how big an air compressor do I need?

[duckfatrules]

My brother in law gave me a $250 Sears coupon because he wants me to add compressed air to my new garage. He says I will need it. What compressor do I buy?
I already have a small 2 HP unit with 3 gallon tank, 4 CFM @ 90 PSI

should I spend the coupon on air tools and use the existing compressor?
Or, assuming I purchase a new compressor from sears how much do I need?
I was planning on plumbing my new work shop/ 3 car garage for compressed air. I dont have any air tools, yet. therefore I dont know what I will need. what is a good starter size above the existing model?
should I plumb my lines with metal pipe per the other posts, I was planning on using PEX water pipe, but per the other post, should I use metal piping?
Looks like that piping investment alone will run me over $600.
In addition, are there any negatives with installing the air compressor upstairs in an uncooled, unheated attic room? I was planning on putting it up there to eliminate noise and get it out of the way and I have plenty of room in upstairs of garage.

 

[bobcatdan]

The biggest you can afford. I'm use to endless air at work so to sit and wait for a compressor to catch up is unbearable for me. Stuff like a die grinder or cut off wheel take a lot of air and even a 60 will struggle. Honestly, do it right and get an 80. 80 gallon commonly come in 17 cfm and 24 cfm. For home shop use, a 17 cfm would probably be fine, but eness air is nice.

 

[AndyA]

The biggest you can afford

+1

Too big of a compressor is never a problem (except for your wallet). Single phase electrical power will probably top out around 25 cfm.

 

[devoncoolman]

80 gallon would be my suggestion. Its worth it. But if your not going to use air often. A 60gal will do u fine.

 

[duckfatrules]

why is everyone replying with the size of the tank?
is not the CFM @ 90 psi the most important atribute? or am i missing something?

 

[larry_g]

why is everyone replying with the size of the tank?
is not the CFM @ 90 psi the most important atribute? or am i missing something?

They reply tank size because they do not understand. You are correct in that the volume of air delivered must meet the demands of the tool using the air. So the OP has to be realistic on what he is doing with what tools for what duration. You can spend a lot of money on a big compressor and if you only fill tires and change from winter so summer tires 2x per year then a much smaller compressor will do.

To the OP I would suggest that you get your air tools and see how the compressor you have handles them. For you it may do fine and you can tolerate the fill times. It may fail miserably and you can upgrade to what you need.



lg
no neat sig line

 

[kunkernator]

why is everyone replying with the size of the tank?
is not the CFM @ 90 psi the most important atribute? or am i missing something?

If I recall correctly, the CFM @ 90psi is the amount of air flow the pump can maintain at 90psi. That is with the pump running.

Air tank size is just as, if not more important. You do not want your pump continuously running, so you have a "reservoir" of air in the tank. Then you can draw from the tank (an infinite amount of flow) for X amount of time before the pump kicks in.

Your 3 gallon compressor will not beable to handle ANY air tool (for a sustained amout of time/power) other than a nail gun. No use, IMHO, in purchasing a bunch of air tools and then being disappointed in having no power from your 4 gallon tank. A lot of air tools have a CFM rating on them, and VERY few will be able to run off <4 CFM.

I started out with a compressor just like yours, then I bought a 20 gallon, then a 29 gallon, and now I have 89 gallons.

What kind of work will you be doing? The tools you use will directly relate to what type of air compressor you need.

 

[bobcatdan]

Tank directly effects output. You want the compressor run as little as possible. Mostly from the stand point you don't want to listen to damn this run all the time. I some times forget to turn my compressor on and can use impacts, fill tires or blow stuff off with stored for a half a day before I realize I didn't turn it on.

 

[devoncoolman]

I kind of take that as a insult. Tank size has everything to do with it! Cfm output is how fast the tank fills. Yeah your punny little compressor will suit your needs if all you want to do is fill tires. This question has been asked a million times. Even in the last couple weeks. This is redundent. Your almost lucky anyone even responded. If your going to do automotive work or sandblast or paint get a 80gal atleast 17cfm or higher. If your going to do random work like pull a wheel here and there or fill a tire just get a 30gal.

You asked an open ended question without any details. We can suggest All we want according to what we use our compressors for. But in the end we have no idea what u do.

 

[woody 73]

For my two cents:

Take your very nice gift from your brother-in-law and start saving your extra egg money for a good used unit from Cl (see below):

http://columbus.craigslist.org/tls/4083579112.html

Then you will be set as they say for any thing that comes your way!

 

[duckfatrules]

what if I just buy an extra 30 gallon tank and connect in series with the old unit. does that count for having a larger tank?
Or if I buy a new 26 gallon unit from sears and then add another 30 gallon tank ?
does that work?

 

[kythri]

I kind of take that as a insult.

Chill out. The OP wasn't the person that responded about people not understanding. He's simply asking questions.

 

[Davefr]

It's putting the cart before the horse to size a compressor for tools you haven't even decided on.

Here's how to do it:
1. Make a list of all the air tools you'd like to use now and in the forseable future.
2. Now get the CFM specs of those tools.
3. Now highlight those tools that will run at high duty cycles. (ex: sanders, drills, grinders, blasters, etc)
4. Now pick the tool that has the highest CFM and runs at a high duty cycle.
5. Pick your compressor to deliver that CFM continuously. I'd add 20% to that value just to be on the safe side.


If you're right on the borderline with that compressor's CFM output then opt for the larger tank. Make sure you get cast iron/oil lubrication.

If you choose to buy used, then make sure parts are readily available. Nothing worse then buying a used compressor and finding out that valves and/or overhaul kits are all discontinued.

 

[ilovevocs]

I would never buy a craftsman compressor. I echo the above; quality used unit off craiglist. 80 gal. Assuming it is a quality unit with original pump and motor CFM will be the least of your concerns.

 

[kythri]

what if I just buy an extra 30 gallon tank and connect in series with the old unit. does that count for having a larger tank?
Or if I buy a new 26 gallon unit from sears and then add another 30 gallon tank ?
does that work?

Theoretically, you're prolonging the operating time at your set pressure output between compressor cycles, so, theoretically, yes, you're increasing the size of the tank.

I'm sure there's some kind of math involved in something along the lines of efficiency loss or something, but, for sake of simplicity, yeah.

Both sides of the argument here are correct. Tank size matters, but compressor CFM output also matters.

As has been mentioned, if you're just going to be zipping some lug nuts off with an impact and inflating some stuff, then your existing compressor will do you fine.

If you're going to get a bit more intense, something with a bigger tank is desirable.

When I first started getting into this stuff, I started with one of these:

http://www.alltradetools.com/catalog/21-835486-5-gallon-twin-tank-air-compressor-reconditioned.html

Bought it at a Schuck's store (now O'Reilly). 5-gallon tank, 3.3CFM @ 90PSI. Along with a cheap pawn-shop Craftsman impact ($5? $10?), it worked out fine for very basic stuff. It's on semi-permanent loan to my father, who uses it for a bunch of his small hobby stuffs.

In 2006 or so, anticipating installing a suspension lift on my Explorer, I bought a Craftsman 33-gallon upright model. One of the oil-less jobs, I think it's 5.1CFM @ 90PSI. Upgrade my cheapo impact gun to an Earthquake from HF, bought a few more air tools, and it worked out quite well. It's big failing showed when trying to use tools that had major air requirements, like die grinders and cut-off tools. These **** major air, and would drop the tank down to the compressor's cut-in quickly, and I'd have to sit there and wait for the tank to get back up to pressure so I could use the tool again.

This is the point that bigger/better compressors start becoming handy.

If I had a bigger tank, I could use the tool longer between cycles. If I had a bigger pump/motor, I would wait less time for the tank to fill up.

If I had both? I might never have to wait again.

Your compressor purchase really depends on what you think you might be doing now and in the future.

If it's going to be years before you need a high-capacity/high-output unit, you could probably easily get by on the Craftsman 33-gallon unit or something similar.

Remember, keep it in good shape, and you can always sell it later when it's time to upgrade. The 33-gallon units at Sears are $340 right now, and regularly drop to $300 or less during sales. Christmas is right around the corner, so I expect to see this happen again soon.

Around here, at least, these easily sell for $200-$250 used, so, if you do buy it now, you're not losing much at all.

When it comes time to buy the big burly unit, shop around. Craigslist is good, and local compressor service/sales places may have something for a heck of a deal. I scored a used 80-gallon/27CFM/7.5HP Campbell Hausfeld unit for incredibly cheap from one of these places.

On your local area Craigslists:

http://greensboro.craigslist.org/tls/3966024421.html

http://charlotte.craigslist.org/tls/4084151609.html

The IR one on the Charlotte site is rated 11CFM @ 90psi, per the pictures. I'd imagine the CH one on Greensboro is likely the same.

Both aren't much more expensive than a new 33-gallon Craftsman, but are likely vastly superior. Of course, you can't use your gift card on CL.

 

[RECox286]

I would not buy a compressor from Sears, or HF or most other

retail outlets. Seeing as there are always deals to be had in

the "Items for Sale" of CL or Trader and like For Sale publications.

Roam around here on GJ by using the search function and

boning up on compressors before you are ready to pull the

trigger, and you will probably be much better informed and more

knowledgeable about what you want in a large(r) piece of equipment.

Then you may know the answer to the question you posed without

needing to ask the question.

Good hunting

Uncle Bob

 

[kythri]

There's nothing wrong with Sears/Craftsman compressors, and, in fact, the HF compressors have gotten quite good reviews from other members here.

They serve a particular price point, and work quite well for what they are.

Know what you're buying, know what you need.

 

[CNGsaves]

Welcome to GJ. First off, you SURELY have NOT read enough threads if you are asking:
. . . . a) Should I install PEX or plastic airlines (no, no, no, no, no)
. . . . b) Should I spend FREE $250 from my brother on Craftsman compressor

Instead, call around to Sears stores and see if the 309 piece Craftsman tool set they have is Made in USA. If it is, then immediately join Craftsman Club / Shop Your Way / and spend $199 (less discounts) on that tool set. With rest of money get a few air tools that you might need (impact sockets, air ratchet, impact, etc)

For air compressor, best place to get nice big one affordably is CL, moving sale or garage sale. Look for 60 gal and up and 5 HP and up. Wire your garage for 240volt and that bigger compressor likely all you'll need for lifetime.

Keep your smaller compressor for mobile needs on 120 volt. Also, plan out airline system from black pipe steel (or copper) up around the perimeter walls near ceiling of your garage.

 

[duckfatrules]

this is great information, I really appreciate it.
I just ran my dedicated electrical to where the unit will sit up stairs with a light switch downstairs controling the outlet. I ran 12 awg 2 wire. If I bought a 220VAC would have to rewire and use different switch other than just a light switch, easily done now, since I have no walls & ceiling up yet. only studs and outside walls and a roof.
I did not think I would ever need a 220 unit. not yet retired, but getting everything in place in order to, with the work shop.
I just dont know what tools I will be using?
hard to plan when you have never been there before. thanks for the info, greatly appreciated.

 

[kythri]

Welcome to GJ. First off, you SURELY have NOT read enough threads if you are asking:
. . . . a) Should I install PEX or plastic airlines (no, no, no, no, no)

Normal PEX, no, but PEX-AL-PEX is compressed air rated.

. . . . b) Should I spend FREE $250 from my brother on Craftsman compressor

The brother-in-law did give it to him specifically for an air compressor...

 

[bobcatdan]

It comes down what are doing in the garage. Is it a man cave to drink beer and shoot the **** or is serious working going on. If all you ever plain to do is air a car tire, then your air compressor is fine. Going to fix or restore then bigger is better.

 

[Skin]

Without getting involved in the drama above heres my 2 cents.

Minimum 30-40gal with a 150psi pressure rating. That will give you enough air for general impact wrench use and light die grinder/cut off tool use. Larger units will increase your trigger time. Biggest benefit you can upgrade to is oil lubricated simply due to the reduced noise over an oil free pump/motor combo.

I would not worry about sustained pump CFM unless you're buying the thing to do professional body work or run something like a blast cabinet. A 'crummy' big box store 1-3hp rated unit will pump the tank up and that tank will be filled with plenty of air for something like an impact wrench which is most likely what you'll be using it for 90% of the time anyway.

My home unit is an antique 60 gal / single stage pump run off a 1HP motor. Its 100% adequate for my 3/8" and 1/2" impacts, air hammer, and die grinder usage for any driveway work. By work im talking about

Brakes
Suspension component r&r
Exhaust
Tire rotations
Basic fastener removal/engine work
And simply filling the tires with air

None of this requires a $1200 Quincy or anything like that.

 

[sberry]

Skin, that is entirely too reasonable. The reason the tank size comes up is it is often a generalization for a class of unit, the 60 single stage is nice for home brew type operations. The 17 cfm units are great, they really do it about all, can do body work with one. Most diy chores don't need one.
Simplify the plumbing a little, take 400 now and put toward a better comp, put a t and a plug for all that **** you think you need in the futue and make it simple piping and a hose reel to start, add if you need.

 

[CNGsaves]

Here's a few CL bargains in your area if you're needing tools or compressor:

GearWrench full polish 1/4" to 1" - - - - $65
http://greensboro.craigslist.org/tls/4043373491.html

SnapOn air tools
http://greensboro.craigslist.org/tls/4079245025.html

Craftsman 4 HP 2 cylinder 20 gal compressor - - - $200
This is oil-splash compressor that would likely get you by on 120 volt.
http://greensboro.craigslist.org/tls/3991272477.html

BlackHawk ratcheting combo wrenches 7 piece SAE 3/8" to 3/4" - - - $35
http://greensboro.craigslist.org/tls/4041799019.html

5 HP 60 gal air compressor - - - $250
http://greensboro.craigslist.org/tls/4038057149.html

Craftsman 95 piece mechanics tool set - - - $45
http://greensboro.craigslist.org/tls/4036750490.html

Campbell Hausfeld 6 HP 60 gal compressor - - - $300 (looks brand new)
http://greensboro.craigslist.org/tls/4009960332.html

 

[tomshep]

Save a little more and get a Craftsman Professional. That will be a good mid-range compressor for the home that is oil so it isn't crazy loud. It will be fine for years. You can always upgrade later if you find you are using a lot of CFM.

Tom

 

[ez-duzit]

They reply tank size because they do not understand...

What you don't understand is that specifying a tank size broadly defines the capacity of the compressor and motor size, as well. The typical 80-gallon units will have 5-7.5 hp 220 v motors and produce 20+ CFM.

 

[TennesseeZ]

The biggest you can afford.

Mount it outside if you can, covered, muffle the intake, and go to work. Steel pipe.

 

[Olafur]

Since you don't know what air tools you need, the real question is - what do you intend to do in your garage? Do you need air tools to begin with?

 

[03protege]

why is everyone replying with the size of the tank?
is not the CFM @ 90 psi the most important atribute? or am i missing something?

CFM is king but cost $$$, a large tank allows intermittent use of some tools that have air requirements greater than the compressor's CFM rating. Not ideal but, it may be just enough to get the job done.

Really it comes down to what you plan on using it for, and how much you are willing to pay.

Before you decide on a compressor I would go to tooltopia and browse the airtool section and see if there is anything you think you might decide you want one day. and look at the air requirements it has.


The larger tank also has some other benefits a big one being it has a large surface area to help cool the air that is hot from running through the compressor. Cool air cannot hold as much moisture as hot air.


Also make sure you get an Oil-filled compressor no matter what you decide your CFM needs are!

 

[03protege]

what if I just buy an extra 30 gallon tank and connect in series with the old unit. does that count for having a larger tank?
Or if I buy a new 26 gallon unit from sears and then add another 30 gallon tank ?
does that work?

Problem with this is both tanks drop in PSI equally so after the first "discharge" the compressor will take twice as long to get back up to operating or max PSI as it would for the single 26 gallon unit.

The other issue is that with this increased run time you will probably be running the compressor/motor past their duty cycle (as I imagine the 26 gallon isn't rated for continuous use) and this will lead to an untimely death.

Again I think this depends on what you are using it for, this could be beneficial if you are just taking all your lug nuts off and will not need the air again until your are putting them back on, but any continuous use is bad juju.

 

[kythri]

What you don't understand is that specifying a tank size broadly defines the capacity of the compressor and motor size, as well. The typical 80-gallon units will have 5-7.5 hp 220 v motors and produce 20+ CFM.

This simply isn't true anymore. Very many "budget" 80-gallon units exist that have sub-5hp motors and sub-15CFM compressors. It's a **** shoot, and it's not a reliable gauge of what is a VERY variable range of output.

Sadly, you just can't rely on tank size as an indicator of a high-output compressor these days.

 

[larry_g]

What you don't understand is that specifying a tank size broadly defines the capacity of the compressor and motor size, as well. The typical 80-gallon units will have 5-7.5 hp 220 v motors and produce 20+ CFM.

This simply isn't true anymore. Very many "budget" 80-gallon units exist that have sub-5hp motors and sub-15CFM compressors. It's a **** shoot, and it's not a reliable gauge of what is a VERY variable range of output.

Sadly, you just can't rely on tank size as an indicator of a high-output compressor these days.

Thank you kythri for saving me some typing. I come from an industrial setting and have dealt with pneumatics for over 30 years and do know a bit of what I speak of. Tank size is least important variable in the choosing of a compressor and air system. You are correct that consumer grade compressors with an 80gal tank meet your specs. In the bigger picture there are systems in the <15cfm to >35cfm. sitting on an 80 gal tank. At the end of the day the work done by your air system is determined by the delivery capability of the motor/pump, not the tank size.

lg
no neat sig line

 

[machine_punk]

I'm not too far out from making the change to using air tools. I remember thinking the same thing (what tools will I need?).

I'm sure a bunch of us can help answer those questions, if we get some general information from you...like, what do you plan to use the shop for? If you are just going to fill and rotate the tires, then your current setup, with an inexpensive impact gun (HF 1/2" Earthquake) and tire valve nozzle will do you just fine.

If you are going to do general car repair, there is a next step, which requires a few more tools. In this case, look at the cheap Campbell Hausfield or Husky "combination tool" sets for an idea of what you might need, but then buy a little better version of each tool. Anything specialized you do (car body repair, paint, sandblasting, or in my case, working with solid rivets) will have specific tools you need. Duty cycle of a tool matters a lot too. An impact wrench may or may not take a lot of airflow, but you only use it intermittently to quickly knock the lugs off a wheel. The 90-degree air grinder which I use doesn't necessarily take a huge airflow, but it takes it constantly, for sometimes hours on end...giving my 120-volt, 30-gallon compressor a real workout.

It sounds to me a bit like you are adding air just 'cause it would be neat to have (And, might I say, it IS!). The bigger question is, "What are you going to use the shop for?" That will guide your air tool purchases and guide you in how big of a compressor you need.

There are less expensive kits for plumbing air to your shop out there. As much as I REALLY want copper tubing in my shop, here is the kit I am considering, for price and convenience...
http://www.northerntool.com/shop/tools/product_200484023_200484023
It isn't as pretty as copper, but it looks like it goes up quickly and it is a professionally-designed option, for a decent price.

Looking forward to hearing more about what you plan to do...so we can help you figure out what you need.

Kev

 

[ez-duzit]

Here is a chart that shows tool CFM requirements:
http://www.wiseworth.com/_literature_138586/Air_Tool_Consumption_Chart

 

[EOC_Jason]

I managed for the longest time with a 3HP/22 gallon compressor that you could cart around. Eventually upgraded to a 5HP/60 gallon upright that was free. Man is it nice... It's like you would never think you need it if you didn't have it, but once you have one then you start using it all the time.

 

[GoodEnough]

Minimum 30-40gal with a 150psi pressure rating. That will give you enough air for general impact wrench use and light die grinder/cut off tool use.

A 'crummy' big box store 1-3hp rated unit will pump the tank up and that tank will be filled with plenty of air for something like an impact wrench which is most likely what you'll be using it for 90% of the time anyway.

My home unit is an antique 60 gal / single stage pump run off a 1HP motor. Its 100% adequate for my 3/8" and 1/2" impacts, air hammer, and die grinder usage for any driveway work. By work im talking about

Brakes
Suspension component r&r
Exhaust
Tire rotations
Basic fastener removal/engine work
And simply filling the tires with air

.

This is exactly the type of basic AUTO work I might use it for.
Just to get at a few stubborn bolts on a suspension or exhaust.

It sounds like I need to look for:

• 30-80 gallon. (I need compact, so I will err on smaller)
• Oil lubed for quiet.
• Even 1HP motor is adequate

What is the minimum PSI I'd want?

 

[GoodEnough]

So, tiny 2 gallon tanks are only really good for nail guns?
http://www.amazon.com/dp/B000GZS6NC/?tag=atomicindus08-20

 

[GoodEnough]

How about this for basic automotive work? Not a pro mechanic working all day long, but for doing a weekend repair for an afternoon, once in a while.

Here are some oil-lubed vertical ones:

12 gallon $169
http://www.sears.com/craftsman-12-g...al-air-compressor-with/p-00916640000P?prdNo=5

10 gallon $169
http://www.sears.com/craftsman-10-gallon-oil-lube-portable-air-compressor/p-00916923000P?prdNo=8

27 gallon $479
http://www.sears.com/craftsman-prof...ortable-air-compressor/p-00916474000P?prdNo=6

 

[GoodEnough]

Based on the $169 review, it seems like 1HP takes like 10 mins. to refill.
That would cause trouble with the neighbors.
So, I will look for higher HP ratings.

 

[CNGsaves]

Based on the $169 review, it seems like 1HP takes like 10 mins. to refill.
That would cause trouble with the neighbors.
So, I will look for higher HP ratings.

So why you (GoodEnough) posting all your questions in this guys thread, when you (ie GoodEnough) have very similar "First Compressor" thread with 1,000 questions on "What do I buy" ??? Also have to ask have you even used the Advanced Search feature of GJ (ie up on black line click on Search, then scroll down to Advanced Search)?? There have been hundreds or thousands of threads just like these.

No need to highjack this OP's thread.

Cut and paste all your posts above and create a new post in your own GoodEnough thread at:
http://www.garagejournal.com/forum/showthread.php?t=217166