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-   -   2 small compressors or one large one best? (http://www.hotrodders.com/forum/2-small-compressors-one-large-one-best-213876.html)

HotRodMan 02-03-2012 01:05 AM

2 small compressors or one large one best?
 
I can buy two 60 gallon 10cfm at 90 psi compressors for about the same price as one 80 gallon 15 cfm at 90 psi. I could connect the two compressors in tandem to the same line.

Does anyone know how to figure out if the two 60 gallon compressors or the one 80 gallon compressor would be the best?

Dave57210 02-03-2012 05:11 AM

Whether you have a 60 or 80 gallon TANK - that is still just the tank size - it has NOTHING to do with the compressor capacity!

What you are talking about here is the two times 10 versus 1 times 15 compressors themselves!

So my question back to you would be: Do you have the power available to run 2 motors for the two 10 cfm units?

Second: Are we comparing apples to apples? Are the 2 10 cfm units and the one 15 cfm unit all rated the same way?

And most important - Are they equal in quality?

If all is comparable then what you are asking is "which is better - 20 cfm or 15?"

Tank size is a game played by the manufacturers.

stich626 02-03-2012 07:29 AM

are they all 2 stage compressors, ? next up.. you'll build 2x the heat..
and your power company will love you.. the money you'll save on the unit, you'll give to the power company.. that over time will be allot.

I'd save for a quality 80 gallon compression..
heat= water in the air.. thats bad for your tools, and very very bad for paint..

matts37chev 02-03-2012 07:40 AM

what are you going to be using it for?
I have a 6.5 hp on a 60gal DeVilbiss 2 cylinder, single stage (125 psi)
its rated at 9.4 scfm @ 90 psi and 11.9 scfm @ 40 psi
if you are using good quality air tools, it seems to keep up OK
cheap tools use a lot more air volume

HotRodMan 02-03-2012 12:43 PM

Questions answered about compressors
 
OK, I will try to answer all your questions.

I do have the power available to run two compressors. My garage is 38 feet long and I have a 240 volt dedicated outlet on each end of the garage run with 8 gauge wire and a 40 amp circuit breaker.

As far as I know they are both rated the same way at 90 psi because they are both manufactured by the same company.

As far as the quality goes the larger compressor has 3 pistons, the bigger tank, and a larger motor. Both have cast iron cylinders so the best I can tell the quality is about the same.

The compressors are not two stage. Both are single stage. The smaller compressor has 125 psi max the larger one has 155 psi max.

I plan to use the compressors for body and paint work. A lot of grinding, sanding, and spraying primer, paint, and clear coats.

DanielC 02-03-2012 12:48 PM

I would suggest you buy a single TWO stage compressor.

dtracy 02-03-2012 04:00 PM

I had two - two stage compressors using five HP motors and 60 gal tanks. I replaced both with one - two stage compressor using 10 HP motor and 120 gal tank. Big difference! I had more air, faster, and cheaper than before. Best idea I'd had in a long time.

1971BB427 02-07-2012 11:15 AM

I have two, but only use one at a time. My 80 gal. twin cylinder doesn't get fired up much unless I'm in a project that needs lot of air tools. My 2nd is a small 120v. portable that gets a lot more use for small tasks.
I bought the large stationary to have a great compressor, and was going to sell the little portable, but decided to hang onto it. I'm glad I did a it's a nice little compressor for small jobs.

oldred 02-07-2012 12:36 PM

Quote:

Originally Posted by Dave57210
Whether you have a 60 or 80 gallon TANK - that is still just the tank size - it has NOTHING to do with the compressor capacity!

What you are talking about here is the two times 10 versus 1 times 15 compressors themselves!

So my question back to you would be: Do you have the power available to run 2 motors for the two 10 cfm units?

Second: Are we comparing apples to apples? Are the 2 10 cfm units and the one 15 cfm unit all rated the same way?

And most important - Are they equal in quality?

If all is comparable then what you are asking is "which is better - 20 cfm or 15?"

Tank size is a game played by the manufacturers.



That pretty well covers it and the finial decision would depend on the specific demands of the situation. Obviously if maximum CFM is desired regardless of the other concerns then the two compressors working together would be best but the big question is would the trade offs be worth it? My first thought was if the two smaller compressors cost the same as the single larger one then we are comparing low quality small compressors to a better quality single larger one and since the CFM is close then the larger one would probably be the best choice, but then he said the larger one was a single stage so I don't know if quality would be an advantage in this case. As you so correctly pointed out if the main point is to get two 60 gallon tanks instead of one 80 gallon then clearly buying the two smaller ones is a mistake, as has been said repeatedly a bigger tank does not make a bigger compressor! A 60 gallon tank compressor set up with only 10 CFM is already pushing the limit for tank size and connecting two of them will only compound the problem, you are right about the manufacturers pushing the illusion of a big compressor by using over-sized tanks and that's the case with 10 CFM units mounted on 60 gallon tanks.

Another thing to consider is just how long will a cheaper built 10 CFM single stage pump continue to produce 10 CFM? There's a lot of difference between the actual amount of air produced from a cold pump vs a hot one especially with a cheap single stage compressor and with these little pumps mounted on larger tanks they tend to heat up rather quickly and under fairly heavy use which is commonly the case for a small compressor trying to do normal shop duty. An overheated pump is even worse and high demand situations with small pumps/large tank combos means overheating is easy to do because of insufficient cooling cycles. Even with the aforementioned problems with heat there is also the accelerated wear factor that decreases pump performance on the cheaper outfits so the point is that in a fairly short time that 20 CFM duel rig may very well be producing the same or even less CFM than a single larger unit, provided of course the larger unit is of better quality.


My vote would be to ditch the two small compressors idea along with the large single stage unit and spend the money on a quality built two stage compressor. I could almost guarantee that after a fairly short time of use a good quality two stage compressor of 15 CFM or so will be producing more actual air vs the the two single stage units that are rated at 20 CFM.

MarkhamCornoit 03-06-2012 11:08 PM

I agree with Dave57210. Tank size is a game played by manufacturers. The *important thing is to match the Fluid Cap, Needle, and Air Cap to the kind of materials you will be spraying.* If you use a set up that is for heavy urethanes to shoot lacquers or dyes you will not get proper atomization and you will wind up with runs or orange peel. Generally the information on the correct Fluid, Air, Needle set up for a particular type of material will be included in the manufactures information book in the box with the gun.*


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