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.