Need Electrical Help!!!

[Gilbert Vega]

I only have two 240v plugs in my garage. I have been using one (20a) for my tablesaw and for my Supermax 37-2 sander. For dust collection I used my Delta120v collector. That has been replaced with a Powermatic model 75 (3 hp). Now I need a second 240 20a outlet.

The second outlet is a 240v 50a circuit for my tig welder. I need yo finish a Mesquite display case I'm building for the entry. I am in the process of making a short extension cord to allow me to plug into the 50a receptacle (3 wire 3 angle flat blades). On the other end I will have a 20a twist lok female plug. On the twist lok, I have the green wire on the green colored terminal (l shaped blade) the other two wire are connected to the remaining terminals. On the 3 angled blades plug, where does yhe green go? Instructions say to use the white wire on the verticle blade snd the green and black on the two angled blades.

I assume the green acts as a ground/ commom. Correct?
On the 50a plug, are the two angled blades the hot wires?

Need help.
Gilbert

[Bob Wingard]

Do you have a meter or a 110v test lamp ??? If so, it should be pretty simple to identify which lead at the outlet is ground ... the other two are both hot, and it doesn't matter which lug gets which hot ...

[Dennis Ford]

What you are doing will work but there is some danger involved. You will have a circuit that is only good for 20 amps but the protection is a 50 amp breaker. If something goes wrong, you may have melted copper (or a fire) by the time the 50 amp breaker trips.

[Gilbert Vega]

This is a temporary fix until I can add a small sub-panel fed by the 6 ga. wire and adding a cut off switch for the 50a circuit and a breaker for the 20a circuit. Can anyone tell me the max amp draw with a 6 ga. wire. Can I run 70 amps on it?

I took Bob's advice and used a test light to identify the hot blades and it turned out I had it wired correctly. Tested and everything works.

[Anthony Whitesell]

14g 15A
12g 20A
10g 30A
8g 40A
6g 55A

[Jim Neeley]

As you move to the higher current, the ampacity rating varies whether you're running "Single Insulated Conductors" or "Not more than 3 current carrying conductors in Raceway, Cable or Earth (Directly buried)" due to the reduced ability of "bundles" of wire to dissipate heat.

Per the NEC, for 60*C insulation rated cable (types TW, UF) and "not more than 3 current-carrying conductors", copper wire
8ga 40A
6ga 55A
4ga 70A
3ga 85A
2ga 95A
1ga 110A
1/0 125A
2/0 145A
3/0 165A
4/0 195A
250MCM 215A

For 75*C (type RHW, THHW, THW, THWN, XHHW, USE, ZW).
8ga 50A
6ga 65A

For 90*C (TBS, SA, SIS, FEP, FEPB, MI, RHH, RHHW-2, THHN, THW-2, THWN-2, USE-2, XHH, XHHW-2, ZW-2) and special 90*C rated THHN and XHHW,
8ga 55A
6ga 75A

If you need 70A, it may be worth looking around (and paying extra) for 90*C wire to use 6ga unstead of jumpung up to 4ga at 60*C. It varies depending upon where you're having to run it. YMMV.

[Joe Angrisani]

.....For dust collection I used my Delta120v collector. That has been replaced with a Powermatic model 75 (3 hp). Now I need a second 240 20a outlet....

Are you sure that 3hp dust collector doesn't need 30A? A 20A circuit seems low for 3hp.

[Rod Sheridan]

Hi Joe, a good quality 3 HP motor will be in the 12 to 13 ampere range at 240 volts, so a 20 ampere circuit would be fine.

If it's a low PF, low efficiency motor it could be as high as 17 or 18 amperes, in which case the 20 ampere circuit is small.

As always, motor nameplate current is required info before sizing a circuit.............Rod.

[Dan Hintz]

Are you sure that 3hp dust collector doesn't need 30A? A 20A circuit seems low for 3hp.

I run my 2HP DC and 3HP bandsaw on the same 30A circuit... for what it's worth.

[Curt Harms]

What you are doing will work but there is some danger involved. You will have a circuit that is only good for 20 amps but the protection is a 50 amp breaker. If something goes wrong, you may have melted copper (or a fire) by the time the 50 amp breaker trips.

I'm not an expert but AFAIK what's at risk is the short "extension" cord. All the wiring in the wall is -or should be - rated for 50 amps. As far as the circuit breaker protecting the load, how is a small kitchen appliance protected when plugged into a 20 amp circuit required for kitchens? The circuit breaker is intended to protect the wire between the breaker and the outlet, not loads plugged into the outlet.

[Curt Harms]

I run my 2HP DC and 3HP bandsaw on the same 30A circuit... for what it's worth.

I'm going the same thing with a G1023 3 h.p. saw rated at 18 amps and Penn State dust collector rated at 8 amps. The breaker has not tripped once.

[Gilbert Vega]

I have 3 large tools on 240v. A PM 66 saw (3 HP, manual says 30a, a PM 75(3HP, manual says 20a) and a Supermax 37-2 (5HP, manual says 20a) I have been using the saw on a 20a circuit without any problems. I am surprised thar the 5 hp (Leeson) runs fine on a 20a breaker.

Gilbert

[Randy Bonella]

My experience has been that the current ratings listed are the max draw/surge which usually happens when the motor is switched on or put under extreme load. Leeson/Baldor motors appear to have better soft start designs so that they don't draw near the load of the cheaper motors at start. A buddy of mine has an older cheap DC 1.5 HP that routinely trips his 20A 110V breaker when he switches it on. We measured the current surge and it spikes over 20A once in a while at startup but once running is sitting at about 8A.

Randy...

[Jim Neeley]

To define the basic performance and mounting parameters of a motor, the National Electrical Manufacturers Association (NEMA) defines some basic design and dimensional parameters in NEMA Standard
MG 1... These parameters are then coded onto the motor nameplate.

Allen-Bradley, a major electrical equipment manufacture has developed a document entitled "What Do All Those Things On An AC Motor Nameplate Mean?"

As you will see from the page 3 of the document (page 4 of the PDF), the current on an induction motor nameplate means:

Current. Rated load current in amps is at nameplate horsepower (HP) with nameplate voltage and frequency.

I have attached this document. Unfortunately the document is too large to upload in one part so I broke it into 2-page chunks. To download the document whole, Google the title.

Jim Neeley, E.E.