Setting The Air/Gas Ratio; Setting The Co/Co2 - Worcester GREENSTAR Ri Installation And Servicing Instructions

SERVICE AND SPARES
6.6

SETTING THE AIR/GAS RATIO

NOTICE: THE SETTING OF THE GAS RATIO
MUST BE CARRIED OUT BY A COMPETENT
PERSON. SETTING OF THE GAS RATIO
MUST NOT BE ATTEMPTED UNLESS THE
PERSON CARRYING OUT THE TEST IS
EQUIPPED WITH A COMBUSTION
ANALYSER CONFORMING TO BS 7927 AND
IS COMPETENT IN ITS USE.
6.6.1 SETTING THE CO/CO
B Refer to section 6.2 and ensure that the gas inlet
pressure is correct before continuing.
B To adjust the CO/CO
2
operate the boiler at maximum output.
B Refer to section 6.4 for setting the boiler to maximum
and minimum output.
B Refer to table 20 and check the CO/CO
and if required adjust for maximum using a 2.5mm
Allen key.
B Check CO is less than 200ppm.
B Set the control to minimum.
B The boiler will go to minimum power.
B Measure the CO/CO and check against table 20.
2
If required set the minimum CO/CO
on the gas valve until the correct measurement is set:
– Remove dust cap with flat bladed screw driver.
– Using a 4mm Allen key adjust CO
– Replace the dust cap.
B Check that the CO is less than 200ppm.
B Return the boiler control to maximum and re-check
the CO/CO .
2
If correct, set the boiler control to normal "NORM".
B Re-fit the control cover
B Re-fit boiler outer case.
44
2
it will be necessary to first
at maximum
2
via adjuster (2)
2
.
2
MAX
1
2.5 mm
MIN
2
4 mm
Fig. 61 Gas valve adjustment
CO/CO settings for Greenstar Ri
2
CO/CO should be measured after 10 minutes.
2
Gas type
Natural gas 12 Ri
Natural gas 15/18/24 Ri
L.P.G.
NOTE: 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 tolerances given above, then the tolerance
is ± 0.2.
CO - less than 200 ppm (0.002 ratio)
Tab. 20 CO/CO settings
2
6 720 644 744a (2010/10)
6720643895-66.1Wo
CO max. CO min.
2 2
9.65% ± 0.5 8.65% ± 0.5
9.8% ± 0.5 9.2% ± 0.5
11.0% ± 0.5 10.5% ± 0.5