Right Size for an Air Compressor

[beandip]

I have been using two different compressors during my restore/redo of my Z. My Son in law has a portable, Sears compressor that is rated at 9+ CFM at 90 psi , I believe, Could be bigger than that. I think he paid about $200.00 on sale. My own unit is the kind used by contractor's for nailers, the type with two small tanks . What I am getting at is. What are your intentions in the use of the compressor and your air tools. I am not a professional mechanic or body man. The larger unit I used , I found ample to run die grinders and a DA sander and what ever I wanted. Occasionally I did need to stop and let the unit recover with the more '' air hungry'' tools. It was just fine for painting my Z as well. If I were going to be doing this type of work on a daily basis I would definitely buy a commercial compressor. My little unit will run a impact gun, flat ratchet, and die grinder fine for occasional use now that my Z is done. As if they are ever done. When I was in construction I always bought the best tools I could . And was never sorry. Now I have no need for such quality , because they are not used on a daily basis. What DeesZ has posted is right on the money on choosing the right unit. You just need to decide what your intentions are and how much you will be needing the full capacity in the future. I am not planning on a future project car, Gary:rambo:

[Go240Zags]

Anyone have any experience with this Harbor Freight compressor - would this be adequate for most jobs. My mind is starting to swim over all the numbers. It's not rated as high as the one Beandip describes, but would this work for most applications? http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94667

[Walter Moore]

I bought a similar compressor at Big Lots a few years back. Mine appears to be the same motor and pump, but with a smaller, horizontal tank. The specifications for mine are very similar to that unit as well.

I paid around $99, on clearance. (Clearance... at Big Lots... )

Within a year the pressure switch broke. The cheap plastic body just came completely apart. When that happened the motor would never shut off. It ran non-stop. (There is a small emergency pressure relief valve to keep the tank from exploding.)

But the copper tubing that connects the pump to the unloader valve on the tank split at the same time that the pressure switch broke. ( I suspect that one failure caused the other, but do not know which one happened first.) I have heard that the pipe is copper to act as a pneumatic fuse of sorts, but am not sure if that is true.

Anyway, to repair it I had to buy a new pressure switch, and some 3/8 black pipe. (I don't have access to the copper tubing.) The pressure switch was around $50 (Granger's) and the black pipe was more than $20. (For some reason 3/8 pipe is hard to find.

By the time I got it running again I had put an additional $70 into my $99 compressor. All that and I still don't have the volume to do much more than inflate tires, and run my "air vac" while bleeding brakes.

I guess what I am saying is that going cheap rarely pays in the end.

[CoastGuardZ]

Anyone have any experience with this Harbor Freight compressor - would this be adequate for most jobs. My mind is starting to swim over all the numbers. It's not rated as high as the one Beandip describes, but would this work for most applications? http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94667

That's not much more output than what I have now, which is nowhere near adequate. It's my opinion that the minimum to look at is 9+ SCFM @ 90psi, and looks like this number is more efficiently met with a 220v (208v-240v) motor. You should figure out what the most air hogging tool you have or plan to use is and go 1.5 times more than that. For example, my angle die grinder requires around 6 SCFM, so 9 SCFM is a good place to start. A very important thing to look at is Duty Cycle... the closer to 100% the better.

Here is a Harbor Freight one that I am considering...

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92504

Nate

[kurtwwalters]

One thing I had to consider was if buying a 220V compressor, I would have had to get an electrician out to the house to wire it. I don't know about you guys, but I don't have 220 in my garage... though next time I have one come out to fix some other problems I'll have him wire my old oven so I can do powdercoating...

[CoastGuardZ]

It's not hard... you can do it. Many people are afraid of it for some reason, but it is quite easy and safe if just take your time and pay attention to what you are doing. Lowe's will even show you how...

http://www.lowes.com/lowes/lkn?action=howTo&p=Improve/220outlet.html

[ncz]

Hey guys, back up after a time off. I hear you on the compressor quandry, been there. Started with the Craftsman 5hp 30gal tank(6scfm I think). Won't run a cutoff tool or strait line or da sander. Also won't run the air sabre saw nor a small abrasive blaster without blowing up. Also if you want to paint with an HVLP gun, you need higher CFM at low pressure. Go to Home Depot, they will have a two stage compressor that is about 3-5hp with a 60 gal tank, that will get you up to about 12 scfm/10.5 scfm at 40/90. You can get this model for $799 in my area. They have a bigger one on display(80 gal, 7hp) but it is $1699. The smaller one will work for most of us hacks. Also dittos on the noise. The old Craftsman would bring everyone out to the garage to yell at me about the noise, funny to see my daughter holding her ears and telling me to be quiet she can't hear Sponge BobLOL . Thats the best deal I found for the money. PS, if you can, get the best air dryer you can afford, will save your tools and help greatly if you want to paint. Ok, someone help get my welding back on track!!!

[geezer]

I just checked mine out to see what's up. Either this is one of those products that has come down in price over the years, or maybe I paid too much. Mine is an Ingersoll-Rand 5HP 230V single phase, double reciprocating pump with a centrifugal unloader. 80 gal. tank. It has a baseline rating of 23.1 CFM @ 100 psi. Weight 630 lbs. The total price with sales tax came to $1551.35 CDN. That didn't include the starter switch that I bought separately, but they tossed in an airfile. Looking back I would say it was worth the money. It is now 23 years old, is used quite frequently and has never had new rings or bearings. The only thing I've done is change the oil & filters yearly and clean the valves and change the belts, every few years. The thing I find interesting about this topic is the seemingly out of whack CFM ratings.

[Go240Zags]

One thing I had to consider was if buying a 220V compressor, I would have had to get an electrician out to the house to wire it. I don't know about you guys, but I don't have 220 in my garage... though next time I have one come out to fix some other problems I'll have him wire my old oven so I can do powdercoating...

It's not hard... you can do it. Many people are afraid of it for some reason, but it is quite easy and safe if just take your time and pay attention to what you are doing. Lowe's will even show you how...

http://www.lowes.com/lowes/lkn?action=howTo&p=Improve/220outlet.html

The 220 thing has always been a sticking point for me. My old electrical box doesn't have any room for any new breakers. When I needed a new 220V for my submersible well pump the electrician had to get two of these special breakers where twin switched breakers fit in a slot where only one would go normally. Then one from each of these new double breakers (the two switches adjacent to each other, in the middle) was used for the 220V and the two remaining switches (on the outside) were left at 110. I don't know if my description makes sense, but it worked. I'd have to go the same route for my garage, but might be able to get away with tapping into the well pump line, as it runs right by the garage. But I'll leave these things to the electrician. I get nervous installing a new light fixture.

[CoastGuardZ]

I can see how no room in the breaker box might pose a small issue...

Well, I went to HF today and checked out their compressors and I think I found the one I'm going to get, it's only $400...

http://www.harborfreightusa.com/usa/itemdisplay/displayItem.do?itemid=3848&CategoryName=AIR%20COMPRESSORS&SubCategoryName=AIR%20COMPRESSORS

I also found that HF has two websites, their catalog site www.harborfreight.com and their retail store site www.harborfreightusa.com

I did a little research on this compressor (U.S. General US660V) and found that the compressor motor itself is the same one used (made) by the company producing Bel-Aire compressors. Not really sure if that's a good or bad thing but I found it out none-the-less.

Do any of the air compressor guru's see any issues with this model? Will I run into any issues with it being a 135psi model?

[DeesZ]

Geezer.... Others may not agree or see the issue the same way, but I think you made a good buy on that compressor. It was a chunk of change back then, but look at what you got.... how many years of excellent service you have gotten?.... over twenty so far.... and it's likely going to work well for the next generation of your family. Ingersoll-Rand made a fine compressor back then, and there wasn't much competition from the Japanese and especially Chinese import goods. You "bought well, and bought once", and there is a true economy to that approach. Had you started small or medium and worked up the ladder to what you now have, you would have paid perhaps twice that amount in total (considering you would have taken a beating on 2 or 3 other compressors by the time you got your last one). And 23.1 CFM @ 100 psi is nothing to sneeze at, even today. Most compressors are delivering a fraction of that. Your needs have been well met, and you have a considerable volume of excess capacity. The out of whack CFM ratings you reference do seem that way and I think it is because there are so many units being offered at discount prices - with the "I wish I knew that when I bought this" sacrifice of SCFMs. As I posted earlier, my advice to someone looking to buy, is to look at the SCFM need you will have, multiply it by 1.5 or 2, and buy accordingly.

For those of you considering a purchase, don't be fooled by a big tank. They are an important part of the "delivery" equation, but there is a lot more to it than just the tank. And "delivery" is exactly what you are looking for. You want a machine that will "deliver" enough air to truly satisfy your needs, so focus on the SCFM, and make a purchase that solves your needs. And if you are thinking about growing into a larger one, you will likely spend less in the long run by meeting your needs with your first (or next) purchase. I truly realize what happens when you go to buy one. Been there. Once you figure what you really need now and in the future, and get by the analysis paralysis (I had a bad case of that) the sticker shock sets in. For many of us the range faces $1000.+, and that's way too much to justify. The wife and kid will need clothes too, and It's nice to feed then every now and again. I found myself compromising to make my needs fit my budget. I resolved that I would buy on the lower end so I could at least get one. Then I ran in to one being sold by a friend - nice big unit in good shape! Bigger than what I needed, and half the price of a new one... in other words "excess capacity for the price that I could afford". Well, I guess I was too excited, or something. The guy decided to hook it back up and keep it. So, knowing that I can get what I need affordably If I look around and wait for a good used one, that's what I did. Glad I did, too, because I got one that should last a lifetime and satisfy all future needs for less than the first one I almost bought. There are thousands of good units out there not being used in somebody's garage that will exceed your needs for less than the cost for the new one that doesn't really do the job. Unless you must buy a "new" one for some reason, look around for a while and see what comes up. It tool me 6 months or so, but I ended up spending one-third of what I was going to spend, and I got twice the SCFM than I was going to "settle" for before. The wife and son were able to eat, and I was happy.... a rare combination around my place. They want crab legs - I want Castrol.....

A good compressor can easily become the heart of your garage. Purchase wisely, or purchase often. I have nothing against used - but very well cared for - equipment. I will never buy another new vehicle again, either for similar reasons. I guess it boils down to the issue of "value": Getting something that meets your needs & pleases you, at a reasonable cost.

[geezer]

A couple of points I would like to make. It is pretty hard for the average hobbiest to lay out the amount of coin it takes to buy a compressor which suits their wants. What ever you buy, there is a bigger, better one beckoning you. Practicality and price, becomes the issue and will usually determine what you buy. The only reason I bought the one I did was, I needed it. At the time my brother and I were operating a small shop specializing in custom body & paint. It was just a sideline for me, but was his livelihood. After he moved on to bigger and better things, we divvied up the equipment and the compressor stayed with me. Otherwise I would still only have the 2 HP Cambell Hausefield (25 yrs old and going strong).

If your plans are just restoring one car, it is hard to justify buying anything other then one like CoastGuardZ is considering.

John brings up a great point. Buying a good quality used one is the smart way to go. Especially if you know the history of it. If I had to buy another that’s the way I would go. I just want to make clear, I am no expert on this subject, and the choices out there today are just as mystifying to me.