Instruction manual

McQuay OM 920 37
Keypad/Display Menu Structure
Min EWT is an adjustable item that sets the minimum allowable entering water temperature.
Mechanical Cooling is disabled when the entering water temperature sensor input falls below
this setpoint
Head Pressure Setup Menu
Head Press DB is an adjustable item that sets a deadband around the Head Pressure Setpoint
parameter.
WRV Period is an adjustable item which sets the “sampling time” used in the PI control
function of the water regulating valve.
WRV Gain is an adjustable item which sets the “proportional band” used in the PI control
function of the water regulating valve.
WRV PAT is an adjustable item which sets the “project ahead” used in the PI control function
of the water regulating valve.
WRV Max Chg is an adjustable item that sets the maximum value for an increase or decrease
of the water regulating valve.
Init Op Time The first compressor runs for an editable Initial Operation Time (InitOpTime)
with the WRV at an initial start up position (InitPos).
Min WRV Pos is an adjustable item used which sets the minimum WRV position (default
10%).
Min WRV Tmp is an adjustable item which is used to set the edited temperature where WRV
at a minimum position is OK.
WRV Act Time is an adjustable item which is used to set the time required for the WRV to be
driven from 0 to 100%.
Max WRV Tmp is an adjustable item which is used to set the edited temperature where WRV
at 100% is OK.
Min WRV Time is an adjustable item which sets the minimum WRV time (default 60
seconds.
Table 31: Head Pressure Setup Menu
Menu Display Name Item Display Name Default Setting Range Password Level
Head Press Setup Head Press DB= 10psi 0-50psi 4
WRV Period= 10s 0-999s 4
WRV Gain= 3.6 0.0-100.0 4
WRV PAT= 10s 0-999s 4
WRV Max Chg= 7% 0-100% 4
Init Op Time= 60s 0-3600s 4
Min WRV Pos= 10% 0-100% 4
Min WRV Tmp= 58°F 20-150°F 4
Max WRV Tmp= 105°F 20-150°F 4
WRV Act Time= 60s 0-300s 4
Min WRV Time= 60s 0-3600s 4