Compressed Air Dryers Explained (Refrigerant vs Desiccant)
Clean, dry air is essential for every compressed-air system. Without proper drying, moisture causes rust, damages tools, contaminates products and shortens compressor life. This guide explains how compressed-air dryers work, the difference between refrigerant and desiccant dryers, and how to choose the right option for your setup — whether you run an ABAC Genesis screw compressor, Atlas Copco GX, FINI MK, NUAIR Belt-Drive or HPS industrial system.
1. Why You Need an Air Dryer
When air is compressed, water vapour condenses into liquid. Even a small 5 kW compressor can produce several litres of water each day. If that moisture isn’t removed, it corrodes tanks, clogs valves and damages pneumatic tools and paint finishes.
Adding a dryer ensures only clean, dry air reaches your network. It also protects filters, improves product quality and helps you meet ISO 8573-1 air-quality standards.
2. How a Compressed-Air Dryer Works
All dryers operate on the same principle — they remove moisture from compressed air before it reaches downstream equipment. The method used determines the achievable pressure dew point (PDP), which is the temperature below which condensation begins.
- Refrigerant dryers: cool air to around 3 °C PDP
- Desiccant dryers: use adsorption to reach –40 °C to –70 °C PDP
3. Refrigerant Dryers
Refrigerant dryers are the most common type for workshops and light industry. They use a small refrigeration circuit to cool compressed air, condensing water vapour into liquid which is then drained away.
Advantages
- ✅ Low running cost and simple maintenance
- ✅ Suitable for most general workshop and factory applications
- ✅ Compact and reliable with automatic condensate removal
Typical Uses
- Garages and bodyshops
- Food packaging (non-critical zones)
- General manufacturing
- Pneumatic tool operation
Models such as the ABAC Dry 240 or Atlas Copco FD series are popular examples. A correctly sized refrigerant dryer typically removes 95 % of moisture from compressed air and requires little more than filter and drain maintenance.
Key Buying Tips
- Size the dryer for minimum 20 % above compressor output (to handle hot summer air).
- Install after the receiver tank for stable pressure and temperature.
- Pair with a zero-loss drain to save energy.
4. Desiccant Dryers
Where ultra-dry air is required — for paint booths, electronics, medical or pneumatic control systems — choose a desiccant dryer. These use twin towers filled with an adsorbent material such as activated alumina or molecular sieve. As air passes through one tower, moisture binds to the desiccant. The other tower regenerates before switching roles automatically.
Advantages
- ✅ Very low dew points (–40 °C to –70 °C)
- ✅ Essential for frost prevention and sensitive equipment
- ✅ Works effectively in cold or outdoor environments
Disadvantages
- ⚠️ Higher energy use (for regeneration)
- ⚠️ Requires regular desiccant replacement (every 2–3 years)
- ⚠️ Slightly more complex control system
Typical Applications
- Spray-painting and powder-coating lines
- Instrumentation and pneumatic controls
- Dentistry and laboratories
- Outdoor installations subject to freezing
Popular examples include ABAC ADQ, Atlas Copco CD/BD series and HPS D-Series desiccant dryers.
5. Choosing Between Refrigerant and Desiccant
| Feature | Refrigerant Dryer | Desiccant Dryer |
|---|---|---|
| Typical Dew Point | +3 °C | –40 °C to –70 °C |
| Energy Efficiency | Low energy use | Higher due to regeneration |
| Maintenance | Filter & drain checks | Replace desiccant every 2–3 yrs |
| Ideal For | General workshop / factory | Paint, medical, instrument air |
| Initial Cost | £400 – £2 000 | £1 000 – £5 000+ |
If you operate in normal indoor conditions and don’t need ultra-dry air, a refrigerant dryer is usually sufficient. If your system must deliver oil-free or medical-grade air — or operates in cold or outdoor locations — a desiccant dryer is the safer choice.
6. How to Correctly Install an Air Dryer
- Mount on level ground with 0.5 m clearance for ventilation.
- Install after the receiver tank but before the main air line filters.
- Fit a particulate pre-filter to protect the dryer core.
- Connect a condensate drain to an oil-water separator for environmental compliance.
- Ensure electrical supply matches rating and isolate before servicing.
7. Pairing Dryers with Filters and Receivers
For best performance, combine your dryer with high-efficiency filtration and a correctly sized receiver tank:
- Coalescing filters remove oil aerosols before drying.
- Receiver tanks stabilise flow and allow condensate to settle.
- Automatic drains prevent water carry-over.
We supply complete dryer packages and spare parts — including solenoid drains, service kits, and replacement desiccant cartridges — for most ABAC, Atlas Copco, FINI and HPS models.
8. Maintenance & Service Tips
- Check differential pressure monthly and clean filters.
- Inspect condensate drain operation daily.
- For desiccant dryers, test dew-point sensors and replace desiccant every 2–3 years.
- Keep vents and fans free of dust for efficient heat exchange.
Regular maintenance keeps running costs low and ensures reliable protection against moisture — helping your compressor oil, filters and tools last longer.
9. Energy Efficiency Considerations
Refrigerant dryers can include energy-saving features such as cycling operation or digital scroll compressors. Desiccant models may use purge-saving control that minimises air loss during regeneration. Ask our team for guidance on selecting an efficient model suited to your duty cycle and climate.
10. When to Upgrade or Replace Your Dryer
- Frequent water in air lines despite proper drainage
- Rising dew-point readings
- Corrosion or oil contamination downstream
- High energy consumption or noisy refrigeration circuit
Replacing an ageing dryer can reduce operating costs and improve air quality immediately. Modern units are quieter, smaller and more efficient than older designs.
11. Compliance and Environmental Notes
All dryers must comply with UK CA or CE certification and F-Gas regulations for refrigerant handling. Dispose of used desiccant and filters responsibly. Fit an oil-water separator to ensure condensate discharge meets UK environmental standards.
12. Ready to Upgrade?
At CompressorParts.co.uk, we stock and source a full range of:
- Refrigerant and desiccant dryers
- Inline filters and service kits
- Condensate drains and oil-water separators
- Air receiver tanks and accessories
Our technical team can help you match the correct dryer to your compressor’s flow rate, pressure and duty cycle. Get in touch today for tailored advice or a quote on replacement dryers and spares.
FAQs
What dew point do I need?
For general workshop use, +3 °C PDP from a refrigerant dryer is fine. For paint, pharmaceutical or outdoor applications, aim for –40 °C or lower using a desiccant dryer.
Can I run two dryers in series?
Yes. A refrigerant dryer followed by a desiccant unit is common for critical air systems — the first removes bulk water, reducing desiccant load and energy use.
Do dryers reduce pressure?
Yes, slightly. Expect 0.2–0.3 bar drop across a refrigerant dryer and up to 0.5 bar across a desiccant system. Keep filters clean to minimise loss.