Economizer; Economizer Changeover Select - Carrier WEATHERMASTER 48/50Z030-105 Operation And Service Manual

Table 55 — Dirty Filter Switch Points
ITEM EXPANSION
→
Configuration UNIT Filter
→ →
SENS FLT.S Stat.Sw.Enabled ?
→
Inputs GEN.I Filter Status Input DRTY/CLN FLTS
→
FLT.S
Monitoring of the filter status switch is disabled in the
Service Test mode and when the supply fan is not commanded
on. If the fan is on and the unit is not in a test mode and the
filter status switch reads "dirty" for 2 continuous minutes, an
alert is generated. Recovery from this alert is done through a
clearing of all alarms or after cleaning the filter and the switch
reads "clean" for 30 seconds.
NOTE: The filter switch should be adjusted to allow for the
operating cfm and the type of filter. Refer to the accessory
installation instructions for information on adjusting the switch.
The economizer control is used to manage
Economizer —
the outside and return air dampers of the unit to provide venti-
lation air as well as free cooling based on several configuration
options. This section contains a description of the economizer
and its ability to provide free cooling. See the section on indoor
air quality for more information on setting up and using the
economizer to perform demand controlled ventilation (DCV).
See the Third Party Control section for a description on how to
take over the operation of the economizer through external
control.
The economizer system also permits this unit to perform
smoke control functions based on external control switch
inputs. Refer to the Smoke Control Modes section for detailed
discussions.
Economizer control can be based on automatic control
algorithms using unit-based set points and sensor inputs. This
economizer control system can also be managed through exter-
nal logic systems.
The economizer system is a factory-installed option. This
option includes a factory-installed enthalpy control device to
determine the changeover condition that permits free cooling
operation. This unit can also have the following devices
installed to enhance economizer control:
• Outside air humidity sensor
• Return air humidity sensor
• Outside airflow control
NOTE: All these options require the controls expansion mod-
ule (CEM).
The Z Series economizer damper is managed by a commu-
nicating actuator motor(s) over the unit's Local Equipment
Network (LEN). This provides the ability of the control system
to monitor, diagnose and report the health and operation of the
actuator and damper system to the local display and CCN
network, thus providing extensive diagnostic tools to servicers.
SETTING UP THE SYSTEM — The economizer configura-
tion options are under the Local Display Mode Configuration
→
ECON. See Table 56.
Economizer Installed? (EC.EN) — If an economizer is not
installed or is to be completely disabled the configuration
option EC.EN may be set to No. Otherwise in the case of an in-
stalled economizer, this option must be set to Yes.
Economizer Actuator 2 Installed? (EC2.E) — For 48/50Z055-
105 units, a second economizer actuator is required. For sizes
055-105, set this configuration to Yes.
Economizer Minimum Position (EC.MN) — The configura-
tion option EC.MN is the economizer minimum position. See
CCN
RANGE
POINT
Enable/ FLTS_ENA
Disable
65
the section on indoor air quality for further information on how
to reset the economizer further to gain energy savings and to
more carefully monitor IAQ problems.
Economizer Maximum Position (EC.MX) — The upper lim-
it of the economizer may be limited by setting EC.MX. It de-
faults to 98% to avoid problems associated with slight changes
in the economizer damper's end stop over time. Typically this
will not need to be adjusted.
Economizer Trim for Sum Z? (E.TRM) — Sum Z is the
adaptive cooling control algorithm used for multiple stages
of mechanical cooling capacity. The configuration option,
E.TRM is typically set to Yes, and allows the economizer to
modulate to the same control point (Sum Z) that is used to
control capacity staging. The advantage is lower compressor
cycling coupled with tighter temperature control. Setting this
option to No will cause the economizer, if it is able to provide
free cooling, to open to the Economizer Max. Position
(EC.MX) during mechanical cooling.
ECONOMIZER OPERATION — There are four potential
elements which are considered concurrently which determine
whether the economizer is able to provide free cooling:
1. Dry bulb changeover (outside-air temperature qualification)
2. Enthalpy switch (discrete control input monitoring)
3. Economizer changeover select (E.SEL economizer
changeover select configuration option)
4. Outdoor dewpoint limit check (requires an installed out-
door relative humidity sensor installed)
Dry Bulb Changeover — Outside-air temperature may be
viewed under Temperatures
constantly compares its outside-air temperature reading against
the high temperature OAT lockout (OAT.L). If the temperature
reads above OAT.L, the economizer will not be allowed to per-
form free cooling.
NOTE: If the user wishes to disable the enthalpy switch from
running concurrently, a field-supplied jumper must be installed
between TB201 terminals 3 and 4.
Enthalpy Switch — The state of the enthalpy switch can be
→
viewed under Inputs GEN.I
installed as standard on all Z Series rooftops. When the switch
reads high, free cooling will be disallowed.
The enthalpy switch opens (reads high) when the outdoor
enthalpy is above 24 Btu/lb or dry bulb temperature is above
70 F and will close when the outdoor enthalpy is below
23 Btu/lb or the dry bulb temperature is below 69.5 F.
NOTE: The enthalpy switch has both a low and a high output.
To use this switch as designed the control must be connected to
the low output. Additionally there is a switch logic setting for
the enthalpy switch under Configuration
This setting must be configured to closed (CLSE) to work prop-
erly when connected to the low output of the enthalpy switch.
There are two jumpers under the cover of the enthalpy
switch. One jumper determines the mode of the enthalpy
switch/receiver. The other is not used. For the enthalpy switch,
the factory setting is M1 and should not need to be changed. See
Fig. 8 for a diagram showing the settings on the enthalpy switch.
Fig. 8 — Enthalpy Switch Jumper Positions
→ →
AIR.T OAT. The control
→
ENTH. Enthalpy switches are
→ →
SW.LG ENT.L.