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Quotes - Engineering - SalesWhat a paint booth asks of its dryer
Flow from the guns, quality from the filters, no hardware inside the booth
A spray gun draws 10 to 15 SCFM while the trigger is pulled, a dual-action sander about the same, a supplied-air hood 6 to 15 SCFM continuously, and a booth with two painters and their prep station reaches 60 to 80 SCFM at its peak. The dryer delivers dry air; the two filters behind it deliver clean air; and all of it lives outside the booth's classified area.
One gun, one painter
- 10 to 15 SCFM at the gun, 30 to 45 psig inlet
- Dryer size 20 to 25 SCFM
- Small body shops, cabinet finishing
Two guns plus sanders
- 30 to 40 SCFM peak
- Dryer size 42 to 50 SCFM
- Collision shops with a prep station
Two painters with supplied-air hoods
- 40 to 60 SCFM peak
- Dryer size 65 SCFM
- Hoods take their own breathing-air filter after the dryer
Production booth, four guns
- 80 to 100 SCFM peak
- Dryer size 105 to 125 SCFM
- Truck, trailer and industrial finishing lines
Booth duty to dryer size
Peak draw from the guns and hoods that can spray at once. Dryer sizes at plant-temperature inlet and 100 psig; the second column applies the 0.88 factor for a compressor room or paint mix room that reaches 110°F in summer.
| BOOTH DUTY | PEAK AIR DRAW | DRYER SIZE AT 100°F | DRYER SIZE, HOT ROOM (110°F) | DRYER BAND |
| One spray gun | 10 to 15 SCFM | 20 SCFM | 20 to 25 SCFM | 5 to 50 SCFM |
| Two guns plus two DA sanders | 30 to 40 SCFM | 42 to 50 SCFM | 50 SCFM | 5 to 50 SCFM |
| Two painters with supplied-air hoods | 40 to 60 SCFM | 65 SCFM | 65 to 75 SCFM | 65 to 250 SCFM |
| Booth plus prep station and blow-off | 60 to 80 SCFM | 85 to 90 SCFM | 100 to 105 SCFM | 20 to 250 SCFM cycling |
| Production booth, four guns | 80 to 100 SCFM | 105 to 110 SCFM | 125 SCFM | 65 to 250 SCFM |
| Booth fed from a 10 hp piston compressor, no aftercooler | 35 to 40 SCFM | Aftercooler plus 42 to 50 SCFM | Aftercooler plus 50 SCFM | 7.5 to 10 hp piston page |
Non-cycling dryers for booths that spray all day
Production finishing lines keep the guns busy most of the shift, and a 20 to 125 SCFM non-cycling dryer holds 38°F continuously on 115 V. The 25 to 50 SCFM cabinet units and the direct-expansion line from 10 SCFM up both fit on a wall bracket outside the booth.
- 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.
- 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.
Cycling dryers and filters for shops that spray in bursts
A collision shop sprays for twenty minutes and then sands for an hour, so a 30 to 130 SCFM cycling dryer rests between coats. Behind either dryer the filter set is the same: 1 micron prefilter, 0.01 micron oil-removal coalescer, activated carbon for oil vapor.
- TMC Series: Thermal-mass cycling dryer from 30 to 635 SCFM; stores cold in a thermal mass so the refrigeration compressor rests when air demand drops.
- NXC Series: Cycling dryer in 19 sizes from 20 to 2,000 SCFM with a dry thermal mass and up to 80 percent power savings at part load.
- HF Series Filters: Modular inline filter family in 22 housing sizes from 20 to 21,250 SCFM; one housing, seven push-on element grades from bulk-liquid separator to activated carbon.
Installing the dryer and filters for a booth
The dryer and filters go outside the booth in a clean area, the drops inside the booth are short, and the filter order is fixed: prefilter, dryer, coalescer, carbon.
A spray booth is an electrically classified area, and a dryer with a compressor, fan and controller does not belong inside it. Put the set in the compressor room or the mix-room corridor and run a dedicated line to the booth drops. The 1 micron prefilter ahead of the dryer removes bulk oil and rust; the 0.01 micron coalescer after it takes oil aerosol down to under 0.01 mg/m3; and the activated carbon element last removes the oil vapor a coalescer cannot see, the vapor that recondenses on cold panels and makes craters. Change the carbon element by hours, not by pressure drop, because it never blocks.
Give the set a bypass so the shop can spray primer during an element change, and drain every bowl to a container, not the floor of a finishing area. Where painters wear supplied-air hoods, their line takes a breathing-air filter package of its own after the dryer; the dryer removes the water, not the carbon monoxide.
Two painters with hoods are the 65 SCFM dryer at 100°F and the same 65 in a hot room only if the mix room stays under 105°F; past that it is the 75 or 85.
Size a dryer for my paint booth
Paint booth dryer questions
For a booth kept above 60°F, yes: air at 38°F pressure dew point cannot condense in a line that is warmer than 38°F, and the spray gun sees no liquid water. Booths in unheated buildings, or lines that run outdoors to the booth, are the cases for a desiccant dryer behind the refrigerated unit.
Fisheyes are usually oil or silicone, not water. A refrigerated dryer removes water only; the 0.01 micron coalescer removes oil aerosol and the activated carbon element removes oil vapor, and a carbon element more than 1,000 hours old lets vapor through. Fit both and check that the compressor's oil carryover has not risen.
It can share the dryer if the dryer is sized for the shop plus the booth and the booth drop carries its own coalescer and carbon filter. A separate dryer for the booth makes sense where the shop dryer is undersized or the header is long and picks up water on the way.
Outside the booth and its classified zone, on a wall in the compressor room or a service corridor, with the filters beside it and a dedicated line to the booth drops. Keep the run inside the booth short and sloped back toward the filters so nothing pools at the gun drop.
They add 6 to 15 SCFM per hood to the booth's continuous draw, and they need their own breathing-air filter and monitor downstream of the dryer. Add the hoods to the peak draw before picking the dryer size; two hoods on a two-gun booth move it from the 42 SCFM size to the 65.
