Air Compressor--max pressure question

[ms fowler]

I have a single stage vertical air compressor with a 60 gallon tank
This one: http://www.homedepot.com/p/Husky-60...9rsp2RKskoY9K39QMF-CSb4xxgHYUU6kZQaAi8L8P8HAQ

It seems to take a long time to go from 120 PSI to its shut off at 135 PSI. I know the extra 15 PSI benefits me on the initial use of air as there is more capacity at 135 than 120 PSI. But when running for a longer time, it seems that it wastes too much energy in that last 15 PSI. I try to not use air when the compressor is running so that it gets a time to cool off.
Would the compressor run less if I lowered the max pressure down to 110 or 120 PSI. Nothing I use for long time use requires more than about 50 or 60 PSI.
Am I missing something that would make it a bad idea to lower the shutoff pressure?

 

[The Cobbler]

lowering top pressure is OK. raising is not .

 

[jav]

If you can live with the lower pressure it will help the compressor in that it will stress it less. However- understand that by lowering the high limit, the low limit will also be lowered. But if your max pressure requirement it 60 psi- that shouldn't be a problem. If you use long rubber hoses or anything like an impact wrench, air ratchet or nail gun, the lower pressures will quickly prove problematic.

 

[btdobie]

Piston pumps do become gradually less efficient as the pressure gradient increase so you might save some energy by doing that. That is actually one of the advantages of 2 stage pumps; they remain more efficient at higher pressure gradients.

 

[sberry]

A bit but you are not using this for efficiency but to get work done. Make sure belts are tight. This comp will make the most air and do the most work just before it shuts off and its recovery time will be a lot faster if you DO NOT let it shut off.

 

[CrashmanS]

Mine runs about 110 before shutoff. Most tools are rated at a max of 90 psi anyways.

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[Richard Cranium]

The lower the kick off pressure the easier it will be on the compressor, and the more cost effective for power.

 

[Handyfarmer]

you will find few single stage compressors rated for above 125 psi, even my two stage compressor I have the top end about 140 psi, I just like starting above 100 psi so there is not pressure drop on the power tools when using, (as stated most are rated for 90 to 100 psi).

 

[redmondjp]

Nothing wrong with lowering the pressure - mine shuts off at about 115-120psi (depending upon which gauge you believe).

But your thinking is backwards on not using air while the compressor is running - that is exactly when you do want to use the air. Now if it has been running for ten minutes continuously (for that unit) then yes, allowing it to cool for 20-30 minutes is a good idea.

 

[EOC_Jason]

I dialed mine back to 115, as you and others said it can take more time to get those last 10-15 psi because the pump & motor are having to work harder. Nothing I do needs that high of pressure either.

However, when the compressor kicks on while you are working I would continue to work, unless the pressure drops so low that whatever you are doing isn't operating properly, then I would let it build back up.

 

[Schurkey]

Mine runs about 110 before shutoff. Most tools are rated at a max of 90 psi anyways.

Which for most folks means 125+ in the tank, to achieve 90 psi at the tool, with the tool running.

Which means that most single-stage compressors are unfit for air tool use except with the shortest, least-restrictive plumbing between the tool and the tank. The fact that many folks use single-stage compressors is because they're satisfied with less-than-rated power from their air tools.

But your thinking is backwards on not using air while the compressor is running - that is exactly when you do want to use the air. Now if it has been running for ten minutes continuously (for that unit) then yes, allowing it to cool for 20-30 minutes is a good idea.

It all depends on the duty cycle rating for the compressor. Some are rated for "continuous" duty, others for much less. Far as I know, duty cycle for compressors is like duty cycle for welders--it's based on ten minute intervals. A compressor rated at 70% duty cycle can run for seven minutes out of ten. A compressor rated for 20% duty cycle could run for two minutes out of ten. Cooling for twenty or thirty minutes isn't called-for.

I looked at some of the downloads for the OP's compressor, and there's no mention of duty cycle at all. I'm reluctant to believe that the thing is intended to run continuously; but if they're not going to mention it, they must consider it to be "continuous duty". (Suspicious Me, I'd contact them and ask what the duty cycle is, and if they say "continuous", I'd demand it in writing.)

'Course, in one place it says "3.7 horsepower" and in another it's rated at 3.2 horsepower. They don't seem to know.

 

[Know Wosad]

WFO. Regulator-gauge on the tool itself.In my case it's on the cart. I run 145 off the head and regulate down to 100 at the cart and lower on the tool itself, as needed. If it blows up buy another one.Good compressors run 30-50 years with half assed maintenance. Its an engine. Keep the intake-filter clean.Drain the tank.Change the oil every 5 years. Let it rock.

 

[Schurkey]

WFO. Regulator-gauge on the tool itself.In my case it's on the cart. I run 145 off the head and regulate down to 100 at the cart and lower on the tool itself, as needed. If it blows up buy another one.Good compressors run 30-50 years with half assed maintenance. Its an engine. Keep the intake-filter clean.Drain the tank.Change the oil every 5 years. Let it rock.

For the record, the OPs compressor has a "3-year" warranty, except that EVERYTHING that can go wrong is specifically excluded. Oil consumption? Excluded. Piston ring wear? Excluded. Motor brushes? Excluded. Motor and pump seals? Excluded. Check-valves? Excluded. Tank rust? Excluded. What the hell is left? Some copper tube, and the electrical switches, I guess.

Oh, you're expected to change compressor oil at 50 hours, and then EVERY THREE MONTHS after that. Nobody is going to change compressor oil that often, so the warranty is void three months into your ownership.

 

[Showkey]

I have Speedair cast iron series compressor 10.5 cfm at 90 psi. Single stage that is at least 20 years old.
Run it at 135 psi cut off, when bead blasting it might run an hour or two straight and keeps up just fine. This has been going on for years. Changed the oil maybe twice. Duty cycle

When painting or blasting......run the air through an intercooler to control water.

Waiting for it to die.......it just won't....knock on wood. I will buy a larger compressor the next time around.

 

[CrashmanS]

It all depends to on the duty cycle of your compressor. I had a craftsman compressor when I started my home body shop. Scattered that compressor in a few weeks. Duty cycle was about 20%. The replacement has a 100% duty cycle. Been using that one for 10+ years with no issue.

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[Bandit]

Lower the cut out # to 115 or 120 and the unit will last a lot longer

 

[btdobie]

Someone please correct me if I have wrong information, but compressor duty motors are essentially continuous duty motors with allowance made for the fact that the load on them is modulating and not constant. The part that fails from continuous running is the reed valve in the compressor from overheating.

So if you lowered the pressure the compressor is running at then there would be less heat generated and it could run longer???

 

[EOC_Jason]

So if you lowered the pressure the compressor is running at then there would be less heat generated and it could run longer???

Yes. And the motor wouldn't get as hot or have to work as hard either, and wouldn't consume as many amps so there would be some cost savings, though unless you were a daily user it probably wouldn't be noticable.

 

[sberry]

Even if you used it daily it wouldn't be noticeable. It takes a while to put an hour real work on a comp or welder in a hobby garage. Takes a long time to use a dollar of electric and the savings would be but a pinch of that. It would only add a few cents in a busy work day to a machine operating correctly.

 

[sberry]

We need to keep some perspective. this type of comp cost 50 cents an hour to run when its running, car or pickup truck, 10$ an hour for fuel. Air comp 25 cents investment cost per hr, car,,, ha 50 cents a mile, up to 30$ an hour and we obsess about efficiency on an air comp???????????? Or how fast it wears out, 400$ for a machine can last decades.

 

[sberry]

People spend 4$ on a Starbucks or 2$ on a bottle of water, 6 bucks for a pack of smokes and then fuss over 10 cents an hour in power.

 

[CompressorWorld]

You'll have less air loss running the compressor at lower pressures. Therefore, the compressor will generate more air at a lower pressure setting.

If you only need 60-70 psi, we would recommend setting the compressor to turn off at 110 psi and insert a regulator after the tank, set it for 75 psi.

This will help the compressor start/stop less, offer additional flow (b/c it's running at a lower psi) and help the compressor last longer as it's not being stressed.

Good Luck!

 

[bczygan]

People spend 4$ on a Starbucks or 2$ on a bottle of water, 6 bucks for a pack of smokes and then fuss over 10 cents an hour in power.

Common sense has no place on this forum!

 

[ms fowler]

Great answers, all ( Well, of course they are great because they are what I originally thought!!)
Thank you all.