Filter
Top Products
d. After installation is complete, calculate the mini-
mum airflow across the economizer. To calculate the
minimum airflow, the following data is needed:
total cfm (cfm
3
), temperature of the total cfm (T
3
),
temperature of the return air (T
2
), and tempera-
ture of the entering outside air (T
1
). Cfm
1
is the
outside air cfm, which will be the minimum airflow.
Insert the data into the following equations:
T
1
(cfm
1
)+T
2
(cfm
2
)
=T
3
cfm
3
cfm
2
= (cfm
3
− cfm
1
)
Therefore:
T
1
(cfm
1
)+ T
2
(cfm
3
− cfm
1
)
=T
3
cfm
3
Use this equation to determine cfm
1
, which is the
minimum airflow across the economizer.
(T
3
−T
2
) cfm
3
cfm
1
=
(T
1
−T
2
)
If cfm
1
does not match the desired minimum air-
flow from Step 1, readjust the minimum position
setting screw.
6. Determine the enthalpy changeover set point from
Fig. 28. The enthalpy changeover set point should be
set to return the outdoor air damper to the minimum
position when enthalpy rises above the set point. The
settings areA, B, C, and D. Set the enthalpy changeover
per the setting in Fig. 29.
7. Replace outdoor-air opening panel using screws from
Step 2. Replace filter access panel. Ensure the filter
access panel slides along the tracks and is securely en-
gaged. See Fig. 30.
8. Fasten hood top and side plate assembly (Fig. 31) to
outdoor-air opening panel with screws provided.
9. Slide outdoor-air inlet screen into screen track on hood
side plate. While holding screen in place, fasten screen
retainer to hood using screws provided. See Fig. 32.
NOTE: Refer to Fig. 33 for PARABLADE economizer baro-
metric relief damper characteristics.
MINIMUM
POSITION
OPEN
3
1
T
P
P1
T1
4
2
5
S
S
O
D
C
TR
B
REV. B
198818A
%
H
U
M
I
D
I
T
Y
90
70
60
30
10
D
C
B
A
60
65
70
75
55
50
85
80
DAMPER
DAMPER
CLOSED
OPEN
OUTDOOR TEMP.
°F
REV.
97-3672
CW–SETPOINTS–CCW
CONTACTS SHOWN IN HIGH ENTHALPY
RUSH AT 24VAC
3 mA MIN. AT 11 VDC
CONTACT RATINGS: 1.5A RUN, 3.5A IN
OR UNPOWERED STATE
1
2
3
TR
TR1
24VAC
ENTHALPY
CONTROL
Fig. 25 — Outdoor-Air Thermostat/
Enthalpy Control Installation
OAT — Outdoor-Air Thermostat
NOTE: See unit wiring diagram for details.
Fig. 26 — Wiring Connections for Outdoor-Air Thermostat
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
100
200 300 400
500 600
700
800
CFM
PRESSURE DROP (in. wg)
Fig. 27 — Durablade Economizer Barometric Relief
Damper Characteristics
—15—