VSX SERIES STEAMER - SERVICE PROCEDURES
Page 22 of 80
Check the thermocouple output voltage (DC
millivolts) with a VOM. If a meter is not available,
replace the thermocouple with a new one and
recheck operation. First, take a closed circuit
reading (adaptor required) with the pilot on. Next,
take an open circuit reading by disconnecting the
thermocouple tube from the valve and connecting
meter leads to the tube and threaded end. Manually
press and hold down OFF/PILOT/ON knob and light
the pilot. Allow the pilot to heat the thermocouple for
one to two minutes and compare the readings with
the chart below.
THERMOCOUPLE
MV
READINGS
CLOSED
CIRCUIT
OPEN
CIRCUIT
Typical 15
Range 10 - 20 20 - 35
If either of the readings is less than the minimum or
thermocouple is not operating as described, replace
the thermocouple. To replace, remove the pilot
assembly by disconnecting thermocouple and pilot
gas supply tubing from the combination control
valve and remove the two screws holding the pilot
to its bracket. Replace the thermocouple or pilot
assembly and check for proper operation. If after
replacing thermocouple, the pilot or main burners
are still not functioning properly, then a problem in
the gas combination control valve exists as well.
Replace the combination control valve as outlined in
“GAS COMBINATION CONTROL VALVE
REPLACEMENT” then check for proper operation.
NOTE:
Gas combination control valves are not
serviceable and should not be disassembled. Once
you have isolated the problem to this control,
replace it. Do not attempt to repair the assembly.
The main burners are lanced port steel burners (5 or
7 burners, depending on the unit) and have
adjustable air shutters. Fixed orifice type hoods are
used to establish the gas flow to each burner. Set
each burner air shutter opening just large enough to
eliminate any yellow tip in the burner flame.
To remove main burners, lift burner and slide it to
the rear just enough to clear the gas orifice hood.
Lower the front end of burner and bring it forward
under the manifold pipe. When reinstalling burners,
ensure that locating pin is in the hole for proper
positioning and to prevent burner from rolling over.
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 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.
Terminals:
1. Main Voltage
- 24V AC 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
- 24V AC 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. 24V AC Input.
7. High Voltage to spark electrode (The pilot
flame current is sensed by the Ignitor Module
via the spark electrode high voltage wire and
terminal #9).
