extension cord

[astjp2]

Ok, my garage does not have 220 power so I need to run an extension cord to run my lathe. It is a 2hp 220v lathe that is about 7.5 amps. Would I be ok to run a 10/3 extension cord? Or will I need to go larger? The run from the house to the garage is 75', I am using a 50 amp circuit on the outside of my house that was used for a hot tub that I am moving an outlet over to the end of the house. I planned on swapping the ends of the extension chord over to match the lathe and the outlet. Any advice would be appreciated, extension chords are rated for 120v, so I just halved the amp rating of the cord.... Tim

 

[FOMOGO]

I'd run 10 gauge THNN in plastic conduit. Leave your self a little extra wire and bury it in the spring. Cheaper than 10 gauge extension chord and a permanent fix. It's just two 110 lines, but because of the distance I'd use the #10, and run four wires, two hots, neutral and ground four future possible use as a sub panel. Do you have a sub panel in the garage? Mike

 

[Meta Key]

10 AWG is good for 15 amps in the power transmission use-case.

American Wire Gauge Chart and AWG Electrical Current Load Limits table with ampacities, wire sizes, skin depth frequencies and wire breaking strength

AWG Wire size chart and ampacity table for design engineers including skin depth frequencies and tensile strength data; electrical cable size

www.powerstream.com

You can calculate the voltage drop by using Ohms Law and using the resistance given in that table scaled to your total wire length.

You also need to know that your extension cord is adequately built for 240 VAC. I usually use 600 VAC rated cable for 240 volt stuff.

-MetaKey

 

[macardoso]

Understand that electrical code limits the use of extension cords for permanent wiring. To be code compliant, you should use solid conduit. Certain types of flexible cable (like SOOW) can be used for connections between machines and outlets. This is NOT an extension cord and should never be terminated by connectors on each end.

Consult an electrician for conformance to code. I run SOOW cable between my machines and outlets connected to the subpanel by conduit. You can use the NEC tables to calculate the required wire size. Unless you know the reasons why you can use the 75 or 90C tables, you should stick to the 60C table.

SOOW cable can be purchased rather inexpensively from electrical suppliers or McMaster Carr.

 

[astjp2]

Ok, so burial is not going to happen until I jackhammer out some asphalt or concrete across part of the driveway. I just want to use an extension cord once in a while to use my lathe...when I am done, roll it up and hang it in the garage. I plan on back feeding through the same outlet for my generator, I know its not per code, but I know how to disconnect the main so no one gets hurt down line...

 

[markba633csi]

Sounds safe enough if you take the proper precautions. A roll of romex is a bit cheaper than an extension cord... just roll it up and stash it if an inspector is comin' around

 

[Eddyde]

Ok, so burial is not going to happen until I jackhammer out some asphalt or concrete across part of the driveway. I just want to use an extension cord once in a while to use my lathe...when I am done, roll it up and hang it in the garage. I plan on back feeding through the same outlet for my generator, I know its not per code, but I know how to disconnect the main so no one gets hurt down line...

You will be fine electrically with the 10 gauge. As long as you disconnect the cord between uses, I don't see any safety hazard either. One note, you should put a smaller breaker. 50 amp is over the capacity for the wire and way more than the machine is drawing, I'd go with a 20 amp.

 

[tjb]

Ok, so burial is not going to happen until I jackhammer out some asphalt or concrete across part of the driveway.

There are tools available to tunnel under the driveway as long as it is not up against a building. Probably cheaper jackhammering and re-paving/concreting.

Regards,
Terry

 

[ConValSam]

Funny story about extension cords and a detached workshop:

I used a 10/3 SJOOW cable from a dryer outlet out the window, across the yard, across the driveway and into the shop subpanel. I kept it plugged in except when we were using the dryer (besides running the machines, it also powered a heater to minimize humidity and keep me toasty.) One day the forecast calls for the first snow storm of the year: I move cars and set up a sawhorse in the driveway so there is no chance the plow will damage the cable. Except the plow guy decides he should plan for lots of snow all winter and pushes back across the lawn. Somehow, the cable stretched and never broke, the rubber jacket had no tears and the power still flowed.

Needless to say, I buried the power the next spring.

 

[astjp2]

There are tools available to tunnel under the driveway as long as it is not up against a building. Probably cheaper jackhammering and re-paving/concreting.

Regards,
Terry

Yeah the asphalt is unfortunately against the garage...