Extension cords

[cathouse willy]

As part of moving the wood shop I need to get 220v power for the larger tools.The only feasable way is to get approx 55 ft to a 220 receptacle with an extension cord.There are lots of tables on the web that say 12/3 cabtire will be large enough for 15 amps at that length.None of them say at what voltage this rating is at. 110 or 220v. It makes a lot of difference in the power used.The biggest motor draws 13 a at 220v.My plan is to use the 12/3 cabtire. My question is will it handle the load over 55 ft?

[TerryLL]

IIRC, my pocket reference says #12 wire at 15 amps and 240 volts single phase is good for runs up to 95 feet. Best to check with an electrician if you have doubts.

[Paul Scheuer]

The voltage drop (lost in the line) will be the same no matter what the source voltage is for a specified current.

[Gordon Bartlett]

Paul’s statement about voltage drop is certainly correct but a bit misleading. Yes, the voltage drop is the same regardless of source voltage. But the effect of that drop is much less noticeable at the higher voltage. For example, a loss of 12 volts on a 240 volt circuit is a 5 percent loss. Not great but still within the 5 percent range many electricians shoot for. (some use more or less) But that same 12 volt loss is a ten percent loss on a 120 volt circuit, quite a large drop and unacceptable to most people.
By the way, your #12 wire should be fine. I don’t know what cabtire is but, assuming it has copper conductors, at 13 amps it only imposes a loss of 2.8 volts. This isn’t much more than a one percent loss at 220. Even at 120 it’s less than 2 ½ percent. Keep in mind, however, that this is only the loss imposed by the extension cord, and doesn’t take into account the length of run from your service entrance to the outlet you’re plugging the cord into (the branch circuit). It is possible that the branch circuit itself is long enough to cause problems which will only get worse when the additional length of the extension cord is added.
Anyway, good luck with the move.

[Gary E]

When I owned my machine shop I had a welding machine running on 460/3/60 wired with an extension cord aprox 50 or so feet long, it worked fine...

Think about this...
Your power plug is in a location "A"..
your machine is near it, you wire it and it runs fine.

Now you need the machine 100 ft away from "A"
What is the difference between using 3 separate conductors, run in conduit to the new location where you will install an outlet for the machine or use an extension cord the same length?

I think your 12/3 will do fine... Single Phase?? as in typical home electric power?? It's was a long time ago, but I think the wire you want is 12/3 SO... the electrical supply house will know. If your talking about 3 phase, use 4 conductor, you need a ground.

[paladin]

The number 12 wire will be an absolute minimum....especially based on solid wire as in a conduit circuit. Stranded wire has a much smaller cross sectional area, and I would go at least one wire size up.

[rddrappo]

I've run up to 255' of 12/3 (3 cords, 85' each) on jobsites numerous times without problem. That's only at 110v. My large wetsaw draws a ton of power, and it's never given me a problem. I run a good surge protector with 10 outlets on it and half of them are usually running battery chargers and lights. I doubt a workshop would use any more power than I do, and it's been fine so far. You can go with a 10 gauge cord and feel even better about it. Not sure how much they cost though.

[paladin]

I finally checked my engineering guides....
Based on stranded copper wire....for a run of 55 feet from an outlet, based on 110 volts system and a current draw of 15 amperes, the minimum wire size will be 10 ga. I would not change the wire size for 240 volts, primary reason is that when the primary conductor is reduced in size, the insulation may also be downgraded. Absolute minimum should be 600 volts as a peak "spike" can be as high as 480 volts on that type of system.

[cathouse willy]

Thanks for the replies.The power is single phase 220. the branch cct is 20 ft from the panel and is fed with 12/3 solid copper.The cord will be 12/3 stranded rubber covered rated for 600v.My electrian neighbour says it will be fine. Just as an aside I just missed on a 1960's craftsman table saw. Asking price was $125.The seller called just prior to my leaving to look at it to say it was sold. Sigh, snooze you lose.

[TerryLL]

"Cabtire" had me scratching my head too. Google led me to this explanation:

"...'cabtire' is Canuk for heavy duty flexible line cord..."

BTW, the numbers I gave above for #12 wire at 95 feet were for a maximum of 2% line drop at 15 amps and 240 volts. 50 feet would have a line drop of just over 1%, about 2.5 volts.

I run 10/3 for a 25' extension cord for my 3HP, 220-volt table saw. Probably way overkill, but I had the cable on hand.

[Gary E]

I finally checked my engineering guides....
Based on stranded copper wire....for a run of 55 feet from an outlet, based on 110 volts system and a current draw of 15 amperes, the minimum wire size will be 10 ga. I would not change the wire size for 240 volts, primary reason is that when the primary conductor is reduced in size, the insulation may also be downgraded. Absolute minimum should be 600 volts as a peak "spike" can be as high as 480 volts on that type of system.

That does not sound right.. and if it is right then every wire to every outlet in every house would be #10

[George Roberts]

75' (main breaker to the tool), 240v, 15amp, 14 gage produces a 3% voltage drop.

14 gage is sufficient. I use 12 gage for extension cords because it has a better feel, but 14 gage is sufficient.

[paladin]

Gary...I am using a marine wiring guide for onboard a.c. systems. When you use stranded (flexible) wire the cross sectional area is less than the solid wire used in house wiring....

[Gary E]

The National Electrical Code [NEC] requires their own cable sizing for premises wiring. Refer to the NEC rules to determine building wiring, as this page relates to electronic equipment wiring. For reference, the ampacity of copper wire at 300C for common wire sizes
14 AWG may carry a maximum of 20 Amps in free air, or 15 Amps as part of a 3 conductor cable.
12 AWG may carry a maximum of 25 Amps in free air, or 20 Amps as part of a 3 conductor cable.
10 AWG may carry a maximum of 40 Amps in free air, or 30 Amps as part of a 3 conductor cable.
8 AWG may carry a maximum of 70 Amps in free air, or 50 Amps as part of a 3 conductor cable.

Use this and plug in 15 amps..240 v.. 55 ft
see what it says
http://www.jhlarson.com/ind_tables/volt/calc_wiresize.htm

It says 90 ft and #12 is fine

[pcford]

. Just as an aside I just missed on a 1960's craftsman table saw. Asking price was $125.The seller called just prior to my leaving to look at it to say it was sold. Sigh, snooze you lose.

You are fortunate. I suffered with one of those for several years. A POS.

[rddrappo]

I'd probably go with Paladin's recommendation. He seems to be pretty bright about electrical stuff, and as I posted earlier, 12 gauge should be fine, but 10 is a safer bet, and I've seen what happens when cables fry. It's not pretty.

[Gary E]

I'd probably go with Paladin's recommendation. He seems to be pretty bright about electrical stuff, and as I posted earlier, 12 gauge should be fine, but 10 is a safer bet, and I've seen what happens when cables fry. It's not pretty.

So.. you dont believe the NEC which already has a huge safety factor built in?

Makes no dif to me, it's your money but if you worked for me and it was my money , you'd hear about it.

[rddrappo]

I didn't say I don't believe the NEC. I'm just saying that I'd rather trust the advice of someone older and more experienced than myself, that's all. I'm a tilesetter by trade, and I tend to build showers that surpass what is required by code or by the TCA. I'm not saying you or the NEC are wrong, I'm just a "better safe than sorry" kind of guy.

[boylesboats]

You'll be better off and safe with 10/3 at 50 ft...

[Ron Williamson]

Code assumes a permanent installation buried in a wall or conduit,where heat can be a problem because it can build up and not be noticed.
A cord will get noticably warm even if it's not too light of a gauge.
BTW it's pretty common to feed a 50A welder with a NMD 10/2 extension cord that never gets warm.Welders draw lots for a short time and they are rarely set to full amperage.

willy
you might want to slide your cabtire into some plastic conduit in areas where it could take some damage.
R

[George Roberts]

"Use this and plug in 15 amps..240 v.. 55 ft
see what it says"

I used it. It said #14. I must have done something wrong.

[htom]

NEC also presumes solid wire, not stranded.

[Gary E]

NEC also presumes solid wire, not stranded.

When you see this...
12 AWG may carry a maximum of 25 Amps in free air, or 20 Amps as part of a 3 conductor cable.

When you see the word "cable" that means stranded wire wraped with insulation and in this case 3 stranded wires all wrapped individually and then covered with more insulation and finally wrapped in a rubber cover.

I do not know of solid wire, insulated, then wraped together and covered with more insulation and finally a rubber cover... such as "SO" cable...
But, I could be wrong....maybe there is such a thing... can you imagine how stiff that would be?

[George Roberts]

Gary E ---

I think that htom simply misspoke. Very little house wiring is solid. I don't believe any extension cords are (with the exception of the temporary extension cords made from NM cable).

[Ron Williamson]

Most house wiring smaller than 8g. is solid.
R

[boylesboats]

Most house wiring smaller than 8g. is solid.
R

Depend.....
rule of thumb for standard house wiring in my area
14ga wires on 10 - 15 amp. services
12ga wires on 20 amp. services
10ga wires on 25 - 30 amp. services

[TerryLL]

Very little house wiring is solid.

Huh???

ALL the wiring in my house is solid except the service to the range, dryer, and water heater.

What we are talking about here is an extension cord, stranded, each conductor insulated, wrapped in an outer sheath.

I have to apologize here, because the numbers I gave at the top of this thread were for SOLID wire, and that probably set this thread off in the wrong direction. Paladin provided the numbers for STRANDED wire, which indicate that #12 is marginal, and #10 would be a safer choice.

[htom]

I don't know of any permanent POWER wiring in my house that isn't solid, other than some appliances that are wired with stranded; I presume this is because of vibration. (I have not looked at the main feed; it's underground.)

[George Roberts]

"ALL the wiring in my house is solid except the service to the range, dryer, and water heater."

Yes, you are correct I lost my train of thought. Not unusual.

I had intended to make some comment along the lines of: stranded or solid the NEC assigns the same properties to all wires of the same gage. So 14 gage stranded is allowed to carry the same amount of current as 14 gage solid.

[Tom Lathrop]

Wait a minute guys, extension cords are stranded because they have to be flexible. No need for flexibility here unless he plans to keep wiggling the wire around for some unknown reason. #12/3 solid with weatherproof jacket will be just fine in this instance. When he prices a long length of weatherproof #10 stranded with ground, that #12 solid will look very attractive.:)

[TerryLL]

Yup, 10/3 stranded service cable is about three times the price of 12/3 UF-B Romex. If flexibility is not an issue, then the solid Romex would do.

Here's a pic of my wiring job. A 10/3 service cable feeds three 220 outlets. The factory power cord on the tablesaw is #12. Saw is 3HP, single phase, drawing 13 amps.

http://i325.photobucket.com/albums/k365/TerryLava/P1010017.jpg?t=1231808343

[cathouse willy]

I never thought this thred would generate this much interest, extension cords are a bit dull.But... thanks for the interest. It is possible to run a new cct to the new shop area via power panel, breakers and receptacle, prolly much cheaper too. The power panel is 100 a mp service and has 4 empty slots for new ccts.I don't want to use them up for a redundant 220v source.The cord will run along the unfinished ceiling to an existing plug used only for an air compressor. I'm ok with sharing it with the new shop.There's plenty of 110v for smaller tools there already.The price of the 12/3 cabtire and ends will be about $110. just part of the project.Terryll I just noticed your picture nice looking saw. Much larger than what I have room for.