Carrier WEATHERMASTER 48/50Z030-105 - Manual (Page 68)

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Control Angle Alarm Configuration — The economizer ac-
tuator determines its end stops through a calibration at the
factory. Field-installed actuators may be calibrated in the
Service Test mode. When an actuator learns its end stops
through calibration, it also determines its control angle. The
actuator will resolve this control angle and express its operation
in a percent (%) of this learned range.
If the economizer has not learned a sufficient control angle
during calibration, the economizer damper will be unable
to control ventilation and free cooling. For this reason the
economizer actuator used in the Z Series control system has a
configurable control angle alarm low limit (Configuration
→ ECON → ACT.C → C.A.L1 or C.A.L2). If the control angle
learned through calibration is less than C.A.L1 or C.A.L2, an
alert will occur and the actuator will not function.
NOTE: This configuration does not typically need adjustment.
It is configurable for the small number of jobs which may
require a custom solution or workaround.
UNOCCUPIED ECONOMIZER FREE COOLING — This
Free Cooling function is used to start the supply fan and use
the economizer to bring in outside air when the outside
temperature is cool enough to pre-cool the space. This is done
to delay the need for mechanical cooling when the system
enters the occupied period. This function requires the use of a
space temperature sensor.
When configured, the economizer will modulate during an
unoccupied period and attempt to maintain space temperature
to the occupied cooling set point. Once the need for cooling has
been satisfied during this cycle, the fan will be stopped.
Configuring the economizer for Unoccupied Economizer
Free Cooling is done in the UEFC group. There are three
configuration options, FC.CF, FC.TM and FC.LO.
Unoccupied Economizer Free Cooling Configuration
(FC.CF) — This option is used to configure the type of unoc-
cupied economizer free cooling control that is desired.
0 = disable unoccupied economizer free cooling
1 = perform unocc. economizer free cooling as available dur-
ing the entire unoccupied period.
2 = perform unocc. economizer free cooling as available,
FC.TM minutes before the next occupied period.
Unoccupied Economizer Free Cooling Time Configuration
(FC.TM) — This option is a configurable time period, prior to
the next occupied period, that the control will allow unoccu-
pied economizer free cooling to operate. This option is only
applicable when FC.CF = 2.
Unoccupied Economizer Free Cooling Outside Lockout
Temperature (FC.LO) — This configuration option allows
the user to select an outside-air temperature below which unoc-
cupied free cooling is not allowed. This is further explained in
the logic section.
Unoccupied Economizer Free Cooling Logic — The follow-
ing qualifications that must be true for unoccupied free cooling
to operate:
• Unit configured for an economizer
• Space temperature sensor enabled and sensor reading
within limits
• Unit in the unoccupied mode
• FC.CF set to 1 or FC.CF set to 2 and control is within
FC.TM minutes of the next occupied period
• Not in the Temperature Compensated Start mode
• Not in a cooling mode
• Not in a heating mode
• Not in a tempering mode
• Outside-air temperature sensor reading within limits
• Economizer would be allowed to cool if the fan were
requested and in a cool mode
• OAT > FC.LO (1.0° F hysteresis applied)
• Unit not in a fire smoke mode
• No fan failure when configured to for unit to shut down
on a fan failure
If all of the above conditions are satisfied:
Unoccupied Economizer Free Cooling will start when both of
the following conditions are true:
{SPT > (OCSP + 2)} AND {SPT > (OAT + 8)}
The Unoccupied Economizer Free Cooling Mode will stop
when either of the following conditions are true:
{SPT < OCSP} OR {SPT < (OAT + 3)} where SPT = Space
Temperature and OCSP = Occupied Cooling Set Point.
When the Unoccupied Economizer Free Cooling mode is
active, the supply fan is turned on and the economizer damper
modulated to control to the supply air set point (Setpoints →
SASP) plus any supply air reset that may be applied (Inputs →
RSET → SA.S.R).
OUTDOOR AIR CFM CONTROL — If an outdoor air cfm
flow station has been installed, the economizer is able to
provide minimum ventilation based on cfm, instead of
damper position. The outdoor air cfm reading can be found in
Inputs → CFM → O.CFM. During cfm control, the economizer
must guarantee a certain amount of cfm at any time for ventila-
tion purposes. If the outdoor air cfm measured is less than the
current calculated cfm minimum position, then the economizer
will attempt to open until the outdoor air cfm is greater than or
equal to this cfm minimum position. The following options are
used to program outside air cfm control.
Outdoor Air Cfm Sensor Enable (OCF.S) — If this option is
enabled, the outdoor air cfm sensor will be read and outside air
cfm control will be enabled.
Economizer Minimum Flow Rate (O.C.MX) — This option
replaces the Economizer Minimum Position (Configuration
→ ECON → EC.MN) when the outdoor air cfm sensor is
enabled.
IAQ Demand Vent Minimum Flow Rate (O.C.MN) — This
option replaces the IAQ Demand Ventilation Minimum
Position (Configuration → IAQ → DCV.C → IAQ.M) when the
outdoor air cfm sensor is enabled.
Economizer Minimum Flow Deadband (O.C.DB) — This
option defines the deadband of the cfm control logic.
The configurable deadband is added to the economizer’s
minimum cfm position and creates a range (ECMINCFM to
ECMINCFM ± OACFM_DB) where the economizer will not
attempt to adjust to maintain the minimum cfm position.
Increasing this deadband value may help to slow down exces-
sive economizer movement when attempting to control to a
minimum position at the expense of bringing in more ventila-
tion air than desired.
ECONOMIZER OPERATION CONFIGURATION — The
configuration items in the E.CFG menu group affect how
the economizer modulates when attempting to follow an
economizer cooling set point. Typically, they will not need
adjustment. In fact, it is strongly advised not to adjust these
configuration items from their default settings without first
consulting a service engineering representative.
In addition, the economizer cooling algorithm is designed to
automatically slow down the economizer actuator’s rate of
travel as outside air temperature decreases.
ECONOMIZER DIAGNOSTIC HELP — Because there are
so many conditions which might disable the economizer from
being able to provide free cooling, the control has a display
table to identify these potentially disabling sources. The user
can check ACTV, the “Economizer Active” flag. If this flag is
set to Yes there is no reason to check DISA (Economizer
Disabling Conditions). If the flag is set to No, this means that at
least one or more of the flags under the group DISA are set
to Yes and the user can discover what is preventing the econo-
mizer from performing free cooling by checking the table.