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Paul Alciatore
03-07-2011, 06:37 PM
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
03-07-2011, 07:39 PM
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
03-07-2011, 07:49 PM
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
03-07-2011, 08:10 PM
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
03-07-2011, 08:40 PM
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
03-07-2011, 08:44 PM
How to choose a compressor (http://www.jennycompressor.com/howtochoose.html) 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! :D

Gravy
03-07-2011, 09:46 PM
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
03-07-2011, 10:16 PM
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
03-07-2011, 10:24 PM
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
03-07-2011, 11:42 PM
"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
03-08-2011, 12:06 AM
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
03-08-2011, 09:14 PM
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
03-09-2011, 12:59 AM
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
03-09-2011, 08:43 PM
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
03-09-2011, 11:15 PM
Gravy, I have just got to ask, what is your kick on using a propane tank?
James

Jaakko Fagerlund
03-10-2011, 12:09 AM
At work we usually use a screw compressor outputting 1.5 m per minute but a couple of weeks ago it failed. It was very silent, like a humming sound only We brought in a 360 liters per minute piston compressor that has an oil bath in the crankcase and this was very noisy, the sound was awful even with ear protection on.

I modified the air input where the air filter is by removing the top, installing a thick piece of rag (tested by my own mouth that it breaths) over the air input and reinstalling the top cover. The sound output dropped so much that one can be without ear protection in the same room :)

The sound in piston compressors mostly comes from the air intake valve in the compressor head, as it is a leaf valve clapping away, so I really suggest using rags or thick ar filter elements to suppress that noise.

Paul Alciatore
03-10-2011, 03:59 AM
Great comments, thanks!

I never intended to go oilless. I have worked with some and know the problems when used in constant service. I do want a good quality unit that will last. Only one comment on a system like I envisioned. But it appeared to work. I have to think.

David Powell
03-10-2011, 05:50 AM
Your need for air is low and / or intermittent and a small compressor will keep up. My big tank is outside, under the deck, the lines are small and , in winter often the condensate will freeze in them and the tank gets isolated in winter( December-April ) here in Ontario. Getting the big tank up to pressure at the beginning of a work day takes my little compressor 1/2 hr but then for my uses It keeps up. So my outfit is fully usuable and complete only May -November If you have room for a large tank indoors and can make and keep a leakless system then a smaller, quiet running compressor running most of the time may be the answer, but if you are going for high consuming air tools or need air to run devices, or model engines for test then , no matter how big the tank you use you will be cursing sooner rather than later. Regards David Powell.

Paul Alciatore
03-10-2011, 03:23 PM
David, thanks for the further info. I am in south Texas so freezing is not a problem. Many winters, like this one, we get no freezes. When it does freeze, it usually thaws the next morning. Besides, mounting it outside is not an option as it would be too visible from the street and neighbor's yard. So an additional tank would also have to be inside, probably next to or above the compressor.

I am well aware of condensation problems as I have fought them in systems I have installed in TV stations in humid climates. You can check past posts for my experiences there. But I doubt that this will need any such extreme measures as I had to take there where they had to run 24/7/365 without down time and a single drop of water getting through was a disaster. Imagine spraying water on the video tape in your VCR just before it gets to the scanner. But this does not need to be anywhere that moisture free. I may add one jar or just a drip loop with a drain valve.

I am glad to hear that I am not the only one who has considered such a system and that they have been used with some success. I am not planning on any air operated tools, just blowing things out and tire inflation at this time. I may want to use it for a mist coolant system later, but that is not definite. And I do not do model engines at this time. If I did make any, they would probably be a model aircraft type (glow or diesel) and compressed air would not be needed. If I get into modeling again, it would more likely be trains with electric motors. I would love to have a backyard RR or a big HO layout. I would like to use it for occasional spray painting and that is the main reason why I feel additional capacity may be needed.

I am leaning towards a small to medium sized compressor and may reserve the space to add an additional tank later and just see how things work out.

Again, thanks to all.

lost_cause
03-10-2011, 04:00 PM
last year i plumbed in a compressor and air lines in my shop. i have a relatively small shop - 24x28, and i consider what i do to be that of an aggressive hobbyist, bordering on light professional. i went with a vertical tank, because it has a smaller footprint than any horizontal tank. i also went with a 60 gal as opposed to an 80 gal, as the larger diameter would interfere with the width of the overhead door opening.

as far as performance, i would have ideally went with a two stage (when the time comes i probably will upgrade in that direction) for approximately $1000 but for now i bought a single stage 60 gal. it's not the greatest, but for most things it will do. also, it had a retail of $400 (local big box store) and at the time of purchase they were offering a $100 gift card with the purchase of any 60 or 80 gal compressor. figure that you will always use the $100 gift card on things you would normally buy, so it basically is like a free $100 off the price. at $300 i will get my money's worth out of it and then some.

garagemark
03-10-2011, 05:06 PM
Sorry I didn't read all these posts, but I'll tell you what I did.

Instead of buying a reserve tank, I plumbed a header around my shop/garage from 1 1/2" pipe. I then made 1/2" pipe drops in strategic locations (and added other tees in the header above in case I wanted others. By the time all was said and done, I had (have) a rather nice reserve tank all around the ceiling (two 50' runs and one 36' run). I did install a ball valve at the source so it will hold pressure in case I want to disconnect the compressor (I never disconnect, but I could).

Just another way.

Gravy
03-10-2011, 08:54 PM
Gravy, I have just got to ask, what is your kick on using a propane tank?
James

James,

I have no problem with using a propane tank as long as it was designed to handle the pressure and has provision for a condensate drain valve. I suspect that given equal pressures, propane tanks are built to a higher standard than homeowner air tanks. Seems to me that propane tanks have to contend with both static pressure and flammable/explosive contents.:eek:

That said, I have no freakin' idea whether propane tanks are designed for higher or lower pressures than air compressor tanks. That could be a critical issue. Maybe somebody with better information will chime in.

Don Young
03-10-2011, 09:00 PM
I believe ASTM air tanks have some reserve thickness/strength to maintain a suitable safety margin with some degree of rusting, but I do not know the details.

Gravy
03-10-2011, 10:05 PM
I believe ASTM air tanks have some reserve thickness/strength to maintain a suitable safety margin with some degree of rusting, but I do not know the details.

Me neither. To complicate things, a lot of light duty compressors do not have ASTM tanks. I first noticed that in a Grainger catalog years ago. An ASTM tank adds at least a hundred bucks to the cost of an otherwise identical new compressor.

In the absence of other evidence, I would judge the integrity of a new air tank by it's empty weight. I recently cut up a cheap 60gal air compressor tank and was appalled by the lack of wall thickness. The bottom quarter has a new life as a hibachi. I may have saved somebody's life.

fixerdave
03-10-2011, 10:18 PM
James,

I have no problem with using a propane tank as long as it was designed to handle the pressure and has provision for a condensate drain valve. I suspect that given equal pressures, propane tanks are built to a higher standard than homeowner air tanks. Seems to me that propane tanks have to contend with both static pressure and flammable/explosive contents.:eek:

That said, I have no freakin' idea whether propane tanks are designed for higher or lower pressures than air compressor tanks. That could be a critical issue. Maybe somebody with better information will chime in.

I suppose if you could find a propane tank that was never used for propane then it would just be a pressure/safety issues. The problem I ran into, and everyone else I've talked with that ever admitted to trying it, is that propane - as shipped to the customer - stinks. Yes, I know this comes from a deliberate additive used for safety. But, that doesn't mean it doesn't stink. In fact, it's designed to stink, and stink (big time) it does, especially the crap left in the bottom of an "empty" tank.

Now, creative people might figure out how to de-stink said tank before using it, without smelling like they got into a wrestling match with a family of skunks, but by that point you really have to ask "why bother?" I picked up a used 60gal air tank for cheap - the compressor died, the tank was fine. Pretty common I guess, seeing as how the tank doesn't have a whole lot of moving parts.

David...