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8 Gas Valve Cross Reference
Hot Surface Ignition (HSI)
The thermostat calls for heat and energizes the HSI control. If
system is equipped with prepurge, the purge fan is energized and
power will be delayed thirty seconds before application to the Hot
Surface Ignitor. If prepurge is not selected, the ignitor is powered
within one second. The ignitor heats up and at the end of the
heating period, the redundant and main valves are opened. A
ame must be detected within a xed time period or both valves
close, the ignitor is turned off and the HSI control locks out unless
the system is equipped with retry. Retry indicates the ignition
sequence will be repeated for a total of three tries if ame is
undetected or lost within 30 seconds of ignition.
Direct Spark Ignition (DSI)
The thermostat calls for heat and simultaneously energizes the
DSI control module and gas valve solenoid. Sparks at the ignition
electrodes ignite the gas at the main burner. Flame is sensed
through the electrodes by the ame detection circuit and shuts off
the sparking. If ame is not established within a xed time period
(lock-out time) main and redundant valves close, sparking ceases
and the control module locks out.
►System Applications
M
V
2
T
R
G
N
D
T
H
M
V
1
L
2
F
P
L
1
H
S
1
THERMOSTAT OR
CONTROLLER
ALTERNATE
LIMIT
L1
(HOT)
L2
LIMIT
CONTROLLER
FLAME
PROBE
RED
ADAPTER
BLUE
HOT
SURFACE
IGNITER
MV2
MV1
BURNER
GROUND
H
S
2
TRANSFORMER
GAS
VALVE
M
P
C
External
Jumper
Typical Wiring for Hot Surface Ignition System
Typical Wiring for Direct Spark Ignition System
ALTERNATE
LIMIT
TRANSFORMER
THERMOSTAT OR
CONTROLLER
L1 (HOT)
L2
SPARK
PROBE
MV
(GND)
LIMIT
CONTROLLER
FLAME
GAS
VALV E
MV
VAL
TR
TH
GND
FLY
LEAD
SPARK
Burner Ground
FLAME
PROBE
(GND)
MPC
External
Jumper