4.
Install the pressure regulating valve cap. Tighten
it handtight.
HEAT - GAS MODELS
Pilot, Thermocouple, Gas Combination Control
Valve, Main Burners
When heated, the pilot thermocouple supplies a
millivolt signal (DC) to an internal solenoid valve on
the gas combination control valve. The solenoid valve
is designed to shut off the gas flow to the pilot and
main burners in case of a malfunction in the system.
When energized by the thermocouple voltage, the
valve is held in the open position to permit gas flow.
The pilot burner flame is controlled by an adjustable
needle valve located under a small cap screw on the
combination control valve.
When experiencing nuisance pilot outages, visually
check pilot flame (Fig. 11) for the proper contact on
thermocouple and the flame color. Also, check to see
that unusually strong floor drafts are not interfering
with proper heating of the thermocouple by the pilot
flame.
NOTE:
If adjustments in gas or pilot pressure settings
are made, always replace the adjustment cover screw
to assure proper gas control operation.
The pilot flame should be a steady blue flame that
envelopes the thermocouple tip. The flame should be
about one inch long with half its length extending
beyond the outer edges of the pilot shield. If the pilot
flame does not appear to be this length and color, then
an adjustment is necessary. See Pilot, Thermocouple,
Gas Combination Control Valve, Main Burnersfor
examples of unsatisfactory pilot flames.
Fig. 11
NOTE:
The pilot operates unregulated at gas supply
pressures while the pressure regulator in the
combination control valve regulates pressure to the
main burners only.
Turn clockwise to decrease pilot flame and
counterclockwise to increase.
If adjustment does not result in a pilot flame of proper
size, then gas might not be flowing properly to the
pilot. Check for:
•
Plugged pilot orifice.
•
Kinked or plugged pilot gas supply tube.
•
Low gas supply pressure.
If these are acceptable, visually check:
•
The thermocouple tip (hot end) and tube lead for
kinks and pinches.
•
The thermocouple connector tip for corrosion,
tarnish and/or dirt.
If the pilot flame is correct and there are no drafts, then
the problem is in the thermocouple output voltage or
the gas solenoid valve in the combination control.
NOTE:
If a meter is not available, replace the
thermocouple with a new one and recheck operation.
VSX BOILER BASE SERIES CONVECTION STEAMERS - SERVICE PROCEDURES
Page 21 of 82
F24627 (0916)
