Asking for help. Have a General 350 table saw not currently hooked up. Will be moving it to a barn/workshop. Motor specs are: 3 HP, 220 V, 1 Ph., 11.7 A Will 10/3 w/ground and a 30 A 220 breaker satisfy the load requirement? Thanks for any help. Dick in Texas
That's really too much breaker for the saw. A 15A (double) breaker ought to work just fine. Likewise, the wire can be 14/3 if the saw is the only load. Use 20A and 12/3 if other items will be on the circuit at the same time (dust collector, for example).
Joe
Dick
No one can answer your question without knowing if you are referring to the branch circuit in the barn/workshop and or the feeder to the barn/workshop. We would also need the number of wire feet in each circuit.
-- Tom Horne
Actually 12/2 w/ground would do on a 20A DP breaker. No need for the neutral on that saw.
sOn 2/13/2009 4:10 PM Joe spake thus:
True. However, 10 ga. wire won't hurt; it'll make sure there's less voltage drop, with the saw less likely to bog down on heavy cuts. If you don't mind the little extra $$, use #10. (No need for the neutral, as someone else pointed out, so you can use 10/2.)
Actually, 14 gauge wire is too small. Motor circuits are sized differently than normal circuits, see article 430 of the NEC for details. Briefly:
The requisite branch circuit ampacity is 125% of the tabular current value determined from the motor HP and voltage--you don't use the name plate current. That tabular value is 17 amps for 3HP 240V, and 125% of that is 21.25 amps. That means at least a #12 Cu branch circuit, which has an ampacity of 25 amps. Note that the small conductor ampacity limits of 240.4(D) [#14 = 15A, #12 = 20A, #10 = 30A] do not apply to motor circuits.
If the branch circuit is protected by an inverse time breaker (the usual thermal/magnetic breaker), it can be sized up to 250% of the tabular current value. The oversizing is allowed because (1) the motor must have its own overload protection, e.g. an integral thermal protector, so the breaker is only protecting the branch circuit from short-circuits and ground-faults, not overloads and (2) the motor starting current will be much higher than the full load current, so an increased size is needed to avoid nuisance trips.
For this motor, 250% of the tabular value of 17A is 42.5A. This can be rounded up to the next "standard" size of 45A (which may not be commonly available), so you can use a 45A breaker to protect your #12 Cu conductors. But I'd probably start with a 30A breaker to be conservative, and only use a larger breaker if there are nuisance trips on starting.
Yours, Wayne
Dick
No one can answer your question without knowing if you are referring to the branch circuit in the barn/workshop and or the feeder to the barn/workshop. We would also need the number of wire feet in each circuit.
-- Tom Horne
Tom
I think the following will describe my situation: Power underground from pole to meter on house (320 A service). From circuit box at house through garage to barn on a 100 A breaker. Garage is separate from house. Distance from meter to barn is about 70-80 feet. Someone who knows this stuff will be wiring that part but, to conserve a few $ I'm going to pull the wires inside the buildings from the breaker boxes. I'd like to do it right and safe. There will also be a 2 HP dust collector involved but I have a gizmo that starts the collector automatically a couple seconds after the saw starts running. I apologize for perhaps not using correct terminology. Thanks for your input. Dick
If you're contemplating more than just the saw in the future on the circuit I'd go w/ the 10/2 (as somebody else noted, for a 2-pole standard 220V outlet you don't need the neutral; that's needed only for dual-voltage stuff like ranges and clothes driers, etc.) although 12/2 would be plenty for the saw alone.
Also, the comment someone made about the breaker being too large for the saw--the breaker is there to protect the wiring, not the load and 30A is fine. A 15A would likely cause some nuisance trips. There will be overload protection at the motor itself for the purpose of protecting it; that's not the function of the circuit panel breaker.
--
I used a #10 wire for a 220v circuit installation, not that it needed it, but more that's what I had available at the time. I run a 3HP saw, 1.5 HP DC, 4HP lift, possibly all three running at the same time. Working with #12 is certainly easier than #10, glad there were only 5 outlets to fuss with. I guess a more interesting question is what is the maximum distance using 10/3 wire with a 3HP load? BTW, nice table saw choice.
These are all 220V motor loads? I assume you mean that each one has its own circuit wired with #10 copper. If they are all on one circuit, it should be #6 copper, as the required ampacity is 55 amps.
Cheers, Wayne
You bet! It's a great saw. I bought it about 15 years ago. Table extends over 5' to the right of the blade. Using a Paralok fence that operates like a drafting table. Sets up super accurate. Unfortunately Paralok is out of business. Dick
THEM AND A WHOLE LOT MORE WILL BE BEFORE OBAMMY IS DONE.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.