FAQ: Refrigeration: The Art of Dryer Sizing

When you’re in the market for a compressed air dryer, it’s imperative that you determine the appropriate size you need. One machine does not fit all jobs! If you purchase an air dryer that is too small, you won’t get the results you want and vice versa.  To figure out the right size you need, keep reading!

When you compare compressed air dryers, you need to know that the rating for each machine is based on normal, or standard, conditions.  So if a dryer is rated to a specific moisture level, this rating is based on the “normal” conditions. But you know that your conditions frequently change! Temperature and air pressure both affect the amount of water air is capable of holding. As temperatures rise, so does the air moisture levels. Opposite of temperature, when pressure rises, the air moisture levels drop.  So how do you get a dryer that is the right size when you rarely experience “normal” conditions?

Correction Factors

Manufacturers understand the discrepancy between “normal” conditions and the conditions the dryer will actually have to work in, providing correction factors.  These scale pressure and temperature, allowing you to determine which dryer will be the right fit. You need to take the extreme scenarios of the conditions your dryer will be used in. For example, let’s pretend you live in the dry desert heat of the southwest.  In these conditions, you don’t need to worry about how your dryer will perform if it’s 30 degrees out. But if you live in the northeast, you would have to make sure the compressed air dryer you choose will function in both freezing temperatures and up into the 90s with 100% humidity. In this instance, you would have to look at both of these extremes to determine which dryer will do what you need it to, all year round.

Other Points to Consider

Don’t base your decision solely on the temperatures and pressures of where you live.  You also need to look at the compressed air dryer itself and its specific ratings.  Buying a smaller compressed air dryer than what you actually need might be cheaper now, but it will have to run at full capacity every time you use it, using more energy and causing damage faster. Choosing an air dryer with a higher maximum air flow than your compressor delivers will help you keep the pressure settings lower, getting you the dew point you need.

You also want to look at the maximum pressure of the dryer as well as the maximum air temperature. You want a dryer that at least matches the pressure of the compressor you’ll be using. You also need to ensure the air that your compressor is putting into the dryer is not hotter than the maximum air temperature the compressed air dryer allows.

The most important thing to know when you’re purchasing a compressed air dryer is not to rush the process!  There are a lot of factors that need to go into the decision to ensure you get the dryer that will do what you need it to.