Table Saw wiring problem...

[Brian Fulkerson]

I have run into a problem and I have a question.

I bought a new table saw that I was told draws 20.5 amps running. I realized that my existing dedicated 240v circuit is only 20 amps. I know that there are many solutions to this and I want to get your input on the one that was advised to me. (So far anyway).

I am running one strand of 1/2" conduit that feeds two circuits. One 120v and one 240v. The 240v has 12 ga wire running to it that is too small for higher amp ratings. This is what was told to me as a quick fix and relatively inexpensive solution.



Replace existing 20 amp breaker with 30 amp

Run 10 ga wire to replace 12 ga

replace existing plug with 30 amp

install a "30 amp fuse delay" to protect amperage spikes durring table saw startups.


I would install a 40 amp circuit though I want to avoid running another strand of conduit. Only 10 ga wire will fit with the other 120v circuit and remain in code.

Suggestions???

Brian

[Art Mann]

My first step would be to see if the saw would actally run on 240V with a 20A breaker. I say the chances are very good that it will. If so, then don't make any changes. If not, then do as you have proposed, but don't waste money on a special breaker. I guarantee you the saw will run on a standard 30A circuit. I believe you may have a misconception about startup current. You really don't have to worry about it because it won't last long enough to trip a standard 30A (and I suspect 20A) breaker. You absolutely do not need a 40A circuit and putting one in is a waste of money and effort.

[Brandon Shew]

20.5 A at 240V - that's a lot of current. Is it a 5 HP saw?.. I'd do what Art suggested and see how it runs on a 20 A breaker. Worst case you swap the breaker to a 30 A and run lower gauge wire.

[Rob Russell]

Depending on what conduit you ran, you could install a 240v, 40-amp subpanel via the 1/2" conduit. That means the conduit would have to be EMT and the raceway (conduit) would serve as your Equipment Grounding Conductor.

Rob
Addy protocol: unlicensed, homeowner electrician

[Richard Madison]

Brian,
Please describe the saw that you have. What you were "told" about the operating current may not be accurate.

[Joe Chritz]

A 5HP single phase will draw a bit over 20 amps normally and is designed to run on a 25 or 30 amp circuit.

The manual should list what breaker is required (minimum) for the saw. Size the wire to fit and you are GTG. I expect it is 25 or 30 amp which would require 10 gauge.

Joe

[Alan Schaffter]

Check the motor ID plate for FLA (full load amps). It must be a 5 hp, since a 3 hp Unisaw only draws around 13 amps. Last month I bought an old Delta 20" planer. Before I picked up and checked it out, an intermediary "said" it drew 40 Amps!!! One model had a 7.5 hp motor but is 3 phase, this one had a 5 hp motor. It had a 40 amp clothes dryer plug on it, but the truth is that it only drew slightly over 20 amps @ 240V!

[Darrin Vanden Bosch]

Just go ahead and replace the wire with 10 ga. and the plugs (male and female) and the breaker with ones rated for 30 amps and I would replace the emt with a 3/4 run. It will be a lot easier to pull the wire in, trust me on this. Minimal cost and its done and safer and correct (if done right that is).;)

Darrin

[Rick Christopherson]

I'm with Art on this one. You already have the 20 amp circuit in place, so there is nothing to lose in trying it out first. If the motor is rated for 20.1 amps FLA, then the only time you will hit 20.1 amps is if you nearly bog the motor down. It is pretty tough to bog down a 4 to 5 hp TS motor. If the circuit breaker trips frequently, then it is time to upgrade the circuit to 30 amps with #10 wire.

[Dennis Parslow]

I hope you don't mind me asking a similar question. If I should start another thread, please let me know...
I am getting my Jet 3 hp Xacta and just had my 100A Cutler-Hammer sub-panel installed. Bare garage walls with no ceiling yet, and I will be installing 2-3 receptacles on this one circuit in case I move the TS near the door on sunny days, etc.

I want to clarify a few things based on how you just answered his question. He may want the same answers...
30A Breaker - should this be a 2 pole, 240v GFI, or other?
10/3 wire, right?
Exactly which male end do I need?

Thanks,Dennis

[Tom Veatch]

...
I want to clarify a few things based on how you just answered his question. He may want the same answers...
30A Breaker - should this be a 2 pole, 240v GFI, or other?
10/3 wire, right?
Exactly which male end do I need?
...

If you're running a 240v/30a circuit, you will need a 2 pole 240v breaker and 10ga wire. If you're using NMC then you'll need 10/2 cable (2 conductors + ground). You'll need NEMA 6-30 plugs and receptacles for the 240v loads. You can use the white wire in the cable for the second "hot" conductor, but you should identify it at the receptacle boxes with something like colored shrinkwrap (some color other than white or green).

You only need 10/3 cable (3 conductor + ground) if you want to make 120v available on the circuit. In that case you'll need NEMA 5-30 plugs and receptacles for the 120v loads.