Can I size down a 60gal Compressor motor?

[BlackwaterDSM]

Hey all, I figured I’d post this question to those much wiser than myself. Before we begin, I’m definitely no electrician and don’t mess with power, hence I’m trying to ask the right person. A deal came across my lap that I couldn’t pass up and I got (3) 60gal Husky compressors from a shop that was going out of business for $100 each. I’d like to take one of these to my house, but I only have 110/115v at the house and these are all wired for 220+ (one of them was hard-wired straight into a sub-panel). I know re-wiring the motors to run on 110 is possible but can be very problematic, so my question is, can I just do a straight swap-out of the electric motor on one of them to a smaller motor (like a 2hp/3hp 100v motor) and have it run the pump that’s already on it? This will see VERY little use in my home garage and I’m not super worried about the lifespan on the electric motor as they are a dime a dozen on OfferUp. Once it’s charged, it might recharge ONE more time each time I use it, so I don’t forsee a huge strain on a smaller motor. Not like I’ll be running it hours on end. I have an old Datsun I’m restoring and just need enough air to feed an occasional sander or to feed a spray gun when it comes time to lay down some paint. I’ll attach pics of the compressor pumps for reference. Thanks in advance for any and all help!

 

[LopezBart]

Sure... just change the pulleys to give you more reduction proportional to the drop in hp. current motor pulley size * new motor hp / Current motor hp = new motor pulley size. There is a practical minimum size, and you'll need a capacitor start motor. But air sanders draw a LOT of air, so be careful there.

Btw, it's unusual to have only 120V at a house. You might not have any 240V outlets, but a 120V feed is unusual.

 

[BlackwaterDSM]

Sure... just change the pulleys to give you more reduction proportional to the drop in hp. current motor pulley size * new motor hp / Current motor hp = new motor pulley size. There is a practical minimum size, and you'll need a capacitor start motor. But air sanders draw a LOT of air, so be careful there.

Btw, it's unusual to have only 120V at a house. You might not have any 240V outlets, but a 120V feed is unusual.

Barrrrt! How’s it going man? Thanks for your help the other week with my 60gal “broken fitting”. She’s running like a champ (at work)! I’m not sure what all is running through my panel, but I do know every outlet (including my “Energy efficient” washer and dryer) are all standard household outlets. I’ve had to replace a couple and saw they are marked as 12a outlets. So I guess what I meant to say is there is no outlet to feed a 60gal compressor, not even in the garage. I called a couple electricians who all wanted over $1000 to install one in the garage and that’s a bit pricey for me since I may be moving sometime soon anyhow. The air sanders won’t be on a whole lot and I’ll be mindful of the compressor the whole time. I do quite a bit of plasma cutting using my 33Gal and my Everlast Plasma and after a few breaker trips in the past, I quickly learned the limits at my house. Lol. You get about 60 seconds before it goes dark. So I go 45 seconds and then wait a few minutes for everything to cool down. I’m a patient man when I need to be, since it’s easier than calling the fire department. Lmao.

 

[BlackwaterDSM]

Sure... just change the pulleys to give you more reduction proportional to the drop in hp. current motor pulley size * new motor hp / Current motor hp = new motor pulley size. There is a practical minimum size, and you'll need a capacitor start motor. But air sanders draw a LOT of air, so be careful there.

Btw, it's unusual to have only 120V at a house. You might not have any 240V outlets, but a 120V feed is unusual.

Wouldn’t a reduction in pulley size also cause the compressor pump to run faster? If I reduce electric pulley and/or oversize pump pulley, that would make the comp. pump run too fast, no?

 

[Steve_P]

I'm doubtful that you could get a 120VAC motor to spin that pump at pressure. Which is why they have 240V ~15A motors on them. To operate on a typical outlet, you're looking at half the available power and wanting to rotate the same thing.

If you have an electric clothes dryer, you have a 240V outlet.

 

[LopezBart]

Wouldn’t a reduction in pulley size also cause the compressor pump to run faster? If I reduce electric pulley and/or oversize pump pulley, that would make the comp. pump run too fast, no?

If you make the motor pulley smaller (which is what I meant to suggest), the pump will spin more slowly, just as shifting the front derailleur on a bike to a smaller chain ring will reduce the speed of the rear wheel for a given pedal cadence.

 

[LopezBart]

An air compressor pump basically takes torque proportional to the output pressure to spin, and hp proportional to the product of rpm and pressure (torque). If you halve the speed of the pump, it will take half as much power (basically) to spin it. If you halve the pressure, the same.

 

[BlackwaterDSM]

I'm doubtful that you could get a 120VAC motor to spin that pump at pressure. Which is why they have 240V ~15A motors on them. To operate on a typical outlet, you're looking at half the available power and wanting to rotate the same thing.

If you have an electric clothes dryer, you have a 240V outlet.

It’s an electric dryer… upstairs… and it actually runs on a 12a 120v outlet. That was my concern regarding a motor swap was I figured I’d have to change the gearing which would alter pump speed. I mean, it would be awesome to have a 60gal at home, but not for the $1200 expense just for an outlet install.

 

[BlackwaterDSM]

An air compressor pump basically takes torque proportional to the output pressure to spin, and hp proportional to the product of rpm and pressure (torque). If you halve the speed of the pump, it will take half as much power (basically) to spin it. If you halve the pressure, the same.

My curiosity is that spinning at a slower speed, it may not make full pressure. The smaller one is rated at 135psi, but there’s 2 black twin Husky’s that are rated at 155psi and the pumps seem slightly different than the 135. I do know it’s the pressure regulator that changes that, but I’m wondering if the 135psi pump is a different design and can handle running slower and still make the 135psi? “Things that make you go ‘Hmmmmmmm’ “

 

[BlackwaterDSM]

An air compressor pump basically takes torque proportional to the output pressure to spin, and hp proportional to the product of rpm and pressure (torque). If you halve the speed of the pump, it will take half as much power (basically) to spin it. If you halve the pressure, the same.

I'm doubtful that you could get a 120VAC motor to spin that pump at pressure. Which is why they have 240V ~15A motors on them. To operate on a typical outlet, you're looking at half the available power and wanting to rotate the same thing.

If you have an electric clothes dryer, you have a 240V outlet.

Here’s a pic of the specs, which factory claim is only 3.7hp and they do make 3hp 120v motors (or so they claim… I’ve read that true 3hp is impossible from 120v, but again, I’m no electrician). Either way, I got all 3 of them for $300, so the price couldn’t be beat. I’ll hang on to 2 of them for shop/future home and re-sell the 3rd. Weird that the 155psi say 3.7hp and the 135psi says 7hp???

 

[LopezBart]

The air compressor's maximum pressure is governed by the pressure shut-off switch. The volume of air it produces is determined by the rpm of the compressor. Running it more slowly will not change the pressure at which it shuts off, just how long it takes to fill the tank.

 

[finn]

I’ve never heard of a 12 amp outlet.

What am I missing?

My Kobalt 2hp “spl” belt drive motor draws 15 amps when wired for 120v, and 7.5 amps wired for 240v.

I doubt you’ll be able to find a motor and pulley combination that will work. The compressor head sounds like it has too much swept volume to run on what I suspect is a 15 amp ( not 12 amp) circuit.

 

[BlackwaterDSM]

I’ve never heard of a 12 amp outlet.

What am I missing?

My Kobalt 2hp “spl” belt drive motor draws 15 amps when wired for 120v, and 7.5 amps wired for 240v.

I doubt you’ll be able to find a motor and pulley combination that will work. The compressor head sounds like it has too much swept volume to run on what I suspect is a 15 amp ( not 12 amp) circuit.

12a outlet on a 15a circuit. I’ve removed and replaced actual 12a outlets. They are stamped 12a/125v on the back/side of the outlet itself. I’m not saying that’s the power on the circuit, that is what is stamped on most of my outlets which as they’ve died, I’ve replaced with 15a ones.

 

[seber]

If you show us a photo of the motor information plate, you will get more informed answers.

 

[BlackwaterDSM]

The air compressor's maximum pressure is governed by the pressure shut-off switch. The volume of air it produces is determined by the rpm of the compressor. Running it more slowly will not change the pressure at which it shuts off, just how long it takes to fill the tank.

Ahhhh, okay. Makes sense. I just thought running it at a slower speed wouldn’t produce the same psi. I’m not worried about how long it takes to charge (as long as the motor doesn’t overheat. Lol), I could just really use more air at home. Worst case scenario, the price I paid was worth the 60gal tank and regulator/lines anyhow, so I could always swap a smaller motor AND pump if it becomes too much of a problem. I also have a 5000w generator with a 240v plug, but it’s as loud as can be and don’t really wanna piss off the neighbors too much.

 

[BlackwaterDSM]

If you show us a photo of the motor information plate, you will get more informed answers.

They are currently at my shop and I’m not, but tomorrow I will try to snap and upload photos. I know they always fudge numbers on their marketing stickers. Like “7hp!!!” End up being 3hp “running”. Lmao

 

[strutaeng]

You may be able to get by with a true 2HP motor. I've got an older Emglo (now Jenny) 17 gallon that has a giant GE motor with a rated amp draw of 19A (apparently the motor is original.) Mine will run fine on a 20A, but will trip a 15A circuit. The rated output is like 8.1 CFM @ 100 psi.


Those motors on those compressors are like the SLP or whatever they have for the HP rating, and they are 3450 RPM.

Just figure out what motor pulley is needed to slow the pump a certain percentage.

May take some trial and error to get the right pump RPM and a ammeter to ensure you are not overloading the motor. I don't believe there are pump curves for those little pumps.

The other thing to keep in mind is that a lot of pumps (the ones that actually have specs) have a minimum recommend rpm to keep them lubricated, usually 550-800 rpm or somewhere in that range.

It's probably just easier to sell that one and get yourself a 120V compressor.

 

[BlackwaterDSM]

You may be able to get by with a true 2HP motor. I've got an older Emglo (now Jenny) 17 gallon that has a giant GE motor with a rated amp draw of 19A (apparently the motor is original.) Mine will run fine on a 20A, but will trip a 15A circuit. The rated output is like 8.1 CFM @ 100 psi.


Those motors on those compressors are like the SLP or whatever they have for the HP rating, and they are 3450 RPM.

Just figure out what motor pulley is needed to slow the pump a certain percentage.

May take some trial and error to get the right pump RPM and a ammeter to ensure you are not overloading the motor. I don't believe there are pump curves for those little pumps.

The other thing to keep in mind is that a lot of pumps (the ones that actually have specs) have a minimum recommend rpm to keep them lubricated, usually 550-800 rpm or somewhere in that range.

It's probably just easier to sell that one and get yourself a 120V compressor.

I got 3 of them for $100/ea, so even if I have to retro-fit it with smaller motor and pump, still ahead money-wise. I enjoy stupid little OfferUp projects from time to time. Hahahaha. I also turned a 30gal into a gas operated one to use in the field cause a brand new one was well over $1,000… got a HF 212cc motor for practically free and spent maybe $100 on the necessary stuff to make it run. I like the thought of 60gal at the house, even if it takes longer to charge up. Biggest problem is with my smaller 30gal and plasma cutting I run out of air in just under a minute, my 30gal compressor kicks on, and then plasma and air are both running on same circuit and trip the breaker. With a 60gal I could double up on that time even if I have to just charge the 60 up, turn it off and run a cut, then stop cutting while it charges back up. Basically, I just need to move to a whole new house to do fun stuff. Lmao! I do like your ideas though and will do some research. I know there’s a pulley calculator online I’ve used before making a go-kart.

 

[BlackwaterDSM]

Totally forgot… they also came with a spare motor. I tested all 3 compressors to make sure they all charged to max psi, but they also had a spare motor they included from some other tool that died previously. They kept the motor because it was the only thing salvageable I guess. They tossed it in with the deal. I don’t necessarily have to use it, but hey, it was $Free.99 so I grabbed it. 22a draw so it may be useless for now, but we’ll see. Here’s the pics…

 

[The Cobbler]

Sure... just change the pulleys to give you more reduction proportional to the drop in hp.

but you have to be careful to stay within the rated specs of the pump or you may not have enough splash lubrication with too low an RPM

also, I find it hard to believe the OP only has 120v at the house ( in this day & age)

 

[BlackwaterDSM]

but you have to be careful to stay within the rated specs of the pump or you may not have enough splash lubrication with too low an RPM

also, I find it hard to believe the OP only has 120v at the house ( in this day & age)

I appreciate the advice on the pump and will do some research on the minimum RPM. As per the second part… you sure about that? CRAPifornia house built in 2005. Every single appliance runs on 120v. Including washer and dryer which can run at the same time without tripping the breaker. Trust and believe I wouldn’t be on here asking about lowering the efficiency of a 60gal compressor and running my $4k welder on only 120v if I had a 240v receptacle within a mile of me.

 

[The Cobbler]

is that a California thing , to only have 120 at the house ? seems weird to me. and what sense does it make?

 

[BlackwaterDSM]

is that a California thing , to only have 120 at the house ? seems weird to me. and what sense does it make?

You tell me man. It makes no damn sense at all. House was built in 2005, had a mix of 12a and 15a 125v outlets, and absolutely NO 220v-240v outlets anywhere. The garage door runs on 120, washer and dryer, refrigerator, and dishwasher, all 120. Water heater and stove are gas (now outlawed in CA, I’m a gangster though and cook my eggs with FIRE! Lmao). But yeah… it was huge decision when I was buying my newest welder so I made sure I could run dual voltage before I bought it and I’m limited to like 1/8” steel because of it (unless the obvious root/hot/cap method is used for thicker material).

 

[BlackwaterDSM]

is that a California thing , to only have 120 at the house ? seems weird to me. and what sense does it make?

There’s been like 20 people on various forums INSISTING that I have more than 120 and I just have to laugh it off cause of my weird-a$$ house. I own 11.5ac in San Diego and I’m trying to get a house build together and that one is gonna have a dedicated panel just for the “shop” to run my welders and large compressors. Until then, I just have to make due I guess. Only a couple more years of “tinkering” instead of actually “working”. Grrrrrr….

 

[The Cobbler]

I'd like to see a picture of your main panel .

 

[LopezBart]

Keep in mind while you may not have any 240v breakers or outlets, you almost certainly have both phases in the panel.

 

[mike93lx]

You tell me man. It makes no damn sense at all. House was built in 2005, had a mix of 12a and 15a 125v outlets, and absolutely NO 220v-240v outlets anywhere. The garage door runs on 120, washer and dryer, refrigerator, and dishwasher, all 120. Water heater and stove are gas (now outlawed in CA, I’m a gangster though and cook my eggs with FIRE! Lmao). But yeah… it was huge decision when I was buying my newest welder so I made sure I could run dual voltage before I bought it and I’m limited to like 1/8” steel because of it (unless the obvious root/hot/cap method is used for thicker material).

Never heard of a 12a receptacle and nothing comes in a Google search. Feel like something is being missed or mistaken there

If you are buying receptacles that are labeled 12A, I would assume they are junk

 

[BlackwaterDSM]

I'd like to see a picture of your main panel .

I think the only thing that might be 220 is the AC unit, and it’s for sure hardwired to the panel and way up in the attic above the house. I’ll try to get out and take a pic.

 

[manwithtools]

PLEASE post a picture of your power distribution panel with the door open and the breakers visible. It will take that to convince me you don't have 240 volts available in any house in the USA built in 2005!

Also include a picture of the panel part number.

 

[The Cobbler]

I think the only thing that might be 220 is the AC unit,

so, there is 240v at the house.

only have 110/115v at the house

 

[BlackwaterDSM]

Keep in mind while you may not have any 240v breakers or outlets, you almost certainly have both phases in the panel.

Oh, I wouldn’t doubt it does, especially for the AC unit. I’m sure it has one hell of a power draw since it costs me nearly $600/month to run in the summer time.

 

[BlackwaterDSM]

PLEASE post a picture of your power distribution panel with the door open and the breakers visible. It will take that to convince me you don't have 240 volts available in any house in the USA built in 2005!

Also include a picture of the panel part number.

I never said “not available”, I said no OUTLETS/RECEPTACLES. No plugs. Nothing I can just grab a plug, push it in, and use.

 

[The Cobbler]

I only have 110/115v at the house

in all fairness. you did imply you didn't have 240 at the house. that's quite different than what you;re saying now