Vulcan-Hart VSX24G Service Manual page 23

VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
Automatic Ignition Systems
When the main power switch is turned ON and the
ignition control modules reset switch is in the ON
position, the ignition control module (Fig. 12) is
energized with 24 volts between terminals five and six.
High voltage is sent from terminal nine to the spark
electrode and an output of 24 volts is sent from
terminals two and three to the pilot coil in the
combination valve, allowing gas to flow to the pilot.
The sparking will continue for 90 seconds or until the
flame sensor has confirmed that an adequate pilot
flame is present.
Once the pilot flame is confirmed, a 24 volt output from
terminal one will be sent, allowing the cycling coil of
the combination valve to operate at the request of the
cycling pressure switch.
Fig. 12
Terminals
1. Main Voltage. 24VAC will be present on terminal
#1 with the pilot sensing electrode sensing an
adequate pilot fame. This output will remain
present as long as the pilot flame remains
adequate.
2. Common (MV/PV).
3. Pilot Voltage. 24VAC will be present on terminal
#3 at the instant an input voltage is supplied to
the module. This voltage will remain present on
terminal #3 providing an adequate pilot flame is
established within 90 seconds. In the event that
an adequate pilot flame is not established within
90 seconds this output voltage will drop out.
4. Ground (Burner).
5. Ground (24VAC Neutral).
6. 24VAC Input.
7. High Voltage. This signal is supplied to spark
electrode (The pilot flame current is sensed by
the module via the spark electrode high voltage
wire and terminal #9).
Spark Ignition Control Test
1. If the ignition control module does not appear to
be sparking to ignite gas, perform the following
checks:
A. Check to ensure that all electrical terminal
connections on the ignition control module
and the ignitor are clean and tight.
B. Verify that the ignition control module and
the ignitor have good ground wire
connections. The ignitor mounting bracket
should have good metal to metal contact to
its mounting surface.
C. Turn the main power switch ON. Turn the
ignition control modules re-set switch OFF
then ON.
D. Check for 24VAC output on the ignition
control module transformer.
1)
2)
2. If the ignition control module and transformer are
functioning properly, then check the following
ignitor conditions.
A. The gap between the spark probe (Fig. 13)
and the ground clip should be approximately
1/8 inch. If the gap appears to be excessive
or poor sparking is occurring, remove the
electronic ignition pilot and adjust gap.
Page 23 of 82
If 24VAC is present then replace
ignition control module and re-test.
If 24VAC is not present then ensure
that transformer is receiving 120VAC
input. If ignition control module
transformer is receiving proper
voltage, then replace ignition control
module transformer and re-test.
F24627 (0916)