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7.6.
Checking the gas valve setting
This Dorchester DR-SG storage tank has been adjusted
in the factory to work with group H (type G20) natural
gas with a supply pressure of 20 mbar.
IMPORTANT:
Any operations involving adjusting
the gas valve must be performed by
a qualified Gas Safe engineer or in
IE by a competent person.
The valve must be adjusted on the boiler operating at
the maximum power and the minimum power levels.
Valve adjustment must be done in “Manual power
setting mode” (see the instructions for the NAVISTEM
H3100 boiler controller) which allows a direct switch to
maximum power or minimum power (0% or 100%).
Start the burner at maximum power.
Using a combustion analyser, measure the CO
2
level in
the flue gas at the smoke nozzle..
Check the CO
2
value at maximum power and, if
necessary, adjust the gas flow screw of the valve in
order to obtain the CO
2
values that correspond to the
model (see following table).
Change to minimum power Qmin and check that the
CO
2
value is within the range in the table below. If
necessary, adjust the Offset regulator.
If the setting is adjusted to minimum power, go back
to maximum power and check the CO
2
value again.
Repeat the operation until two compliant values are
obtained.
Return to the standard operating mode.
figure 21 - Gas valve
Gas valve
Dorchester DR-SG XX-210
CO
2 adjustment screw
Qmax
Venturi
OFF SET
Qmin
CO
2 adjustment screw
Qmax
Venturi
Gas valve
Dorchester DR-SG XX-356
OFF SET
Qmin
CO
2 adjustment screw
Qmax
OFF SET
Qmin
Gas valve
Dorchester DR-SG XX-538
13.01.2023
Page 47 / 104
DORCHESTER DR-SG -
Installation, Operation and Maintenance