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ST9103A Blower Control Board (Figure 8)
−5 units
All O23, OHR23 and OF23 −5 oil units utilize the ST9103A
(A15) blower control manufactured by Honeywell. The
ST9103A is a printed circuit board which controls the supply
air blower and monitors the limit controls and oil burner opera
tion. The control has a nonadjustable, factory preset fanon"
timing. Fan off" timing is adjustable. See figure 8 and
table 3 for ST9103A terminal designations
DANGER
Shock hazard. Avoid personal injury. Make sure to
disconnect power before changing fan off" timing.
Blower Operation and Timing
The fan on time of 30 seconds is not adjustable. Fan off
time (time that the blower operates after the heat demand
has been satisfied) can be adjusted by moving the delay
switches on the fan control board. Fan off time will affect
comfort and is adjustable to satisfy individual applications.
See figure 7. Set the heat fan off delay switches to either
60, 90, 120, or 150 seconds. The factory setting is 90 sec
onds.
NOTEIf fan off" time is set too low, residual heat in
heat exchanger may cause primary limit S10 or auilary
limit S21 to trip resulting in frequent cycling of blower. If
this occurs, adjust blower to longer time setting.
Thermostat Connection
Thermostat wires are connected directly to the terminlas on
the ST9103A board. See figure 8.
Continuous Blower
If the ST9103A blower control board is wired for continuous
blower, the blower will energized on low speed and remain
energized when heat or cool demand is satisfied. Continuous
blower will also energized when indoor thermostat is left in the
OFF mode.
150 sec
Figure 7
Fan Off Delay Switch Settings
120 sec
90 sec
60 sec
ON
ON
ON
ON
Figure 8
ST9103A Blower Control Board
thermostat
terminal strip
fan off
delay switches
120V
TABLE 3
BLOWER CONTROL A15 TERMINAL DESIGNATIONS
J58 Pin #
Function
1
Limit S10
2
L1 120V
3
T1 24V
4
L2 Common
5
Jumpered to Pin 4
6
T2 24V
7
Combustion Air Inducer
120V
8
Jumpered to Pin 7
9
Limit S21 (if used)
Thermostat Connections
G
Blower Demand
W
Heating Demand
R
24V
Y
Cooling Demand
C
Common
24 VAC CONNECTIONS
X
24V Transformer
C
Common Transformer
120 VAC
S2
Line
S3
120V To Transformer
N, 2, 3, 4, 6, 7
Neutral
CONT
Continuous Blower
COOL
Cool Tap
HEAT
Heat Tap
