Dedicated Outdoor Air Unit 19
Factory-Installed Refrigeration System Components
Packaged DX Cooling with Three Way Hot Gas Reheat and Hot Gas Bypass
1. Compressor
2. High Limit Pressure Switch
The switch opens when refrigerant pressure
increases above the set point in the discharge line.
A manual reset is then required.
3. Hot Gas Reheat Valve (optional)
Units equipped with a reheat coil use a three-
way valve with actuator to control the supply
air discharge temperature of the unit during
dehumidification mode. The unit controller provides
a 0-10 VDC signal to control the amount of reheat
to meet the supply temperature set point
4. Hot Gas Reheat Coil (Optional)
5. Hot Gas Reheat Check Valve (Optional)
6. Condenser Fans
7. Condensing Coil
8. Liquid Receiver (Optional)
9. Liquid Line Filter Drier
10. Sight Glass
11. Fan Cycle Switch(es)
The switch(es) open or close based on liquid
refrigerant pressure to control the condensing fans
to maintain liquid pressure.
12. Thermostatic Expansion Valve (TVX)
Each unit is equipped with a TVX on each
refrigerant circuit. The valve controls the flow of
liquid refrigerant entering the evaporator coil by
maintaining a constant, factory-set superheat of
10°F. The valve is adjustable and is located on the
side of the evaporator coil and can be accessed
through the coil access panel.
13. Evaporative Coil
14. Low Limit Pressure Switch
The switch is installed on the suction line and
disables the DX system when the suction pressure
drops below the set point. The switch will auto reset
when the pressure rises above the auto-reset set
point.
15. Service Access Ports
16. Hot Gas Bypass Manual Shut Off Valve (Optional)
Used to disable hot gas bypass for service and
troubleshooting procedures.
17. Hot Gas Bypass Valve (Optional)
On units equipped with hot gas bypass, hot gas
from the compressor is injected into the liquid line
of the evaporator coil after the TVX.
Valve Adjustment - To adjust the valve, connect
a pressure gauge to the suction line and block the
entering air to the evaporator coil. The valve should
begin to open when the suction pressure drops to
approximately 115 PSIG for R-410A (the valve will
feel warm to the touch). Adjustments are made by
first removing the cap on the bottom of the valve
and then turning the adjusting stem clockwise to
increase the setting pressure (counterclockwise
to decrease). Allow several minutes between
adjustments for the system to stabilize. When
adjustment is complete, replace the cap on the
valve.
18. Pressure Gauge & Transducer (Optional EC
condenser fans only)
See Optional Electronically Commutated (EC)
Condenser Fans under the component operation.
To Next Page
Loading...
