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Old 09-16-2007, 09:40 AM
oldred oldred is offline
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That particular IR (the first one) has been the subject of discussion here before and there have been many discussions on how the compressor builders tend to exaggerate their claims. There is simply no way that thing will produce that kind of CFM at that pressure and those numbers are nothing more than sales tactics arrived at by using "smoke and mirror" engineering to estimate performance. At 5 HP and the fact that IS a good single stage pump, for a single stage anyway, I think around 12-14 CFM would be a lot closer to fact. If you can afford the extra cost of the two stage then don't even consider the single because in addition to better CFM on a given HP rating it will run quieter, cooler and last longer, the second IR you list is a good choice and the numbers should be a lot closer to real than on the first one. Might I suggest you check out the Eaton compressors as they are a REALLY good compressor at a good price and you can believe the numbers they claim. When looking at the Eatons, and there are other good brands, it may seem like the performance is a bit low per HP than some of the competitors when in fact the opposite is true because they tend to tell the truth, we have become so accustomed to seeing the non-sense numbers from most outfits that the real performance does not look all that impressive. Almost all of the "econo" compressor outfits exaggerate the performance almost to the point of ridiculous and in some cases so bad they have landed in court over it but most of the really good companies like Eaton, Quincey (my personal favorite) and even IR are much closer to the truth but IR has been guilty of fantasy numbers on some of the smaller models like the one you listed. Some of the things to look for would be an American made motor such as GE or Baldor and a pump with a low RPM design whether you go with two stage or single. A 60 to 80 gallon tank is about right for a compressor in this power range and a 60 will perform just as well as the 80 as far as running tools so don't base your decision on tank size. Avoid any compressor that lists "peak" or "max developed" HP numbers as these are pure non-sense and proves the compressor is lying about performance, likewise walk away from anything that lists "tank assisted" CFM as this is the biggest scam of all. The 80 gallon will offer a slight advantage in service life and power consumption due to fewer start/stop cycles during any given use period but this advantage is VERY slight and not worth spending a lot of extra cash for. It certainly would be a BIG mistake to pass up a better performing pump/motor to get a bigger tank but this happens all the time and the builders of these things know that a lot of people will buy the biggest tank they see so over-sized tanks are common. Remember CFM (true CFM and not phony numbers) is what will make your tools run and big HP numbers and a huge tank don't mean squat if the CFM is not there.
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