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• If there is no voltage at the holding coil, check the compressor overload and safety
devices, the control transformer, the smoke alarm interlock, the airflow proving switch, or
the optional voltage monitor relay.
• If the dehumidifier uses a non-standard controller, or if the compressors are cycled by the
building management system, consult with the controls contractor.
• Confirm that the compressor “knife” switches from air balancing section have been closed.
4.3 High Pressure Alarms / Readings Above 575 PSIG
The unit contains a pressure transducer and control sequence that will interrupt power to the
compressor if the refrigeration system pressure is excessively high. The alarm will be active on the
local display and the building management system (if equipped). The alarm can be reset at the main
alarm screen on the display.
• Check that all service valves and ball valves in the compressor discharge line are fully
open.
• Verify that the reheat condenser is clean and free from debris. Use a Magnehelic® or an
inclined manometer to check the air volume through the reheat condenser.
See Section 3.2 for more detailed instructions.
• Check that there is adequate water flowing through the pool water condenser (on units
equipped with this option). Verify the operation of the water flow switch.
• Check the remote condenser fuses, fan motors, and fan cycling switches (on units
equipped with this option). Verify that the fans are not obstructed and that they blow the air
vertically upward.
• Check the three-way heat reclaim valve for proper operation. This valve, which is installed
in the compressor discharge line, diverts hot refrigerant vapor to the various condensers
(on units equipped with optional pool water heating or remote condensers). The valve
spool may be stuck in the middle of the valve, where it blocks the outlets to both
condensers. You can verify its operation by first running the compressor and then
measuring the temperature of both condenser outlets. If the valve is shifting normally, the
active condenser outlet will heat up rapidly.
• Check for air or other non-condensable in the refrigeration circuit. Desert Aire installs
purge ports in the highest point of each condenser’s discharge line. To purge these gases
from the system, temporarily run the compressor while you energize the selected
condenser. Slowly depress the Schrader core at the high point purge of the condenser.
You can do this procedure to keep the system running, but it is a temporary fix. It is not a
long term substitute for proper evacuation with a vacuum pump.
• If the dehumidifier uses an outdoor air duct with a field-installed preheating coil, verify that
the coil is only active during the heating season.
• If the system is overcharged or excessively cold, migrating refrigerant can liquefy and fill
a condenser and its discharge line during the “off-cycle”. If the compressor starts and the
three-way valve shifts to this flooded condenser, the high pressure switch will trip almost
immediately. Remote outdoor condensers are particularly susceptible to this problem
during the winter months.
Desert Aire - SP Manual
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