Outdoor Air Cfm Control - Lennox LCH036 Installation Instructions Manual

Optional Outdoor Air CFM Control
Outdoor air CFM Control is a factory-installed option
available on units equipped with a supply air variable
frequency drive (VFD) and economizer.
The Unit Controller modulates outdoor air dampers to
maintain a constant amount of outdoor air regardless of
blower speed. This
requirements are met at lower supply air volumes.
The Unit Controller uses a velocity sensor (A24) to
modulate dampers. The sensor is located in the outdoor air
stream. See figure 51.
Set Outdoor Air CFM Mode DIP switches as shown in
figure 52.
Set Damper Minimum Position
1-Operate unit at full supply air CFM with all zone dampers
open. Refer to VFD Supply Air Blower Start-Up section
in this manual.
2- Use an air flow hood to measure the outdoor air CFM
entering the unit.
O
N
VAV GP
GP VAV
MGV
AO2
AO1
RLY HB
507232-02 9/2015
ensures minimum ventilation
OUTDOOR AIR CFM MODE DIP SWITCHES
O
N
A133
O
N
VAV GP
GP VAV
MGV
RLY
GND
A4 A3 A2 A1 NO H C D2 D1
RLY HB
TB18
S−BUS
− S +
SCALE 2.000
3- Adjust the minimum % open damper position until the
air flow hood reads the design minimum outdoor air
CFM. See figure 36.
NOTE - Refer to local codes or authorities having
jurisdiction when determining design minimum outdoor air
requirements.
DOWNFLOW
OA FILTER
OUTDOOR
AIR
SENSOR LOCATION IN
DOWNFLOW DIS­
CHARGE APPLICATIONS
1 2
RLY
AO2 GND
AO1 A4 A3 A2 A1 NO H C D2 D1
TB22
24VAC O 24VAC
THERMOSTAT
L O
G W1 Y1 Y2 O G
R C W2 R C
FIGURE 52
Page 49
VELOCITY SENSOR LOCATION
SENSOR LOCATION IN
HORIZONTAL DISCHARGE
APPLICATIONS
HORIZONTAL
OA FILTER
RETURN AIR
FIGURE 51
SENSOR
SENSOR OUTPUTS SMOKE INPUTS
IAQ
24VAC
DI1
AI1 HUM TMP
D01 D02
R C DI2 R DI3 R
HUMIDISTAT
DI4 C