Dust Collector Extension Cord

Hi all,

Recently bought a 3HP DC for the basement. I need to add about 40' to the current length of the cord so I run it to the dedicated 30-amp, 14-30r outlet.

Question that I'm embarrassed to be asking after the amount of research I've already attempted. Should I:

1. Buy a 50' extension cord?
2. Rewire the DC? If so (and here's the one that's confused me most), what type of cord won't break the bank? I think I need 10/3, right? But I tried to do this with Romex the other day before realizing it wasn't stranded. I'd needed stranded right?

Help a dummy out!

Thank you!

Disclaimer: I'm not an electrician, but I've seen enough pros at work to be dangerous LOL. Don't know the code inside and out, but I'm pretty sure I'm right saying long extension cords to run 220V machines are not a good idea, and probably not code.

Best to run a dedicated circuit from the panel to a receptacle within reach of the motor. For most 3HP #12 wire and 20A double pole breaker will do the job.

If you are not familiar with this type work, I strongly recommend hiring an electrician to do the job.

You don't need 10G for that DC. The NEC Table 430.248 FLA for a 3HP 230V motor is 17A. Your motor is almost certainly less than that. 14G is rated for 18A. 12G is 25A. Either will work.

At 50' voltage drop needs to be checked. At 17A and 75C the 14G will be about 5V and the 12G 3.5V. With a 240V supply either will yield higher voltage than the 230V rating of the motor.

My personal choice would be a generic 12G extension cord. I would cut off the 120V connectors and replace them with appropriate ones. I certainly wouldn't want a 50' tail on a machine, and would prefer to shorten the existing cord to make it easier to unplug the machine for maintenance purposes.

And no, the cord size doesn't have to match the outlet, only the machine.

Hi all,

This is super useful. Thank you. Just to be sure, for future endeavors - for making these types of connections, I need stranded right?

Jon

Quote:

---

Originally Posted by Jon Kleiman

Hi all,

This is super useful. Thank you. Just to be sure, for future endeavors - for making these types of connections, I need stranded right?

Jon

---

If buying bulk, look for SO, SOJ, SOOW, or similar specification (:: stranded).
David has it nailed (of course), and if you purchase 'extension cord', likely it will be in this SO-series.

Yes. Specifically, you need "Service Cord". Romex (type "NM") is only for permanent installation. Service cord will be type "S..." or "SJ...". S is rated for 600V and has a heavier jacket. SJ (Service Junior) is rated 300V.

Thank you!

Quote:

---

Originally Posted by David L Morse

Yes. Specifically, you need "Service Cord". Romex (type "NM") is only for permanent installation. Service cord will be type "S..." or "SJ...". S is rated for 600V and has a heavier jacket. SJ (Service Junior) is rated 300V.

---

I'll just add emphasis that NM cable is only for permanent installation where it's not subject to mechanical injury. That's a very important point. NM cable will quickly be destroyed when used as an extension cord.

You can buy a 50 foot 30 Amp RV power cord that is ready made. They are stranded.

Quote:

---

Originally Posted by Lee Schierer

You can buy a 50 foot 30 Amp RV power cord that is ready made. They are stranded.

---

I did similar for my CNC, but it was a generator cable because for my particular application, I needed four wire. (dual voltage) These heavy, pre-made cords are readily available and nicely flexible with durable covers so there's no issue with routing them along the floor.

Quote:

---

Originally Posted by Lee Schierer

You can buy a 50 foot 30 Amp RV power cord that is ready made. They are stranded.

---

But he only needs 20 amps, so 10ga is overkill, and overly expensive. Buy the standard 12ga extension cord, and replace the ends. You can save a bunch of money by buying cord ends from ebay sellers.

Jon,
Maybe I missed something, you said "I need to add about 40' to the current length of the cord".
Just curious, what is the overall length of the run, (40' + X)?

Ed

If your state is one where people off the street can buy from a dedicated electrical supply store, it will cost a lot less (maybe even half) to buy the cords, and ends, from such a place, than to buy a premade cord.

Buy some variety of type SO wire (not SJ), and plugs rated for your load. With the proper sized wire, and devices, there is no difference in having a 40' cord, or 40' of wire in the wall.

I have had short pigtails on all my large tools for decades, with twist lock plugs, and never any problems from such a setup. It makes it much easier to move them, or unplug one when working on the machine.

Cheaper to buy 40 feet of cable and one junction box then that much cord. NM cable is much less costly then good stranded cord. I would recommend you remove the outlet and connect 40 feet of #10 cable to it. terminate the cable near the machine and install the old outlet in a new box.
Total cost one box, two cable clamps, one blank box cover to fit old box, 3 or 4 wire connectors, cable.
If it was me I would remove old outlet and box and install a subpanel there. Then I would install the old box and outlet at the new location with new cable. I would probably add a 120 volt outlet at the subpanel.
Bill D.
Offhand I woud guess cord is double the cost of nm cable.

Where I live an extension cord cannot be used as a substitute for permanent wiring.

You should put in a suitable circuit for the cyclone...Rod