starting from the box, I have a two pole barred 20 amp breaker, #12 3 wire going to a junction on the wall and then across the floor in a flex to a plug box with a 20 amp 4 prong socket... black to X, Red to y, white to W, and green to G, ran same wire to to switch on saw with black going to one black screw on bottom of switch, red to other black screw, tied the white to white and grounded switch to box, ran same 12-3 to motor with black and red on gold screws at top of switch, whites tied together and as indicated, I clamped the ground on the incoming power feed to the switch together with the ooutgoing 12-3 ground to the motor and grounded both to the inside of the metal switch box which is attached to the front of the saw. I get a trip. Everything seems OK up to the plug since I got no trip the first time I tried without the saw plugged in. Also, when I tried resetting the breaker once, I got a large flash, enough to scare me into pulling out the breaker and consulting. I am a GC and have some layperson knowledge about electrical but someone please educate me here. Why the tripping?

You have a single throw-double pole switch right? Not a three way or a 4 way? Short of there being a knick in the wiring it sounds like its crossing phases. Is the plug factory or did you add it?

Why did you use 12/3 and a 4-prong receptacle?
What are you connecting the white to? A neutral is not normally needed for a 240v tool. Is there a light or something?
What are the connections inside the motor?

I suspect that the motor is wired using the white and black, like is typical in a 240v circuit, and you are getting a back fed or short somehow.

Check nomenclature tag on motor. Is motor 240 or 120/240. Look inside motor wiring terminal cover for wiring instructions.
How big is motor? Could it be 3 phase?

It is 120/240 and it is single phase

I used 12-3 cause I thought it was better to run a hot red & hot black + neutral + ground. Motor has 5 wires in conn housing... P1, P2, and T3,4,5, no T8
It was wired 110 as t3 +P2, and hot to either t4 or t5, P1 was conn to white.

Here is what the breaker says,, it's a 20----20 with the bar connecting each pole...

2 poles Type/MP-T
Interrupting Rating
Max.RMS.SYM.AMPS.
10,000 120/240V^
HACR TYpe 40C

CU-AL 60/75C Wire
Conductor 60/75C
AWG14-8
lbf-in 25
mm2 2,1-8.4

N-m 2.8 Hard to read...

Yes the plug is one I added, both the plug and receptacleplug recept. To make matters worse, I cannot find a wiring diagram (including the one on the motor housing) that equates with what I have in wiring in the teminal box


Mine only has P1 and P2 plus T3, 4, and 5 in the connection box


It was wired for 110 as T3 and P2 capped together, P1 was capped with white incoming and T4 and T-5 were ground and black (hot) though I don't remember which was ground and which was to hot. The saw worked fine like that.

Mine has no T-8 to speak of.

I do not believe I have a cut in the wire anywhere. I could attach some pics if I could figure out how to.

I used 12-3 cause I thought it was better to run a hot red & hot black + neutral + ground. Motor has 5 wires in conn housing....P1, P2, and T3,4,5, no T8
it was wired 110 as t3 +P2, and hot to either t4 or t5, P1 was conn to white. Why would you think that was "better"?
A 240v motor will NOT require a neutral, nor will there even be any place to connect it to. It should NOT be connected to any wires in the motor splice box.
If it is wired for 120v then it will be shown in the wiring diagram on the motor plate where to connect the neutral.

Either way 12/2 was all you needed.

OK, I see. I just finsihed capping off all the whites. I guess I could use it (white) later as a 110 line and runs some plugs off the junction box before the saw and recept, correct? Does breaker type look correct? Thanks!!

First, you need to understand that there is no neutral in a 240V circuit. Therefore, you only need a 2 wire with ground cable.

The plug and receptacle need to match the voltage and amperage.

Second you need to understand that there is no advantage to converting this from 120 to 240V. You do not get any more power, you do not save any energy. Converting to 240 only allows you to reduce the size of the cable from the panel to the saw. Don't know the amperage draw of the saw but 12 gauge wire should be quite adequate.



It was wired for 110 as T3 and P2 capped together, P1 was capped with white incoming and T4 and T-5 were ground and black (hot) though I don't remember which was ground and which was to hot. The saw worked fine like that.

I don't think I follow all you are saying here.

P1 and P2 will be incoming power connection.


P1 was capped with white incoming

Assuming that that means that P1 was connect to the white incoming wire, that would mean that P1 is the neutral for a 120V set up.


T4 and T-5 were ground and black (hot)

That is not logical. Normally ground would be connected to frame of motor, This may be a multi speed motor or it may be a reversible motor.

Is there a wiring diagram on the inside of the motor terminal connection box cover.

Suggest you put it back the way it was and run as 120V, no advantage to you to convert to 240V.