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AIR PRESSURE SWITCH
The air pressure switch is calibrated at the time of manufacture. The pressure switch contacts are
adjusted to close when the pressure detected at the test point is 150Pa or greater. Depending on the
installation it may be necessary to adjust the pressure switch setting.
WARNING: Under no circumstances is the pressure switch to be adjusted to cause the
contacts to close at a pressure less than 150Pa. Operation at a pressure of less than 150Pa
will cause damage to the water heater due to incomplete combustion.
If a pressure of 150Pa cannot be achieved it may be necessary to increase the fan speed from low to
medium or high. Refer to the section on 'Fan Speed Adjustment' on page 36.
To adjust the pressure switch
a.
Remove the fan chamber top panel.
b.
Remove the sealing screw from the test point in the tube between the
pressure switch and the fan (refer to figure 1 opposite).
c.
Connect a digital manometer to the test point (refer to figure 2 below).
NOTE: Ensure the manometer is calibrated prior to connection.
d.
Slightly loosen the union between the test point and the tube sensing
fan pressure.
e.
Undo the Phillips head screw (refer to Figure 4, item 1) and remove
the cover from the pressure switch.
f.
Allow the main burner to light.
The fan will be rotating during this procedure. Keep hands and
fingers will clear of the blade to prevent injury.
g.
Carefully rotate the pressure tube (refer to figure 3 below) away from
the fan while observing the pressure reading on the manometer.
h.
Rotate the dial (refer to figure 4, item 2) clockwise to increase the
pressure at which the contacts open or anticlockwise to decrease the
pressure at which the contacts open, the pressure setting is indicated
by the pointer (refer to figure 4, item 3). NOTE: The pressure marking
on the dial is indicative, some variance occurs due to losses in the
pressure tube.
i.
Once the correct pressure setting is achieved reposition the pressure
tube to the original position and tighten the union to prevent further
movement during operation.
j.
Remove manometer, refit test point screw and pressure switch cover
k.
Refit top panel.
ADJUSTMENT
35
Figure 1
Figure 2
Figure 3
1
3
2
Figure 4
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