PRESSURE
VALVE
APPLY LOCTITE
BYPASS GAS
SUPPLY TUBE
PILOT BUTTON
COMPRESSION
NUT
PRESSURE VALVE
COMPRESSION NUT
INJECTOR BODY
PILOT CONTROL VALVE
A. Removal
1. Loosen gas supply tube compression nuts and
remove gas tube. See Fig. 18.
2. Remove pressure valve from injector body by firmly
grasping the pressure switch and turning it counter
clockwise.
ATTENTION
■
The replacement pressure valve will ship with a small
tube of Loctite thread lock.
■
Apply Loctite sparingly (normally 2 drops is sufficient)
to the upper threads of the adapter. See Fig. 19.
■
Thread the pressure valve into the injector body. The
bottom of the valve should contact the injector body,
and the gas inlet of the valve is perpendicular to the
injector body.
FIG. 18
FIG. 19
B. Adjustment
The pressure valve is responsible for delivering gas to the
secondary orifice and in turn to the combustion cones.
Under normal operation, heaters within a specific zone will
modulate the heat output through a gas pressure range of
10 in. W.C. to 5 psig. To accomplish this full range of heat
modulation, gas pressure is constantly supplied to the
primary burner orifice and to the secondary orifice via the
pressure valve. The pressure valve is factory-set to open at
50-54 in. W.C. (approx. 2 psig) pressure. When the
thermostatic head opens on a call for heat gas pressure
between 2 and 5 psig gas is delivered to the combustion
cones through both the primary and secondary orifices for
full heat output.
Although rarely needed, the pressure valve may require
adjustment after significant operation time if it is observed
the pressure valve of a heater opens at a slower or faster
rate than other heaters within a zone. The opening point of
the pressure valve is indicated by observing the inner
combustion cone flame color and size. As the pressure
valve opens, the flame at the inner cone changes from a
light blue flame to a larger red/orange flame. This
procedure may require the assistance of another person.
INITIAL PPREPARATION
-- Close fuel supply to zone panel.
-- Clean heater thoroughly.
-- Connect an accurate 0-100 in. W.C. pressure gauge
to zone panel.
-- Remove spring from zone panel regulator. Replace
it with spring that allows pressure adjustment
range to 65 in. W.C. (Available from L.B. White,
Part # 21876)
-- Open fuel supply to zone panel and light heaters.
-- Adjust thermostatic head back to minimum setting.
PROCEDURE
It is suggested to perform this procedure in a low light
condition. Slowly increase gas pressure at zone panel
regulator to 52 in. W.C., observing the opening point of the
pressure valve. If the pressure valve opens at any pressure
other than 52 in. W.C., perform the following:
-- Remove pressure valve cap.
-- Turn the valve’s adjusting screw all the way in
(clockwise).
-- Set zone panel pressure to 52 in. W.C.
-- Slowly turn the pressure valve screw out
(counterclockwise) until the pressure valve opens.
COMPLETION
-- Replace pressure valve cap.
-- Adjust thermostat on zone panel to highest setting.
-- Remove test spring from regulator on zone panel
and replace with original spring.
-- Adjust thermostatic head to minimum temperature.
-- Set zone panel regulator to 10-12 in. W.C.
-- Set thermostatic head to desired temperature.
17
MAIN BURNER PRESSURE VALVE
GAS SUPPLY
TUBE
