Wiring for table saw

[chris64]

Hi All.
I just replaced my condenser on my AC, and they told me that my 220 wire was not grounded properly. The fix, to run a new line to the unit. No problem. However, when I do this, I want to run a 2nd 220V line to my garage to power my hopefully in the somewhat near future purchase of a 3HP cabinet table saw. What amperage breaker/wiring would you use? (This may be the wrong terminology but you probably get the gist of the question.)
Thanks
Have a nice day.

[LCHIEN]

15Amps @ 220V should cover 3+ HP, you might go 20A for a bit extra headroom.

[chopnhack]

+1 with what lchien said. I would go with 20a as well. Most big box stores have two pole 15 or 20 a breakers readily available. Wire size and type will be determined by length and how its run. Probably 12 gauge thhn in some type of conduit. Check with your local inspectors or code books.

[cabinetman]

I would suggest to consult with a local electrician familiar with your needs and local codes. An on site evaluation would benefit you. We can't see what you have there as to the condition of your electrical layout.

.

[BadeMillsap]

Yep .... as stated ...

Having JUST gone through this for the new shop with a Griz 1023SL (3hp 220v)which calls for a 15Amp circuit ... I agree that 12 gauge on a 20amp paired breaker is a good choice. It's true the length of the run matters but unless it's REALLY REALLY long the 12 gauge should carry you nicely. I used 12-3 NM (Romex) in a pvc conduit ... the run from the breaker box is only about 25' in my case.

[chopnhack]

Having JUST gone through this for the new shop with a Griz 1023SL (3hp 220v)which calls for a 15Amp circuit ... I agree that 12 gauge on a 20amp paired breaker is a good choice. It's true the length of the run matters but unless it's REALLY REALLY long the 12 gauge should carry you nicely. I used 12-3 NM (Romex) in a pvc conduit ... the run from the breaker box is only about 25' in my case.

Please tell me that you misquoted the wire type... Romex or NM can never be run inside of conduit... I am pretty sure its a violation of UL or at least when I last checked it was a violation of my local codes. The explanation given was that the NM wires are meant to be in unobstructed areas with adequate air space - there are even provisions for de-rating when in exceptionally hot locations like attics. NM run in conduit may possibly overheat when used at or near capacity for long periods of time. Typically THHN type wires are run in conduit.

[BadeMillsap]

For this SHORT run across the floor it is considered a "shield" ... open on both ends ... I'm not worried.

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[chopnhack]

"Sleeve" - never say never right

I agree with you "SHORT" in the real world, I just remember all the codes from having done work and making sure everything flies by inspections.

[BadeMillsap]

Yeah ... this from NEC was what I hung my hat on ...

Article 334.15 (B) NM - Exposed work (B) Protection from physical damage The cable shall be protected from physical damage where necessary by conduit, EMT, schedule 80 PVC NMC, pipe, guard strips, listed surface metal or nonmetallic raceway, or other means.

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[chopnhack]

Yeah ... this from NEC was what I hung my hat on ...

Article 334.15 (B) NM - Exposed work (B) Protection from physical damage The cable shall be protected from physical damage where necessary by conduit, EMT, schedule 80 PVC NMC, pipe, guard strips, listed surface metal or nonmetallic raceway, or other means.

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Did they even look at it twice or no issue at all? I have had one inspector tell me no go in a garage because being in a garage it was subject to "potential damage" and wanted emt from box to box...

[cabinetman]

With the doubts and differences in suggestions so far it's obvious that consulting an electrician in your area would be a wise decision.

.

[BadeMillsap]

it's just possible that was wired after all the city inspections were signed off on ... hmmmm ... funny I have no recollection of that specific instance ... ...

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[chris64]

Thanks for all the replies. Yes, an electrician is doing it. It is a pretty short run, probably 25 feet. I will see how it goes. If the cost isn't too outrageous, I will probably shoot for the 20A, 12 gauge run.

[chopnhack]

it's just possible that was wired after all the city inspections were signed off on ... hmmmm ... funny I have no recollection of that specific instance ... ...

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LOL

As to what cman is saying if you are not really familiar with NEC and local codes, then having a sparky come out is a good idea. Unfortunately the codes and NEC are subject to a lot of latitude just depends on who is doing the inspection. For that reason when I do work for myself I will try and only use matched UL listed parts and watch for ratings as well as follow good practices whenever possible. Watch your electrician work and ask a few questions if it doesn't seem to interfere with his work (not while measuring, marking or terminating large groups of wires) you will learn alot chris64

[woodturner]

Romex or NM can never be run inside of conduit... I am pretty sure its a violation of UL or at least when I last checked it was a violation of my local codes.

It could possibly be a violation of your local codes, but NEC allows - even requires, in some cases - that NMB be run in conduit. For example, exposed wiring such as in a garage must be "protected" against physical damage, and conduit is one common way to meet this requirement.

The explanation given was that the NM wires are meant to be in unobstructed areas with adequate air space

Not really - NM can be run in insulated walls, in contact with insulation. The derating and temperature rise are specifed at the out sheath of the cable, and is safe for use in contact applications.

Possibly you are thinking of THHN or similar single conductor wire, which is rated for higher current in free air space. For example, utilities typically install smaller wire to the weatherhead - because it is in free air and the current rating can be increased.