Advice on Air Compressor System for Shop

[Paul Alciatore]

As some of you may recall, I am in the process of setting up a permanent shop in my garage. One thing that I feel I need is an air compressor for general purpose use. I will probably run an air line down the middle (on the ceiling) and have several outlets, including one at the garage door for outside use on cars and bikes.

I plan to locate the compressor and tank in a small utility room in the rear corner of the garage which it will share with the water heater and my grinding equipment (to help keep the abrasive dust away from my other machines). So I will probably use extra filtration on the air intake or run an intake pipe throuth the wall to the garage itself.

Anyway, now for my questions.

First, I have an idea to purchase a somewhat small, portable compressor, probably with a small tank. My needs for air are not large and my bank account is somewhat small. Making it portable will allow it to be used in other locations. But, I may need larger quantities of air at times. So I am thinking about getting a larger tank and adding it to the system. It would be located downstream from the original tank and could either be filled at the same time or in increments with a solenoid valve and timer circuit. I am concerned with the run time of a smaller compressor and do not want to overheat it or otherwise exceed it's capacity and incur an early death.

I could use a timer circuit to limit the run time to some safe value and then let it rest for enough time to cool off before running again. It would take several such run-rest cycles to fill the big tank.

Or I could use a solenoid valve between the tanks and leave the original compressor's controls as is. The solenoid valve would open at intervals to allow the bit tank to fill from the smaller one. The time between these openings would assure the rest time for the compressor. It would only open for a few seconds to allow the pressures to equalize between the tanks. When the big tank reaches full pressure, it would stop operating.

Does anybody see any problems with either of these methods? Which would be better?

Second question would be about the pressure I should go for. I would think 60 or 75 PSI would be the minimum. Perhaps 100 or 150 would be better. Any thoughts here? I did say general use so I have no specifics here beyond the occasional tire inflation.

Third question would be on the sound level. I have installed air systems for commercial use and they were almost always loud. They were installed in an out of the way corner where the noise would be least likely to be heard. But this would be in my house, about 20 feet away from my neighbor's house - bedroom wing. So I don't want any complaints. Any advice on brands or types of compressors in this regard would be appreciated. Also, any suggestions on sound absorbing materials for the room. All I can think of so far is fiberglass insulation. That would also help with the AC bill in summer here in south Texas.

TIA

[mechanicalmagic]

Paul,
A few thoughts. A "small portable air compressor" usually means one of the oil-less designs. In my opinion, they are for very intermittent work, like filling tires. If you can find a compressor that has crankcase with oil, you will be MUCH better off. Spend the money for a good compressor, and forget the valves, you don't need them.
Sound deadening; I would use sheetrock connected to staggered studs, with insulation between. A few extra studs are cheap. If you want to spend more money, cover the outside with concrete backer board.

DJ

[Black_Moons]

Get a proper low RPM (600~800rpm or so at the compressor head) oil filled compressor. And it will be quite enough that it will be quieter then your oilless pos with all the sound dampening in the world. And it will likey cost less then all that sound dampening, extra tank, solanoids and maintence on the oilless would of cost. (And they DO need maintence, And by maintence I mean, replacement pistons and such)

[Arthur.Marks]

This stuff is basically over my head. That said, here has been my experience with a small shop + compressor. I bought a Craftsman 7-gallon 1HP oil-lubricated compressor. The general advice I read was that it was a complete, utter POS that would break down, not work, etc. It works fine. I primarily use it for blow-off application but also use a misting system on my mill/drill. It works okay for the mister, but the motor must run continuously which is annoying. In fact, if you fill the tank, use a blow gun and run it continuously, it will hold a max of only 60psi. After a while, the motor heat and condensation starts to produce quite a bit of water in the line/spray. Based on this, I would say a 20gallon tank is the minimum I would recommend regardless of shop size. I'm not sure if the above problems would be remedied by such, though. For a small shop that doesn't need to use air tools continuously it would probably suit you and your wallet pretty well, as it has mine. I can get a few minutes of decent pressure (i.e. 80-90psi) before the compressor levels out at 60psi as I mentioned. This is usually more than enough time to complete whatever operation I am doing. Then the compressor has time to recycle and refill the tank. I know you can't really specify at the moment, but I might suggest making a "possibles" and "wish" lists for things you might use the compressor for before buying.

[wierdscience]

Paul I can highly recomend Makita's line of small compressors.They run 1800 rpm as opposed to 3600 and are very quiet,much more so than the Sears or CH ?They also feature REAL pleated air filters instead of foam rubber and IIRC they also have cast iron cylinders.

http://www.google.com/products/catalog?hl=en&q=makita+air+compressor&rlz=1W1GGLL_en&um=1&ie=UTF-8&cid=15197939948697881275&sa=X&ei=2IZ1TaTfI8Oy0QHa0PnjBg&ved=0CDoQ8wIwAA#

http://www.google.com/products/catalog?hl=en&q=makita+air+compressor&rlz=1W1GGLL_en&um=1&ie=UTF-8&cid=17411137838681196793&sa=X&ei=O4l1TdakDYOJ0QGvgYXqBg&ved=0CDMQ8wIwAQ#

http://www.google.com/products/catalog?hl=en&q=makita+air+compressor&rlz=1W1GGLL_en&um=1&ie=UTF-8&cid=3800790525139572635&sa=X&ei=2IZ1TaTfI8Oy0QHa0PnjBg&ved=0CEAQ8wIwAg#

I also have a friend in a similar situation who bought two of the smaller pumps and set them up with a duplexing control.It will run one pump at a time alternating between the two,or with the flip of a switch run both at once for more volume.Works pretty good,but still gets into $800-1000 single tank compressor territory.

[PTSideshow]

How to choose a compressor here is great information, it applies to what ever compressor you choose.

Buy the largest compressor you can afford or save for, so you don't have to upgrade in 3 months. You can always add hose to use it out and around the shop/garage. If you need a portable a pancake one would work for later and if you have electricity.

People seem to under estimate the size and needs for an air compressor. Bigger is better, as it always ends up being MORE AIR!

[Gravy]

Paul,

The smallest cheapest compressors beat the snot out of a bicycle pump, but that's about it.

The old school standard portable compressor that was sold by Sears and a host of others for decades was good enough for most home shop/garage uses. It had a two cylinder belt-driven pump on a 12-20 gallon tank, with two wheels and a handle. You've seen a bunch of them.

It put out about 5 to 6 SCFM(Standard Cubic Feet per Minute)@90PSI (Pounds per Square Inch). Those are the important numbers. It was acceptable for rotating tires with a 1/2" impact wrench if you weren't in a hurry. It would run a small paint spray gun intermittently, and inflate tires and air mattresses.

That should be your minimum standard. It was good enough for millions of users from the 1950's until pretty recently. If you are certain you aren't going to buy a bunch of air tools, don't worry too much about oil vs oilless, or direct vs belt drive. Just make sure it's rated for at least 5 SCFM at 90PSI. Anything less will have you swearing at yourself for being just a little too cheap. I think something like that will cost you $250-$400 new if you shop a little.

If you spend much less, you will fall out of the air compressor category and into the tire inflator class. OTOH, for a couple hundred bucks more, you can move from portable to stationary compressors and get something that will keep up with anything short of a small sandblaster.

If you are buying used, you can get really serious about air power.

That's my long-winded way of advising you NOT to buy any compressor that's "just big enough".

It won't be.

[Dr Stan]

Paul,

I too recommend one with an oil bath instead of an oil less as they last much longer. As to keeping the noise level down a trick I learned from an HVAC tech is to line the inside of the space with acoustic tile. Fairly inexpensive and really helps.

Stan

P.S.

You also need to consider the horizontal/vertical question, especially if you plan to move it around. Verticals are nice in that they take up less room and in general you'll get less water into your pneumatic tools. However, they can be very top heavy. I had a 5 hp vertical cast iron twin cylinder 30+ gallon that was frankly dangerous to move around. It had a frame similar to a two wheel dolly so I was able to add some 1" sq tubing and some casters that allowed me to tip it back at a 30 degree angle without it falling on top of me.

[David Powell]

I can hear the advice echoing-----

Paul, do not cheap out, not having " quite" enough air is a misery. Believe me I know! To usefully keep up with even my limited needs my little ( Home brewed , underpowered, oiled crankcase, single cylinder ) outfit is chugging around most of the time, get a twin cylinder oiled crankcase job driven by a proper 2 hp or more motor and have a 20 -50 gallon tank in the system. You will not regret going " too big" but you will forever curse going" just enough for now" Regards David Powell.

[millwrong]

"My needs for air are not large..."
Start by determining what your needs are numerically,i.e. generate a total CFM usage. That usually starts the game and the size of the ante.

[Mr Fixit]

Hello Paul,
I had the same plan as you do now and when I did get the first air compressor it was an oiless one. It just did not keep up with even the simple uses in the shop I.E. cleaning the sawdust out, air tool use, and some early trials at spray painting. Ultimatly it under performed. Why I am telling you this is, do try and get the oil in the crank case 2hp or larger system. I have seen them here in Oregon, LOTS of air comps for sale some very new ones and some real dogs. Do a little homework just like this question thread and shop used you can get a real good buy if you keep looking. I have finally upgraded to a 10hp 3phase 60 gallon so I can do some sandblasting of car parts that I am restoring. I got the whole thing for $350.00 and do not regret it at all. good luck on you quest keep us informed.
Just adding one more thing, you should go read the favorites sticky on air compressor distribution it may give you some good ideas.
Chris
Mr. Fixit in the family

[Gravy]

I think we have a consensus here.

Paul - listen to your friends. Get something at least twice as big as what you've been trying to convince yourself is "enough". Get something that turns relatively slowly and has a big tank. Get something that will do all you need and then some, at a relaxed pace. You probably don't need a full industrial unit, but you do need something better than a minimal homeowner compressor.

We're talking about a cost difference of maybe $200-$300. This will save you money and frustration - not just in the long run, but in the next year.

If you have to save pennies to feed the baby, disregard my advice. If you are trying to save a buck to buy a better tennis racket or putter, maybe you should re-evaluate. If you need to save a few bucks to lubricate diplomatic relations with SWMBO...never mind. I never said nuthin'. Best of luck to you.

[fixerdave]

I run a 'small' (20gal tank) compressor (hung from the ceiling for space) with a second 60gal tank I leave outside. Put a valve between the two, so you can fill the small one only when you're in the rush for air. In doing this, you will need a safety pop-off valve on both tanks, just in case. You will also need accessible drain valves (or suitable plumbing) for both. I also run a separate regulator (and filter) outside.

In going the small compressor - lots of storage route, the most important thing is your max pressure. You will need 90psi to run most tools and, as such, the only real storage worth having in what's over 90psi. In other words, if your compressor runs 90psi and your tools need 90psi then all that storage is not going to amount to much of anything. On the other hand, if you can get up to 135psi, then that extra tank will make a difference.

Also, 'small' doesn't necessarily mean junk. My compressor is a cast iron oil-bath unit with a 100% duty cycle, or so the manufacturer claimed and backed it up with a 5 year warranty (I even called the stupid 1-800 number to confirm this). It's out of warranty now and still going strong. It routinely runs for 30 minutes straight, longer if I'm working on something.

Air is wonderful... impact guns are serious problem solvers and it's amazing how useless air chisels are, until you figure out how to use them, and then they're great too Again, buy quality, because air tools are one place you really, really notice the difference.

David...

edit... don't even think about using an old propane tank for extra air storage... this board is probably full of creative people that made that mistake and are too proud to admit it

[Gravy]

I run a 'small' (20gal tank) compressor (hung from the ceiling for space) with a second 60gal tank I leave outside. Put a valve between the two, so you can fill the small one only when you're in the rush for air. In doing this, you will need a safety pop-off valve on both tanks, just in case. You will also need accessible drain valves (or suitable plumbing) for both. I also run a separate regulator (and filter) outside.

In going the small compressor - lots of storage route, the most important thing is your max pressure. You will need 90psi to run most tools and, as such, the only real storage worth having in what's over 90psi. In other words, if your compressor runs 90psi and your tools need 90psi then all that storage is not going to amount to much of anything. On the other hand, if you can get up to 135psi, then that extra tank will make a difference.

Also, 'small' doesn't necessarily mean junk. My compressor is a cast iron oil-bath unit with a 100% duty cycle, or so the manufacturer claimed and backed it up with a 5 year warranty (I even called the stupid 1-800 number to confirm this). It's out of warranty now and still going strong. It routinely runs for 30 minutes straight, longer if I'm working on something.

Air is wonderful... impact guns are serious problem solvers and it's amazing how useless air chisels are, until you figure out how to use them, and then they're great too Again, buy quality, because air tools are one place you really, really notice the difference.

David...

edit... don't even think about using an old propane tank for extra air storage... this board is probably full of creative people that made that mistake and are too proud to admit it

That's a well thought out system. If I hadn't lucked into my bigger compressor, I would likely use your ideas. I think Paul would do well to follow your lead - get a small compressor with a really good pump, and add storage as needed.

[J. Randall]

Gravy, I have just got to ask, what is your kick on using a propane tank?
James