You size the OCP and min. branch circuit wiring off the HP rating...What model # dust collector is this? The motor nameplate says 22 amps continuous so I believe the minimum branch circuit wiring for a single motor @ 125% is 27.5 amps.
I wasn't aware there was a rule like that. Thanks.What model # dust collector is this? The motor nameplate says 22 amps continuous so I believe the minimum branch circuit wiring for a single motor @ 125% is 27.5 amps.
You know this, buz, but it's worth saying for others: What buz says is true for sizing the conductors; you must comply with the code for wiring the circuit that the nameplate says it requires. It's nearly always OK to underfuse a circuit, though. So you must wire a circuit sized for 40A. However, you can then put a 30A breaker on the circuit, and if it'll start on that without tripping, no harm done.If the manufacturer states it must be on a 40A circuit, it must be on a 40A circuit.
Except voiding the warranty. :whistling2:You know this, buz, but it's worth saying for others: What buz says is true for sizing the conductors; you must comply with the code for wiring the circuit that the nameplate says it requires. It's nearly always OK to underfuse a circuit, though. So you must wire a circuit sized for 40A. However, you can then put a 30A breaker on the circuit, and if it'll start on that without tripping, no harm done.
Really? I'm not saying they wouldn't, but how would they know? As long as the breaker doesn't trip, the circuit should behave exactly the same.Except voiding the warranty. :whistling2:
Thats interesting. I can use #12 and a 40a breaker if I hardwire. There would only be about 25' for cable, so the voltage drop would be trivial. I think a 40a breaker is overkill; I can use a 30a breaker can't I?You size the OCP and min. branch circuit wiring off the HP rating...
3 HP @ 240 v. = 17 AMPS
17 AMPS X 250% = maximum breaker size, = 40 Amp breaker
17 AMPS x 125% = minimum branch circuit wiring, = 21.25 #12AWG is good for 25 amps in this scenario,
This of course is for hard wiring the motor.
Do I run MC from the panel to the switch box, or can I run romex to a junction box and MC from the junction box to the switch box?I would be sure to hard wire it. You will need to run some sort of conduit to the dust collector I would run mc wire or liquid tight. And I would also do a 40 amp circuit to the dust collector.
For bonus points, if someone wants to explain how a 3hp motor can draw 20a, I would like to know. I thought maybe that was with no load, but it is 20a while working the machine. Seems really really high.
Last time I checked, #12 needs to be protected by a maximum 20 amp breaker.Thats interesting. I can use #12 and a 40a breaker if I hardwire. There would only be about 25' for cable, so the voltage drop would be trivial. I think a 40a breaker is overkill; I can use a 30a breaker can't I?
I know I can't just run the romex to the switch box; I would have to run romex to a junction box and run some sort of whip to the switch box. What are the requirements for that?
I take it that everything changes if I go to a plug. What do I need then?
I appreciate the help.
What did you "check" to find that? That is a common misconception among DIY'ers who don't read the ENTIRE code.Last time I checked, #12 needs to be protected by a maximum 20 amp breaker.
Thanks for pointing out my error.What did you "check" to find that? That is a common misconception among DIY'ers who don't read the ENTIRE code.
Mark
Stickboy's post #9 above cites the code sections and includes a diagram.Thanks for pointing out my error.
Enlighten us DIY'ers as that's why we're here.
Thanks.
Pugsy
