20A or 30A breaker for G1023SLX TS

[Ryan Marcoux]

I just got my G1023SLX!!!! The question I have is that the manual says to wire to a 20A, 220V breaker but both electricians that I talked to want to put a 30A breaker in because the motor draws 18A, what would you do or what have you done?

Either way, I assume 10/2 wire will be sufficient, any thoughts?

Thanks!

[Steve Clardy]

My older 1023 is on a 30amp
10 gauge wiring

[Greg Cole]

Inrush current on starting that motor will be much higher than the listed 18A. I''d go along with the electrician on the 30A breaker.

Cheers.
Greg

[Von Bickley]

Depends on the size of your wiring....

#10 copper - good for 30 amps.

#12 copper - good for 20 amps.

[Montgomery Scott]

That seems rather odd that the motor draws 18A as I assume it's a 3hp motor. My unisaw states it draws 12A. I have it on a 30A circuit as I also use the circuit to power my 4.8hp MM16 that has a stated current requirement of 22A.

[Curt Harms]

Disclaimer-I'm not an electrician or electrical engineer. Having said that I suspect a 20 A. circuit wired with 12-2 copper would be fine, 30 amp. circuit wired with 10-2 is fine as well. As far as inrush current, yup, it'd be more than 20 amps. I suspect it'd be a bunch more than 30 amps too but for less than a second. I'm pretty sure circuit breakers and wire will safely carry considerably more than rated amperage for short periods of time. The Grizz cabinet saws have magnetic starters that should include overcurrent protection for the motor.

Worth what You paid for it

Curt

[Jason Brown]

I think that 18 amp value listed in the manual must already consider the peak inrush current. By my calculation 3hp = 2237 watts. For a 220V circuit, this translates to about 10 amps. I guess I'd call Grizzly direct to confirm.

N.B.: I'm not an electrician, nor do I own a G1023.

[SCOTT ANDREWS]

I have my 1023 on a 20 A breaker with 10/3 wire and have never tripped it.

[Greg Funk]

If you're starting from scratch and wiring in a new circuit you may as well go 30A as the incremental materials cost will be small and you will have capacity for future growth in case you want to upgrade to 5HP.

Greg

[Chris Friesen]

I think that 18 amp value listed in the manual must already consider the peak inrush current. By my calculation 3hp = 2237 watts. For a 220V circuit, this translates to about 10 amps.

You forgot about efficiency and power factor. Rule of thumb is 5A/HP at 240V, so the Grizz motor is probably less efficient than some.

Normally the motor nameplate does not include inrush current, but is rather the "full load amperage" of the running motor. Peak inrush can be 4-6 times as much.

[Chris Friesen]

I just got my G1023SLX!!!! The question I have is that the manual says to wire to a 20A, 220V breaker but both electricians that I talked to want to put a 30A breaker in because the motor draws 18A, what would you do or what have you done?

The simplest route is to use a 30A breaker with #10 wire and a 30A receptacle. This would require changing the saw plug to a 30A plug as well.

The code is interesting for motors. Based on 430.22A, for "continuous" motor loads you're supposed to wire for 125% of the motor full load current rating. You don't actually have a continuous load, so based on table 430.22E a continuous-rated motor on an intermittent "tool head" load should have conductors rated for 140% of the nameplate. (Beats me why a continuous load needs less ampacity than an intermittent one...)

[David DeCristoforo]

Technically speaking, if the recommendation is for a 20A circuit, that's what you should use. The "logic" that, if you use a 30A circuit, you will have more "headroom" is flawed because the "protection value" of the rated circuit will be defeated. In a "perfect world" all of your 220 machines would be on dedicated circuits. The only reason to use a higher rated breaker would be if you plan to run more than one machine at a time on the circuit. But, as pointed out already, you also have to be sure that your wire size is correct for the breaker value.

[Gary McKown]

No expert here, but my experience:

My 5-YO 1023 was put on an existing 20-A circuit, #12 wire with a short 15-ft. run to the box (plus another 10 ft. with the cord). I have never had any indication that it does not work well.

The startup on mine is eye-blinking quick - much less than a second to full speed. At first, it actually kinda made me jumpy that there is almost zero wind-up, compared to the 2-4 seconds on the old Craftsman or my 2-hp DC. Makes sense, I guess, with 3-hp cranking only an arbor and saw blade. Sometimes I wish that it came with some sort of soft-start mechanism.

I do not have a peak-hold or surge ammeter, but I did measure the no-load running current at about 9 amps. Haven't measured it under load, but it has never labored even when cutting 10/4 oak material with a Forrest WWII, at modest feed rates.

[Rick Christopherson]

You don't need a 30 amp circuit, but it won't hurt either, so it all comes down to cost and convenience. If you are doing the wiring, working with #10 wire can be a pain, but if you are having the electrician install the circuit and outlet, then it makes no difference to you. If they are going to charge about the same for either size, then go with the #10, but if the difference is significant, then stick to the 20 amp circuit.

It is not necessary to derate the circuit (125% of load) because this is a cord and plug application, so it is perfectly within NEC code to use the 20 amp circuit for an 18 amp (max) load.

Furthermore, you will not likely ever load a 3 hp saw to the point of reaching its full load amperage rating unless the saw is in a binding situation, in which case, you would be happy to have the breaker trip. When idling, a motor will draw about 1/2 of it full load amperage, so this saw will be drawing 9 amps when not cutting, and about 15 amps when doing moderate cutting.

I also agree that the 18 amps FLA sounds incorrect for even a poor motor. Power = I x V x pf x eff, so with a low efficiency of 0.8 and a powerfactor of 0.8, the 3 hp motor would be drawing 14 amps FLA.

[Ryan Marcoux]

Thanks guys! I am going with 30A and 10/2 wire.