Instruction manual

38 McQuay OM 920
Keypad/Display Menu Structure
Chilled Water Setup Menu
Clg DB an adjustable item which sets a dead band around the discharge cooling setpoint
parameter. For example, if the discharge cooling setpoint parameter is set to 55ºF and the Clg
Db parameter is set to 2ºF the dead band around the set point would be from 56.0ºF to 54.0ºF.
Clg Period is an adjustable item which sets the “sampling time” used in the PI control
function of the chilled water valve.
Clg Gain an adjustable item which sets the “proportional band” used in the PI control function
of the chilled water valve.
Clg PAT is an adjustable item which sets the “project ahead” used in the PI control function of
the chilled water valve.
CW Max Chg is an adjustable item that sets the maximum value for an increase or decrease
of the chilled water valve position.
Stage Time is an adjustable item used to set a minimum time period for staging between
minimum cooling operation and economizer operation.
OAT Clg Lock is an adjustable item which sets the low outdoor air temperature mechanical
cooling lockout point. Mechanical cooling operation is disabled when the outdoor air
temperature sensor input falls below this set point.
OAT Diff is an adjustable item which sets a differential above the OAT Clg Lock parameter.
Mechanical cooling operation is re-enabled when the outdoor air temperature sensor input
rises above the OAT Clg Lock value by more than this differential.
Economizer Setup Menu
Econo DB is an adjustable item which sets a dead band around the discharge cooling setpoint
parameter. For example, if the discharge cooling setpoint parameter is set to 55ºF and the Clg
Db parameter is set to 2ºF the dead band around the set point would be from 56.0ºF to 54.0ºF.
Econo Period is an adjustable item which sets the “sampling time” used in the PI control
function of the economizer actuator.Econo Gain is an adjustable item which sets the
“proportional band” used in the PI control function of the economizer actuator.
Econo PAT is an adjustable item which sets the “project ahead” used in the PI control function
of the economizer actuator.
Table 32: Chilled Water Setup Menu
Menu Display Name Item Display Name Default Setting Range Password Level
Chilled Water Setup Clg DB= 2.0d°F 1.0-10.0d°F 4
Clg Period= 20s 0-999s 4
Clg Gain= 1 0.0-100.0 4
Clg PAT= 40s 0-999s 4
CW Max Chg= 15% 0-100% 4
Stage Time= 5min 5-60min 4
OAT Clg Lock= 55°F 0-100°F 4
OATDiff= 2°F 0-10°F 4
Table 33: Economizer Setup Menu
Menu Display Name Item Display Name Default Setting Range Password Level
Economizer Setup Econo DB= 2.0d°F 1.0-10.0d°F 4
Econo Period= 30/40s (air/water) 0-999s 4
Econo Gain= 1-Oct 0.0-100.0 4
(air/water)
Econo PAT= 60/40s 0-999s 4
(air/water)
Econo Max Chg= 10/15% 0-100% 4
(air/water)
Flush Econo= Yes No 4
Yes
Econo Diff= 2°F 0-10°F 4