MicroMetl ECD-SRT SA Series - Economizer Configuration; Economizer Control Modes; Occupancy Control

5
d. The minimum position for the outdoor damper can be
congured at the controller. When not using CO2 sensors,
set the DCV Max potentiometer to completely closed
(CCW) to insure that the Minimum Position potentiometer
functions correctly. When using a remote minimum position
potentiometer, the Min Pos Pot on the controller must be fully
CW. See Fig. 11.
e. Settings on the, power exhaust and CO2 sensor can be
congured at the controller. See Fig. 11.
17. Check all wiring for safety then reapply power to the unit.
Verify correct operation and setting of the accessory(s) per the
Conguration and Operations sections of the instruction.
18. Replace the indoor fan motor access panel.
19. Replace the lter access panel. Slide top of panel into track and lift.
Push bottom of panel into place.
20. Install the economizer hood lter(s) by opening the lter clips which
are located underneath the hood top. Insert the aluminum lter(s)
into the bottom lter rack (hood divider). Push the lter into position
past the open lter clips. Close the lter clips to lock the lter into
place. (See Fig. 4.)
CONFIGURATION
ECONOMIZER CONTROL MODES — Determine the economizer
control mode before set up of the control. Some modes of operation may
require different sensors (See Table 3). The economizer kits for eld
installation are supplied from the factory with supply air temperature
sensors, low temperature compressor lockout switches, and outdoor air
sensors.
Table 5 - Supply Air Sensor Temperature/
Resistance Values
TEMPERATURE (F) RESISTANCE (ohms)
-58 200,250
-40 100,680
-22 53,010
-4 29,091
14 16,590
32 9,795
50 5,970
68 3,747
77 3,000
86 2,416
104 1,597
122 1,080
140 746
158 525
176 376
185 321
194 274
212 203
230 153
248 116
257 102
266 89
284 70
302 55
Fig. 11 - Economizer Controller Potentiometer
and LED Locations
Exhaust Fan
Setpoint
LED Lights When
Exhaust Contact
is made
Minimum Damper
Position Setting
Maximum Damper Demand
Control Ventilation
Setpoint
LED Light when Demand
Control Ventilation Input is
Above Setpoint
Demand Control
Ventilation Setpoint
LED Light when Outdoor Air
is Suitable for Free Cooling
Enthalpy
Changeover Setpoint
THERMOSTATS — The economizer control works with conventional
thermostats that have a Y1 (cool stage 1), Y2 (cool stage 2), W1 (heat
stage 1), W2 (heat stage 2), and G (fan). The economizer control does
not support space temperature sensors. Connections are made at the
thermostat section of the central terminal board located in the main unit
control box.
NOTE: When using differential enthalpy control and “integrated
economizer operation” is desired, a 2-stage cooling thermostat is required
even on 1-stage cooling units (e.g. 2-6 ton rooftop units). A thermostat
lead must be made between Y2-output on thermostat and Y2-input on
rooftop unit’s Central Terminal Board (CTB). Internal wiring between
Y2-input on the unit CTB and the economizer controller’s Y2 input
already exists in unit wiring harness and the economizer plug, so no eld
modications are required.
OCCUPANCY CONTROL (R22 MODELS) — The factory default
conguration for the economizer control is occupied mode. Occupied
status is provided by the black wire from Pin 3. When unoccupied mode
is desired, install a eld supplied timeclock function interrupting the
black wire to the N terminal. (See Fig. 7) When the timeclock contacts
are closed, the economizer control will be in occupied mode. When the
timeclock contacts are open (removing the 24-v signal from terminal N),
the economizer will be in unoccupied mode.
OCCUPANCY CONTROL (R410A MODELS) — The factory default
conguration for the economizer control is occupied mode. Occupied
status is provided by installing a eld-supplied timeclock function on
the OCCUPANCY terminals on the CTB (Central Terminal Board) in
the unit’s main control box and cutting the “CUT FOR OCCUPANCY”
jumper on the CTB (See Fig. 17). When the timeclock contacts are
closed, the economizer control will be in occupied mode. When the
timeclock contacts are open removing the 24v signal from terminal N,
the economizer will be in unoccupied mode.
SUPPLY / MIXED AIR TEMPERATURE (SAT) SENSOR — The
supply air temperature sensor is a 3 K thermistor located at the inlet of
the indoor fan. (See Fig. 9) This sensor is eld installed. The operating
range of temperature measurement is 0° to 158° F. See Table 5 for
sensor temperature/resistance values. The temperature sensor looks like
an eyelet terminal with wires running to it. The sensor is located in the
“crimp end” and is sealed from moisture.
LOW TEMPERATURE COMPRESSOR LOCKOUT SWITCH —
The economizer is equipped with a low ambient temperature lockout
switch located in the outdoor airstream which is used to lock out the
compressors below a 38° or 42° F ambient temperature. (See Fig. 1)