Refrigerated Air Dryers and Summer Heat: Why Capacity Drops When Temperatures Climb
A refrigerated air dryer is rated at fixed conditions, typically around 100°F inlet air, 100°F ambient air, and100 psig. As ambient and inlet temperatures rise above those conditions, the dryer’s real drying capacity drops. Push a compressor room past 90°F, and a dryer sized for cooler air can fall behind, resulting in excess water in compressed air lines that can move downstream and into tools and product.
Tavoron’s dryer re-rate calculator shows a dryer’s true capacity at any set of conditions, which is key to accurate refrigerated air dryer sizing – and ensuring your dryer will keep up, even as temperatures climb.
Why Isn’t My Air Dryer Keeping Up in the Heat?
A compressed air dryer’s job is to remove moisture from compressed air. However, a refrigerated air dryer’s capacity (how much air it can effectively dry) changes depending on the temperature of the incoming air.
This means summer heat and humidity present a real challenge because air dryers lose capacity as temperatures soar. And the effect is exponential: For every 20°F increase in temperature, the moisture-holding capacity of the air doubles, significantly reducing the ability of refrigerated air dryers to do their job, which results in excess water in compressed air lines.
How Ambient and Inlet Temperature Affect Dryer Capacity
Ambient and inlet temperatures directly impact the capacity of refrigerated air dryers in the following ways:
- Ambient temperature effect on air dryers: Air cooled refrigerated air dryers rely on a condenser to reject heat. If the ambient temperature is hotter than usual due to summer heat, the dryer cannot shed heat efficiently, causing the system to run hotter, decreasing system efficiency and drying capacity.
- Inlet temperature effect on air dryers: When the air coming out of your compressor is hot, it carries more moisture as it enters the dryer, making the dryer work less effectively.
Air Dryer Correction Factors Explained
Air dryers are typically factory tested and rated at 100 psig pressure, 100°F inlet temperature, and 100°F ambient temperature. Any deviation from these factors will alter dryer performance. For this reason, three air dryer correction factors are used to adjust the manufacturer-rated capacity of a compressed air dryer to match the actual operating conditions, making refrigerated air dryer sizing more accurate.
Here’s a closer look at air dryer correction factors and how they impact dryer performance:
Inlet temperature factor:
When the inlet air (the air coming into the dryer) is 100°F, your factor is a baseline of 1.00. As the air gets hotter (110°F or 120°F), it carries extra water, causing the factor to drop below 1.00 (to roughly 0.82 or 0.76, respectively), meaning. Your dryer will only process a fraction of its rated airflow. If the inlet temperature is below 100F, dryer capacity increases above rated airflow.
Ambient Temperature Factor
Air cooled refrigerated dryers rely on the ambient air, or the air surrounding the compressor, to reject heat. If your compressor room is 90°F, the dryer vents heat easily, pushing your factor above baseline (around 1.05), meaning it can manage slightly more than its rated capacity. However, if the room is 110°F, the factor drops (to around 0.87), reducing dryer capacity.
Inlet Pressure Factor:
When air is compressed to a higher pressure, the moisture is “squeezed out” before it reaches the dryer. This means high-pressure air contains less moisture per cubic foot, which makes drying more efficient at higher inlet pressures. If a system runs at 70 psig, the factor drops below baseline because the air is holding onto its water. If it runs at 150 psig, the factor increases, making the air easier to dry and increasing dryer capacity.
Refrigerated Dryer Capacity vs. Temperature
A real example makes it easier to understand how temperature affects dryer capacity. The table below demonstrates how a 500 CFM refrigerated air dryer’s capacity drops from 545 CFM to 500 CFM (a loss of 45 CFM of drying capacity) when the ambient temperature increases from 75°F to 95°F.
| Ambient Temperature | Correction Factor | True Dryer Capacity | Performance Impact |
|---|---|---|---|
| 75°F | 1.09 | 545 CFM | The dryer runs very efficiently |
| 95°F | 1.00 to 1.01 | 500 to 505 CFM | The dryer runs at or near the standard factory rating |
| 100°F (Standard Baseline) | 1.00 | 500 CFM | The dryer runs at rated capacity |
While a 500 CFM dryer can effectively handle a 500 CFM load at 95°F, when temperatures creep above 100°F to 110°F, the capacity of a 500 CFM dryer is further reduced to 435 CFM, potentially causing moisture to carry over into your air lines.
CFM Dryer Sizing: How to Find Your Dryer’s Real Capacity
Because air dryers are sensitive to the temperature and pressure of the air they treat, refrigerated air dryer sizing should account for the actual conditions in your facility based on the three air dryer correction factors. This is called compressed air dryer derating.
Tavoron offers a refrigerated dryer re-rate calculator that simplifies the compressed air dryer derating process, ensuring your dryer will be properly sized so it keeps up with summer heat and humidity.
Simply plug in your conditions, including your rated dryer capacity, ambient air temperature, inlet air pressure, and inlet air temperature, to unlock your re-rated air dryer capacity in less than one minute. Run the dryer re-rate calculator here:
FAQ
Why is there water in my compressed air in summer?
During the summer, air dryers struggle to keep up with excessively hot inlet air temperatures. Air dryers are typically rated for an inlet temperature of around 100°F. For every 20°F increase above that temperature, the moisture load in the air doubles, quickly overwhelming the dryer’s capacity, resulting in wet compressed air that can damage downstream tools and product.
How does ambient air temperature affect a refrigerated air dryer?
Because high ambient temperatures force the dryer to work harder just to stay cool, its overall moisture-removing capacity – and efficiency – drops.
How hot is too hot for an air dryer?
Most air dryers can handle temperatures around 100°F to 110°F. When temperatures climb above this range, the dryer will not shed heat efficiently and the refrigeration system will struggle, reducing cooling and drying capacity.
What to Do When Your Dryer Falls Behind
If you’re experiencing wet downstream air due to soaring summer temperatures, the experts at Tavoron can help you safeguard your air system and products.
Our team is available to help you right-size your dryer, provide air compressor preventive maintenance service, or add a back-up rental solution for the summer season. Contact us or book a free compressed air system check today to ensure that your dryer does its job, even as temperatures climb.
