Heating: Multistage; Temperature Control - McQuay MicroTech II Operation Manual

Face and Bypass Damper Modulation. When the
Disch Air= value rises above the Effective Discharge Cool-
ing Set Point by more than half the Discharge Cooling Dead
Band, the face and bypass dampers position is increased to
the face. When the Disch Air= value falls below the Effec-
tive Discharge Cooling Set Point by more than half the Dis-
charge Cooling Dead Band, the face and bypass damper
position is decreased to the face.
The controller uses three PID control loop parameters to
modulate the face and bypass dampers as the discharge air
temperature changes. Theses are the Cooling Proportional
Band, Cooling Integral Time and Cooling Period. Although
these parameters can be adjusted, for most applications, the
factory default values for these parameters provide the best
control. For detailed information regarding tuning PID con-
trol loop parameters, refer to "MicroTech II DDC Features"
on page 99.
Effective Discharge Cooling Set Point Adjustment.
When the Ctrl Temp= value rises above the Effective Cool-
ing Enable Set Point by more than half the Cooling Enable
Dead Band, the Effective Discharge Cooling Set Point is
decreased. When the Ctrl Temp= value falls below the Effec-
tive Cooling Enable Set Point by more than half the Cooling
Enable Dead Band, the Effective Discharge Cooling Set
Point is increased.
Note: When the unit first enters the Cooling operating
state, the Effective Discharge Cooling Set Point is
set to the current Disch Temp= value.
The controller uses three PID control loop parameters to
raise and lower the Effective Discharge Cooling Set Point as
the Ctrl Temp= value changes. These are the Zone Cooling
Proportional Band, Zone Cooling Integral Time and Zone
Control Period. Although these parameters can be adjusted,
for most applications, the factory default values for these
parameters provide the best control. For detailed information
regarding tuning PID control loop parameters, refer to
"MicroTech II DDC Features" on page 99.
Cooling to Econo Operating State
When economizer operation is available, the unit will leave
the Cooling operating state and enter the Econo operating
state when the Ctrl Temp= value falls below the Effective
Cooling Enable Set Point by more than half the Cooling
Enable Dead Band and either of the following are true:
1. The chilled water valve is closed for more than one
Cooling Interstage Timer period.
2. The Effective Discharge Cooling Set Point has been at
the Maximum Discharge Cooling Set Point for one
Cooling Interstage Timer period.
Cooling to Fan Only Operating State
When economizer operation is not available, the unit will
leave the Cooling operating state and enter the Fan Only
operating state when the Ctrl Temp= value falls below the
Effective Cooling Enable Set Point by more than half the
78
Cooling Enable Dead Band and any of the following are
true:
1. The chilled water valve is closed for more than one
Cooling Interstage Timer period.
2. The Effective Discharge Cooling Set Point has been at
the Maximum Discharge Cooling Set Point for one
Cooling Interstage Timer period.
3. All cooling is disabled for any reason. Refer to "Clg Sta-
tus" on page 43.

Heating: Multistage

Temperature Control

Table 41: Programmable Parameters
Keypad/Display ID
Menu Name Item Name
Eff Htg Spt= ____ °F
Zone Heating Occ Htg Spt= 75.0 ºF
Htg Deadband= 1.0 ºF
Min Htg Spt= 55.0 ºF
Discharge Heating
Max Htg Spt= 65.0 ºF
Heating Setup Stage Time= 5 Min
Entering Heating Operating State
The unit enters the Heating operating state from the Recirc
or Fan Only operating state when the Ctrl Temp= value falls
below the Effective Heating Enable Set Point by more than
half the Heating Enable Dead Band.
When the unit is in the Heating operating state, heating
stages are turned on and off to maintain the Ctrl Temp=
value at the Effective Heating Enable Set Point.
Note: Unless it is set by a signal from an option space
temperature sensor or by the dehumidification func-
tion, the Effective Heating Enable Set Point is set
by the controller equal to the Heating Enable Set
Point.
The controller activates the first stage of electric heat as it
enters the Heating operating state. When the Ctrl Temp=
value is below the Effective Heating Enable Set Point by
more than half the Heating Enable Dead Band and the Heat-
ing Interstage Timer has expired since the last stage change,
heating capacity is increased by one stage. When the Ctrl
Temp= value is above the Effective Heating Enable Set Point
by more than half the Heating Enable Dead Band and the
Heating Interstage Timer has expired since the last stage
change, heating capacity is decreased by one stage.
Parameter Name
Effective Heating
Enable Set Point
Heating Enable Set
Point
Heating Enable Dead
Band
Minimum Discharge
Heating Set Point
Maximum Discharge
Heating Set Point
Heating Interstage
Timer
OM 138