SRL Service Manual
Revision 00
July 2007
Page 59 of 56
13. Confirming Dryer Sizing
The first step to troubleshooting any problem with a refrigerated air dryer is to confirm the dryer is
sized correctly for the operating conditions it is experiencing. Many problems, especially High Dew
Point (Hd) or High Pressure (HP) alarms can be directly attributed to operating conditions that exceed
the dryers maximum capacity.
In order to confirm the dryers maximum capacity at any given set of conditions, the following data is
required:
•
Air Flow (maximum),
•
Inlet Air Pressure (minimum),
•
Inlet Air Temperature (maximum), and
•
Ambient Temperature (maximum).
Additional information will allow an even more accurate determination of the dryer’s capability,
however the above is to be considered the absolute minimum information required to confirm a dryer
is sized properly.
In most applications, temperatures, pressures, and air flow will fluctuate considerably with time.
Please ensure that the maximum temperatures and air flow and the minimum pressure is used, as
these will correctly reflect the worst case scenario. Do not use simply the instantaneous or average
values.
If the operating parameters only exceed the maximum capacity of the dryer by a relatively small
amount, often the dryer will continue to operate, however the outlet dewpoint will rise. However, if
conditions greatly exceed the dryer’s maximum capacity, it will eventually reach a point where the
dryer cannot reject all the heat it is absorbing, and the refrigerant circuit will rapidly rise in temperature
and pressure until the unit shuts down.
The correction factors given below make several assumptions and approximations, and as such,
provide only a rough method of determining a dryer’s maximum capacity. If possible, the SRL
selection software should be used, as this will provide more accurate sizing data. In addition the
sizing software can provide actual performance criteria of the dryer at the input operating conditions.
Contact Sullair for further information.
