I weary of the various “air compressor” threads that speak of “Brand A” or “Brand B.” None of these threads tell me what I really need to know: How much compressor do I need?
What is the minimum size – tank capacity and horsepower- do I need if I’m using a trim nailer? A framing nailer?
Better yet, how do I convert the requirements of the tool into a compressor size?
Let’s assume, as an example, that I am using a framing gun whose specs say it uses .082cf per shot at 100 psi – and it can do a maximum of 12 shots per second. Figure that for the ‘typical’ connection I’ll fire as many as four nails in quick succession- with a pause as I move on to the next connection.
Do I choose a 2hp compressor with a 2-1/2 gal. tank … or a 1hp compressor with a 4 gal tank? Or, do I ignore those figures and decide based upon CFM? If so, what’s a realistic way to guess at my CFM needs?
It’s almost like the tool makers and the compressor makers have teamed up – to present their products in the least helpful manner possible!
Don’t just say “bigger is better.” Remember, you have to carry the things around, and not every circuit has 20 amps of 125 volt power available.
What say you?
Thanks.
Replies
easy to get too caught up in figures here....
All that horsepower/cfm stuff is confusing. I wonder how much you can trust the figures anyway, Then there's the tank size.
If all you are doing is driving nails though I believe you can pretty much go by the manufacturers general recomends. Go up in size some for each additional crew member even if only one nailer will be active at once. If you are going to paint or other more consumptive uses then maybe you need to break out the pencil.
I haven't seen any portable compressors that exceed 15 amps at 120 v. in recent history. I'm pondering some compressor replacement myself and don't see anything under 50# looking suitable for me.
Right- It is confusing!
A quick glance at a site selling 'hand carry' DeWalt compressors shows a range of prices from $170 to $327. While two are branded as 'trim' compressors, you're completely without any guidance.
A visit to the local box store revealed that Porter-Cable, at least, has little cartoon pictures on theirs, showing various tools suggested for use with the compressor.
Nail cun makers are silent when it comes to compressor recommendations.
If compressors are marketed in the same manner of other power tools, I'll agree thqat 'horsepower' ratings are pure fantasy, and you'll have to look to the full-load amps for guidance. Is that the case?
I referenced the power limitations, as many portable compressors "choke" when hooked up to 100 ft. of #14 extension cord. It's not the running draw, as much as the starting load required, Heck, there can easily be 50 feet of #14 in the house, lust getting from the panel to the outlet! Yet another reason that 'bigger' isn't always 'better.'
I've left noise out of the discussion, just for now. You're right, though: noise can be a big issue. Noise control, comes at quite a premium, though, with the truly quiet units costing into the thousands of dollars. I'll admit that I - and my neighbors - really liked the quiet compressor mounted on the truck of the crew that replaced my roof!
Let's look to my own circumstances: We're talking about one amateur operating one nail gun for small jobs- such as framing one wall or replacing the siding on his house. I go to even a box store, and I'm faced with a bewildering array and little guidance beyond what color I like and how much credit is left on my card.
For that matter, we've left out another possibility: How about a small compressor, then add an additional $75, 5-gallon tank for the larger jobs? Has anyone tried that approach?
Yuo'd think somebody, somewhere, had a chart showing compressors vs. typical tools.
Noise.
They make some pretty good compressors these days at reasonable prices, even cheap. The trade off is noise. If you are going to be using it more that occasionally try to get the quietest one you can.
I have a 1HP (actual power not the sticker) and it keeps up with any nail gun I have without working very hard. I kept 3 roofers going when we put the roof on. Where I see it straining is when I am using an air hammer, D/A or paint sprayer. I end up having to stop and wait for it to catch up.
You asked "What is the minimum size - tank capacity and horsepower- do I need if I'm using a trim nailer? A framing nailer? "
The short answer? Any compressor, even the smallest pancakes, have enough CFM to run one finish nailer. The smallest compressors may suffer trying to keep up with a framing or roofing nailer though. Tank capacity, horsepower...they're sort of all related, but you don't buy on those specs. You buy on the CFM that the compressor can actually output.
The long answer? Ignore HP and gallons for now. Well, don't completely ignore them. But for now focus on the SCFM of the guns you plan to use, as well as the SCFM of any compressor you are trying to buy.
The SCFM of a gun is spec'd out for so many cycles per minute. Say 60 cycles, or 60 nails driven per minute. A nail a second. It'll be in the specs of the gun. Will you continuously fire a nail a second out of each gun all day long. Of course not. Unless perhaps your construction site is overrun with zombies.
A 3-1/2" coil roofing nailer I have is about 9 SCFM.
A 3-1/4" framing nailer 8.5 SCFM.
An 18ga finish nailer is less than 1 SCFM .
If I wanted to run the roof and framing guns at the same time, and at the worst case rate of a nail per second per gun, with the guns I have I'd want 17.5 plus 10% fluff, or a compressor that can output about 20 CFM of air. Can I shoot at the 100% rating? Sure, for short periods. I can even exceed that for short periods when bounce-nailing sheathing. But the nail strips will be consumed if I'm bounce firing, so there wil be natural downtime to reload the gun, to reposition materials, the hose, my feet, etc.
Considering running at 25%, or averaging a nail every four seconds out of each of the two guns, that'll drop my 20 CFM to 5 CFM.
So I'd want a compressor that can output 5CFM. That's the academic answer. Then there is the real world translation.
The main compressor I've been using for the past 15 or so years is a Thomas 2820, it's a twin tank rated at 5CFM at 100psi. I just looked at the Thomas website and they say "Its tool capacity is five finish nailers, or three roofing nailers, or three framing nailers." And I agree. I've had three framers running at once. I've had one framer and two coil nailers running at once. And I never had a problem or never had to slow down and wait for the comressor to recycle. It just seems that very seldom is everyone bounce firing at the same time. Personally I don't advocate bounce firing at all. I used to do it myself, but not anymore. The guns have gotten faster and I've gotten slower. I am the lowest common denominator and for the past 4 or 5 years I'm fine with the slower rate.
Without researching specs, most mid-range pancake compressors can output 2-3CFM. That output can run one or two finish nailers full time, or just a single framing or coil nailer at a roughly 25% rate, or 15 shots per minute. The tiny pancakes can output less than 0.5 SCFM, they're only good for a single finish nailer.
You move up to the twin tank hot dog style compressors like my Thomas 2820, they get up to around 5 SCFM. They can run two framers all day easy. More if needed.
Simply look at the gun's CFM requirement. Figure out an appropriate derate since you'll not be running 100% all the time. Then adjust the gun's air requirement appropriately, and look for a compressor that offers that CFM requirement.
You did that wth your initial "...I am using a framing gun whose specs say it uses .082cf per shot at 100 psi - and it can do a maximum of 12 shots per second. Figure that for the 'typical' connection I'll fire as many as four nails in quick succession- with a pause as I move on to the next connection."
If you fire 4 shots over 4 seconds, move, then 11 seconds later fire 4 shots over four seconds, move...you'll be shooting roughly 16 shots a minute. 16 x .082 = 1.3SCFM required. Let's say you go nuts and double that. Two guns, or you're working fast. Then you need 2.6 SCFM, with a bit of fluff thrown in, say 3 SCFM.
Find a compressor that can output 3 SCFM at 100psi and you'll be all happy.
PSI? Pretty much all guns need 70-120psi, and pretty much all compressors can provide that pressure.
I do recommend checking out the noise (dB) ratings of the compressors. Example, if you needed 2SCFM for your guns and you bought a 2SCFM compressor, the compressor is going to be running pretty much full time. That can get noisy. Even noisier indoors, where the compressor can vibrate the floor and the sound can reverberate off the walls.
That's why it's sometimes good to go over your needed capacity. You future-proof your needs, and you reduce the amount of time the compressor is running.
Great Answer
Now, Mongo ... THAT is an answer!
From your method, it looks like I can find an appropriate, decent-brand compressor for $200-$250. There's a figure I can deal with.
I'd be really pissed if I spent $170 for a compressor that didn't do the job. Neither my accountant, nor my back, would thank me if I unnecessarily bought an oversize 77-lb unit.
I find it amusing that one maker calls an 80-db noise level "quiet." Makes me wonder what the level is for a 'loud' one! Still, that's 80 db for a $200 compressor, as compared to an "ultra quiet" 70db competetor for $285. I think we can rule out the 40-db model, as it lists at more than $1700!
Who to buy? Hmm. I find it enlightening that some of the more popular brands will not provide any sound levels ... so I expect they're over the 85 db where hearing protection becomes mandatory.
That's the tough thing about nail guns versus compressors. It's all how you use the gun. Bounce versus single fire. The fact that framers push about 7 or 8 times the air that finish nailers do. So the numbers have to be taken into consideration with how the gun or guns will be used.
If you end up borderline or get close on two compressors, another nut-breaker can be "recycle time", or how fast the compressor can fill and empty tank.
You probably know that the dB scale is a log scale, but just in case...A difference of 10dB means that one compressor will be twice as loud as the other. ie, "A" is 60dB. "B" is 70dB. "C" is 80dB.
"C" is generally twice as loud as "B". "B'"is twice as loud as "A". "C" is four times as loud as "A". Or so they say. Now that I'm deaf, they all sound the same.
For framers, they can pump out a lot of air when you fire off a nail. Most guns have rotating discharge ports so you can direct the discharge in one direction or another. That way you don't puff yourself in the face when in tight quarters.
Good luck with your shopping.
That was a great answer from Mongo indeed and I want to follow up with a less great answer and just experience. As far as what to buy: Thomas as Mongo said. The company holds the patent on the original oil-less piston pump. You cannot kill these compressors. I should know, I've killed many different brands with similar specs that were in the $250-$300 range. The Thomas Compressors, I use the 2820 all day every day, is quiet, not too heavy, and draws low amps so it can be run off an extension cord. To me, best compressor for the money. I think about $500.00 6 or 7 years ago.