Alpha 240, 280, 500 Instruction

Instructions for setting the b urner

pressures on the gas v alve

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.

Modulating
coil spring
clip

Modulating
coil

Burner pressure
test point

Room sealed
chamber
pressure tube

Inlet gas
pressure
test point

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.

Boiler Maximum Burner Pressure

mbar

36.6

35.0

35.0

LPG

in wg

14.6

14.0

14.0

240 Range
280 Range
500E

Nat gas

mbar

9.6

11.8

10.8

in wg

3.84

4.70

4.32

Locking nut (C)

Spindle (B)

Minimum burner
pressure adjusting
screw (A)

Minimum Burner Pressure

Nat gas LPG

mbar

in wg

mbar

in wg

1.1

1.5

1.9

0.44

0.60

0.76

6.2

4.0

5.8

2.84

1.60

2.32

Alpha Therm Limited.
Nepicar House, London Road, Wrotham Heath,
Sevenoaks, Kent TN15 7RS
Tel: [phone]

email: [e-mail]
website: www.alpha-boilers.com

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.

Compiled and designed by Publications 2000, Tel [phone]

02/04/D163