LENNOX
INSTALLATION INSTRUCTIONS
STANDARD MIXING BOX
INDUSTRIES INC.
ECONOMIZERS
LXIMB05
JUNE 7, 2004
EMD17 - 95 THRU 275
INSTALLATION INSTRUCTIONS FOR EMD17 MIXING BOX USED WITH CB17, CBH17
95 THROUGH 275 TON SERIES UNITS
I—SHIPPING AND PACKING LIST
RETURN AIR DAMPER
Package 1 of 1 contains:
1 - Mixing Box Assembly
1 - Wiring Diagram Sticker
3 - Wire Ties
12 - #10 - 18 x ½ SDST Screws
II—APPLICATION
EMD7 Mixing Boxes are used for automatic sensorcontrolled introduction of outdoor air into the system
through an electro-mechanically controlled damper.
III—INSTALLATION
1—Disconnect all power to unit.
FRESH AIR DAMPER
2—Determine the application upflow or horizontal.
Note: Wiring and controls are the same regardless of
size or application.
CONTROL ACCESS PANEL
Figure 1
A—For Upflow Application.
3—Attach mixing box over return opening with screws
provided. See Figure 2.
SUPPLY AIR OUTLET
4—Remove control access panel on mixing box and unit.
5—Remove and discard existing jumper (P3) on unit wiring
harness. Route mixing box harness and mixed air
sensor wiring over indoor air blower and make
necessary connections. Mixing box wiring harness
connector (P4) plugs into mating jack (J3) of unit wiring
harness or appropriate control module jack. Use wire
ties to secure excess coiled wire to blower motor
capacitor leads. See Figure 8 for jack/plug pin
designations.
WARNING
DO
NOT
CONNECT
ECONOMIZER PLUG P4 TO UNIT JACK J3
WHEN USING A TEMPERATURE CONTROL
SYSTEM (I.E. W973 CONTROL, W7400
CONTROL, WARM-UP KIT, OR NIGHT KIT).
CONTROL DAMAGE COULD RESULT. SEE
CONTROL WIRING DIAGRAM SECTION FOR
PROPER JACK/PLUG CONNECTIONS.
RETURN AIR INLET
CONTROL ACCESS
Figure 2
6—Replace control access panel on mixing box and unit.
SUPPLY AIR DUCT
7—Place return air duct and fresh air duct to mixing box
and seal weather tight. See Figure 3.
Note: Mixing box section maybe rotated 180o for
bottom return air connection. See Figure 4.
RETURN AIR DUCT
8—Locate mixing box wiring diagram sticker next to unit
wiring diagram.
9—Restore power to unit.
FRESH AIR DUCT
Figure 3
SUPPLY AIR DUCT
FRESH AIR DUCT
RETURN AIR DUCT
Figure 4
Note: Wiring and controls are the same regardless of
size or application.
B—For Horizontal Application.
3—Attach mixing box over return opening with screws
provided. See Figure 5.
4—Remove control access panel on mixing box and unit.
5—Remove and discard existing jumper (P3) on unit wiring
harness. Route mixing box harness and mixed air
sensor wiring over indoor air blower and make
necessary connections. Mixing box wiring harness
connector (P4) plugs into mating jack (J3) of unit wiring
harness or appropriate control module jack. Use wire
ties to secure excess coiled wire to blower motor
capacitor leads. See Figure 8 for jack/plug pin
designations.
RETURN AIR INLET
CONTROL ACCESS
Figure 5
WARNING
DO
NOT
CONNECT
ECONOMIZER PLUG P4 TO UNIT JACK J3
WHEN USING A TEMPERATURE CONTROL
SYSTEM (I.E. W973 CONTROL, W7400
CONTROL, WARM-UP KIT, OR NIGHT KIT).
CONTROL DAMAGE COULD RESULT. SEE
CONTROL WIRING DIAGRAM SECTION FOR
PROPER JACK/PLUG CONNECTIONS.
RETURN AIR DUCT
SUPPLY AIR DUCT
6—Replace control access panel on mixing box and unit.
7—Place return air duct and fresh air duct to mixing box
and seal weather tight. See Figure 6.
Note: Mixing box section maybe rotated 180o for
bottom return air connection. See Figure 7.
8—Locate mixing box wiring diagram sticker next to unit
wiring diagram.
FRESH AIR DUCT
Figure 6
9—Restore power to unit.
SUPPLY AIR DUCT
FRESH AIR DUCT
RETURN AIR DUCT
Figure 7
15-PIN PLUG
TERMINAL DESIGNATIONS
NOTE-Flattops indicate pins 1, 3 and 14.
Male (Plug)
Reference Tab
Indicates Pin 1
and top of plug
Female (Jack)
Flattop opposite
pin 1 is pin 3
Reference Tab
Indicates Pin 1
and top of plug
Single flattop on opposite side
of plug is pin 14
NOTE-To find a certain pin number, locate pins 1, 2 or 3 and
add 3 for each row as you proceed downward
Figure 8
2—On a call for heat during night operation (requires
optional night thermostat with clock), damper will
remain closed.
IV—OPERATION
A—Cooling Mode
1—On a call for cooling, with ambient temperature and
humidity above enthalpy control set point damper will
open to minimum vent position and cooling demand is
satisfied by compressor.
2—On a call for cooling, with ambient temperature and
humidity below enthalpy control set point the damper
will modulate to control supply air temperature at 55° F
(13° C). If additional cooling is required, compressor
will be energized through second stage of thermostat.
B—Heating Mode
C—Enthalpy Control
The enthalpy control senses both temperature and
humidity or the heat content of the outside air. It controls
whether outdoor air is brought into the system. When the
heat content of the outside air is below control setpoint, the
control permits outdoor dampers to operate. When the
heat content rises above control setpoint, the control
closes outdoor dampers to minimum position. The
recommended setpoint is “A”. If Economizer is allowing air
which is too warm or too humid to enter the system, control
may be changed to a lower setpoint (B, C, or D). Refer to
Chart 1.
1—On a call for heat during day operation, damper will
open to the minimum vent position.
Chart 1
V—SYSTEM CHECK
1—Disconnect main power to unit.
HONEYWELL DAMPER MOTOR
2—Install jumper to auxiliary contacts of blower contactor
in main unit control box.
3—Turn thermostat control to “OFF” position.
4—Remove control access cover. See Figure 1.
5—Install jumper on damper motor terminal T and T1. See
Figure 8.
6—Restore power to unit. Damper should drive to fully
opened position (requires 1 ½ minutes for full travel).
Observe travel for proper damper operation.
7—Disconnect power to unit. Damper should spring return
to closed position.
8—Remove jumper installed on Step 5 then restore power
to unit. Adjust minimum vent position on potentiometer
on control module. See Figure 9. Replace control
access cover.
9—Disconnect power to unit and remove jumper on
auxiliary contacts of blower contactor in main unit
control box. Restore power to unit.
Figure 9
VI—MAINTENANCE
1— Damper motor is prelubricated and does not require
further lubrication.
2—Make visual inspection of dampers and linkage
assemblies during routine maintenance.
ENTHALPY CONTROL
SETPOINT ADJUSTMENT
MINIMUM POSITION
CONTROL MODULE
Figure 10