Reznor YDSA Unit Installation Manual - Manual (Page 32)

Form I-Y, P/N 273646R6, Page 32
Optional Hot Gas
Bypass Valve
Check Hot Gas Bypass Valve Setting - On the circuit with a hot gas bypass valve,
connect a pressure gauge to the suction line and block the entering air to the evapora-
tor coil. Suction pressure will drop, and the hot gas bypass valve should begin to open
at approximately 115 psi and will be fully open at 95 psi. When the valve begins to
open, it will be hot to the touch (see caution below).
CAUTION: Do not touch the hot gas bypass valve when operating.
Use caution when checking and adjusting the valve. Wear
appropriate safety gear.
If pressure needs to be adjusted, remove the cap and turn the adjusting stem clock-
wise to increase the pressure setting or counterclockwise to decrease the pressure
setting. Make adjustments in small increments. Allow five minutes between adjust-
ments for the system to stabilize. When finished, replace the cap on the adjustment
stem and remove the pressure gauge.
8.0 Controls 8.1 System Controller
The digital controller has an integral display allowing for complete access to unit test
features, schedules, discharge air set points, fan control, alarms, and other unit opera-
tional set points. The controller is programmed to react to signals from various stan-
dard and optional sensors to provide the operation required to maintain the set points.
Space Temperature Control
System (Option D19) - applies
to Model YDSA and Model YDHA
NOTE: For additional information
about Option D19 refer to
Form CP-Y-D19.
routed directly to the evaporator coil. With Option AUC8, at least one circuit per stage
has a hot gas bypass valve. Hot gas bypass valves are factory set.
Sequence of Operation
● Supply air constant volume
● Supply air variable volume
»Duct static
»Summer/winter fan speed
»High Low Speed Control ● Power exhaust control
● Mixed air damper controls
»Demand ventilation
»Manual & external control
● Energy recovery
● Thermostat control
Neutral Air Control System
(Option D21) - applies to
Models YDMA and YDHA
Sequence of Operation
● Neutral air control
● Space temperature reset
control
● Tempered air control
● Process control
● Supply air constant volume
● Supply air variable volume
»Duct static & building static
»Demand ventilation
»Exhaust fan matching
»Summer/winter fan speed
»Space fan speed control
»Manual & external control
● Power exhaust control
● Mixed air damper controls
»Duct static & building static
»Demand ventilation
»Exhaust fan matching
»Manual & external control
● Energy recovery
NOTE: For additional information
about Option D21 refer to
Form CP-Y-D21.
7.8 Compressors (cont’d)
7.0 Electrical and Wiring (cont'd)