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4.4 Low Pressure Alarms/Evaporator Coil Icing
The unit contains a pressure transducer and control sequence that will interrupt power to the
compressor if the refrigeration system pressure is excessively low. The alarm will be active on the local
display and the building management system (if equipped). In this active alarm state, the circuit will stop
and not restart until the Suction Pressure in that circuit rises 48 psi above the Low Suction Pressure Trip
Set Point. Although the circuit will restart automatically, the red ALARM LED on the display will stay lit
until the alarm is acknowledged, even after the alarm condition is cleared, to alert the operator the alarm
occurred. The alarm can be reset at the main alarm screen on the display.
• Check the return air ductwork. Poorly designed, restrictive ductwork can cause stratification or
faulty air distribution. Resize the return air ductwork and grilles, or add turning vanes if necessary.
• Verify that the evaporator and return air filters are clean and free from debris. Use a Magnehelic®
or an inclined manometer to check the air volume through the evaporator coils. See Section 3.2
for more detailed instructions.
• Check the temperature and humidity of the return air. The SA evaporators are designed for
maximum efficiency at typical swimming pool conditions. If the return air wet bulb temperature
drops below 60°F, these coils may frost. Never introduce unconditioned outdoor air into the return
duct of an SA series dehumidifier!
• Check that all service valves and solenoid valves in the liquid line are energized or fully open.
• Verify that there are no restrictions or debris in the liquid line solenoid, the filter/drier, the
expansion valve, or the distributor.
• Check to see that the system is properly charged and that the liquid line sight glass shows no
bubbles. The refrigerant on an undercharged system can migrate to the coldest condenser on
the “off cycle”, causing the receiver to lose its liquid seal.
4.5 The Pool Water Is Too Cold
This section applies to Desert Aire dehumidifiers with the pool water heating option. If the pool water
requires heating, the standard controller will command the dehumidifier to heat the water. If the
dehumidifier cannot heat the pool, due to inadequate water flow or no demand for dehumidification, the
water temperature will drop slightly. The controller will then energize the auxiliary water heater, if one
has been installed. See Section 5.5 in the Appendix for more details. If the problem is not
controller-related, check the following:
• Make sure that the refrigeration circuit containing the pool water condenser has not locked out on
a safety trip.
• Check the “Pool Water Flow” indicator on the controller display panel (for dehumidifiers with the
standard controller). The fault indicator will flash if the water flow proving switch does not
sense water flow. When this happens, the dehumidifier will not run in the pool water
heating mode. All other modes will operate normally. The fault indicator will automatically stop
flashing when the problem has been corrected.
• Temporarily raise the pool water heating set point to verify that the auxiliary pool heater energizes
on call for second stage pool heat.
• If an auxiliary pool heater has not been installed, remove the “air/water priority” jumper from the
electrical panel of the dehumidifier. See the wiring schematics and Section 5.5 in the Appendix
for details.
• Make sure that the water filters are not clogged.
Desert Aire - SA Manual
Summary of Contents for SA Series
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