Tools, Sharpening and Power Machinery - 220v Compressor question

I built a compressor this spring from a bunch of stuff I had lying around the house. A 100 lb propane tank (about 25 gallon), a 1 hp electric motor and I machined a custom head for an old briggs and straton engine to pump the air. Bought the rest of the stuff like the pressure switch, regulator, guages and a check valve.

Been working really nice so far but the electric motor I'm using could be better. I'm working it a little too hard (in terms of pulley ratios) and if I'm doing something that requires a lot of air, for a long time, the motor gets hot and cuts out. I know I could just run a smaller pulley to put less load on the motor, but that would affect my CFM.

I have a chance to buy a 3hp 220v motor for a good price. Thinking about getting it because I could actually run the pump faster, getting more CFM and it still would not be working as hard as my current motor. Certianly shouldnt overheat.

I'm concerned that the 220v line I have available has a 40 amp breaker. The motor is only 15 amps. It will certainly run fine, but i'm wondering what will happen if something fails and the motor stalls? God only knows how long my homemade pump will last hehe. If something goes wrong there and it ceases, I dont want my new motor to burn up too.

My current motor will just trip the 15a breaker if it stalls. What can I do to have some protection here other than running a 220v 15amp line from the panel?

Is this a dedicated line? If it is, you can just replace the 40 amp breaker with a 15 amp one. If it's not, you may want to put in a small subpanel with a 15 amp line and breaker set-up and run your compressor off that. But also, your new motor probably has thermal overload protection, so it should cut out if overheated.

mmurray70,

The correct breaker would be in the range of 25% over the nameplate amperage.

The proper way to size the pulleys on your set up would be to use a clamp on ammeter on the motor.
You would select your pulley size so that the motor runs at just under the amperage draw of the motor.

Make sure you have a good pressure relief device and you'll have to tip it to get the water out.

All air compressors use reed valves so it'll be interesting to see how it stands up.

Thanks for the replies guys. The motor is thermally protection so if you are running it slightly too hard for a long time it will cut out. But will this do anything to help me in an all out stall condition?

The line I'm using kinda doesnt have a breaker. Now before you guys give me a lecure let me explain. We have a 220v line leaving our house going to the garage, that has a 40a breaker and controls everything in the garage. In the garage we have a smaller panel but the only 220 line is just wired in direct, no breaker there. So the only protection is the 40a breaker that controls the whole garage.

Sizing pulleys shouldnt be much of a problem. I'm guessing the pump is my limiting factor. I think I'm going to run it at 1500 RPM. Running at 860 RPM now off and drawing just under 15a on 115v. So I should have power to spare from the motor.

This one uses reed valves too. I machined a custom head for it out of a solid block of aluminium. I bought 3 Campbell Hausfeld reedvalves that belong to a little powerpal compressor my father had. They were just a few bucks each. Used 2 for the intake and 1 for exhaust. The exhaust valve only lasted a few pump up cycles. The three that I had were really intake valves. I had some old reed valves lying around from a snowmobile engine that were thicker, chopped them up to a suitable size and just used them! Pump has been working great all summer. Be interesting to see how it reacts to that RPM though.

Back on topic now...

I was thinking about using one of those "inline fuse holders". Put it between the wire and motor terminals. You guys know the ones I'm talking about?

I know they are redily available in the automotive industry. As long as it had 14 guage wire it should work ok right? Would the extra voltage caust a problem?

Throw in a 15a slow blow fuse then and I should be fine. If it ever stalls it will just blow the fuse. What do you guys think?

You said you are currently running this thing off 115 volt but are planning to install a 220 volt motor.
Your last post mentions 14 guage and 15 amps. Is this for the 220 volt motor?
You don't say what the nameplate amperage of the 220 volt motor is so any planning is only speculation.

An automotive fuseholder is only rated at 12 volts and is not suitable for 220.
If a 12 volt rated fuse opens in a shorted condition the glass usually shatters and melts the fuseholder.
You are able to get 220 volt rated fuses of the same dimension as auto fuses but the fuse holders are not cheap and they have to be mounted in an approved enclosure.
If you are wanting to protect the motor and are expecting it to stall, a motor starting switch with appropriately sized heaters would be the device to use.

If the panel in your garage does not have space for a 220 volt breaker you could replace it with a panel with more spaces. They are not expensive.
If this unfused line for the compressor is just piggybacked under another wire this is a code violation and could be a hazard.

Greg, as i said in my first post I'm currently using a 1hp motor. Its 115v and draws 15a. Been using it this way all summer, but it runs hot after some use and i'm planning on replacing it with a 220v motor I can get a good deal on.

The line is not completley unfused. If something shorted it will trip the main breaker for the whole garage which is 40a. We run a large welder off the line from time to time so we needed some decent power there.

I'm thinking of those glass slow blow fuses. Most of those are 250v rated. Is it important that I get a 220v rated fuse holder? Alot of the holders i've seen dont even have voltage ratings?

A small sub-panel that would hold 2 - 15A slo-blo fuses shouldn't cost much. I would hazard a guess that you could get one at HD for about $20 ~ $25 + the fuses (and a receptacle, or just hard wire it if it doesn't need to move much).

You are the first person that I've heard of that made his own pump head though. That's on the cool side, even cooler that it's working. Good show.

Yeah the pump is working awesome now. I wouldnt reccomend many people to try this but i'm kind of a "backyard machinst" so to speak. Its a hobby anyway. I'm getting a little oil mixed with the air comming from the pump though. Is a small amount to be expected? The engine did have some very minor scufs in the cylinder. Guess i cant complain.

And by the way, I got an inline fuse holder and just installed it just outside the motor wiring plate. The 15a slo-blow fuse is working great, I tried a 15a fast acting and it blew on startup so I know i'm safe.

New motor is great. Turning the pump 1509 RPM now and its cycling on and off in about 35 seconds with a 25 gallon tank. My buddies got a 6 CFM oilless that cycles almost the exact same time but his tank is 15 gallon. So it must be putting out close to 10. And now I can run it hard with no worries of overheating. Runs amazingly cool. And its just a cheap import? Quite happy with it.

I can post some pics for you guys if youd like to see the contraption.

Love to have a look.