Alpha CB Boiler Range Instructions For Adjusting A Replacement Printed Circuit Board

Instructions for adjusting a
replacement printed circuit board
Alpha CB/SY/C Boiler Range

1. GENERAL

When the Printed Circuit Board (PCB) is replaced the following adjustments must be carried out:-
a. Set the ignition gas rate so that the ignition of the burner is smooth and quiet.
b. Adjust the central heating output.
c. Ensure that the JP1 plug is correctly positioned for the type of gas the boiler is being used with.
MET - Natural Gas
d. Ensure that all electrical plugs and connectors are pushed fully home and soundly connected.
Note: Before fitting a new PCB ensure the polarity of the electrical supply is correct by testing the supply, using a
suitable multimeter, as follows:-
Live to Neutral
Live to Earth
Neutral to Earth
Note: i) Before fitting the PCB, carefully bend the red and yellow neons through 180° so that they locate into the
control panel - see Fig. 1 or 2.
ii) When the selector switch is turned to the reset position, there will be a delay of approximately 30 seconds
before the PCB will reset.

2. FIT AND ADJUST THE REPLACEMENT PCB

Refer to the Installation and Servicing instructions for gaining access to and for replacement of the PCB. To adjust the
PCB the gas valve burner pressures must be measured. Loosen the burner test point screw on the gas valve and
connect a pressure gauge. After adjusting the PCB disconnect the pressure gauge, tighten the test point screw and
test for gas soundness using a suitable leak detection fluid.

Set the Ignition Gas Rate (IGR)

When there is a demand for either Heating or Hot Water, the burner will light at the IGR approximately 5 - 10 seconds
until the flame sensing electrode detects the flame, then the burner pressure will increase to the required output.
During the first 5 seconds the IGR pressure must be read on the pressure gauge. If the ignition gas rate is incorrect,
adjust the IGR pressure as follows:-
a. Set the selector switch to
b. Carefully locate a small insulated screwdriver into the potentiometer P3 (IGN CAP) - see Fig. 1 or 2.
c. Fully open a hot water tap so that the boiler fires and record the IGR.
d. If the IGR is incorrect, rotate the screwdriver (Clockwise to Increase - Anticlockwise to Decrease), to achieve a
smooth ignition (see table below).
e. After each adjustment of the potentiometer, repeat the above process from paragraph c.
LPG - Liquefied Petroleum Gas
240 Volts AC
240 Volts AC
zero Volts AC
(DHW only) and turn the hot water thermostat to the maximum position.
Boiler
CB24, CB24X, SY24
CB28, CB28X
CB50
C23/27
IGR Pressure (Approx.)
Nat. Gas
mbar in w.g. mbar
5.0 2.0 10.0
5.0 2.0 10.0
3.0 1.2 10.0
5.0 2.0 10.0
LPG
in w.g.
5.2
5.2
5.2
5.2