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67
Economizer Actuator Communications
The configuration Economizer Control Type determines the
communication method, either digital or analog, used to
communicate between the ECB and the economizer actuator.
Economizer Control Type is accessible via the Scrolling
Marquee at
Configurations
→
ECON
→
E.CTL
.
The power to
the unit must be cycled after
E.CTL
is changed.
E.CTL = 1 (Digital/Position)
When
E.CTL
is set to 1, the ECB will communicate with the
economizer actuator using the digital protocol. The ECB 4 to 20
mA output will represent the actuator’s actual position. Because
the wiring has a built-in 500-ohm resistor, the 4 to 20 mA signal
is converted to a 2 to 10-v signal that is accessible via field
connection terminal board TB1-8 and TB1-9. However, before
this signal can be read, the violet wire that connects the actuator
to field connection terminal board TB1-J10-8 must be removed
or cut.
E.CTL = 2 (Digital/Command)
When
E.CTL
is set to 2, the ECB will communicate with the
economizer actuator using the digital protocol. The ECB 4 to 20
mA output will represent the actuator’s commanded position.
Because the wiring has a built-in 500-ohm resistor, the 4 to 20
mA signal is converted to a 2 to 10-v signal that is accessible via
field connection terminal board TB1-8 and TB1-9. However,
before this signal can be read, the violet wire that connects the
actuator to field connection terminal board TB1-J10-8 must be
removed or cut.
E.CTL = 3 (Analog Control)
When
E.CTL
is set to 3, the ECB will communicate with the
economizer actuator using the 4 to 20 mA analog signal wired to
TB1-8 and TB1-9 along with the 500-ohm resistor producing a 2
to 10-v signal for the actuator. While in this mode, the actuator’s
built-in 2 to 10-v feedback signal is accessible via TB1-9 and
TB1-10.
Unoccupied Free Cooling
The unoccupied free cooling algorithm attempts to maintain the
building space at the occupied cooling set point during
unoccupied periods if the conditions in the building and the
outdoors are suitable. Three different configurations define this
algorithm:
Unoccupied
Free
Cooling
(
Configuration
→
ECON
→
UEFC
), Free Cooling Preoccupancy
Time (
Configuration
→
ECON
→
FC.TM
) and Free Cool Low
Temp Limit (
Configuration
→
ECON
→
FC.LO
).
Configuration
→
ECON
→
UEFC = 0 (Disabled)
When
UEFC
= 0
, unoccupied free cooling is disabled.
Configuration
→
ECON
→
UEFC = 1 (Unoccupied)
When
UEFC
= 1
, unoccupied free cooling can occur whenever
the building is unoccupied.
Configuration
→
ECON
→
UEFC = 2 (Preoccupancy)
When
UEFC
= 2
, unoccupied free cooling can only occur when
the time to the next occupied period is less than
Configuration
→
ECON
→
FC.TM
minutes.
Configuration
→
ECON
→
FC.TM
FC.TM
is the configuration that determines how many minutes
before occupancy that free cooling can occur.
Configuration
→
ECON
→
FC.LO
Unoccupied free cooling cannot occur if the Outdoor Air
Temperature (
Temperature
→
AIR.T
→
OAT
) is less than
FC.LO
.
Power Exhaust
To enable power exhaust,
Configuration
→
ECON
→
PE.EN
must
be set to
ENBL
. If power exhaust is enabled, Power Exhaust 1
will turn on when the economizer position is greater than the
value of
Configuration
→
ECON
→
PE.1
. If power exhaust is
enabled, Power Exhaust 2 will turn on when the economizer
position
is
greater
than
the
value
of
Configuration
→
ECON
→
PE.2
. There are small time delays to
ensure that rapid cycling does not occur.
Optional Humidi--MiZer
t
Dehumidification
System
Units with the factory-equipped Humidi-MiZer option are
capable
of
providing
multiple
modes
of
improved
dehumidification as a variation of the normal cooling cycle. The
Humidi-MiZer option includes additional valves in the
liquid
line and discharge line of each refrigerant circuit, a small reheat
condenser
coil
downstream
of
the
evaporator,
and
Motormaster
®
variable-speed control of some or all outdoor fans.
Operation of the revised refrigerant circuit for each mode is
described below.
NOTE
: x = refrigerant circuit A, B, or C
Normal Cooling
Refrigerant flows from the outdoor condenser through the
normally open Cooling Valve (CV.x) to the expansion device.
Reheat1 Valve (RH1.x) and Reheat2 Valve (RH2.x) are closed.
(See Fig. 9.)
Reheat 1 (Subcooling Mode)
This mode increases latent cooling and decreases sensible cooling
compared to normal cooling. Refrigerant flows from the outdoor
condenser, through the normally open Reheat 1 Valve (RH1.x),
and through the reheat condenser coil to the expansion device.
Cooling Valve (CV.x) and Reheat2 Valve (RH2.x) are closed.
(See Fig. 10.)
Reheat 2 (Hot Gas Reheat Mode)
This mode provides maximum latent cooling with little to no
sensible capacity. This mode can operate to provide
dehumidification when there is no cooling demand. Like Reheat
1 mode, refrigerant flows from the outdoor condenser, through
the normally open Reheat 1 Valve (RH1.x), and through the
reheat condenser coil to the expansion device. The Cooling Valve
(CV.x) is closed. Reheat2 Valve (RH2.x) is open which provides
some compressor discharge gas to the reheat condenser to further
increase the reheat of the evaporator airstream. (See Fig. 11.)
48/
50P
G
C
03
--
16