20 amp circuit
 

I bought a new air compressor. It fills the tank just fine, but if the pressure in the tank drops enough that it has to refill the tank, it stutters and trips the 15 amp breaker. I called the manufacturer and they recommended a 20 amp breaker on a dedicated circuit.

I've run a 15 amp circuit, and I know that circuit breakers exist to protect wiring. I'm guessing this means that running a 20 amp circuit would require different wiring. What, specifically, should I be using for a 20 amp circuit?

12/2 wire for the 20 amp circuit.

Most houses run 12 gauge wire for outlets and that will be enough for a 20 amp circuit. First is to check the existing wire gauge for the circuit in question. Then, note the type of 12 gauge wire used as different types are capable of carrying more amperage. The lowest amperage wire, NM-B or UF-B, will handle 20 amps. THW, THWN, can handle 25 amps.

In short, you may not need to change the wiring if you have a 12 gauge circuit already.

If your house was built to comply with any building codes used in the civilized world, just install the 20amp breaker and be done.

Of course, your location says “state of failure”, so....

NEC Says 14 gauge for 15 Amp breaker, 12 gauge for 20 Amps. Most of the time a residential circuit protected by a 15 Amp breaker is going to be 14 Gauge. Unless you have a different local code (which I doubt) just swapping breakers would not be a code legal install.

I'm going to run a dedicated circuit for the air compressor anyway, and I want that circuit to be up to code.

Thou shalt consider the length of the wire run when selecting the gauge of the wire.

Just in case it’s a long one...

I'll measure and post here, but the room the main panel is in in the basement directly abuts the area of the garage that the air compressor will be in. I'd think it would be no more than 30 feet, as I want to put the air compressor against an exterior wall and my plan was to run conduit from the utility room, up the interior garage wall, across the ceiling, and down the exterior wall.

Lots, not all 12 gauge romex-style wire has a yellow sheath. Easy way to tell if you can see it.

What does the motor plate on the compressor show for HP and current draw and voltage?

If the unloader on the compressor is working properly the motor's starting current shouldn't be any more when pumping up a 90% full tank than when pumping up an empty tank. That hiss you hear when the motor stops pumping is the unloader releasing and isolating the pressure in the tank from the air pump. When it starts again, it should be working against 0 pressure just like it was an empty tank.
OTOH, if the compressor was rated for a 20 amp circuit, you should have 12 g wire and a 20 amp breaker.

It looks like it would be about 50 feet of wiring from the box to where I want to put the air compressor. If I put it on the wall closest to the utility room, it would be about 22 feet of wiring.

The manual says:

Label:

http://forums.pelicanparts.com/uploa...1554857169.jpg

If you were to run new wiring, and have new circuit breakers, why not go the whole hog and put in a heavier setup so you can use a welder. Or a plasma cutter plus compressor running at the same time.

Since you are running new, make it 240.

If you are planning on running a new circuit (which I doubt is totally necessary) then run a 12/3 and change the compressor over to 240v. Or course you'll need a double pole breaker. Most would run a 10/3 and a 30 amp breaker for other uses like a small welder, but the 12/3 on a DP 20A is fine.

Hah! BD and VV were posting as I was typing.

The guy at the store told me I would be able to do that, the manual said nothing about it, but it appears (if I'm reading the label correctly) that I can go 240.

Working backwards, I have a 150 amp main panel. We're thinking of adding on to the house. I should probably just bit the bullet and get my service and the main panel upgraded.

"220...221 Whatever It takes"

Chris - you say this is a brand new compressor. Tripping a breaker on start-up with the tank under pressure is symptoms of a faulty unload valve. If the compressor starts fine with an empty tank but not with a tank under pressure - I don't think that the issue is electrical.

https://fix-my-compressor.com/compressor-trips-the-breaker-on-restart/

That's the thing, the unload valve does dump the pressure in the cylinder itself.

Also, I was able to figure out that our half bath is on the same circuit as the garage outlets, so even if I unplug everything in the garage, I can't prevent a kid from leaving lights on in the bathroom.

Dont make this too complicated, I'm good for that too often. If you have physical space, 2 hots and a ground, straight forward if you are comfortable and safe. Follow the high or low on the motor to wire for either. Nice thing is the 240v gives you options for a welder or whatever, if you are so inclined. Or, now is the time to add a sub panel.. :) Really, KISS.

In a perfect world you can put a single phase 220 volt circuit to provide the power.
Looking at the plate on the compressor, It looks like the amperage is 15 amps at 120 volts and 7.5 amps at 240 (210/220/240). no matter.
Now... I know I am going to get thrown under the bus with this but believe me, I know...
If you upgrade the circuit breaker to 20 amps and leave the wiring at 14 copper... you are not going to have any problems. Not code? Yes. Have I ever seen a #14 wiring on a 20 amp breaker fail? No.

In my last house I had a large garage with no electrical panel, just 120V romex. I pulled a fat cable in there and set a panel. Fifty or sixty amp panel, I think. I never did get a welder but I think 240 is a nice feature for a garage.

Now I am living in a house with the main service panel in that garage, but very few outlets. I need more outlets. I need another project like I need another kick in the ass.

NO! NO! NO!

Swapping a 20a breaker on 14/2 is not per code anywhere in the civilized world.....

Well if you get out your NEC (National Electrical Code) book or your Ugly's, You are correct.
A compressor that has a starting current at 6 times the running current (15 amps) and only runs continuous for a couple minutes is not going to heat up #14 THHN or any Romex protected by a 20 amp thermal circuit (Home Depot) breaker.
The electrical engineers that come up with the codes always over protect.

40 years in IBEW and IAM. Everything from 500 thousand volt transmission protection to
lowly 12 thousand volt distribution circuits and God forbid... House wiring... a 15 amp running current @ 120 Vac on a #14 wiring circuit protected by a 20 amp beaker is not going to cause any electrical problems.
Code? No.

No way in hell I'd give that advice. A malfunction in the compressor and the wire melts down and so does the house.
Do it the way it's supposed to be done.