What size compressor for HVLP sprayer?

[Jason White]

I want to get a small-ish shop compressor. I've seen a couple of 30-35 gallon compressors on wheels that look pretty good.

Most of the time I'll only use it to power nail guns and blow dust off of stuff. I don't currently have an HVLP sprayer, but I'm sure at some point I'll want to use one for occasionally spraying furniture projects. Is a 30-35 gallon compressor big enough to handle this?

Jason

[Todd Jensen]

Way more than enough; I use my 4 gallon dewalt/emglo for my shop and it works great for the following uses: HVLP/cup gun spraying, any size nailgun, Ingersoll-Rand 1/2" Impact driver, etc, etc... I wouldn't go any smaller than what I'm using, but this size and bigger will do pretty much anything you want unless you step up into multiple framing nailers/multiple impact drivers, and the like. The thing with HVLP is that though your volume is increased, you'll have it set at a lower psi(40 or so), and so the compressor has plenty of time to catch up. It will blow off tools for days, air up the tires on my 3/4ton crew cab, and fits on the shop floor under one of my workbenches out of the way. I think a lot of people 'overbuy' on their compressors and you would do just fine with a solid, good brand(dewalt/emglo, Thomas, etc.) in the 4 gallon twin tank variety.
Just my opinion on the pile, good luck in your decision, and most importantly have fun with your upcoming new toy!:)

[Todd Burch]

As Todd said, it should be plenty big enough. However, do your due diligence.

Pick out an arbitrary HVLP that is within your hypothetical budget. Research the CFM requirement for the gun. Then, compare that to the compressor you are looking at.

Todd

[Allen Bookout]

Research the CFM requirement for the gun. Then, compare that to the compressor you are looking at.

Todd

This is the important part. The CFM output of the compressor is paramount. The size of the tank is secondary.

Spraygunworld is a good place to look at requirements of various guns and get a pretty good education at the same time.

[Tim Sproul]

IME, there is more to think about than the spec'd CFM requirement for a given spray gun.

1. What will you be spraying? Prefinishing sheets of plywood or do you mainly make things with expansive surfaces like dining tables and conference room tables? If so, you'll want to go with a compressor that is rated on the higher end for the air it can deliver. Spraying things like chairs or furniture without a lot of expansive surfaces requires less compressor output because you will pause more often as you are spraying lots of different surfaces rather than a few expansive surfaces.

2. How efficient is your gun? In general, you will get what you pay for. Less expensive guns will generally give you less transfer efficiency and they will require more air to atomize the finish properly. These 2 things go hand-in-hand.

I've been doing fine with a PC hot dog oilless compressor. It has a 1.5 HP induction motor and I run a 10 gallon accessory tank in addition to the 4 gallon capacity. I don't spray a lot of expansive surfaces and I don't use a cheap gun. I keep thinking I should get a higher capacity compressor and will once my current compressor gives up the ghost. I can spray a full-size HVLP gun continuously using water based finish and the compressor keeps up. It doesn't get much in the way of a break but I've NEVER continuously sprayed for more than 5 - 10 mintues. My spray sessions often run longer than 10 minutes but those sessions always have pauses as I move parts to dry or rearrange the current piece to get to another surface, etc. This gives the compressor a break. IIRC, the manual specifically stated the duty cycle was 1/2 and that the compressor should not be run for more than 30 minutes in a given hour. I definitely don't come close to that.

[David Weaver]

I do exactly like Tim does, but with a Harbor Freight 8 gallon 15-amp compressor. It's probably 1.5 horsepower, even though the tank says 2. It's rated at 5 cfm at 90psi, which is well less than what the gun I use is capable of consuming (up to 12 or 14 or something).

At any rate, I also only spray one piece at a time, and I do light coats - water based lacquer. The compressor has no trouble keeping up, but I wouldn't want to get less (i.e, if you're going to be stuck with a 110v compressor, get one that has a 15 amp motor and about 5+ cfm delivery at 90 psi). I could get ahead of it if I kept the gun on the trigger pulled for a couple of minutes straight, but I never build pieces that would have me slogging on that much finish recklessly.

If you want to go cheap, get one the HF oil-lube compressors - they're about $89-$200 on sale, depending on what tank size you get. You won't need 35 gallons to spray, though - 8 works fine for me. You may prefer 35 gallons if you start using tools that consume more (sanders, etc...), but at that point, you should also be looking at compressors that have more power than you can run on 110 voltage, too.

[frank shic]

jason, how much space do you have? how much noise does the air compressor make as it charges up? i bought an hvlp conversion gun a few years ago from gleempaint.com and used it on a porter cable 6 gallon pancake compressor and it worked miserably for spraying cabinets. it took FOREVER for the compressor to catch up and the noise was deafening. i bought a fuji hvlp q4 off of craigslist.org and it takes up much less space and makes very little noise.

[Jim Becker]

I have to say that "bigger is better" when spraying finishes is involved. You certainly can do good work with a 30-35 gallon unit like the IR GarageMate. But for similar money, you can put in a 60 gallon unit that will have a lot more reserve air, resulting in less running and less noise. That all said, you need to insure that the unit you buy can deliver the required SCFM of the devices you intend to use with it...including your spray gun. HVLP conversion guns do use a lot of air; some more than others.

[Carroll Courtney]

Jason,I also echo what Jim said that bigger is better.If the budget allows,purchase a stationary compressor that is two stage.CFM is important,the more the better.Just because a compressor is bigger some do not product no more cfm's than the pancake type so look closely.With the more cfm's you will have a better selection of spray guns to choose from.Most hvlp guns require around 10-12 or more cfm's.You can purchase spray guns that only require 3-6cfm's but you can purchase a compressor for what they cost.I have been down the same dusty road you are on right now,save yourself some aggravation and shoot for at less 10cfm's.

[Todd Jensen]

I use a standard cup gun and have had no problem at all spraying laquer on bookcases to workbenches. I've also used the same gun for water based finishes with equally good results. I think some of the problems spraying have to do with how your gun is set up, the viscosity of your finish, and the temperature/humidity of your work area.

I just wanted to re-iterate that I've never had a problem with my current setup, and present the science that supports my claims(please don't get me wrong, I'm still a quack).:D

For example, lets look at a cup gun that requires 7cfm@40psi. My compressor is rated at 4cfm@90psi.
A way to calculate changing psi at different cfm is:

CFM*((PSI+14.696)/(X+14.696) = Y
X = PSI you are converting to, Y = Resulting CFM @ X

For example, my flowrate at 90psi is 4cfm, then at 40psi, it is:

4*((90+14.696)/(40+14.696)) = 7.66cfm, plenty to run the aforementioned cup gun.

[Roy Hatch]

Todd said, "I just wanted to re-iterate that I've never had a problem with my current setup, and present the science that supports my claims(please don't get me wrong, I'm still a quack)"

Todd, I have no reason to even suspect you are a quack, but you have presented a formula that leads me to assume that my little MAC 2400 might be adequate for some HVLP spraying.

I tried once in the past to determine the output of my compressor at 40 psi and was told the only way to do that was to actually measure it. (Mine is rated at 4.2 CFM @ 90 PSI.) It's obvious that you get more CFM at a lower pressure, but this is the first time that I've seen a formula. I was lead to believe that only one of the spray guns selling for hundreds of dollars would work with the smaller compressors. So perhaps that's bullfeathers?

Would you perhaps choose to grace us with a reference?

Roy (who is not an engineer)

[Todd Jensen]

I'll post video on Sunday Roy. Your Makita 2400 would do just fine; a lot of stair guys including myself have sprayed rails in the field with only $100 cup gun and a twin tank with great results. If I was running a production cabinet shop I'd get the biggest tank I could afford and the Porsche of HVLP sprayers, but I promise you'd be surprised what you can do(both quantity and quality) with my setup.

[Steve Clardy]

I spray staircases with a PC PSH1 and a 6 gallon pancake compressor.

[Art Mann]

jason, how much space do you have? how much noise does the air compressor make as it charges up? i bought an hvlp conversion gun a few years ago from gleempaint.com and used it on a porter cable 6 gallon pancake compressor and it worked miserably for spraying cabinets. it took FOREVER for the compressor to catch up and the noise was deafening. i bought a fuji hvlp q4 off of craigslist.org and it takes up much less space and makes very little noise.

Are you talking about the Wagner conversion gun that Jim has? My experience has been that the gun works well. Did you have a problem with the actual finish put down by the gun or was your problem the fact that the loud little compressor ran all the time? I used it with a 25 gallon, 1.75 HP (real, not phoney "peak" HP rating) compressor rated at 7 CFM @ 40 psi. Over a 30 minute spraying session, I heard the compressor cycle a few times but it didn't seem excessive. My compressor is located in another room from where I spray so noise isn't a big issue for me.

I have been so impressed with the Wagner conversion gun that I no longer can justify an expensive turbine unit and, by my observation, the gun outperforms the cheap turbine sets.

Edit: I just checked and my compressor is rated at 7.7 cfm @ 40 psi.