The Dryer Light Is On So Why Do I Still Have Wet Air?

Aug 25, 2015

We all assume that if a light is on it must be working, right?

When we take a look at the refrigerated dryer in our compressor room we assume that everything is okay. Then later that day or the next morning someone tells us that water is showing up in the production equipment.

So now what?

Well, the dryer may be working and there are 5 simple checks that you can do to see what is really going on in your system.

Step 1

What I call the “cough test,” which is reaching to the cabinet opening in your dryer to find the condensate separator or the outlet line – it should feel very cold, around 38° F – if it isn’t cold the dryer has a problem. Action Item: have the refrigeration circuit checked and make sure the condenser is clean.

Step 2 

It or not one of the most common issues is that the bypass valves are either left partially open or do not close completely – if they seem to be closed, that is good, but you might want to check further. Action Item: check by closing all three valves see if the pressure down line starts to drop over a 10 minute period – if it doesn’t drop substantially you may need to inspect/clean or replace one of the bypass valves

Step 3

Inlet air temperatures to the dryer should be no more than 100° F – if you can put your hand on the compressor discharge pipe and it doesn’t feel hot to you, that is good – if it feels hot to the touch, that may be the problem. Action Item: check the aftercooler on the compressor to make sure it is clean and the air temperature is no more than 15° F above room temperature – may have to remove and clean thoroughly.

Step 4

As mentioned above your compressor room really should not be any hotter than the outside temperature – 90° F on a 90° F day – if it’s more than 10° F above the outside temperature you could have a problem for all of the equipment in the room – dryers are designed to run at 100° F ambient. Action Item: get your HVAC or compressor vendor to review your compressor room ventilation.

Step 5

Check to see if there is any condensate coming out of the dryer drain trap – if a sizable amount is not accumulating from the trap on an hourly basis it means the dryer may be working but you’re not removing the water from the system and it is going down line. Action Item: isolate the drain trap to inspect/clean/repair or replace it – REPLACE ONLY WITH A DEMAND TYPE TRAP

If you’ve taken these 5 steps and the issue persists, then it’s time to call your compressed air vendor to find out what’s going on.

Our Service Department is available 24/7 – Call us today at 800-366-1323 or submit a service request online at