Temperature Control - McQuay MicroTech II Operation Manual

Temperature Control

Table 31: Programmable Parameters
Keypad/Display ID
Menu Name Item Name
CntlTemp Src= Return
Eff Clg Spt= ____ °F
Zone Cooling
Occ Clg Spt= 75.0 ºF
Clg Deadband= 1.0 ºF
CntlTemp Src= Return
Eff Htg Spt= ____ °F
Zone Heating
Occ Htg Spt= 70.0 ºF
Htg Deadband= 1.0 ºF
Zone Temp
Spt Source= Keypad
Setup
Control Temperature
The "Control Temperature" is defined as the unit tempera-
ture input used to make the heat/cool changeover decision
which determines whether the unit is controlling to the
Effective Cooling Enable Set Point or the Effective Heating
Enable Set Point. Also, when cooling is active, the "Control
Temperature" is maintained at the Effective Cooling Enable
Set Point and when heating is active the "Control Tempera-
ture" is maintained at the Effective Heating Enable Set Point.
Either the return air or space temperature sensor can be
selected as the "Control Temperature."
When the Control Temperature Source is set to "Return", the
unit return air temperature sensor acts as the "Control Tem-
perature."
When the Control Temperature Source is set to "Space", the
unit space air temperature sensor acts as the "Control Tem-
perature."
Note: The Control Temperature Source can not be set to
"Return" on a 100% OA unit and it can only be set
to "Space" when the unit is equipped with an
optional space sensor. This means that an optional
space sensor is required on a 100% OA unit.
The current value of the "Control Temperature" can be dis-
played be viewing the Ctrl Temp= parameter in the Temper-
atures menu.
66
Once enabled by the "Control Temperature" cooling or heat-
ing capacity control operates as described in "Economizer"
on page 68, "Cooling: Multistage" on page 72, "Cooling:
Modulating" on page 77, "Heating: Multistage" on page 78,
or "Heating: Modulating" on page 80 as applicable. The fol-
Parameter Name
lowing sections describe in detail how the "Control Temper-
ature" enables cooling and heating operation.
Control Temperature
Source
Note:
Effective Cooling
Enable Set Point
Cooling Enable Set
Point
Cooling Enable Dead
Set Points and Dead Bands
Band
Control Temperature
In determining whether heating or cooling operation is
Source
enabled, the controller compares the "Control Temperature"
Effective Heating
input with the Effective Cooling Enable Set Point and the
Enable Set Point
Effective Heating Enable Set Point.
Heating Enable Set
Point
Keypad/Network Source Set Points. When the Zone
Heating Enable Dead
Set Point Source Flag is set to "Keypad", the Effective Cool-
Band
ing Enable Set Point and the Effective Heating Enable Set
Zone Set Point Source
Point are set to the Cooling Enable Set Point and the Heating
Flag
Enable Set Point. The Cooling Enable Set Point and the
Heating Enable Set Point can then be set as required via a
network signal.
Tstat Source Set Points. When the Zone Set Point
Source Flag is set to "Tstat", the Effective Cooling Enable
Set Point and the Effective Heating Enable Set Point are set
based on an analog signal from an optional space tempera-
ture sensor with set point adjustment capability.
To set the Effective Cooling Enable Set Point and the Effec-
tive Heating Enable Set Points based on the remote set point
input, the controller first determines the difference between
the Cooling Enable Set Point to the Heating Enable Set
Point. The controller then sets the Effective Cooling Enable
Set Point to the current setting on the space sensor plus half
this difference. The controller then sets the Effective Heating
Enable Set Point to the current setting on the space sensor
minus half this difference.
For example, if the Cooling Enable Set Point is set to 75°F,
the Heating Enable Set Point is set to 70°F and the set point
adjustment on the space temperature sensor is set to70°F, the
Effective Cooling Set Point would be set to 72.5°F and the
Heating Enable Set Point would be set to 67.5°F.
Cooling. When the "Control Temperature" rises above the
Effective Cooling Enable Set Point by more than half the
Cooling Enable Dead Band, cooling operation is enabled and
the controller starts to increase the cooling capacity. This is
shown as Point A in Figure 8.
Although enabled based on the "Control Tempera-
ture", cooling or heating operation can be disabled
for other reasons. Refer to "Clg Status" on
page 43and "Htg Status" on page 44.
OM 138