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Instructions for setting the burner
pressures on the gas valve
Alpha 240, 280 and 500 Boiler Range
1. GENERAL
The maximum and minimum burner pressures are factory set and should not require adjusting. However, if the gas valve
has been replaced, then these burner pressures must be set by adjustment on the gas valve. Refer to the Installation and
Servicing instructions for gaining access to and for replacement of the gas valve.
Note: Ensure that the plastic tube between the gas valve and the room sealed chamber is fitted correctly.
2. SET THE MAXIMUM BURNER PRESSURE
a. Loosen the burner pressure test point screw on the gas valve
and connect a pressure gauge.
b. Release the modulating coil spring and remove the coil from
the spindle (B).
c. Turn the screw (A) fully in by hand in a clockwise direction.
d. Release the locking nut (C) securing the spindle (B) to the gas
valve.
e. Set the selector switch to (DHW only) and fully open a hot
tap.
f. Rotate the spindle (B) to set the maximum burner pressure, i.e.
clockwise to increase the burner pressure, anti-clockwise to
decrease the burner pressure.
g. When the correct maximum burner pressure is obtained with
the room sealed chamber panel fitted, carefully tighten the
locking screw (C) to secure the spindle (B) - take care not to
allow the spindle to turn.
Note: With the locking nut tightened, check that the maximum
burner pressure is correct.
3. SET THE MINIMUM BURNER PRESSURE
The maximum burner pressure must be correctly set as described
above before the minimum burner pressure is set.
a. Turn the screw (A) anti-clockwise until the minimum burner
pressure is obtained with the room sealed chamber panel
fitted.
b. Replace the modulating coil and ensure it is secured with the
spring clip. Recheck the maximum burner pressure. Continue
to adjust and check until both the maximum and minimum
burner pressures are as shown in the table below.
c. Set the selector switch to '0' to turn off the boiler. Disconnect
the pressure gauge and tighten the test point screw.
d. Test for gas soundness using a suitable leak detection fluid.
Burner pressure
test point
Room sealed
chamber
pressure tube
Inlet gas
pressure
test point
Modulating
coil spring
clip
Modulating
coil
Locking nut (C)
Spindle (B)
Minimum burner
pressure adjusting
screw (A)
Boiler Maximum Burner Pressure
LPG
240 Range
280 Range
500E
Nat gas LPG
mbar
9.6
11.8
10.8
in wg
3.84
4.70
4.32
mbar
36.6
35.0
35.0
in wg
14.6
14.0
14.0
mbar
1.1
1.5
1.9
in wg
0.44
0.60
0.76
mbar
6.2
4.0
5.8
in wg
2.84
1.60
2.32
Minimum Burner Pressure
Nat gas
02/04/D163
Compiled and designed by Publications 2000, Tel (01670) 356211
These instructions have been carefully prepared but we reserve the right to
alter the specification at any time in the interest of product improvement.
© Alpha Therm Limited 2004.
Alpha Therm Limited.
Nepicar House, London Road, Wrotham Heath,
Sevenoaks, Kent TN15 7RS
Tel: 0870 3001964
email: [email protected]
website: www.alpha-boilers.com
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