Unit installation

20
→HT.2), power is supplied to the second stage of the main gas
valve. If both stage 1 and stage 2 of the gas valve close, gas will be
turned off to the main burners.
Economizer
If an economizer is installed, then Economizer Installed
(Configuration→ECON→EC.EN) should be set to YES. The
economizer damper is controlled by the Econo Commanded
Position (Outputs→ECON→EC.CP) on the Economizer Control
Board (ECB). Feed back from the economizer actuator is output to
the ECB and is displayed as Econo Actual Position (Outputs
→ECON→EC.AP). The Economizer is used for ventilation,
cooling and to control the power exhaust. If the Indoor fan is not
on, the economizer will not operate.
Economizer Actuator Communication
The economizer actuator used with the 48/50LC units is a
Multi--Function Technology (MFT) actuator. This allows the
ComfortLink system to communicate with the actuator digitally
using Belimo MP protocol. The configuration Economizer
Control Type (Configuration→ECON→E.CTL) determines the
communication method, either digital or analog, used to
communicate between the Economizer Control Board and the
economizer actuator.
NOTE: The power to the unit must be cycled after the
Economizer Control Type (Configuration→ECON→E.CTL)
configuration parameter is changed.
E.CTL = 1 or 2 (Digital/Position or Digital/Command)
When Economizer Control Type (Configuration→ECON
→E.CTL) is set to 1, the Economizer Control Board will
communicate with the economizer actuator using the digital
protocol, from Economizer Control Board plug J7--1 to actuator
pin 5. The commanded position and the actuators actual position
are communicated back and forth between the actuator and the
Economizer Control Board. When the Economizer Control Board
and actuator first initiate communication, a Control Angle
(Operating Modes→ECON→C.ANG) is provided to the
Economizer Control Board and defines the actuator’s range of
motion. The control angle must be greater than the Min Actuator
Ctrl Angle (Configuration→ECON→M.ANG). During this
digital control, the Economizer Control Board analog 4 to 20 mA
output will represent the actuator’s actual position when E.CTL = 1
or commanded position when E.CTL =2. Because the wiring has a
built--in 500--ohm resistor, the 4 to 20mA signal is converted to a 2
to 10VDC signal at the actuator.
E.CTL = 3 (Analog Control)
When E.CTL is set to 3, the Economizer Control Board will NOT
communicate with the actuator using digital MFT. It will instead
control the economizer actuator directly with the 4 to 20mA analog
signal wired with the 500--ohm resistor producing a 2 to 10VDC
signal for the actuator. While in this mode, the actuator’s built--in 2
to 10VDC feedback signal can be read as actual position any time
because it is not used by the Economizer Control Board.
Minimum Ventilation
The economizer will open to allow ventilation when the indoor fan
is running and the unit is in the occupied state. The economizer
damper position at any given time for ventilation is displayed as
the Min Position in Effect (Run Status→ECON→EC.MP). This
minimum position can be effected by the indoor fan speed and
indoor air quality.
On Direct Drive ECM units, the economizer minimum position
will be equal to the ECON MIN at MAX Fan Speed
(Configuration→ECON→MP.MX), when running High Fan
Speed, ECON MIN at Low Fan Speed (Configuration
→ECON→MP.LO), when running Low Fan Speed, or ECON
MIN at VENT Fan Speed (Configuration→ECON→ MP.VT)
when running Ventilation Fan Speed, unless Indoor air quality
requests something different.
On Belt Drive VFD units, to maintain a constant airflow through
the economizer, as the indoor fan speed decreases or increases, the
damper minimum position will increase or decrease, respectively.
This relationship curve is shown in Fig. 6.
Units can also be equipped with optional CO
2
sensors for
additional indoor air quality control. When unit is equipped with a
return duct CO
2
sensor or return duct CO
2
sensor and outside air
CO
2
sensor the Economizer minimum position will be recalculated
basedontheCO
2
level of the return and/or outside air. On VFD
units the fan speed will also be used in recalculating minimum
position, as shown in Fig. 6. When the Commanded Fan Speed
(F.SPD) is less than the Supply Fan Maximum Speed (FS.MX) the
damper will operate in the shaded area of Fig. 6 based on the IAQ
Level (IAQ). See the Indoor Air Quality (IAQ) section (starting on
page 22) for more details on Demand Control Ventilation (DCV).
Economizer Position %
50
0
100
25
75
EC.MX
Minimum
Fan Speed
0 100 50 75 25 20
Fan Speed %
MP.MX
MP.75
MP.50
MP.25
AQ.MN for DCV
MP.75 DCV
MP.50 DCV
MP.25 DCV
C11544
Fig. 6 -- Minimum Damper Position Curve (on units with multiple fan speeds)
48/50LC