unless you use a quick connect with the 1/2 inch thread, you are going to have to use the reducer.

air fitting sizes are 1/4, 3/8, 1/2, and 3/4.
the most popular is 3/8.

you can buy quick connects from Grainger in the 4 different sizes.

http://www.grainger.com/category/qui...ecatalog/N-o8q

 

A 3HP 240v motor by the NEC tables draws 17 amps.

17 amps x 125%= 21 amp wire.

10-2 Romex or #12 THHN are the minimum wire sizes to feed this motor.

While you're 1/2 HP over that #12 technically meets allowable ampacities however overcurrent protection required cancels it out.

motor loads permits a breaker of up to 250% the full load amps250% of 17 = 42.5 amp

http://www.groverelectric.com/howto/...c%20Motors.pdf

Note #12 isn't listed above 2Hp.

Not an electrician and what I recall from the NEC get to far into it eyeballs start glaze over quick! I do know from past experience I wouldn't run that compressor on #12 wire. I'd run #10 min and might jump to #8 provided didn't exceed branch circuit size of course (not much chance of that or wouldn't run it/install it to start with). I'd wanna be sure it would deliver all the air it was capable of delivering and for years to come.

Didn't get that deep into it however appears 35 amps listed technically excludes #10 as well.

http://www.usawire-cable.com/pdfs/NEC%20AMPACITIES.pdf

I run a portable 4hp compressor on #10 @ 100 feet (multi strand extension cord) when can't plug it directly into the wall for example, #12 at 50 feet.

When an electric motor isn't getting enough power, full power, you can hear the difference.

Then comes down to how you routed the cable reason mentioned safety, couldn't help but picture out window through doorway type routing after seeing your pictures get it running! If so ok if right there with it but not something should be used permanent type arraignment.

 

Not using it much, any way you choose to drain it is probably fine, but if you're going to use it on a regular basis, get rid of the line restriction that was already pointed out, IMO, I would NOT remove the filter, but I would put it on a line drop and a drain valve right after it. But I use mine about everyday.

 

I'll agree my calculations were a bit on the low side, I think yours are on the high side. Walking backwards through a few part manuals from Sears, Lowes, etc. this compressor uses an AO Smith 3.1HP motor. According to the information from that manufacturer it's a 15 AMP motor. I would have no issues using 12 ga. wire on a 50 ft. run for power. YMMV

 

Yea high but tend to go that way most things electrical in nature......More power!! (Examples given its what they dictate).

Also keeping in mind they state must to go by the NEC for HP and not a motors rating plate determine conductor amperage, read that someplace in little bit of research I did.

Once cross over that 3hp mark #12 is taken out of the running, includes following notation.

NOTE!! If the motor is required to start under a heavy load, we
recommend using one size larger wire


Model doesn't appear to be equipped with an "unloader" (no pressure on motor during cut in) so motor will start under load after first charge, cut in pressure = 120psi.

Portable I carry around with me it will run if plugged into a 50' 16g extension cord yea but I wouldn't subject it to it. Hard on it takes it near twice as long to build pressure, cut in after initial charge will tend blow its overload protection.

I'm not an electrician, I'm a Builder as such have to keep tabs on what various contractors are up too. Inspections or rather re-inspections cost money/time. I have no problem stating reading the NEC has always given me a migraine, to that end my latest copy is 02'! (Google now days too)

Not in any way attempting to lay down the last word on this subject nope no way no how!

Just attempting to provide some info for joegeds to work with get the power needed to his compressor......well more than "you need a big extension cord" that is!!. Uses it or disregards it, that's up to him won't hurt my feelings.