The Castair RD59-11K is a refrigerated compressed air dryer rated at 59 CFM at a 37°F pressure dew point. This is the dryer for shops running a 10–15 HP compressor — a busy automotive shop, a body shop with multiple spray guns, a small production floor, or any application where the compressor is producing 40–60 CFM and moisture in the air is a real problem. At 73 lbs with 3/4" NPT connections, it installs into existing air systems without requiring larger plumbing.
The RD59-11K uses R134a or R407c refrigerant — the same environmentally compliant refrigerant used across the Castair dryer line — to chill compressed air to a 37°F dew point. Water vapor condenses out and gets ejected by the automatic demand drain. The result is dry, consistent air at every tool, booth, and pneumatic device in your shop.
How It Works
- Refrigeration cycle: Compressed air enters the stainless steel heat exchanger where Freon refrigerant removes heat and condenses moisture. Air exits cold and dry.
- Dual-function single-body heat exchanger: Pre-cools hot incoming air with cold outgoing air, reducing refrigerant load and improving energy efficiency.
- Automatic demand drain: Cycles only when condensate is present, conserving compressed air. No timer-based drain losses.
- Dew point indicator: Simple visual confirmation — no computer logic, no programming required.
Key Features
- Rated capacity: 59 CFM at 37°F dew point (65 CFM at 50°F dew point)
- Connections: 3/4" NPT inlet and outlet — same size as the smaller RD25-6K, direct retrofit upgrade
- Power: 115V / 1-phase / 60Hz with 9-foot three-prong power cord
- Current draw: 6.5 amps
- Refrigerant: R134a / R407c
- Maximum inlet pressure: 232 PSIG
- Heat exchanger: Stainless steel for corrosion resistance and long service life
- Quick connect: Refrigerant recharge port for field service
- Certifications: UL listed
- Weight: 73 lbs
- Dimensions (W×D×H): 10.6" × 19.1" × 22.4"
What's in the Box
- Castair RD59-11K refrigerated air dryer unit
- 9-foot three-prong 115V power cord (pre-installed)
- Refrigerant pre-charged at the factory (R134a/R407c)
- 3/4" NPT inlet/outlet connections
Note: A properly sized pre-filter is required for warranty. A Castair 3/4" particulate filter (C-FS34) upstream of the dryer is recommended. The Castair #DM75 mount kit is compatible with the RD59-11K and includes a 3/4" NPT 3-ball valve bypass, metal flex hose, and vibration pads for direct compressor mounting.
Available Configurations / Upgrade Path
The RD59-11K sits in the middle of the Castair refrigerated dryer lineup. All models run on 115V/1-phase/60Hz:
- RD25-6K — 25 CFM @ 37°F: For 5–7.5 HP compressors. 57 lbs, 10.6" × 17.9" × 19.6". Step down if your compressor produces 25 CFM or less.
- RD59-11K — 59 CFM @ 37°F: This unit. For 10–15 HP compressors. 73 lbs, 10.6" × 19.1" × 22.4".
- RD71-15K — 71 CFM @ 37°F: Next step up. For 15–20 HP compressors. Upgrades to 1" NPT connections, 110 lbs.
- RD113-60K — 107 CFM @ 37°F: For larger systems. 1" NPT, 119 lbs.
- RD161-37K — 161 CFM @ 37°F: For high-demand shops. 1-1/2" NPT, 137 lbs.
- Larger sizes available — call for pricing.
When Does a Shop Need This vs. Stepping Up or Down
The RD59-11K is right for your shop if:
- Your compressor is in the 10–15 HP range producing 40–59 CFM
- You are running multiple air tools simultaneously or a paint booth with a secondary tool
- Your existing air lines are plumbed 3/4" and you want a direct-swap upgrade from a smaller dryer
- You have standard 115V single-phase power only
Step up to the RD71-15K if:
- Your compressor is 15 HP or larger and produces more than 60 CFM peak demand
- You are expanding your shop with additional bays or a second spray booth
Capacity note: Ratings are based on 100°F inlet air, 100°F ambient, 100 PSI. At 150°F inlet air temperature, effective capacity drops to 55% of rated — approximately 32 CFM for this unit. If your compressor does not have an aftercooler, install one before the dryer inlet to protect dryer performance and capacity.
Technical Specifications
- Model: RD59-11K
- CFM @ 37°F dew point: 59
- CFM @ 50°F dew point: 65
- Inlet/Outlet Connection: 3/4" NPT
- Voltage / Phase / Hz: 115V / 1-phase / 60Hz
- Amperage: 6.5 A
- Refrigerant: R134a / R407c
- Maximum Inlet Pressure: 232 PSIG
- Pressure Dew Point: 37°F
- Heat Exchanger: Stainless steel, dual-function single body
- Drain Type: Automatic, demand-based
- Power Cord: 9 ft, three-prong 115V plug
- Weight: 73 lbs
- Dimensions (W×D×H): 10.6" × 19.1" × 22.4"
- Certifications: UL Listed
Why Buy From Air Compressor Factory Direct?
We specialize in compressed air equipment and have since 2016. When you call, we can help you confirm the right dryer size for your compressor output, advise on pre-filter requirements, and walk through installation options. Free shipping on qualifying orders, free pre-sale technical support, and full Castair manufacturer warranty on every unit.
Call 866-217-0063 for quick answers and help!
