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Quotes - Engineering - SalesThe refrigeration runs all the time, and that is the point
Constant-run refrigeration with hot-gas bypass control, from a 5 SCFM bench unit to a 4,200 SCFM central-plant dryer: the simplest refrigerated dryer and the right one for a compressor that stays loaded.
A non-cycling dryer keeps its refrigeration compressor running whenever the dryer is switched on. A hot-gas bypass valve feeds warm refrigerant back into the evaporator as the air load falls, so the exchanger never ices and the pressure dew point holds near 38°F whether the plant is at full draw or a single tool is running.
That constancy is what the design buys. There is no stored cold to run down, no controller deciding when to restart, and no dew point swing between cycles; a plant that runs its compressor loaded 60 percent of the time or more gets the same dry air as a cycling dryer for a lower price and with fewer parts. The penalty is power at part load: the refrigeration compressor draws close to its full-load current whether it is drying 100 percent of the rated flow or 20.
Four flow bands cover the section. The 5 to 50 SCFM band is the small-cabinet dryer on a 115 V cord behind a 2 to 10 hp compressor; 65 to 250 SCFM serves the 15 to 50 hp rotary screw; 300 to 1,250 SCFM covers 60 to 250 hp and the two-compressor room; and 1,600 to 4,200 SCFM is the flanged central-plant dryer for 300 hp and up. The current direct-expansion series spans all four bands in 27 sizes, the current small-cabinet series covers the first, and the large plant dryer adds 2,500 and 3,000 SCFM units with networked controls.
Send the compressor horsepower or delivered SCFM, the inlet temperature and the room temperature, and we return the band, the model and a price.
Cycling or non-cycling?
Request a QuoteFor a compressor that stays loaded, a dryer that never stops is the cheaper and steadier choice; idle hours are the only thing it wastes.
Load profile decides between constant-run and cycling
Four flow bands, 5 to 4,200 SCFM
Pick the band by the compressor's delivered flow, then the model by inlet and ambient temperature
Every non-cycling series, current and previous generation
HPR Series: Compact non-cycling dryer for 5 to 50 SCFM shop and point-of-use air; the earlier generation of the small cabinet line, still supported with part numbers and replacements.
5 to 50 SCFM · Non-Cycling · 250 psig max inlet · 120°F max inlet
HPRN Series: Non-cycling refrigerated dryer from 75 to 1,200 SCFM for plant air on a single compressor; previous generation, cross-referenced to current models.
75 to 1,200 SCFM · Non-Cycling · 232 psig max inlet · 120°F max inlet
HPRB Series: Current small non-cycling dryer, 7 to 50 SCFM, with low-GWP R513A refrigerant, a 3-in-1 heat exchanger and a built-in separator on the larger sizes.
7 to 50 SCFM · Non-Cycling · 200 psig max inlet · 120°F max inlet
HPRplus Series: Large non-cycling dryer for 2,500 and 3,000 SCFM central plants with digital controls and a low-pressure-drop exchanger.
2,500 to 3,000 SCFM · Non-Cycling · 232 psig max inlet · 120°F max inlet
DXR Series: Direct-expansion non-cycling dryer in 27 sizes from 10 to 4,200 SCFM; the widest single range on the site, with a full data sheet behind every model.
10 to 4,200 SCFM · Non-Cycling · 203 psig max inlet · 131°F max inlet
Selection notes
Three things to settle before choosing a non-cycling dryer
1.
How it works
Inlet air is precooled against the cold outlet air, chilled to about 35°F against the refrigerant, and passed through a separator that takes out the condensate before the air is reheated as it leaves.
The hot-gas bypass valve keeps the evaporator above freezing at any load, which is why the dryer needs no controller and why it draws about the same power at 20 percent load as at 100.
2.
When it is the right choice
A compressor loaded most of the hours the dryer is powered, a process that wants a dew point that does not move, and a budget that favors first cost over the electricity bill.
Three-shift plants, bottlers, continuous process lines and small shops where the dryer draws under half a kilowatt all fit; a single-shift plant with the dryer left on all week does not.
3.
What to check
Delivered SCFM from the compressor data sheet rather than horsepower, the inlet temperature the aftercooler actually achieves in summer, and the compressor room temperature at its worst.
Every 10°F above the 100°F rating point on either figure costs 10 to 20 percent of capacity; the correction factors are on the sizing pages.
Before you settle on constant-run refrigeration
Because that is how it regulates. The refrigeration compressor keeps running and the hot-gas bypass valve recycles warm refrigerant into the evaporator so the exchanger can not ice, which means the motor works about as hard at 20 percent flow as at full flow. A high current reading on a quiet night is not a fault. If the meter matters on a plant that idles for long stretches, the answer is a cycling dryer, not a valve adjustment.
Pressure drop across the dryer climbs, flow to the plant falls, and the dew point can rise as frozen passages force air past less cold surface. The usual causes are a hot-gas bypass valve that has drifted or failed, or a dryer running at very light load in a cold room. Have a refrigeration technician check suction pressure against the valve setting; switching the dryer off and on only thaws it until the next quiet shift.
It depends on the size. A small cabinet unit drawing under half a kilowatt costs so little to leave on that the cheaper non-cycling dryer is usually still the right one. From the 300 SCFM band up, a dryer powered all week behind a compressor loaded one shift spends most of its electricity on idle hours, and a cycling unit is worth pricing. Wiring the dryer to start with the compressor narrows the gap, at the cost of a damp first few minutes.
They are corrected separately and the factors multiply. A dryer standing in a room 10°F above the 100°F rating point, and fed air 10°F above it, loses capacity on both counts, so a unit picked at nameplate in spring can be a fifth to a third short by July. The symptom is water at the far drops on hot afternoons only. Apply both factors from the sizing pages, then pick the next size up.
It handles the water, not the whole job. A 38°F pressure dew point keeps liquid out of indoor spray lines, but compressor oil aerosol and vapor still reach the gun and show up as fisheyes in the finish. Put a 0.01 micron oil-removal filter behind the dryer and an activated carbon stage ahead of the booth regulator. Keep the dryer's own drain working, because a flooded separator sends water straight past the filters.
