User Guide

Command Syntax
Siemens Building Technologies, Inc. 3-7
The ADAPTM damper time constant parameter entry (in
seconds) is calculated using this formula:
tcd = T
downstream coils
+ T
sensor
+ T
damper actuator
Where:
tcd = ADAPTM damper time constant parameter entry (in
seconds)
T
downstream coils
= time constants of coils alone downstream of
dampers (between the dampers and the duct temperature
sensor).
T
sensor
= time constant of the supply air sensor (usually about
30 seconds)
T
damper actuator
= stroke time of the damper actuator (often 30
seconds)
Example
The AHU has mixed air dampers, a heating coil, and a cooling
coil.
The heating coil alone has a 5 second time constant. The
cooling coil alone has a 20 second time constant. The supply
air temperature sensor time constant is 30 seconds. The
damper actuator stroke time is 30 seconds. Therefore, the
damper time constant is:
Heating coil time constant: 5 seconds
Cooling coil time constant: 20
Supply air temp. sensor: 30
Damper actuator: 30
Total 85 seconds
APOGEE PPCL User’s Manual
3-8 Siemens Building Technologies, Inc.
tch Heating time constant (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 dampers and cooling only (no
heating), set tch to the value of tcd.
The time constant of the heating coil alone is calculated using
the following formula:
maxwaterhot
maxair
max
max
coilheating
/L
/L
15.0
GPM
CFM
0.02T
s
s
==
Where:
CFM
max
= Maximum or design airflow rate in cubic feet per
minute
GPM
max
= Maximum or design hot water flow rate in gallons per
minute
l/s
air max
= Maximum or design air flow rate in liters per second
l/s
hot water max
= Maximum or design hot water flow rate in liters
per second
The ADAPTM heating time constant parameter entry (in
seconds) is calculated using this formula:
tch = T
heating coil
+ T
downstream coils
+ T
sensor
+ T
hcactuator
Where:
tch = ADAPTM heating time constant parameter (in seconds).
T
downstream coils
= time constants of other coils alone
downstream of heating coil (between heating coil and duct
temperature sensor).
T
sensor
= time constant of the supply air sensor (usually about
30 seconds).
T
hc actuator
= stroke time of the heating coil actuator (often 30
seconds).
Example
An AHU has a design CFM of 50000 and the design flow
through the heating coil is 465 gpm. The heating coil valve has