VHX SERIES STEAMERS - COMPONENT FUNCT I ON
F24700 (October 2001) Page 10 of 68
COMPONENT FUNCTION

CABINET BASE BOILER CONTROLS

Power Switch (ON/OFF) ......... When turned ON, supplies power to t he c ont rol circuit.
Reset Switch (Manual) .......... Resets the low water level safety circuit on initial startup or the
occurrence of a low water condition and all ows the boiler to fill with
water. Also, resets the high pressure level saf et y circuit on initial startup
or the occurrence of a high pressure condition and al lows the gas
ignition cycle to start.
Boiler Fill Solenoid Valve ........ Admits water to the boiler when demanded by the water lev el control to
maintain the correct water level in the boiler.
Cold Water Condenser
Solenoid Valve ................. Allows cold water flow into the boiler blowdown drain box to condense
steam and cool the hot water before its dischar ge i nto the drain.
Blowdown/Drain
Solenoid Valve ................. A normally open valve (N.O.) that closes to allow boiler to fill and
pressurize when power switch is turned ON and opens when power
switch is turned off to blowdown and drain the boil er. This valve i s
plumbed into the drain line of the boiler.
Cycling Pressure Switch ......... Controls boiler pressure between prescribed l imits by turning the heat
source on and off.
High Limit Pressure Switch ...... Protects the boiler from pressures above 15 psi by removing power from
the heating circuit. This pressure setting is higher than the cycl ing
pressure switch in order to turn off the heat source bef ore the boiler
pressure reaches its limit. Af t er the pressure drops below approximately
12psi, press the rest switch of the front control panel to rest the safety
circuit.
Main Water Level Control ........ A dual functioning control that allows water to fill and maint ai n the
proper level in the boil er providing diff erential water level c ont rol; and
shuts off the main gas val v e if the water lev el drops too low providing
low level cut-off protection. The water level control works by using three
different probe lengths to m onitor the water level. T he pr obes consi st of
a high level (HL), low lev el (LL) and low water cut-off ( LLCO ).
Auxiliary Water Level Control ..... A back up to the low level cut-off on the main control. Protects the boiler
and heating system components from a l ow water cut-off condition by
opening the 24VAC voltage path to t he heat ing system circuit. Also,
energizes the low water "light" on the front control panel.
Transformer ................... Provides 24VAC power to ignition control module and heating circuit.
Ignition Control Module ......... Controls and monitors gas heating. Energi z es pi l ot valve coil to supply
gas to pilot, generates spark to ignite gas at the pi lot, monitors the
presence of flame and energizes the m ain and pilot valv e coils on the
main gas valve upon a cal l for heat.
Main Gas Valve ................ A gas solenoid valve that opens to allow gas flow to the m ai n burner
after the successful igniti on of the pilot burner when a call for heat is
made.
Pilot Gas Valve ................ A gas solenoid valve that opens to allow gas flow to the pilot to ignite the
main burner when a call for heat is m ade. The valve is energi zed by a
time delay circuit on t he relay board during ignition tri al for
approximately 15 seconds. New style control s only.
Combustion Blower ............ Provides forced air to the gas/air mixture for gas pilot and main burner
combustion.