Check the thermocouple output voltage (DC millivolts)
as follows:
1.
Use a VOM and adapter to take a closed circuit
reading with the pilot on.
2.
Take an open circuit reading as follows:
A.
Disconnect the thermocouple tube from the
valve.
B.
Connect the meter leads to the tube and
threaded end.
C.
Manually press and hold down OFF/PILOT/
ON knob and light the pilot,
D.
Allow the pilot to heat the thermocouple for
one to two minutes and compare the
readings with the table below.
Thermocouple Output (DC
Millivolts)
Closed Circuit
Open Circuit
Typical
15
NA
Range
10 - 20
20 - 35
NOTE:
The connection of the tubing from the
thermocouple tip to the control valve is an electrical
connection and must be clean. Do not use any sealing
compound on the threads or over tighten the threaded
connection.
If either of the readings is less than the minimum or
thermocouple is not operating as described, replace
the thermocouple as follows:
1.
Remove the pilot assembly by disconnecting
thermocouple and pilot gas supply tubing from
the combination control valve.
2.
Remove the two screws holding the pilot
assembly to its bracket.
3.
Replace the thermocouple or pilot assembly.
4.
Use two screws to secure the pilot assembly to
the bracket.
CAUTION
Over tightening the nut can crush the
insulator and short the thermocouple.
5.
Finger tighten the thermocouple nut plus 1/4 turn
with a wrench.
All gas joints disturbed during
servicing must be checked for leaks. Check with a
soap and water solution (bubbles). Do not use an open
flame.
6.
Connect the pilot gas supply tubing to the
combination control valve and tighten finger tight.
7.
Check for proper operation.
Shut off the gas before servicing the
unit.
All gas joints disturbed during
servicing must be checked for leaks. Check with a
soap and water solution (bubbles). Do not use an open
flame.
Disconnect the
electrical power to the machine and
follow lockout / tagout procedures.
CAUTION
Gas combination control valves are not
serviceable and should not be disassembled. Do not
attempt to repair the gas combination control valve, it
must be replaced.
If, after replacing thermocouple, the pilot or main
burners are still not functioning properly, the gas
combination control valve should be replaced as
follows:
1.
Remove the two screws and the control box
cover.
2.
Disconnect electrical supply wires and conduit
running to the combination control valve.
3.
Disconnect the thermocouple lead and pilot gas
supply tube from control and pipe connections on
each side of the control.
4.
Reverse procedure to install the replacement
valve.
5.
Check the unit for proper operation.
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.
Replace the main burners as follows:
1.
Lift burner and slide it to the rear just enough to
clear the gas orifice hood.
2.
Lower the front end of burner and bring it forward
under the manifold pipe.
3.
Remove the burner from the unit.
NOTE:
When reinstalling burners, ensure that
locating pin is in the hole for proper positioning and to
prevent burner from rolling over.
4.
To reinstall, reverse the steps above.
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
F24627 (0916)
Page 22 of 82
