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Direction on what to look for when buying a new compressor?

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Cursed_Mongo

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Joined
Oct 4, 2019
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8
Location
Granger, IN
Hi Everyone - First post here, so please be gentle on the roasting. I know this is a long post.
I have a very generic question and need some feedback. I know there is not a one size fits all answer, so I am just asking for everyones opinion.

I am looking at buying my first (and hopefully last) real piston air compressor. I am thinking a 5 hp would be big enough for what I will be doing like tire inflation, impact wrenches, cut off saws and wheels, and air chisels. I want a verticle tank for space and I do not need it to be portable. For power, I have 230V single phase 40 amps available. The budget is pretty open. I just want to buy one that will work and last.

Now, where I start getting fuzzy is on what I should look next, or what is important to look for. I've seen compressors that vary in CFM, tank size, stages, pressure, and starter types.

CFM it seems the single-stage ones put out more CFM, but cannot build the pressure. 2 stage compressors build the pressure but don't have lower CFM. I know the higher pressure is more "stored power" in the tank, but will a higher CFM compressor offset the need.

Tank size - it seems 60 & 80 gallons are the 2 sizes available. Do I really need 80 gallons?

Pressure - Most of my tools require less than 100 psi, do I really need a 2 stage that goes up to 175 psi?

Starter - I can find compressors with a switch starter and magnetic starters. I assume the magnetic starter is better because it costs more, but what is the advantage and is it important?

Drains - Is the ball valve okay, or should I upgrade to an electric drain? I feel like the electric drain would help me remember to drain the tank, but what about wasting air and longevity?

Thank you in advance!
 
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dagofast

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Oct 15, 2006
Messages
411
Location
The QC in AZ
First, great screen name! Welcome to GJ.

Most folks would advise you to buy as much compressor as you can afford. Which is good basic advise.

But first, ask your self some basic questions: how often will you be using your compressor? Daily? For 8 hours a day? Tons of people can get by with a 20 gallon single stage compressor for home use. I do. I've even seen shops run the heck out of one or two of them and get by. For awhile, anyway.

Do I occasionally have to wait for it to build back up? Sure, but I'm old, retired and usually not in a hurry. And truth be told, by then I probably am ready for a rest period myself! :) So I'll saunter off to the shop fridge for a cold drink and take a break.

Be honest with yourself about your needs and your budget and chose accordingly. If you decide you need a nice big compressor, from reading around on this sight, one of the best vertical 60 gallon compressors is available from Harbor Freight. It has an Italian compressor pump and I think a US made motor or tank. And on sale, it is a screaming deal.

As far as pressure, the higher the pressure stored in the tank is simply more stored energy. Most people run a regulator to keep line pressure at around 100 PSI anyway. So for example, a 60 gallon tank with 175 PSI can be effectively as much work energy as an 80 gallon tank with 100 PSI in it. (For illustrative porpoises only. Not real numbers. Not an engineer, didn't stay at a Holiday Inn)

A ball valve works for me, but I'm in "Its a dry heat" Arizona. The electric ones are nice if you're running the compressor all day long in a humid environment. Inexpensive retrofit units are all over eBay and Amazon.

A magnetic starter usually carries a higher duty rating. But contacts are contacts. Eventually those will wear out just like the contacts on a simple pressure switch. It again comes down to a question of the amount of use/abuse you intend to dish out vs. a cost factor. And keep in mind heavy duty always costs more upfront and also to replace. A magnetic contractor is usually harder to source and more expensive to replace than a generic pressure switch. So, trade offs.

CFM's are harder to explain simply. But in general, a higher CFM will in theory fill a tank faster or power a high volume tool like a bead blaster better. But there is some difference in the working pressures involved. For the same fixed size displacement, a single stage compressor can flow more CFM at certain pressures better because the displacement of both cylinders are available. In a dual stage compressor, one cylinder feeds it output of lower pressure to the other high pressure cylinder so the CFM or flow is ultimately less. (I hope that explains it!)
 
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sk farmer

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Mar 4, 2009
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Location
nd
unless you need to be portable, a 60 gallon vertical tank with an oil lubed twin cylinder pump would be a great choice. only slightly more money than a good portable and much more capacity.an 80 gallon 2 stage is really overkill for a home shop. unless i am running my 1 inch impact or blowing dust off the combine i never notice the jump from 60 gallon twin to 80 gallon 2 stage other than the 2 stage running slower and therefor quieter but enclosing the compressor would help that.
 
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strutaeng

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Dec 12, 2011
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2,282
Location
Dallas, TX
Welcome to the forum!

Those are all questions. It is apparent you have been doing your homework. Generally, buy the highest CFM compressor with lowest pump RPM (oil-lube, of course) would be my best, watered-down advice.

However, before making a decision, you need to know what your air needs are. Single man shop? What tool has the CFM demand? Take highest CFM tool and muliply by 1.25-1.5 and you are in business...

Sort of like: need what you are hunting before you figure out what caliber to pick...
 
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tarbellb

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Joined
Apr 17, 2011
Messages
5,760
Location
Oregon
DO:
Champion, Saylor Bell, Atlas Copco (Belair), or Emax for cheaper featured packed foreign made

DONT:
Quincy (unless you go QR/QP)
 
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Cursed_Mongo

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Oct 4, 2019
Messages
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Granger, IN
Thank you 930dreamer. I have heard good things about the Gardner Denver Champion brand. It seems to be a well built proven unit.
 
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engineer2

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Dec 13, 2009
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11,814
Location
Chicago burbs
Champions are good compressors. Zero problems with ours at work. They run fairly quiet. Some pumps have a 1 piece cylinder and head so there is no head gasket to seep oil.
 
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arcier

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Oct 6, 2019
Messages
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Location
Punta Gorda, FL
I have a Campbell Hausfeld 5hp vertical 80 gallon 2 stage compressor that is capable of 13.5 SCFM @ 90 psi or 12.5 SCFM at 175 psi. I have it set to 120 psi and it has been more than adequate in my shop for years. Handles all my pneumatic tools, paint spraying tire inflation etc. with ease.
 
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Crabman

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Dec 17, 2017
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Location
Alexandria, VA/Dameron, MD
Mongo,

I have an old Coleman Black Max/Sanborn unit, 80 gallon/5 hp that I got cheap years ago on ebay. It has served me well for about 20 years. What I have found is that it is more than enough for about all I do. The big user in my life is a blast cabinet, and my siphon blaster which I use outside for bigger pieces that will not fit into the cabinet. My cabinet is an old TP Tools 780, which has also served me well. I think they recommended 7-20 cfm. My compressor is in the middle of that range (a little above), and the cabinet will give the compressor a workout.

For air tools, inflating, etc., the compressor is way more than enough.

So my thinking is to look at the cfm requirements of the tools you are going to use. But for the blasting (and I make take up painting), I think I could get by with a much smaller compressor.

I know a lot of people on GJ like the 60 gallon HF unit:

https://www.harborfreight.com/5-hp-...b564d2df434cc4cc34b9fc3c06e24f54cd52ce3a35465

I just got a coupon in my email #27183460 for $100 off, so $799, which is a lot of compressor for the money.

Good luck finding the right fit for your needs.

Bruce
 
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clubairth

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Dec 24, 2014
Messages
263
Unless you are blasting or painting you are looking at a pretty big compressor?
No problem with that but will you even need that much air?

I have a large blast box and man it just eats air! My 7.5HP compressor is rated at 23.7 CFM @175PSI. It is just about balanced as I can get the compressor to shut off while blasting but it does not stay off very long.
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Cursed_Mongo

Member
Joined
Oct 4, 2019
Messages
8
Location
Granger, IN
clubairth said:
Unless you are blasting or painting you are looking at a pretty big compressor?
No problem with that but will you even need that much air?

I have a large blast box and man it just eats air! My 7.5HP compressor is rated at 23.7 CFM @175PSI. It is just about balanced as I can get the compressor to shut off while blasting but it does not stay off very long.
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Click to expand...

I do plan on doing smaller blasting that my 3.5 hp just cannot keep up. I will also use it to blow out my sprinkler system every fall (which is coming up). Thanks again for your input!
 
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