Screw compressor good for a small garage shop?

EwKearns, that funny most all two behind compressors use screw drive in all kinds of weather. They just don't breakdown when there maintained. I've worked on them at a rental company . They are the best ones for quick pressure and cfms . So I think he would have no problems . One time in twenty years we had a customer bring his own in with a problem , no oil and wiped out the bearings in the pump.
 
Can u use a vfd to start a compressor? Didnt know that

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Can u use a vfd to start a compressor? Didnt know that
Yes, but most VFD manufactures do not make a single phase 5 Hp VFD, you need to buy a 10Hp and derate it to run on single phase. So you are looking at an expensive proposition, and then you also have the refrigeration drier load on a scroll. A few people have posted using the Chinese HY VFD 7.5 or 10Hp to run a 3 phase 5Hp compressor, but not sure of the long term reliability of those VFDs.
 
I would go for the screw compressor if it is within your means. As for running with a VFD, most screw compressors start at no load and the load comes on shortly after startup. Additionally, screw compressors don't start and stop, instead they load and unload, some even modulate to meet the demand for air. Many of them have timers set up so that once the compressor has been running unloaded for a certain period of time, it will then shut down.

I used to manage and maintain a bank of four Sullair 20 HP rotary screw compressors that provided all of the air for an entire manufacturing facility. The plant would run most of the time on just two, sometimes required three to meet demand, but we always had a fourth to stand in if we had to take one off line for maintenance. Cut in pressures were staggered so that one compressor would be the 'lead' followed by lag 1, lag 2, and lag 3. Every so often I would change them around so that they would all gain hours evenly, or at least as close as possible. Long story short, it was a fantastic setup. We also ducted the exhaust from the units so that during the summer outdoor air would be drawn in to the compressor room for cooling and the hot air would be exhausted outside. During the winter we used indoor air for cooling and the hot air was ducted out into the warehouse.
 
EwKearns, that funny most all two behind compressors use screw drive in all kinds of weather. They just don't breakdown when there maintained. I've worked on them at a rental company . They are the best ones for quick pressure and cfms . So I think he would have no problems . One time in twenty years we had a customer bring his own in with a problem , no oil and wiped out the bearings in the pump.

I don't have a lot of experience with them, but I know we had 4 Kaeser 50 hp compressors and they were very sensitive to the cold. If the oil got too cold, it would throw an error code and that would be the end of that, until we took steps to heat the cabinet. We finally put thermostatic heaters inside the cabinet. When they work, they are great. The old Ingersol-Rand 11" X 11" I cut my teeth on, never gave this sort of problem....

Personally, I don't see a lot of benefit in one in a home shop, but if you have the money, they are quiet. But how much CFM does the average HSM really need? I don't think they make anything much smaller than 25hp.... I know the new ones don't have a huge inrush current, but how much free amperage is available in the average home shop 3-ph panel?
 
Get the screw compressor. Like you said, its something to grow into, and media blast cabinets consume ridiculous amounts of air. Its a real pain blasting something for 30 seconds, and then waiting 3 minutes for the compressor to catch up.....

Cheers Phil
 
Hey All,

Pretty new here and have a question right off the bat. I'm setting up a small shop in my garage and was about to pull the trigger on quincy 5HP 2 stage piston compressor. Then a great deal showed up on craigslist of a quincy 5HP screw compressor with a built in refrigerated dryer still on the pallet asking about 75% the cost of a new one. I'm going to be using the air for a small blast cabinet mainly and few air tools at first, but within a few years I'd like to get a CNC mill as the finances allow.

It would be about $1500 more for the setup, but it would include the dryer (right now I'm about to spend $2k for the new piston setup). Would that be a good choice? Right now I'm looking at it as buying a compressor I could eventually grow out of vs buying a compressor that I would eventually grow into.

What are your thoughts and opinions on the matter.
Screw compressors generally are set up to run continuously, just loading up and unloading as required, however you can set up a control that will shut it down if its going to idling for long periods of time. Screw compressors also have very specific requirements for oil quality, use the right oil and you shouldn't have any problems. treated right it should last you a lifetime.
 
If you call the compressor shops, they will probably tell you no. They generally, as already pointed out, are continuous run, cycling an intake valve to unload them. The need for a constant circulation of oil, and the subsequent separation and recovery gets a little impractical on a frequently started and stopped machine. They are seen where there is a constant, non fluctuating demand, like a blowmolding plant, or a plant that manufactures plastic bags, which start off as small tubes that are blown larger as they exit the extruder. I have seen them in shops where there are enough machines and operators to keep them running loaded enough of the time. There is a start/stop ratio and time formula for this, but it escapes me at the moment. For a small home shop, it would not be my first choice at all.
 
If you call the compressor shops, they will probably tell you no. They generally, as already pointed out, are continuous run, cycling an intake valve to unload them. The need for a constant circulation of oil, and the subsequent separation and recovery gets a little impractical on a frequently started and stopped machine. They are seen where there is a constant, non fluctuating demand, like a blowmolding plant, or a plant that manufactures plastic bags, which start off as small tubes that are blown larger as they exit the extruder. I have seen them in shops where there are enough machines and operators to keep them running loaded enough of the time. There is a start/stop ratio and time formula for this, but it escapes me at the moment. For a small home shop, it would not be my first choice at all.

Some years ago I worked in a shop where the demand for air varied quite a bit, some times the screw compressor ran unloaded for maybe 20 minute and others it was flat out for maybe an hour or more. The plant electrician made up a smart switch so that if it was unloaded for more than say five minutes and the reserve pressure was still quite high it would shut down, but if the pressure was below a set point it would keep running. This worked quite well.
 
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