Bard Economizer with exhaust WGEIFM-3C User Manual
Page 8
Manual 2100-498C
Page
8 of 17
EXAMPLE:
1. Measure return air temperature (RAT)
(assume 75° F for example).
2. Measure outdoor air temperature (OAT)
(assume 60° F for example).
3. Calculate the mixed air temperature (MAT)
which will result from the desired
combination of OAT (10 percent) and RAT
(90 percent).
.1 OAT + .9 RAT = MAT
or substituting example values
.1 (60° F) + .9 (75° F) = 73.75° F
4. Adjust the minimum position potentiometer
knob until proper mixed air temperature as
calculated above is reached. Care should
be taken to insure thermometer is sensing
air that is well mixed.
5. Mark correct setting on dial of minimum
position potentiometer for future reference.
D. Adjust the economizer logic module to
position A, B, C and D to achieve the
maximum combination of temperature and
humidity acceptable for the installation as per
Table 2. The suggested setting is between
A & B 70° DB @ 55 percent RH. It is
further recommended to always set the
control at C or above.) (See Figure 5.)
E. Switch the thermostat fan control to automatic
and position the heat/cool switch to cool.
Adjust the thermostat temperature to engage
the first stage of cooling only (Y). This will
cause the dampers to modulate to achieve
mixed air temperature of 55° provided outside
air enthalpy is sufficiently low. If enthalpy is
too high for economizing, low enthalpy can be
simulated by temporarily removing and
jumping leads on terminals 2 and 3 of
enthalpy control together. This will also cause
the economizer damper to modulate away
from minimum position. (Be sure to properly
reconnect leads at end of checkout
procedure).
F. Readjust temperature on the thermostat to
engage the second stage of cooling (Y2).
The damper motor should return to previously
set minimum position. Compressor motor
should start.
G. Switch thermostat to OFF fan and OFF heat/
cool positions to de-energize unit.
Economizer damper should return to full
closed (100 percent return air) position.
Checkout is complete.
14. Replace control access panel and mist eliminator.
15. Remove blank off plate or barometric fresh air
damper if installed on the service access panel. Plug
the four (4) holes used to mount the BOP or BFAD
with the plastic plugs supplied with the economizer.
16. Replace service access panel.
17. Economizer is now ready for operation.
TABLE 2
ECONOMIZER LOGIC CONTROL SETTING
l
a
i
D
g
n
i
t
t
e
S
H
R
%
0
2
H
R
%
0
5
H
R
%
0
8
y
p
l
a
h
t
n
E
l
o
t
n
o
C
g
n
i
t
t
e
S
A
F
.
g
e
d
0
8
)
C
.
g
e
d
6
2
(
F
.
g
e
d
3
7
)
C
.
g
e
d
3
2
(
F
.
g
e
d
6
6
)
C
.
g
e
d
9
1
(
B
F
.
g
e
d
6
7
)
C
.
g
e
d
4
2
(
F
.
g
e
d
0
7
)
C
.
g
e
d
1
2
(
F
.
g
e
d
3
6
)
C
.
g
e
d
7
1
(
C
F
.
g
e
d
4
7
)
C
.
g
e
d
3
2
(
F
.
g
e
d
6
6
)
C
.
g
e
d
9
1
(
F
.
g
e
d
9
5
)
C
.
g
e
d
5
1
(
D
F
.
g
e
d
1
7
)
C
.
g
e
d
1
2
(
F
.
g
e
d
3
6
)
C
.
g
e
d
7
1
(
F
.
g
e
d
4
5
)
C
.
g
e
d
2
1
(