User Guide

Command Syntax
Siemens Building Technologies, Inc. 3-9
a 30 second electric actuator. Downstream of the heating coil,
there is a cooling coil with a time constant (alone) of 33
seconds. The time constant of the heating coil alone is:
)sec2(2.2
465
50000
02.0
max
max
02.0 ondstoroundcondsse
GPM
CFM
coilheating
T ===
The tch parameter entry into ADAPTM is:
actuatorhcsensorcoilsdownstreamcoilheating
TTTTtch
+
+
+=
condssetch 953030332 =+++=
tcc Cooling time constant (in seconds).
• This parameter can be a point name, local variable
name, or decimal number.
• This value must be greater than or equal to 3 times the
st value.
• For applications with heating and dampers only (no
cooling coil), set tcc to the value of tcd.
The time constant of the cooling coil alone is calculated using
the following formula:
max
max
/
/
0.2
max
max
25.0
waterchilled
air
coilcooling
sL
sL
T
GPM
CFM
=
=
Where:
CFM
max
= Maximum or design airflow rate in cubic feet per
minute
GPM
max
= Maximum or design chilled water flow rate in gallons
per minute
L/s
air max
= Maximum or design air flow rate in liters per second
L/s
chilled water max
= Maximum or design chilled water flow rate in
liters per second
APOGEE PPCL User’s Manual
3-10 Siemens Building Technologies, Inc.
The ADAPTM cooling time constant parameter entry (in
seconds) is calculated using this formula:
actuatorcc
T
sensor
T
coilsdownstream
T
coilcooling
Ttcc +++=
Where:
tcc = ADAPTM cooling time constant parameter (in seconds)
T
downstream coils
= time constants of coils alone downstream of
cooling coil (between cooling coil and duct temperature sensor)
T
sensor
= time constant of the supply air sensor (often 30
seconds)
T
cc actuator
= stroke time of the cooling coil actuator (often 30
seconds)
Example
An AHU has a design CFM of 15000 and the design flow
through the cooling coil is 258 gpm. The cooling coil valve has
a 30 second electric actuator. Downstream of the cooling coil,
there is a heating coil with a time constant (alone) of 15
seconds. The time constant of the cooling coil alone is:
)sec15(5.14
258
15000
25.0
max
max
25.0 ondstoroundcondsse
GPM
CFM
coilcooling
T ===
The tcc parameter entry into ADAPTM is:
actuatorccsensorcoilsdownstreamcoilcooling
TTTTtcc
+
+
+
=
condssetcc 9030301515
=
+
+
+
=
her Heating end of range (in percent). This parameter tells
ADAPTM what percentage of its output is used for heating. It is
assumed that the beginning of the heating range is at 0%.
• This parameter can be a point name, local variable