Bryant LEGACY 604D-A, Installation Instructions Manual

Page: 42 / 52

42
When demand ventilation control is not being used, the minimum
position potentiometer should be used to set the occupied ventilation
position. The maximum demand ventilation position should be
turned fully clockwise. Adjust the minimum position potentiometer
to allow the minimum amount of outdoor air, as required by local
codes, to enter the building. Make minimum position adjustments
with at least 10
_
F (12.2
_
C) temperature difference between the
outdoor and return--air temperatures. To determine the minimum
position setting, perform the following procedure:
1. Calculate the appropriate mixed air temperature using the
following formula:
(T
o
x OA/100) + (T
R
x RA/100) = T
M
T
O
= Outdoor--Air Temperature
OA = Percent of Outdoor Air
T
R
= Return--Air Temperature
RA = Percent of Return Air
T
M
= Mixed--Air Temperature
As an example, if local codes require 10% outdoor air
during occupied conditions, outdoor--air temperature is
60
_
F (15.6
_
C), and return--air temperature is 75
_
F
(23.9
_
C). (60 x .10) + (75 x .90) = 73.5
_
F (23.1
_
C)
2. Disconnect the supply air sensor from terminals T and T1.
3. Ensure that the factory--installed jumper is in place across
terminals P and P1. If remote damper positioning is being
used, make sure that the terminals are wired according to
Fig. 44 and that the minimum position potentiometer is
turned fully clockwise.
4. Connect 24 vac across terminals TR and TR1.
5. Carefully adjust the minimum position potentiometer until
the measured mixed--air temperature matches the calculated
value.
6. Reconnect the supply air sensor to terminals T and T1.
Remote control of the Economizer damper is desirable when
requiring additional temporary ventilation. If a field--supplied
remote potentiometer (Honeywell part number S963B1128) is
wired to the Economizer controller, the minimum position of the
damper can be controlled from a remote location. To control the
minimum damper position remotely, remove the factory installed
jumper on the P and P1 terminals on the Economizer controller.
Wire the field--supplied potentiometer to the P and P1 terminals on
the Economizer controller. See Fig. 43 and Fig. 44.
604D
--
--
A