, just ask her. I have, a yes from every one

 

[Falcon67]

Had that problem during my framing phase - my 1.5 HP compressor would barely start on a 50' 14 gauge cord. Spent $65 on a real 12 gauge cord and it fixed the problem. Some motors pull a lot of current on startup.

 

[porphyre]

Showing my ignorance here....

I'm in the same boat as the OP.

What's wrong with buying a $20 6' 10/3 dryer cord and putting new plugs on it?

 

[Falcon67]

Showing my ignorance here....

I'm in the same boat as the OP.

What's wrong with buying a $20 6' 10/3 dryer cord and putting new plugs on it?

Well, if you need 50' you are 44' short. You pay more for the cord - just buy 10/3 cord off the roll at the store in the # feet needed and add the plugs.

 

[SixStringMadness]

Starting-current (also called inrush) is the current drawn by a motor during its runup, or acceleration, to normal operating speed. Its value is in Amperes. Typically it can be from 4 to 8 times the rated current. Ignoring the transients of the first 2 or 3 cycles, then starting-current lasts from the time the motor is first energized (breakaway) until the motor nears full speed... often defined as starting-time.

If your piece of equipment has a nameplate, it should give the start-to-rated current ratio, Ia/In.

Starting-current magnitude is determined only by the motor's design parameters. Neither load torque, nor system inertia, influences its magnitude. However, they are extremely important for calculating starting-time.

Two caveats: 1) Wye-Delta starting limits acceleration duty (three phase power system); and 2) sizing of the motor's feeder conductors requires special attention to the derating factor.

Ohm's and Kirchoff's Laws can help you analyze what is happening. Per Ohm's Law, voltage = current × impedance. Per Kirchoff's Law, the sum of voltages around a closed loop must equal zero. If we assume a 0.5-ohm source impedance and a 10A nominal current on a 480V system, the inrush current can result in a drop of 30V to 50V. Therefore, voltage at the load would sag to 430V, down from the nominal 475V level. This sag occurs because the impedance of the motor initially (when the rotor is stationary) looks much like a short circuit. Once the rotor starts turning, the current decreases and eventually goes to a much lower, steady-state value. However, if a load change causes the motor to come close to stalling or remain in the locked rotor condition, another sag can result for similar reasons.

Adding additional length to the current conductors increases this voltage drop even further, thus extending the "motor-start-up" even further as you have experienced. To counter the voltage drop due to length, increase conductor size.

 

[pattenp]

Switch your plug on the saw to a 125V NEMA 5-20P and put in a 20A receptacle. Make up a cord using 10/3 and use hospital/industrial grade 5-20P and 5-20R. I believe the max terminal accommodation is #10 on the hospital/industrial grade plugs and connectors.