Desert Aire SelectAire Plus SP Series, Installation And Operation Manual

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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. Review the
system controller reading and use a Magnehelic® or an inclined manometer to check the
air pressure drop through the evaporator coils. See Section 3.2 for more detailed
instructions.
• Check the temperature and humidity of the return air. The SP 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 SP 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.
Desert Aire - SP Manual