Power Exhaust - Lennox LCH036 Installation Instructions Manual

open at approximately 73°F. If the space temperature is too
warm, change the ODE STPT to "13.6" and the Unit
Controller will allow dampers to modulate open at
approximately 70°F.
TABLE 22
FREE COOLING SETPOINT - ODE STPT MODE
° °C)*
Enthalpy Setpoint F (
73 (23)
70 (21)
67 (19)
63 (17)
*
Approximate temperature at 50% relative humidity.
Free Cooling Differential Enthalpy - DIFF OFFSET
The Unit Controller allows damper modulation when
outdoor air is lower than return air by a differential or offset
temperature and humidity range. To set an offset range of
7°F at a constant relative humidity, enter "4" at the DIFF
OFFSET menu prompt. If return air is 76°F, the Unit
Controller will allow damper to modulate open at
approximately 69°F outdoor air. See table 23. If the space
temperature is too cool or dry, change the DIFF OFFSET to
"3" and the Unit Controller will allow dampers to modulate
open at approximately 71°F outdoor air.
TABLE 23
FREE COOLING SETPOINT - DIFF OFFSET MODE
*Temperature **Relative Hu­
Offset °F midity Offset %
2
3.5
5.3
7
*
At a constant relative humidity. **At a constant temperature.
C-Damper Minimum Position Setting
Use the menu path in figure 36 to set the minimum % open
damper position when outdoor air is not suitable for free
cooling. The minimum setpoint range is 0% open (dampers
closed) to 100% (dampers fully open). On units with staged
supply air blowers, refer to the
section in this manual
Drive
D-Units Equipped With An Energy Recovery Wheel
The economizer minimum damper position must be
adjusted to allow for the air resistance of the ERW.
1- Determine the required outdoor air CFM.
2- Apply the CFM to table 24 to determine the target static
pressure drop across the ERW.
3- Measure the static pressure drop across the ERW. See
figure 39.
Menu Entry - mA
12.0
13.6
15.5
17.6
Menu Entry
mA
6 1
12 2
18 3
24 4
Supply Air Variable Frequency
4- Adjust the minimum % open damper position (see
previous section).
5- Read the static pressure drop across the ERW and
adjust the minimum % open damper position as needed
to reach the target pressure drop.
Counts
150
Outdoor Flow - cfm
173
199
224
Counts
13
26
For example, a unit with an outdoor air flow of 6500 CFM
39
would require an ERW pressure drop of 0.9"w.c.
53
MEASURE ERW PRESSURE DROP
OUTDOOR
AIR
Page 40
TABLE 24
ERW PRESSURE DROP
Static Pressure - in. w.c.
3250
3500
3750
4000
4250
4500
4750
5000
5250
5500
5750
6000
6250
6500
6750
7000
7250
7500
7750
8000
8250
8500
8750
9000
Measure the static pressure
drop across the ERW
POWER
EXHAUST
RETURN
AIR
FIGURE 39
LGH/LCH420, 480, 540, 600
0.45
0.48
0.52
0.55
0.59
0.62
0.66
0.69
0.73
0.76
0.80
0.83
0.87
0.90
0.94
0.97
1.01
1.04
1.08
1.11
1.15
1.18
1.22
1.25