Sequence Of Operations - andrews 24/39 Installation And Service Manual

10 Appendix

10.3 Sequence of operations

Fig. 39
CONNECTION DIAGRAM
UPPER
LOWER
SENSOR
SENSOR
& ECO
GY
BK
GY
BK
BK
1 2
1 2 3
SENSOR 2
E-COM
WHERE USED
SENSOR 1
(SOME MODELS)
W
1
R
2
3 BK
24V
CONTROL
DISPLAY
1
2
SECONDARY
BL Y
1
24V
LOAD
2
LINE
3
120V
TRANSFORMER PRIMARY
WIRING DIAGRAM
GROUND
BLACK
SWITCH
115 VOLTS
Y
TSTAT
SENSE
HIGH VOLTAGE
W
SPARK
R
M
DAMPER MOTOR
Y
NOTE:
IF ANY OF THE ORIGINAL WIRES AS SUPPLIED WITH THE APPLIANCE MUST BE REPLACED.
IT MUST BE REPLACED WITH 18 GA STRANDED 105°C WIRE OR ITS EQUIVALENT.
SI UN DES CONDUCTEURS D'ORIGINE FOURNI AVEC L'APPAREIL DOIT ETRE REMPLACE
UTILISER UN CONDUCTEUR 18 GA STRANDED 105°C OU L'EQUIVALENT.
* For enable option (time control), break terminal
No.1 on secondary side of transformer
76
CONTROL
BR
7 8 9
24V
Y
4 5 6
R
1 2 3
W
SENSE
HIGH VOLTAGE
SPARK
24V
1
W
4 1 R
2
5 2
BK
BK
3
6 3
G
4 Y
W
LINE IN
DAMPER
PLUG CONNECTION
ON/OFF SWITCH
120 VOLTS AC
WHITE
115 VAC 115 VOLTS
W
24V
DISPLAY
PILOT
GAS VALVE
PV
R
R
Y
BR
R
MV
W
BK
1. Thermostat calls for heat.
The control board sends 24 volts from damper terminal #2
on the control plug to the flue damper.
2. Flue damper begins to rotate open. Once the flue damper is
GAS VALVE
fully open, the damper end switch closes and 24 volts is
MV
allowed to continue through damper to damper pin terminal
MVPV
#5.
PV
3. Trial for ignition (three 90 second ignition trials, with 65
PILOT
second pauses between trials).
Control Board simultaneously sends:
O 1. 24 volts from control pin terminal #8, to "MV/PV"
terminal of gas valve (common terminal).
2. 24 volts from control pin terminal #2, to "PV" terminal
of gas valve to establish gas flow at pilot.
3. Low current high voltage from "spark" terminal, to
generate spark at the pilot and ignite pilot gas flow.
M
4. Pilot flame proving signal (measured in micro-amps).
END SWITCH
from the "sense" terminal, to prove pilot flame.
OPEN/CLOSE
OUTPUT
4. Once pilot flame is proven, sparking will stop.
5. Once sparking stops, 24 volts is sent from control pin
terminal #5 on control board, to "MV" terminal on gas valve
to establish main burner gas flow. Main burners ignite from
the pilot flame.
6. The control board constantly monitors pilot flame through the
flame sensor rod. If pilot flame is lost, pilot and main burners
are shut down. After a 65 second inter-purge period, the
control will attempt to re-light the pilot beginning at sequence
3 above.
7. Main burner fires until the thermostat is satisfied. The control
board interrupts 24 volts through the damper and the gas
valve circuit. Pilot and main burners are turned off.
8. Flue damper rotates to the closed position.
LOCKOUT CONDITION
Control board will go into "Soft Lockout" if the pilot cannot be lit
after 3 ignition trials. The water heater display indicates a
lockout condition by showing an error code number (62 or 63)
with "Service Needed" in the display window. Refer to error
codes in the diagnostic section of this Service Manual. In a "Soft
Lockout" condition, the control will wait for 60 minutes and then
make 3 more attempts to light the pilot and establish the main
burners.
Soft lockout reset is accomplished by depressing the lower right
button under "Reset" for 3 seconds.
If the water heater should reach 93°C, then the high limit control
will shut off the burners and the water heater will go into a "Hard
Lockout". Error code 65 will be shown in the water heater
display. The control can only be reset in the "service mode",
which is detailed in the next section of this Service Manual.
Issue 2 14/07/16