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Quotes - Engineering - SalesFour decisions, in the order they should be made
Sizing fixes how much air the dryer must handle. Selection decides what kind of dryer handles it: one that runs flat out or one that rests at part load, one that reaches 38°F or one that has to go far lower, and one that rejects its heat to the room or to the cooling tower.
The first question is not which dryer but whether a refrigerated dryer is the right machine at all. Every unit on this site delivers a pressure dew point of 38°F, ISO 8573-1 class 4, and a few of the special-duty series deliver class 5 or 6. That is dry enough for the great majority of plant air: tools, cylinders, valves, blasting, machining, packaging and paint in a heated building. It is not dry enough for lines that run outdoors below freezing, for instrument air specified at minus 40°F, or for processes that call out class 1, 2 or 3 water. Those need a desiccant dryer, and the second topic below says so plainly.
Once refrigerated is confirmed, the remaining choices are about running cost and the building rather than about the air. A cycling dryer costs more to buy and less to run when the plant spends hours at part load; a non-cycling dryer is the simpler and cheaper machine for a compressor that stays loaded. Air cooling suits a ventilated room; water cooling suits a hot one or a central plant. The four topic pages take each decision in turn with the numbers behind it.
- Dew point: 38°F class 4 from any refrigerated dryer; minus 40°F class 2 or minus 100°F class 1 only from desiccant
- Duty cycle: non-cycling for compressors loaded most of the shift; thermal-mass, digital-scroll or variable-speed cycling for swinging or two-shift loads
- Air quality beyond water: particles and oil are set by the filters around the dryer, not by the dryer itself
- Cooling medium: air-cooled up to a 120°F room; water-cooled builds of the FLXA, AES, VDR, HES and FLX Series beyond it
Answer these before comparing any models.
- Coldest pipe and strictest process both satisfied by 38°F class 4
- Hours at part load counted across nights and weekends
- Summer room temperature and whether tower water is available
The selection topics
One page for each of the four decisions
Cycling vs Non-Cycling: A non-cycling dryer draws the same power at 20 percent load as at 100; a cycling dryer stores cold and stops its compressor. Annual kWh worked for four duty profiles on a 500 SCFM dryer, and how the payback depends on hours at part load.
Refrigerated vs Desiccant: Where 38°F is enough and where it is not, what a desiccant dryer costs in purge air and consumables, and the hybrid arrangement that puts a refrigerated dryer ahead of a small desiccant unit for the one line that needs it.
Dew Point & ISO 8573-1 Classes: The ISO 8573-1:2010 table for water, particles and oil, the difference between pressure dew point and atmospheric dew point, and how to write a purity class that the dryer and filters will actually meet.
Air-Cooled vs Water-Cooled: Heat rejected into the compressor room against heat sent to the tower, the 85°F water rating, condenser water quality, and which series are offered in both builds.
Match the dryer to the load profile, not the compressor
Two plants with the same 50 hp compressor can need different dryers. A machine shop that loads the compressor 80 percent of a single shift and switches it off at night is a non-cycling duty: the dryer runs eight hours, mostly near full load, and the cheapest machine to buy is also close to the cheapest to run. A packaging plant that leaves the compressor up around the clock but draws heavily only on day shift is a cycling duty: the dryer spends sixteen hours a day at a fraction of its load, and a thermal-mass or digital-scroll unit repays its premium in power. The cycling page works the kilowatt-hours for both.
Take the dew point from the process
Ask what the driest point of use actually needs. A paint line wants no liquid water and no oil; a CNC spindle wants class 4 water and class 2 oil; a laboratory or a control cabinet outdoors may need class 2 water. The ISO classes page turns those needs into a purity class, and the class tells you whether the dryer is refrigerated or desiccant and which filter grades go around it.
Then decide where the heat goes
A 1,000 SCFM air-cooled dryer adds its refrigeration load and its motor power to the compressor room, on top of what the compressor already rejects. In a room with an exhaust fan that is manageable; in a room that already sits at 110°F it costs the dryer 12 percent of its capacity and the compressor some of its own. Water-cooled builds move that heat to the tower and hold their rating regardless of the room. The cooling page lists which series come both ways and what the condenser water has to be.
What we ask before we quote
Compressor horsepower or delivered SCFM, line pressure, the compressor room's summer temperature, whether the compressor has an aftercooler, the hours the plant runs and how the load varies across them, the driest point of use, and whether tower or city water is available. With those eight answers we return a corrected duty, a model in each series that fits it, and the running cost difference between them. Call 1-805-484-2992 between 8am and 5pm or use the quote form.
Four decisions behind the right dryer type
There is no single threshold, but the load profile tells you. A compressor loaded around 80 percent of a single shift and switched off at night keeps a non-cycling dryer busy for most of its powered hours, so the cheaper machine wins. A plant that keeps air up around the clock and draws heavily only on days leaves the dryer lightly loaded for about sixteen hours, and that is where stored cold earns back the premium.
Rarely a different dryer; usually different attention to filtration. Both are served by class 4 water from a refrigerated unit at 38°F, and what separates them is oil and liquid carryover. A paint line will not tolerate either, so the coalescing afterfilter and its drain matter more than the dryer frame. A CNC spindle wants class 2 oil, which the same 0.01 micron afterfilter delivers; write the purity class for the stricter point of use and fit the filters to it.
With tower water on hand, water-cooled. At 110°F an air-cooled unit has already lost 12 percent of its capacity, and its own condenser heat pushes the room higher, which also hurts the compressor's cooler. A water-cooled build holds its rating whatever the room does. Without a tower, air cooling stays workable up to a 120°F room, but spend money on an exhaust fan and a low louver before paying for the next frame size.
Lines that run outdoors or through unheated space when it falls below freezing, instrument air specified at minus 40°F, and any process written to class 1, 2 or 3 water. A refrigerated dryer holds 38°F at line pressure, so air in pipe colder than that condenses and then ices. Those few lines do not decide the rest of the plant, which can stay on refrigerated air while the branch that needs more gets its own desiccant unit.
Not all of them. Standard refrigerated units hold 38°F, class 4, but a few of the special-duty lines are rated class 5 or 6, a pressure dew point several degrees higher. That suits shop tools and service bays, where nothing downstream runs cold. Where a process document calls for class 4, check the special-duty unit's rated class before ordering, or fit an aftercooler and use a standard dryer that meets it.
Because the dew point decides which machine is possible, while the duty cycle only decides which version of it costs least. A plant that weighs cycling against non-cycling first and later finds a line specified at minus 40°F has compared two dryers that cannot serve that line at all. Fix the purity class, confirm 38°F covers it, and only then set the running hours against the purchase price.
