|06-07-2011 07:33 PM|
I understand the theory that pumping X amount of air creates Y amount of heat, whether that is done at once or over a period of time. My gun takes 13cfm (15cfm compressor) and I can get an entire coat on a full size pickup before it kicks back on. Add in flash time between coats, and the compressor sits idle for a good long while. If the compressor kicked on 4 times during the coat, I could not keep the air nearly as cool. 15 degrees isn't much of a difference, but in high humidity, there is quite a difference on how fast my desiccant dryer is used up. When the compressor runs continuously for long periods, I can get a 50 degree jump.
I also specifically stated in my first post that 60-80 gallon is negligible and any point you make in saying otherwise is utterly ridiculous. No nowhere did I state that "I didn't agree with the blanket statement that the 60 vs 80 gallon didn't make a difference" as you said. HR has a hive-mind on this subject, and while being generally correct, is just that, a general statement.
I also originally said: "If I had a 20 gallon tank while painting, I would see the same issue as I do now with the DA." My gun is 13 cfm at 26psi, compressor 15 cfm. A 20 gallon tank would empty very rapidly causing the compressor to run near constantly while spraying. I know that with my DA, which causes the compressor to run near constantly water is an issue. I could not effectively dissipate the heat from the compressor on the fly in 95 degree weather, such as today, when the compressor rarely shuts off. I can get a full coat, or nearly a full coat without the compressor kicking on with my 80 gallon. Although the air heats up when the compressor kicks on, it has plenty of time to cool back down between coats.
This isn't just for painting, but for any non-continuous use tool, impacts, air hammers, etc. There may be a time when you will impact for 20 minutes straight, but that is far and few between. There are times when I need all the cfm I can get, the blaster and DA are my only ones, but for 80% of my air usage it is intermittent.
|06-07-2011 07:16 PM|
It doesn't matter who built the motor; if it does not receive the juice it requires it will shorten the life. The issue with these emerson motors is well known and I did a lot of research before buying the IR compressor because of this. Reading about this online and talking with IR, this conclusion makes pretty good sense to me...haven't seen too many failures from those running a thicker gauge wire. I know that a 5hp motor typically uses approx 25 amps under load and uses a 40 amp breaker. I was specifically told to use an 6 gauge because of my distance from the box to the compressor, but shorter distances can use 8. I don't know of a reason for this as I didn't get that far into it, quite possibly these motors have a very high initial amp kick. We use slow-blow breakers that will take considerably more amps for a short amount of time, so this wouldn't be instantly noticeable to anyone, but if the wire (power supply into the building, wherever the weak link is) can't handle the high amp draw, the motor will not get the amps it wants on the initial kick.
It has been a few years since I installed mine so all of the numbers are a bit fuzzy, but I believe the initial amp draw was near 100. I was also researching the 7.5hp versions as well, so that number may be for it. In any case, it was over the current carry capacity of a 10 gauge.
|06-07-2011 07:04 PM|
|oldred||You said you didn't agree with the blanket statement that the 60 vs 80 gallon didn't make a difference and I simply explained what I meant, that it was not a "blanket statement" that it made no difference at all. As far as the 60 gallon vs 80 making a difference while painting that can be a toss up also, you run a bit longer but then you also wait longer IF the compressor has to catch up, if it doesn't have to catch up and can keep up with the spray equipment then it makes no difference. The idea that an 80 gallon tank is going to provide cooler air than a 60 gallon is something you seemed to be saying and that is simply not going to be an issue since it is the amount of time the pump runs in a given work period that will cause the hotter air, when running that sandblaster for 15 minutes (or any tool for more than one run cycle) the pump will run the same amount of time regardless which tank you have and THAT is what heats the air. Having an 80 gallon tank instead of a 60 gallon does not mean the pump will run less during any given work period and it would be the same even with the 20 gallon you mention. You said that with a 20 gallon tank when painting you would have the same issue as you do when sandblasting with the bigger tank but that's not so, when sand blasting the compressor runs almost continuously and accumulates a heck of a lot more run time during the work period than when painting for the same work period. the frequent and short start/stop cycles of the smaller tank would cause some cooling problem but not for the same reasons as sandblasting with the bigger tank nor would the problem be as severe. If you paint for 30 minutes then the compressor will run the same amount of time whether has a 60 gallon tank or an 80 gallon or a 20 gallon for that matter.|
|06-07-2011 06:48 PM|
|JohnnyK81||10 gauge is plenty sufficient for a 5 hp motor, which will draw 22-23 amps at load. 6 gauge is almost ridiculous, unless you have a 7.5hp motor. Not sure I agree with whomever gave you your information. I'm a little skeptical on resistance burning out the motor.|
|06-07-2011 05:42 PM|
I think there is something wrong with your coffee. Besides the single vs 2 stage, I also stated that 60-80 gallon difference is hardly a difference and that I was talking more theoretical than specific to this thread.
There is an issue with the emerson motor on the IR unit. My research has shown that these motors will last when wired properly and given enough juice. They are very sensitive to resistance, and specifically if too small wiring is used they will burn out. I was recommended to go with a 10 gauge wire, which is drastically too small for the load. If most go with the recommendation, there is the issue. I ended up using 6 gauge IIRC, which is the wire actually rated for the amp draw.
|06-07-2011 11:36 AM|
|06-07-2011 07:39 AM|
Brad that IR is at TSC has a couple of problems that we simply can't overlook because too many people ask about compressors here. First they are just flat out lying about that 18+ CFM rating which is just unrealistic for that single stage pump/motor combo and recently some places have started rating it at a more believable 15+ CFM.
Same IR compressor that TSC sells but a full time compressor outfit rates it more realistically
Second they have a terrible reliability record and are notorious for burning out motors, we had a thread here not long ago with four owners of the darn things complaining about burned out motor problems in just that one thread! The IR at TSC is not an industrial USA built Ingersol Rand that the IR name is built on it is a Chinese import and unfortunately has earned a not so good track record. Also your example of hot air from a 20 gallon tank vs an 80 gallon may be valid but not so much for the 60 vs 80 with the differences being slight and even the little tank may not be as bad as it might seem. Because of space limitations we built quite a few high CFM small tank combinations for service trucks, some as much as 40 CFM with a 25-30 gallon "bumper" tank to save space (the rear bumper served double duty as a very heavy walled tank) plus various other combos of small tanks with high CFM and they did get hot but only under very high demand.
Honestly the heat difference between a 60 vs 80 gallon is going to be negligible for the same reason over-all air (in CFM) remains the same, the same amount of air enters the tank carrying the same amount of latent energy (heat) with only a small difference in cooling due to slightly more surface area of the tank, the amount of air flow through the tank is the same regardless. You are correct in your thinking and the extra cooling effect is real but just like the other advantages, energy savings and pump/motor life, the advantages are slight and not worth passing up better performance in the form of CFM and/or better quality. I have in the past harped a great deal on tank size because it is such a mis-understood factor when selecting a compressor. I in no way mean to say that a bigger tank is not better and usually it is but not always and not for the reasons most seem to think. It is useful in that it saves both on power consumption and pump motor/life due to fewer high torque start cycles, this can be substantial over the life of the compressor but negligible in the short term. Making a blanket statement that the 60 vs 80 gallon makes little or no difference is because 90% or better of the compressors being discussed here are in the 10 to 15 CFM range and in that class of compressor 60 vs 80 gallons simply will make little or no noticeable difference.
The point is that many times, far too many times, someone will pass up higher performance just to get a bigger tank and that clearly is a mistake! The compressors being considered in this thread are very good examples of the 60 vs 80 gallon dilemma that comes up so often and in this case the difference between a 60 gallon vs an 80 gallon really is very slight. As CFM increases the size of the tank becomes a more important consideration but up to about 16 to 18 CFM or so 60 vs 80 gallons really is going to be a toss-up. CFM rating, Duty cycle, pump type and construction quality plus the motor AMP rating (true rating) and service factor are all more important considerations when selecting between a compressor with a 60 gallon tank vs an 80 gallon when choosing a compressor of the size being discussed here.
EDIT: Danged if I didn't do it again!! He clearly said the TWO stage IR and I took it as the single stage! I think maybe there must be something wrong with my coffee!
|06-07-2011 07:01 AM|
Consider your compressor as a lifetime choice so get the best one you can and only do it once. My experience over many yeas that your demands on your compressor grows in time as you learn more and more about what it can and will do for you. Your collection of air tools will grow as well and you don't want to limit your future purchases due to limitations of your compressor.
|06-07-2011 02:43 AM|
Occasionally TSC puts the true 5HP, 80 gallon 2 stage IR on sale for $999. It is a good deal if you have a local TSC and don't mind waiting. The quincy is an excellent compressor and the IR isn't too far behind IMO.
I do not agree with the blanket statement that tank size does not matter under the specific condition of painting. My 80 gallon IR kicks on once per coat when painting, but runs nearly continuously blasting or running the DA, as to be expected. The air line gets hot to the touch and overloads my water traps allowing moisture to seep through the lines after about 15 minutes continuous use. If I had a 20 gallon tank while painting, I would see the same issue as I do now with the DA. I use a desiccant filter while painting as extra assurance. The warmer the air, the more water vapor could be present. Humidity here is usually pretty high...and when my air heats up, I get wet air. The more the compressor runs, the hotter the air. If you run a refrigerent drier or desiccant filters, this point is moot anyway as your water problems are completely solved.
Always buy the most CFM you can afford, without a doubt, but a 20cfm compressor on a 10 gallon tank is about worthless IMO. The bigger tank won't help a CFM hungry tool one bit, but it will help keep the air cooler on your less demanding tools. Like said earlier in this thread, 60-80 gallon is hardly noticable, but I gave an extra 100 for the 20 more gallons...it may not help that much, but it sure won't hurt a thing. On the 2 stage compressors, pumping up to approx 175 psi, it is also worth noting that the "amount of air" in those tanks is double a single stage at 90 psi, if you are regulating to 90psi. There is a lot more air storage here for your less demanding tools.
Keep in mind, before I get 100 posts saying I am dead wrong, is that I am not specifically talking about anything in this thread. A 60 gallon to 80 gallon tank difference is barely worth discussing. If this was a 10 gallon to 80 gallon, what I mentioned will come into play. It is more theoretical than anything else as most compressors have a comparable tank size to cfm. I have seen a few high cfm compressors with a small tank, but they are a bit rare and have a specific application.
|06-06-2011 05:34 PM|
|JohnnyK81||No doubt it's a better machine. If you can afford it, go for it. Peace of mind is nice. I had to make some decisions (price) and figured, meh, I can deal with it since it's just a hobby of mine.|
|06-06-2011 05:03 PM|
The only balsting I do is using a presurized sandbaster I bought from Northern years ago. I really don't do much though, just balsting pitted spots and cleaning up engine bays as I said. So sandblasting isn't really an issue for me. But I do a lot of air file and DA sanding and I paint cars using a Sata conventional gun. So I am comfortable with the cfm ratings of any of the compressors I listed. I'm more weighing the cost of stepping up to the Quincy as opposed to all the other ones I've listed.
I went to my local Northern tool and looked over the Quincy and then dropped by Harbor Freight and looked at the US General. They are very different machines considering the cfm's are similar. The Quincy has a V pump that has 2 pistons for each stage for a total of 4 pistons, and the exchange tube between the stages was very long and finned. The US General had one piston per stage and they were side by side in a vertical layout. I was surprised to see the exchange tube wasn't finned. But thwere was a finned casting going part wat towards the tank from the second stage.
I pretty much decided between the two I'd spend the extra cash and go with the Quincy. I'd still like to see the Belaire and Chicago Pnuematic up close.
|06-06-2011 04:45 PM|
I don't know what the heck I was thinking, he never said a darn thing that related to that single stage HF (Belaire) compressor and yet that is what I was thinking he was talking about. Damn this getting old is a real drag! (Until you consider the alternative! )
|06-06-2011 03:04 PM|
Yes yes, Oldred has gone and confused everybody again.
The 2 stage HF 60 gallon is the one I own.. Seems pretty good.. Certainly not a 600 rpm quincy, but not a Home Depot special either.
The 80 gallon as oldred said would have been damn awesome.. Too awesome, as he said.
Define what you mean by sandblasting. Little cabinet? Mine's fine for that? Siphon blaster outside? Mines fine for small parts..
Doing a whole car.. Probably not a wise idea.. Probably end up with a pile of molten aluminum on the floor. I'd feel a lot better if I could find some synth compressor oil around here though!!
|06-06-2011 12:46 PM|
Yea, I don't know how I'm going to weigh the differences. If it was just a $200 difference it'd be easy. But $600 doesn't just grow on trees.
I may have to decide if I want to pay the extra cost for the Quincy as a present to my son 20 years from now.
|06-06-2011 12:20 PM|
You are right I got confused there, I was mistakenly equating the Quincy to the single stage compressor but the price should have been a dead giveaway that I had the wrong compressor, Don't know what I was thinking! Sorry about the confusion I was way off the mark that time!
The two stage HF compressor and the Quincy certainly are more closely comparable and the main differences would be in overall quality and service life plus duty cycle.
The compressor that HF has discontinued is the 7 1/2 HP model which was a real brute and a heck of a deal, must have been too good of a deal!
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