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Respectable paint on 120V compressor?

29K views 43 replies 12 participants last post by  smallac 
#1 ·
Well..I know the reccomendation is a 240V machine to do good paint..Like most things in life we usually have to compromise at times. I tend to think that a good paint job, on a truck in my case, is not impossible with say a 120V, 5 horse compressor. Any words of wisdom out there?

Thanks,

Keith
 
#3 ·
It's done all the time,
It's not the compressor-it's the gun.
(I've painted entire cars with a 1hp compressor)
Depending on the compressor, you may not be able to use a HVLP gun.
You may have to use a conventional one, there's nothing wrong with that.
Cars were painted for years with conventional guns.
Astro makes a Binks copy for under $50.00 that sprays great.
I've used that gun at lower pressure then suggested
(useing less than 4cfm) and it sprayed great.
Did some nice jobs with it when I first started
That will work fine with most smaller compressors.
So check the gun CFM and compare to your compressor output. :pimp:
 
#5 ·
5hp@120v would require in the neighborhood of 65 amps. A far cry from the possible 20 amps you MAY be able to provide. Forget Sears or Home Depots hp ratings they are bogus.

Pay attention to scfm@psi .

The greater the difference between the guns requirement and the compressors output is a good thing. The compressor will run less which will equal dryer air.

As already stated, use a conventional gun with a low air requirement and filter you air good and you will do just fine.
 
#6 ·
Slickriffs said:
I tend to think that a good paint job, on a truck in my case, is not impossible with say a 120V, 5 horse compressor. Any words of wisdom out there?

Thanks,Keith

I know you can find those things "Rated" at 5 HP on 120 volts but that is 100% USDA certified BS! :nono: Actually 3/4 HP would be more like it and maybe even less than that! As pointed out if you must do it on 120 volts then find the one with the highest CFM rating and use a gun with the lowest CFM requirement but unfortunately the numbers you find on those two items tend to be exaggerated too.
 
#7 ·
Hey Gents..Thanks for the info..

No I don't own anything yet..other than a 1 HP sears..I have done epoxy primer with that successfully but need something better for a finish coat.

I believe the 5 HP rating was one I saw advertized..probably was Sears. So it's the CFM's..not the HP..Ok got it.

Someone said possibly I might buy one that can't handle HVLP-why would that be?

What's the deal on "two stage". Is this a big plus?

I haven't bought anything yet so this info is very beneficial..Thanks all.

Keith
 
#9 ·
Take the HVLP gun out of the equation and the compressor size and power is basically a moot point. The HVLP gun is the ONLY reason you need the larger compressor for painting. Sanders won't work worth a darn with the smaller compressor though.

I opened a body shop in 1982 with a 20 gallon 110 volt 2hp compressor (as I remember it was 110 volt) and I not only painted cars, I bought my first house with the money earned from that little compressor. Painted collision work every day and a few show cars and collectables as well. This was in the years before HVLP, big difference.

If you must run 110, a good old Devilbiss JGA-502 gun will do some beautiful work.

However, if you have 220 in the garage, for goodness sakes move up to 220 and a 60 gallon tank minimum. I have never said "Darn I wish I would have bought the cheaper tool". :)

Brian
 
#10 ·
I had a Sears 5hp compressor that was 110volt,
when I checked, the motor was only a 1hp, so I asked Sears
how can it be rated at 5HP, I was told
"it puts out as much air as a 5hp" What BS!!! it doesn't do that either.
I think they got in trouble over that hype, it's only on those
direct drive "oiless" compressors (I think).
Anyway, like the old saying "BUYER BEWARE" :pimp:
 
#11 ·
Matt,Mart,Jc

Thanks,

Feel good about it if I have to go that way..

So where does this two stage business come in to play? Is a 2 stage more efficient?

Also how long of a chord can I use. I just bought one of these for storage and painting. I trying fiqure out how far away from the house I can put it.

http://imagehost.vendio.com/preview/lw/lw1076/4x8partytent.JPG

Thanks gents,

Keith
 
#12 ·
Kieth, I'm not trying to jack the thread I just have a question.

Why are all of you saying that HVLP is not a good gun to use on a small compressor? I figured that the old style would use a lot more air than the newer guns. I got all my paint guns from my grandpa when he passed. One is a binks, old gun but sprays GREAT! And the other is a cheaper Hvlp. I use the Hvlp for the primer but the Binks for the final coats.
 
#14 ·
lol, thanks Keith. Sorry about spelling your name wrong in the last post. Brain is faster than my fingers :p

I just havn't been on here very long (not even 24 hours) and I'm in the process of reading all the posts. I have been a long time member on another Camaro site. Not sure if it's okay to post the url, so I wont. But, I'm one of the more informed members over there on the 4th gen Camaros. But, this will be my first HotRod build and I want to learn some of the tricks of the trade.

But, what you are saying is somewhat logical in my head. I can see what you are saying. I guess it's just the fact that you don't need the pressure, but you just need a lot of air going through the gun so a compressor with a high cfm rating is needed. I have one of those 5hp craftsman 30 gallon compressors and I'm looking for the dual stage 220v 80 gallon to do this little project of mine. I'm just starting to look so I can't reccomend anything at this time.
 
#15 ·
you might be lucky and your comp wont blow up while youre shooting your car, youre painting solid color it should be easier. I definitely wont paint metallic colors with small compressor as I need air when I need it and not wait for compressor to recharge. I have 220V compressor and I like to shoot with plenty of air when I paint to lay out metallic/clear coat properly.
 
#17 ·
Slickriffs said:
Hey Gents..Thanks for the info..


What's the deal on "two stage". Is this a big plus?



Keith
A 2 stage compressor produces air at a higher pressure than a single stage, thereby allowing more air to be stored in a given tank size.
A drawback to this MAY be the introduction of more heat into the air as it is compressed to a higher pressure.
You do not need 175psi for anything in your home garage or most any production shop for that matter.
100psi is the usual max pressure requirement .

Compressed air requirements and air compressor sizing are based on the tools cfm@psi AND the compressors scfm@psi output.
The greater the spread between these 2 factors will allow the compressor to cycle with longer off times.

A single stage compressor producing 18scfm@100 psi, or a 2 stage compressor producing 18scfm@100 psi is the same animal.

The difference is how much volume the storage tank will hold, due to the 2 stage pumping the tank up to 175psi instead of 125psi of the single stage
Either way, ONLY 18scfm@100 psi is available once the tank is at 100psi.

The 2 stage with the higher storage pressure and volume is well suited for a intermittent requirement of a large volume of air, such as the raising of an old skool gas station floor hoist. Took lots of volume to fill , but didn't need to run continuous.

The bottom line: Continuous running of air tools, ie sanders,blasters,paint guns,etc. requires volume NOT hi pressure.
 
#18 ·
Hold on here, the Two stage is producing more pressure, but more volume as well. Here's how it works, the first cyl compresses the air, then that air goes over to the second cyl to compress it again! So you are putting TWICE the volume (in laymens terms) into the tank! No, the two stage will back up the same tool for much longer, even when the tank is empty it will back up a high volume tool.

If you can afford the two stage compressor, get it. Like my brother always says, "I have never said DARN I wish I would have bought the cheaper tool". :)

Brian
 
#19 ·
MARTINSR said:
Hold on here, the Two stage is producing more pressure, but more volume as well. Here's how it works, the first cyl compresses the air, then that air goes over to the second cyl to compress it again! So you are putting TWICE the volume (in laymens terms) into the tank! No, the two stage will back up the same tool for much longer, even when the tank is empty it will back up a high volume tool.

If you can afford the two stage compressor, get it. Like my brother always says, "I have never said DARN I wish I would have bought the cheaper tool". :)

Brian
Resspectfully sir you are not correctly comparing ratings. You must compare ratings at the SAME pressure or the SAME cfm for a valid comparison.

If a compressor is rated at 10cfm@100 psi, it does not matter how many stages it has or its max pressure output. At 100 psi it can only produce 10cfm. You have to compare compressors at the same pressure and cfm to find out what you have.(or do the math)

I do believe the OP is budget conscious and a large single stage will provide the air he needs for less $$ than a 2 stage.

Single Stage 18.1 cfm@90psi -$899 shipped
http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_211720_211720

2 Stage 15.9cfm@90psi - $1299 shipped
http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_290946_290946
 
#20 · (Edited)
A single stage compressor producing 18scfm@100 psi said:
You are close- They would both be producing the same amount of air, that is they would have the same amount of volume at the given pressure setting BUT the two stage would not only be doing it using slightly less power but the volume would be higher at the lower pressures with the two stage thus allowing for less recharge time. The two stage does this by being more efficient because of the principle MartinSr mentioned. All else being equal, the same tank, plumbing and motor with the only difference being a two stage pump vs a single stage the two stage will outperform the single stage by a good margin and produce cooler air doing it (it loses a lot of the heat between the first and second stages).
 
#21 ·
About that comparison with that Ingersoll at over 18 CFM@90 PSI, Unfortunately compressor specs are often overblown and just as "peak" and "maximum developed" HP ratings are often used to mis-lead buyers CFM ratings are sometimes pure fantasy too! There is no cotton pickin way that 5HP single stage inline pump is going to produce those kinds of numbers I don't care what kind of smoke and mirrors they use to arrive at the figures, the laws of physics are the same for everybody! That particular model of IR has been the subject of discussion here in more than one thread and I can say with confidence that if I could attach my flow meter to that darn thing I would be very much surprised to see much over 14 CFM at that pressure IF it could do that much! I have checked the flow on a great many compressors over the last 30 some odd years and I am talking about the good AMERICAN made iron not that piece of Chinese crap with inflated performance numbers (yes that damn thing is CHINESE! :mad: ) and never have I seen a single stage piston pump with only 5 HP produce anywhere near that kind of volume, it just does not work that way.
 
#22 ·
oldred said:
You are close- They would both be producing the same amount of air, that is they would have the same amount of volume at the given pressure setting BUT the two stage would not only be doing it using slightly less power but the volume would be higher at the lower pressures with the two stage thus allowing for less recharge time. The two stage does this by being more efficient because of the principle MartinSr mentioned. All else being equal, the same tank, plumbing and motor with the only difference being a two stage pump vs a single stage the two stage will outperform the single stage by a good margin and produce cooler air doing it (it loses a lot of the heat between the first and second stages).
oldred said:
They would both be producing the same amount of air, that is they would have the same amount of volume at the given pressure setting
but the volume would be higher at the lower pressures with the two stage

Please explain how it can be the same but different :confused:

Compress a gas and you add heat directly corresponding to the pressure increase. The reason a 2 stage "MAY" be providing cooler air is that piece of fin tube between the first stage and the second stage.

Add a refrigerated cooler after the tank and the heat is no longer a problem with either type of compressor.

.
 
#23 ·
Old Fool said:
Resspectfully sir you are not correctly comparing ratings. You must compare ratings at the SAME pressure or the SAME cfm for a valid comparison.

If a compressor is rated at 10cfm@100 psi, it does not matter how many stages it has or its max pressure output. At 100 psi it can only produce 10cfm. You have to compare compressors at the same pressure and cfm to find out what you have.(or do the math)

I do believe the OP is budget conscious and a large single stage will provide the air he needs for less $$ than a 2 stage.
What Oldred said. :)

Do you know of a use for 175 psi? No, so why would anyone ever want a 2 stage? Because they have more volume and keep up better when the tank is empty.

As far as it being the right one for our discussion, that is entirely up to the buyer. All I am saying is IF you can afford the 2 stage, get it, you would never be sorry they "wasted" the extra money.

Brian
 
#24 ·
Listen, I am not engineer to argue the science of these compressors I would be a fool. The thing is, no "real" body shop runs on a single stage compressor. The two stage compressor is a step up, they will keep up with a cfm hog like an 8" orbital ND 900 they will keep up with an CFM hog HVLP gun better, they are just better.

Are they absolutely needed, no. Heck, one could do the whole car by hand and prime and paint with aerosol cans. :)

But if you are going to buy a compressor and have the dough, the 2 stage would be the way to go.

Brian
 
#25 ·
Old Fool said:
The reason a 2 stage "MAY" be providing cooler air is that piece of fin tube between the first stage and the second stage.

Add a refrigerated cooler after the tank and the heat is no longer a problem with either type of compressor.

.

Apparently you seem surprised that the two stage runs cooler? It does (due to that tube which removes a LOT of heat!) and this has always been one of it's selling points although it's main advantage is in volume. Basically it works like this, given a certain amount of power and a fixed ratio you can produce high volume at low pressure or you could produce high pressure at low volume but you can not produce both high volume and pressure at the same time, V @ P = HP. Think of a car with a certain amount of HP and only one gear, depending on which gear ratio it could either accelerate rapidly to a low top speed or with a ratio change it could accelerate less rapidly to a higher speed. Now by using a two speed transmission that same amount of power could be used to both accelerate rapidly AND reach a higher speed. In the case of the two stage compressor vs a single stage with the same rating for each, say 15 CFM@90 PSI, the two stage would produce somewhat more volume at the lower pressures, thus the CFM rating@90PSI would be the same but the two stage would reach it sooner. On the two stage set-ups with a lower cut-out speed (lots of two stage outfits are set up to cut out at around 135 CFM) there is a heck of a lot of difference in recharge time if the pump/motor is geared to reach maximum torque at that cut out setting like the single stage would be.
 
#26 ·
oldred said:
Apparently you seem surprised that the two stage runs cooler? It does (due to that tube which removes a LOT of heat!) and this has always been one of it's selling points although it's main advantage is in volume. Basically it works like this, given a certain amount of power and a fixed ratio you can produce high volume at low pressure or you could produce high pressure at low volume but you can not produce both high volume and pressure at the same time, V @ P = HP. Think of a car with a certain amount of HP and only one gear, depending on which gear ratio it could either accelerate rapidly to a low top speed or with a ratio change it could accelerate less rapidly to a higher speed. Now by using a two speed transmission that same amount of power could be used to both accelerate rapidly AND reach a higher speed. In the case of the two stage compressor vs a single stage with the same rating for each, say 15 CFM@90 PSI, the two stage would produce somewhat more volume at the lower pressures, thus the CFM rating@90PSI would be the same but the two stage would reach it sooner. On the two stage set-ups with a lower cut-out speed (lots of two stage outfits are set up to cut out at around 135 CFM) there is a heck of a lot of difference in recharge time if the pump/motor is geared to reach maximum torque at that cut out setting like the single stage would be.

The total volumetric area of the cylinder per revolution x revolutions per minute /efficiency of cylinder and valve seal determines the output.

If one cylinder displaces .03 cu ft , and then shoves it into a cylinder of .02 cu ft. then the pressure of that single compressed cycled will increase, but the total volume of influent is still .03 cu ft.
It has now been compressed to a higher pressure which occupies less total volume in your supply tank . Nowhere in this process did the compressor magically increase the cu.ft. of air it inhaled in that one cycle.

Now multiply that one cycle by number of cycles per minute and you have the CubicFeetMinute the compressor is rated at.

If a single stage dual cylinder compressor operating at 85% efficiency and has a total displacement per revolution of .008cu.ft and compresses that volume to 90 psi , then it would be fair to say it is rated at .408 cu.ft.per minute.
Multiply that number by rpm's and total output is determined.

If a 2 stage compressor with a first stage cylinder has a volume of .008 cu ft. and its ring and valve seal efficiency is 85% then the output of a single intake cylce will be .008 cu ft, but its pressure is increased by the action of the much smaller secondary cylinder that is not a volume increaser but is a pressure increaser.
The influent of a single revolution is the same as with the single stage example above.

the 2 stage compressor is more efficient at producing high pressure due to the compress and re-compress action of each cycle. The total volume is only determined by the above mentioned factors.
As far as being more efficient from an energy standpoint that is not so. it takes a given number of watts to produce pressure at volume, or volume at pressure , which ever way you wish to look at it.

Shops run a 2 stage compressor to get hi volume storage at minimal cost. Storage tanks cost $, and take up a foot print that also cost $.

Body shops are a minimal cost operation,therefore they run the cheapest option available, not necessarily the best.
A true industry using compressed air will run a multiple stage turbine which has far greater capacity, but the $$ to acquire are far more.

I only question the heat statement as I have not done any tests of compressors to see what the effluent temperature is. Some single stage compressors also run fin tube and have lower operating temps than a non cooled compressor.

Anyone serious about dry air will install a refrigerated air cooler, no matter which type of compressor they have.

I have installed, maintained and rebuilt industrial air compressors for 30 years. Joy(Now Cameron),Sullair, and Fuller are the primary units I am trained on. Have also maintained Ingersol-Rand and Curtis industrial recprocating(piston) type compressors.

Cameron multiple stage centrifical compressor:


1500-2200hp 6500-11800cfm 80-150psi

How about this little boy for a body shop?

Its only a single stage 84 cfm@175 psi 25 hp.
Small foot print, large volume, no oil in the air, why doesn't the local shop have it? its not because their compressor is better, its because it is cheaper.
http://www.sullair.com/corp/details/0,,CLI1_DIV61_ETI8582,00.html


A little guide to types of air compressors:





Bottom line, buy what ever works for you and your budget. If I had the money some of you guys have I would have a Curtis SE7.5TD in my hobby shop :mwink:
 
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