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View Full Version : five HP tablesaw, is 30 amps enough



Bill Dufour
01-29-2019, 3:29 PM
I am thinking about eventually upgrading to a 5hp tablesaw. Will my current 240 volt, 30 amps be enough power. I think if it is 3phase from a vfd the soft start function will mean 30 amps is good but I am not sure for a single phase motor.
How about 7.5 hp, how many amps will that need?
Bill D

Frank Pratt
01-29-2019, 5:01 PM
30A will be fine for a 5HP saw, especially if it's on a VFD.

Martin Siebert
01-29-2019, 6:02 PM
I have a 5hp Powermatic planer that is single phase. It says on the motor that it is rated for 28 amps. The owners manual says it requires 40 amp service. I have 30 amp Hubbel twist lock connectors on a 10ga stranded wire cord. It works okay, but the lights blink slightly when I turn it on. Probably the start capacitor.
I bought it used and the guy that had it had a 12 ga cord with 20 amp connectors...he ran it for years that way, but it really did blink out the lights with that set up. I noticed the cord was getting warm and that plus the lights blinking prompted me to check out what was required per the manual. Bottom line, check the manual and see what it says the machine should have or consult an electrician. One things for sure, any violations of the NEC and your insurance co wont pay a claim {i.e., a fire in the shop, whether or not the saw caused it.}

Frank Pratt
01-29-2019, 6:24 PM
28A is in the upper range for a 5 HP motor. 20A - 23A is more common. And with a VFD the starting current can be very low, so a 30A circuit will probably be fine.

Ole Anderson
01-30-2019, 9:03 AM
I know there is more to it with motor wiring, but I use the 80% rule, so a 30 amp circuit is good for 24 FLA (full load amps) probably on the conservative side.

Frank Pratt
01-30-2019, 9:42 AM
The 80% limit has to do with continuous operation. A circuit breaker may experience nuisance tripping when subjected to over 80% of it's rated current.

Rollie Meyers
01-31-2019, 12:13 AM
You are going to have to use the NEC tables to size a motor circuit, a single phase 5 HP motor will need conductors rated for at least 35A, a VFD needs the circuit sized at 125% of the rated input of the drive.