How hot should compressor get?

[PCustoms]

Possibly dumb question, but how hot should a belt drive compressor head get?

Starts OK, seems to struggle to build pressure, but gage may be bad. Fiddled with the regulator and got 90psi but wasn't climbing. Heads were too hot for me to touch.

Total run time was less then 10 minutes

Am I wrong in thinking the internals are toast?

Also compressor was left behind when previous owner (who did bodywork as a side gig) sold house.

 

[micromind]

The cylinders, heads and discharge piping will be way too hot to touch during normal operation.

 

[PCustoms]

The cylinders, heads and discharge piping will be way too hot to touch during normal operation.

Even after just 5-10 minutes?

Seemed excessive, but been a while since I've dealt with a unit like that.

 

[Hakeem]

Even after just 5-10 minutes?

Seemed excessive, but been a while since I've dealt with a unit like that.

My understanding is that the primary source of heat from a compressor is from the compression itself, not from the friction between the moving parts. (Someone please correct me if I’m wrong). I would definitely expect a compressor running for 5-10 minutes to be too hot to touch. Hell, even my 12v tire inflator gets almost too hot to touch running for a few minutes.

I’d be more concerned about the inability to build pressure past 90psi - hopefully just a faulty gauge. Keep us updated!

 

[OccupantRJ]

They get hot enough that I have a powered wall vent in my 160 sq ft compressor room to keep it below 90f in there when the compressor is in operation.

 

[PCustoms]

Alright, so my thought process was flawed last night.

What I need to do is get an actual pressure gauge on there (and likely undo the 100' hose screwed on) to see what it actually does. Gage on the regulator may be broken/misleading

It did start right up and was smooth and quiet




Looking at this to primarily run a small sprayer

 

[OccupantRJ]

100‘ hose should be fine, but check the pressure before the regulator to see what the unit is really producing. I would want a gauge on the actual tank output permanently anyway.

 

[PCustoms]

100‘ hose should be fine, but check the pressure before the regulator to see what the unit is really producing. I would want a gauge on the actual tank output permanently anyway.

Yes, absolutely what I was getting at.

The gauge on the regulator kind of sucked, so I could have had the tank at 100+ when I gave up.

Unfortunately I didn't have a gauge handy this morning, going to try to pick one up later and at least throw a chuck on it to see what's at the end of the unregulated hose

 

[sparky 1971]

I bought what is probably the same compressor about two months ago so I just used it as a test monkey for you. Everything was 55° to begin with and I let all of the air out before starting. It took 7:50 to fill to 150 psi and when it was finished, one head was 97°, the other 122° the motor was 60°, and the top of the tank had gone up to 68°.

 

[PCustoms]

I bought what is probably the same compressor about two months ago so I just used it as a test monkey for you. Everything was 55° to begin with and I let all of the air out before starting. It took 7:50 to fill to 150 psi and when it was finished, one head was 97°, the other 122° the motor was 60°, and the top of the tank had gone up to 68°.

What did you pay?

I would say I was above 122F as it was uncomfortable, but not burning hot.

Ambient was probably 70F

 

[sparky 1971]

What did you pay?

I would say I was above 122F as it was uncomfortable, but not burning hot.

Ambient was probably 70F

It was on sale for $500.00, but I paid for it with rebates so it didn't cost me any money.

Masterforce® Belt Drive 30-Gallon 155 PSI Portable Electric Vertical Air Compressor

This Masterforce® 30-gallon, oil-lubricated air compressor features a twin-cylinder, cast iron pump that includes a one-piece cast iron crankcase, a thermally stable, cast iron cylinder body, an aluminum head and machined cast iron valve plate, automotive-style ball bearings, curable stainless...

www.menards.com

 

[dscheidt]

My understanding is that the primary source of heat from a compressor is from the compression itself, not from the friction between the moving parts. (Someone please correct me if I’m wrong).

yes, most of the heat is heat of compression -- with a good compressor, the losses in the actual compressor are only a couple percent of the input power. (I think good rotary compressors claim an overall efficiency of 95% -- 95% of the power they consume is used to compress (and thus heat) the air, the rest is motor and friction losses.) It's possible to recover that heat energy, and use it for something else, at least at large scale.

A chemical plant a buddy worked facilities at used a lot of compressed air (they had five or six 400 HP compressors...). They installed a heat recovery system, that transferred heat from the compressed air to heat water fed to the steam plant. That recovered something like 80% of the energy used to compress the air, and saved a huge amount of gas, which paid for the system in a couple of years.

 

[PCustoms]

It was on sale for $500.00, but I paid for it with rebates so it didn't cost me any money.

Masterforce® Belt Drive 30-Gallon 155 PSI Portable Electric Vertical Air Compressor

This Masterforce® 30-gallon, oil-lubricated air compressor features a twin-cylinder, cast iron pump that includes a one-piece cast iron crankcase, a thermally stable, cast iron cylinder body, an aluminum head and machined cast iron valve plate, automotive-style ball bearings, curable stainless...

www.menards.com

Oh, bought brand new.

This was listed for $500, right off the bat got them down. It's mine for $250 but when I ran it last night I had some concerns.

Still need to open the drain, should have done that yesterday...

 

[sparky 1971]

Oh, bought brand new.

This was listed for $500, right off the bat got them down. It's mine for $250 but when I ran it last night I had some concerns.

Still need to open the drain, should have done that yesterday...

I'd be concerned if it didn't shut off. I can only assume that the pressure switch hasn't been messed with and the label says 135psi. I forgot to post that mine hit 135 at around the 6:45 mark while on the way to 150. Even though it's an older unit, it should have climbed to 135 in the time it was running.

 

[PCustoms]

I'd be concerned if it didn't shut off. I can only assume that the pressure switch hasn't been messed with and the label says 135psi. I forgot to post that mine hit 135 at around the 6:45 mark while on the way to 150. Even though it's an older unit, it should have climbed to 135 in the time it was running.

Kind of where my mind was.

I meant to time it, but was fiddling with the gage trying to get it to show.

I'm not sure if it's worth me spending any more time. Granted it's right around the corner and for $250 it will run my coating guns...

 

[sparky 1971]

Kind of where my mind was.

I meant to time it, but was filing with the gage trying to get it to show.

I'm not sure if it's worth me spending any more time. Granted it's right around the corner and for $250 it will run my coating guns...

Where is the gauge even at on it? It looks to me like someone took it off and hooked a hose to where it's supposed to go.

In the end, it's your decision and money, but if the prior owner was using it to paint cars, it's been run a lot. I'd try to get them down a little more by telling them it's going to need a new pressure switch at a minimum. I bought mine so I didn't have to listen to the 60 gallon compressor run every time I used an air tool. It's fine for impact wrenches, airing up tires, and blowing things off but when I'm doing something that uses a lot of air, I use both compressors together. The big one ( it might be 3 HP) couldn't keep up with a cutting wheel or die grinder, but if I use them both at the same time they will keep up, but not gain.

 

[micromind]

Even after just 5-10 minutes?

Seemed excessive, but been a while since I've dealt with a unit like that.

I wouldn't be surprised if it was too hot to touch in less than a minute.

The heat comes from compression, not friction.

 

[PCustoms]

Where is the gauge even at on it? It looks to me like someone took it off and hooked a hose to where it's supposed to go.

Exactly

In the end, it's your decision and money, but if the prior owner was using it to paint cars, it's been run a lot. I'd try to get them down a little more by telling them it's going to need a new pressure switch at a minimum.

Nice couple, but clueless about tools, and this was left in the garage. I actually felt bad after I left and realized I left it pressurized.

Don't want to be a **** and beat them up too bad. Walking away might be the best choice.

If I had need for a 60 gallon I'd buy new in an instant, the reality is I just need to air up tires, blow stuff off and occasionally run an undercoating gun or an hvlp.

 

[sparky 1971]

Exactly



Nice couple, but clueless about tools, and this was left in the garage. I actually felt bad after I left and realized I left it pressurized.

I always leave mine pressurized. It took forever to get it empty this morning.

Don't want to be a **** and beat them up too bad. Walking away might be the best choice

I don't think your beating them up. They don't have anything invested in it and it was left behind for a reason. The reason could be there was no room to take or it was forgotten, but could just as easily be that it's junk.

If I had need for a 60 gallon I'd buy new in an instant, the reality is I just need to air up tires, blow stuff off and occasionally run an undercoating gun or an hvlp.

I wasn't trying to say you should buy a 60 gallon even though that's the traditional GJ way. Just saying that the 30 gallon is extremely limited. I have no clue how much air a sprayer needs. If I'm spraying, it comes out of a can.

 

[PCustoms]

I wasn't trying to say you should buy a 60 gallon even though that's the traditional GJ way. Just saying that the 30 gallon is extremely limited. I have no clue how much air a sprayer needs. If I'm spraying, it comes out of a can.

Yeah, I was saying that if I had a real use case I'll plunk down $1500 if I know I'll use it.

But to spray goop in a gun that needs 5cfm@50psi 2x a year I'd rather not. I should look better at an hvlp and make sure I'm not shortchanging myself because I do need to get a turbine gun or hvlp to finish a bunch of interior projects.

Also there's a lot of $500 new compressors listed for $500 used around here, and old *** craftsman "5hp" oiless models

 

[GeoBruin]

For what it's worth, in that size/output range, I would look really hard at the Harbor Freight Fortress 26 gallon oiless compressor (the 175 psi model). They're $400 new, and can be had for less with the occasional coupon or sale. 4.5 CFM at 90 psi, which should hit the 5 CFM at 50 psi target stipulated earlier. It also puts out 175 psi, which may not be needed often, but is nice to have if you occasionally needed to run an impact or some kind of high consumption tool that could benefit from higher pressure.

Last, but definitely not least, it's QUIET. My friend has one and it sits right next to his little blast cabinet in his shop. Normally, that would ****, bit it's quiet enough that it's no big deal to stand right next to it for extended periods.

I had a 2ish horsepower oil lubed compressor similar to the Husky in question and I had to kick it out of my shop. It was just too loud.

 

[johnre]

If you want confirmation that it's the air compression process itself, not friction in the mechanicals, simply open the tank drain and let it run for your same ten minute test period. There will be no appreciable heat buildup on the cylinder head.

 

[PCustoms]

If you want confirmation that it's the air compression process itself, not friction in the mechanicals, simply open the tank drain and let it run for your same ten minute test period. There will be no appreciable heat buildup on the cylinder head.

So....

They messaged me to come back today, as "they got it working" (had a fitting that sort of fit the QD and had air *******).

I hadn't cleaned up yet it's it's 5 min away so went over. Setup a regulator and hose had 80psi in it. Went to drain the tank for a cold start from 0 and fought with the tank drain (cramped spot dark) and got clean water followed by oil/water. Ok good sign.

Kept screwing it blind, went the wrong way, went the right way. Got down eye level and wound it the way in, still leaking.had it bottomed out on the floor, still leaking.

Fired the compressor up and let it run for maybe 5-10 minutes, with the leak would not get above 20psi. Heads were very warm, could leave hand on them but not for long.

TL;dr somehow got drain stuck open and compressor got hot building no pressure

 

[sparky 1971]

So....

They messaged me to come back today, as "they got it working" (had a fitting that sort of fit the QD and had air *******).

I hadn't cleaned up yet it's it's 5 min away so went over. Setup a regulator and hose had 80psi in it. Went to drain the tank for a cold start from 0 and fought with the tank drain (cramped spot dark) and got clean water followed by oil/water. Ok good sign.

Kept screwing it blind, went the wrong way, went the right way. Got down eye level and wound it the way in, still leaking.had it bottomed out on the floor, still leaking.

Fired the compressor up and let it run for maybe 5-10 minutes, with the leak would not get above 20psi. Heads were very warm, could leave hand on them but not for long.

TLr somehow got drain stuck open and compressor got hot building no pressure

The drain valves that come with those are junk. The first thing I did when I bought mine was get rid of it and replace it with a 1/4" street 90°, 1/4"X6" ******, and a 1/4" ball valve with a hose barb on the other end with about 3' of hose on it. I can point it out the door when I drain it.

I lied. That was the second thing I did. The first thing I did was lose the regulator. Both were completed before turning it on for the first time though.

 

[micromind]

The drain valves that come with those are junk. The first thing I did when I bought mine was get rid of it and replace it with a 1/4" street 90°, 1/4"X6" ******, and a 1/4" ball valve with a hose barb on the other end with about 3' of hose on it. I can point it out the door when I drain it.

I lied. That was the second thing I did. The first thing I did was lose the regulator. Both were completed before turning it on for the first time though.

Just for info, the reason for the street 90 is if the pipe gets stepped on or something, the horizontal pipe will break at the 90 and the 90 can easily be replaced.

If a normal 90 and a close ****** is used, it'll break where it goes into the tank......not quite as easy to replace........

 

[rlitman]

Just for info, the reason for the street 90 is if the pipe gets stepped on or something, the horizontal pipe will break at the 90 and the 90 can easily be replaced.

If a normal 90 and a close ****** is used, it'll break where it goes into the tank......not quite as easy to replace........

Maybe, but I'm not so sure. I'd kind of trust the steel close ****** to be stronger than a cast iron street elbow, and in any case, an ez-out would make short work of a broken ******. If you really want it to break that way, put a brass section of pipe in the horizontal part.

 

[sparky 1971]

Just for info, the reason for the street 90 is if the pipe gets stepped on or something, the horizontal pipe will break at the 90 and the 90 can easily be replaced.

If a normal 90 and a close ****** is used, it'll break where it goes into the tank......not quite as easy to replace........

I didn't look at it that way. I was afraid it would hit the floor if I used a close ****** and a normal 90, there might be 1/2" to spare with it as is. I guess for once I did good without even having to think about it.

 

[johnre]

TL;dr somehow got drain stuck open and compressor got hot building no pressure

Check oil level in the crankcase.

 

[PCustoms]

Check oil level in the crankcase.

Was fine

 

[PCustoms]

Went for a little ride after work:




Guy had it in a race trailer for his tires. Not sure what he was racing, wasn't a big trailer. A few scuffs from being bolted down and shaking in the trailer but looked pretty new. Pumped fast, cycled a few times and was mildly warm at 150psi. Dumped the drain and got a little water then oil, drain closed right up.

It came home, should work fine.

 

[OccupantRJ]

I recently tied both my compressor drains together and exited out the stem wall to make things easier to drain and less messy.

 

[PCustoms]

I recently tied both my compressor drains together and exited out the stem wall to make things easier to drain and less messy.

I'm not OCD, but that long threaded rod would bother me...

 

[OccupantRJ]

I'm not OCD, but that long threaded rod would bother me...

It is there for a special reason and is in one of my threads about moving the compressor.

 

[OccupantRJ]

@PCustoms Sorry, my ipad battery was getting low last night. This is the thread about moving the compressor. I took the dolly apart and stored it in the corner behind the compressor in case of my son ever needing to move it out again after I depart permanently, or in case the upper components need to be hoisted off. Room is too confined for an engine hoist. This way, the dolly and it’s parts do not disappear over time.

Vertical compressor lifting and moving dolly

After restoring a vertical air compressor that I had, I needed to move it through a walk doorway into the back room of the shop. It is a rather top heavy unit, so I developed a special lifting/moving dolly to allow me to safely move it through the doorway, turn a hard right, then roll it down a...

www.garagejournal.com