©2025 Copeland LP.
026-1803 R13 Supervisor I&O User Guide 9 - 20
9.13.13 Economization (Damper)
Control
HVAC economizers can save energy in buildings by using
cool outside air as source of cooling the indoor space. When
the temperature of the outside air is less than the temperature
of the re-circulated air, conditioning the outside air is more
energy efficient than conditioning re-circulated air. When the
outside air is both sufficiently cool and sufficiently dry
(depending on the climate), the amount of enthalpy in the air
is acceptable and no additional conditioning of it is needed;
this portion of the air-side economizer control scheme is
called free cooling.
The AHU economizer control operation depends on whether
a two-position or variable position damper control is used.
The user may also select “None” as the economizer damper
type if no economization is desired.
The Two Basic Operations of the Economizer
Algorithm are Divided into:
1. Determine if economization should occur:
• Is the outdoor air suitable for economizing?
• Is the AHU in heat mode?
• Is there a failure in the AHU?
• Does the control temperature require cooling from
economization?
• Is the supply temperature too low?
2. Determine the analog damper position:
Steps to Determine if Economization Should
Activate
The algorithm begins with determining whether
economization should occur. This is determined by five
inputs:
1. Is the outdoor air suitable for economizing?
2. Is the AHU in heat mode?
3. Is there a failure in the AHU?
4. Does the control temperature require cooling from
economization?
5. Is the supply temperature too low?
Outdoor Air Suitability
The economizer outdoor air suitability algorithm determines
whether outdoor air conditions are suitable for the algorithm
to enable economization. The result of the algorithm is an
“Econ OK” signal. The suitability is determined by comparing
the outdoor air temperature to the control temperature. If the
outside air temperature is cooler, then the Econ OK signal is
set to ON.
In addition to the outdoor air temperature, there is a user-
defined maximum outdoor air humidity setpoint (Max OA
Hum) above which outdoor air is not used for
economization. In this case, the Econ OK signal is set to OFF.
Heat Mode
If the AHU is in heating mode, economization is disabled.
Economization is a cooling function and would therefore be
counterproductive to heating.
Failure Lockout
If the AHU application has detected a failure, economization
is disabled. Failures that can lock out economization are:
• Fan Proof Fail - When fan proof failure is detected,
heating and cooling loads are shut down until the proof
failure goes away or the fan proof alarm is reset or
cleared. If the fan is configured to shut down on a fan
proof failure, the system is restarted by setting the FAN
FAIL RST input to ON or clearing the fan proof failure from
the advisory log.
• SHUTDOWN input is ON - The application goes into a
shutdown mode that turns off the fan. The fan remains
OFF as long as the SHUTDOWN input is ON.
Control Temperature above Economization Set-
point
If the control temperature is greater than the occupied
cooling setpoint minus the occupied economization delta,
then economization is permitted. If the control temperature is
greater than the unoccupied cooling setpoint minus the
unoccupied economization delta, then economization is
permitted. If the either the control temperature or the setpoint
minus the economization delta has a value of NONE, then
economization is not permitted.
Low Supply Temp Lockout
If the supply temperature is below “Econ Lock Temp”, the
economizer is disabled.
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