220 V table saws and ground

Page 9 of 9  
snipped-for-privacy@uiuc.edu wrote:

I think this came out of the old FAQ here, or maybe Lew posted it years ago?
Wire size is determined by the load computed for the branch circuit. The load tells you the size of wire to use and the size of the overcurrent protection to use. Use only 80% of the maximum current capacity of the wire and the overcurrent protection (breaker or fuse).
************************************* | AWG | MAX-AMPS | | ----------------- | --------------|
| 14 | 15 | | 12 | 20 | | 10 | 30 | | 8 | 50 | | 6 | 65 | | 4 | 85 | | 3 | 100 | | 2 | 115 | | 1 | 130 | | 1/0 | 150 | | 2/0 | 175 | | 3/0 | 200 | | 4/0 | 230 | *************************************
Anyway, IME, it's still fairly standard for most US locales.,
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My 220 consists of three leades, two "hot" and one "neutral" but the newest setups (for household appliances 0 like a dryer) include a separate equipment ground and use a four-conductor plug.
As I understand it, a short in your saw could conceivably employ you as the ground (wet shoes, damp floor and a short to the frame).
I may be wrong, but I wire my 220VAC equipment with all four conductors and do have a ground stake for the shop power distribution box (about a 100 feet from the mains I ran it from at the house).
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If you only have three leads, one is a ground not a neutral. Often, like older driers and range installations the ground is used as a neutral, but as you note, this is no longer allowed. Circuits like air conditioners (and saws) that don't need a neutral can still use three wire circuits but the third wire is a ground, not a neutral (it carries no current). Equipment grounds have been required for at least fifty years.

Which is why the equipment ground is a requirement. There would be no neutral current so a neutral conductor is not required.

The *only* place neutral and ground may be (and must be) connected is at the entrance panel. Neutral and ground must be separated everywhere else. If your sub panel is separate from your entrance panel it shouldn't have a separate ground stake, though perhaps it's OK if a *large* enough ground wire connects the two. I'm not sure about this detail because it's easier to not have the ground stake at the sub. If there is a nearby lightning strike you want the house to "ride the wave" (one ground point) not invite the current through your house (two grounds).
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Thank you. My sub-panel is in a barn 80 feet from the house panel. I ran a solid copper (#8?) to the ground stake just outside where the sub is mounted. The connection runs under ground (in HDPE pipe) along with a 10Bast-T and a Coax.
On the suggestion (elsewhere): "Why not just take out the short 2 wire cord and throw it away, and simply attach the long 3 wire to the saw? "
I would say one needs to watch out that the longer "extension" cord is of a suitable gauge as many tools come with a minimum gauge "pigtail" which is "OK" if plugged directly into a suitable (amp-wise) outlet, but not if run through one of those 16 gauge extension cords - espeacially when they are twenty-five feet and more.
If you do re-wire with a longer cord, use at least 10 Gauge wire with a ground (IMHO) to get the most power out of your tool. I use 20AMP cords if "extending" to a Table Saw and the like. I've noticed severe slowing down/loss of power when using lighter cords and the cord (esp at plug end) get nice and toasty.

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That's a different situation. It's not just a sub panel.

Well, ya. Cords must be rated for the current drawn. 16ga is good for 13A, IIRC. I think the only 16GA extension cords I own are used only for lights. For (hand) saws I use only 12GA, even only 25'.

12GA is fine. It's no different than the wiring in the house. A foot of 12GA in the wall is the same as a foot of extension. Yes, if the total run is too long, half of it in 10GA will help. I replaced the cord on my Unisaw with 15' of 12-3 SJ. There's probably 50' of 12-2 w/ G going back to the sub-panel from the wall. Changing the 15' from 12ga to 10ga isn't going to change anything. The saw starts with authority now. ;-)
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12GA is fine. .... The saw starts with authority now. ;-)
Wouldn't doubt it. I do go overboard with my wiring at times. Well, most times. But I did only run three 8's and a ground to the shop. Reading here, I probably should have gone with 6GA to be as bullet proof! :)
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Brian - Truthfully now.
Did you ever imagine your straight-forward inquiry would return 151 (errrrr...152) responses :^} ??
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