Measuring Co Content Of Flue Gas; Setting Gas/Air Ratio (Co 2 ) - Worcester GREENSTAR 24 Installation, Commissioning And Servicing Instructions

With a type C , C or C
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tightness of the flue system can be tested by
measuring the O or CO
2
The O level must exceed 20.6%. The CO
2
exceed 0.2 %.
▶ Remove sealing plug from air inlet sample port [2].
▶ Insert a flue gas probe into the test port and seal the test port
▶ Press the Central heating boost button until the button illuminates
and press once again to select
2
1
6720643895-67.1Wo
Fig. 62 Flue test ports
[1] Flue gas sample port
[2] Air Inlet sample port
▶ Allow the readings to stabilise and measure the O
▶ Refit sealing plug.
8.4

MEASURING CO CONTENT OF FLUE GAS

Use a multiport flue gas probe for this test.
▶ Remove sealing plug from flue gas sample port [1].
▶ Insert a flue gas probe as far as it will go into the test port and seal the
test port.
▶ Press the Central Heating boost button until the button illuminates
and press once again to select
▶ Run the boiler at maximum output for at least 10 minutes.
The CO must be less than 200 ppm
(0.002 ratio)
▶ Measure the CO levels.
▶ Repeatedly press the Central Heating boost button
extinguishes.
The display will show the CH flow temperature.
▶ Refit sealing plug.
8.5 SETTING GAS/AIR RATIO (CO
NOTICE: Gas/Air ratio
▶ Setting the gas/air ratio must be carried out by a
competent person. Testing must not be attempted
unless the person carrying out the combustion check
is equipped with a Combustion Analyser conforming
to BS 7927 and is competent in its use.
▶ Switch appliance off at the ON/OFF switch.
▶ Remove the outer casing.
▶ Switch appliance on at the ON/OFF switch.
▶ Remove sealing plug from flue gas test port (1).
6 720 811 922 (2014/07)
flue system, the gas
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content of the combustion air.
2
level must not
2
= maximum rated output.
1
2
1
2
and CO levels.
2 2
= maximum rated output.
until the light
)
2
▶ Insert a flue gas probe approx. 135 mm into the test port socket (1)
and seal the port.
▶ Hold down the Central Heating boost button
Press the button once again and the display shows the flow
temperature alternating with
▶ Measure the CO level.
2
▶ Using a 2.5mm Allen key, adjust the gas flow throttle [3] to set the
CO level for maximum rated output according to the table.
2
3
2
1
Fig. 63 Gas valve adjustment
[1] Gas supply pressure test port
[2] Adjusting screw for min. gas supply flow rate
[3 ] Adjusting screw for max. gas supply flow rate
Gas type
Natural gas H (23)
Checking tolerance
Adjustment tolerance
When checking an existing appliance the tolerance is  0.5%.
If checking after cleaning or component replacement or for adjustment
when the reading obtained is outside the tolerance given in table 25,
then the tolerance is  0.3 for maximum and  0.4 for minimum.
CO - less than 200 ppm (0.002 ratio)
Table 25 CO/CO Tolerances
2
▶ Press Central Heating boost button
The display shows the flow temperature alternating with
minimum rated output.
▶ Measure the CO level.
2
▶ Using a flat blade screwdriver, remove the dust cap from gas valve
adjusting screw
▶ Using a 4 mm Allen key, set CO
▶ Replace the dust cap after adjustment.
▶ Re-check settings at maximum and minimum rated output and re-
adjust if necessary.
▶ Record the CO levels in the Benchmark Commissioning checklist.
2
▶ Press the Central Heating boost button
extinguish.
The display will show the CH flow temperature.
▶ Remove flue gas probe from flue gas test port (1) and refit sealing
plug.
Service
until it illuminates.
= maximum rated output.
CO CO
2 2
Max. output Min. output
9.6 % 8.7 %
 0.5  0.5
 0.3  0.4
once again.
=
level for minimum rated output.
2
again and the light will
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