Benchmark Alpha E-Tec Plus 28 Installation And Servicing Instruction page 33

6.12 CO SET UP PROCEDURE
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The air gas ratio of the boiler has been factory set and should not require adjusting during first
commission. If adjustment is recommended or required the engineer must be competent to carry out this
work.
Before starting this procedure please check the following:
The front case is fitted.
The flue system is not blocked or restricted and is to the correct specification.
The gas supply working pressure is correct and the system has been purged.
There is no recirculation in the boiler flue circuit.
The condensate trap is pre-filled.
If the flow temperatures are getting up to maximum operating temperature during the procedure it is possible to open a hot
tap to lose the heat.
Attention: the CO checks must be carried out with the case fitted, while the gas valve adjustments must be carried out with
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the front case removed.
Calibration of the minimum CO
Refer to Section 6.6 and enter the chimney sweep mode (with no DHW demand) use the DHW down button to set the output
to minimum (0%). Insert the analyser probe into the flue test point (Fig. 6.3) and check that the CO
in Section 3.1, otherwise adjust the screw (Fig. 6.2) To increase the CO
direction and vice versa to decrease.
Calibration of the maximum CO
When you finish the minimum CO
to set the output to maximum (99%). Insert the analyser probe into the flue test point (Fig. 6.3) and check that the CO
is as specified in Section 3.1, otherwise adjust the screw (Fig. 6.2). To increase the CO
(Fig. 6.2) in a clockwise direction and vice versa to decrease it.
At every gas valve adjustment, it is necessary to wait for the boiler to stabilise itself at the value set (approx. 30 sec.).
Inlet pressure
test point
Fig. 6.2
(minimum output)
2
(nominal DHW output)
2
adjustment, while maintaining the chimney sweep function active, use the DHW up button
2
Outlet pressure
test point
Gas outlet flow
adjustment screw
(Max. CO )
2
Off/Set adjustment
screw (Min. CO )
2
Wiring plug
value, turn the adjustment screw in a clockwise
2
value, turn the adjustment screw
2
Air test point
A (-)
Fig. 6.3
Alpha E-Tec Plus 28, 33 and 38 - Commissioning
value is as specified
2
value
2
Flue test point
F (+)
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