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Quotes - Engineering - SalesNon-Cycling Refrigerated Air Dryers, 65 to 250 SCFM
Plant-air dryers for 15 to 50 hp rotary screw compressors
This is the band for the compressor most industrial buildings actually own: a 15 to 50 hp rotary screw delivering 65 to 230 SCFM through its own aftercooler, loaded for most of the shift, feeding a header that serves the whole plant. The dryer is selected from the models below on delivered flow at 100 psig and 100°F, then corrected for the compressor room and for the discharge temperature the aftercooler really achieves.
Non-cycling control suits this duty because the compressor rarely idles. The refrigeration circuit runs continuously, a hot-gas bypass valve keeps the evaporator from icing at partial load, and the pressure dew point sits near 38°F from the first shift to the last. There is no thermal mass to warm through and no controller deciding when to restart the refrigeration compressor.
The current direct-expansion line covers the band in eight steps from 65 to 250 SCFM: 115 V single phase through 150 SCFM, 230 V single phase at 185 and 230 SCFM, and 460 V three phase at 250 SCFM. The previous plant-air generation, 75 to 250 SCFM, is listed beneath it for replacement matching.
- Rated 65 to 250 SCFM at 100 psig, 100°F inlet and 100°F ambient
- 3/4 in to 1-1/2 in FNPT connections, 0.9 to 3.1 kW absorbed
- 131°F maximum inlet and 203 psig working pressure on the current line
- Digital dew point display and a zero-air-loss drain on every current model
Every 65 to 250 SCFM non-cycling model
Flows at the standard rating point of 100 psig, 100°F inlet and 100°F ambient. Each part number opens its own specification page; the current line is listed first and the previous generation follows it with the series that replaces it.
| PART NUMBER | SERIES | SCFM | CONNECTION | VOLTAGE | STATUS |
| DXR 0065 NA | DXR Series | 65 | 3/4 in FNPT | 115/1/60 | Current |
| DXR 0085 NA | DXR Series | 85 | 1 in FNPT | 115/1/60 | Current |
| DXR 0105 NA | DXR Series | 105 | 1 in FNPT | 115/1/60 | Current |
| DXR 0125 NA | DXR Series | 125 | 1 in FNPT | 115/1/60 | Current |
| DXR 0150 NA | DXR Series | 150 | 1 in FNPT | 115/1/60 | Current |
| DXR 0185 NA | DXR Series | 185 | 1-1/2 in FNPT | 230/1/60 | Current |
| DXR 0230 NA | DXR Series | 230 | 1-1/2 in FNPT | 230/1/60 | Current |
| DXR 0250 NA | DXR Series | 250 | 1-1/2 in FNPT | 460/3/60 | Current |
| HPRN75 | HPRN Series | 75 | 1 in NPT | 115/1/60 | Legacy |
| HPRN100 | HPRN Series | 100 | 1 in NPT | 115/1/60 | Legacy |
| HPRN125 | HPRN Series | 125 | 1 in NPT | 115/1/60 | Legacy |
| HPRN150-1 | HPRN Series | 150 | 1 in NPT | 115/1/60 | Legacy |
| HPRN200-4 | HPRN Series | 200 | 1 in NPT | 460/3/60 | Legacy |
| HPRN250-4 | HPRN Series | 250 | 2 in NPT | 460/3/60 | Legacy |
Series with models in this band
Matching the compressor
A rotary screw in this class delivers 4.3 to 4.6 SCFM per horsepower at 100 to 125 psig: a 15 hp machine makes 65 to 70 SCFM, a 25 hp 105 to 115, a 40 hp 170 to 185 and a 50 hp 215 to 230. Select the dryer at or above the delivered figure rather than the horsepower rule, because two 30 hp packages from different builders can differ by 15 SCFM. Then apply the derates: a 110°F inlet costs 20 percent of capacity and a 110°F room another 12, so a 25 hp screw in a hot mezzanine room is a 150 SCFM dryer, not a 125.
Aftercooler performance sets the inlet
Package aftercoolers on screw compressors discharge air 15 to 20°F above the room, so the dryer inlet is normally 105 to 115°F in summer. That is inside the 131°F allowance of the current line, but every degree above 100°F is capacity given away. A blocked aftercooler core, a compressor boxed into a corner with no exhaust path, or a fan throttled back for noise can push the inlet past 120°F, where the dryer is down to two thirds of nameplate. Clean the core and measure the discharge temperature before blaming the dryer.
What is in the cabinet
Each current model carries a single aluminum exchanger block that precools the inlet air against the cold outlet, chills it against the refrigerant and separates the condensate in an integral separator, with a zero-air-loss drain and a digital dew point display on the panel. The 65 to 150 SCFM sizes run from a 115 V cord; 185 and 230 SCFM need a 230 V single-phase circuit and the 250 SCFM unit is 460 V three phase. The previous generation used stainless plate exchangers with a timed drain and the same 1 in and 2 in pipe sizes, which keeps a swap straightforward.
Piping and filtration at this size
Put the dryer after the receiver so it sees averaged flow rather than the compressor's load pulses, and size the prefilter and afterfilter for the compressor's full delivery, not the dryer's nameplate. A 1 micron coalescing prefilter protects the exchanger from compressor oil; a 0.01 micron afterfilter catches the aerosol that passes through. A three-valve bypass around dryer and filters lets the plant run wet for an hour while an element is changed. The piping and bypass page shows the layout, and the cycling dryers of the same size are the alternative when the plant idles nights and weekends.
Matching a dryer to a 15 to 50 hp screw
Measure the compressor discharge temperature and the room. A package aftercooler in good condition runs 15 to 20°F above room temperature, so a summer day should put 105 to 115°F at the dryer. If the gap is much wider, the core is fouled or the fan is starved, and the dryer is being handed more water than it was sized for. Clean the core first; only if the gap is normal and water persists is the dryer too small.
On the pipe at the dryer inlet, with a contact thermometer, late on a hot afternoon with the compressor loaded. The reading at the compressor panel is upstream of the receiver and piping, and a spring reading flatters the design. Size on the worst figure, because every degree above 100°F gives away capacity, and a number taken on a mild morning is how a correctly sized dryer on paper ends up passing water in August.
For the daily trend, yes: the digital display on every current model gives the shift a number to log and makes a drift obvious. It reads the dryer's own sensor at the dryer, though, while a portable monitor checks what the plant actually receives at a drop downstream and confirms the panel is telling the truth. Take a portable reading once a season, ideally on the hottest week, and compare it with the panel.
The 185 and 230 SCFM sizes need a 230 V single-phase circuit, and in a plant fed at 460 V that usually means a small step-down transformer or a lighting panel that already carries the right voltage. Price that wiring alongside the dryer. Where it adds up, the 250 SCFM unit wired for 460 V three phase may be the simpler choice, provided the compressor's delivery fits it with margin for a warm room.
