SERVICE AND SPARES
6 720 821 670 (2018/06)
47
7.6
SETTING THE AIR/GAS RATIO
7.6.1
Setting the CO/CO
2
▶ Refer to section 7.2 and ensure that the gas inlet pressure is correct
before continuing.
▶ To adjust the CO/CO
2
it will be necessary to first operate the
appliance at maximum output.
▶ Refer to section 7.4 for setting the appliance to maximum and
minimum output.
▶ Refer to table 34 and check the CO/CO
2
at maximum. If required set
the maximum CO/CO
2
via adjuster (1) on the gas valve using a
2.5mm Allen key.
▶ Check CO is less than 200ppm.
▶ Set the control to minimum (MIN).
▶ The appliance will go to minimum power.
▶ Measure the CO/CO
2
and check against table 34.
If required set the minimum CO/CO
2
via adjuster (2) 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
2
.
– Replace the dust cap.
▶ Check that the CO is less than 200ppm.
▶ Return the appliance control to maximum and re-check the CO/CO
2
.
If correct, set the appliance control to normal “NORM”.
▶ Re-fit the control cover
▶ Re-fit appliance outer case.
Fig. 57 Gas valve adjustment
7.7
CLEANING THE HEAT EXCHANGER
▶ Isolate the power to the appliance and remove outer case and base
panel.
1. Refer to figure 58 and remove the clip from gas valve outlet.
2. Pull the gas outlet elbow free from the gas valve.
Fig. 58 Gas valve connection
▶ Remove electrical connector and earth wire from fan.
▶ Disconnect spark electrode and flame sensor connections.
1. Refer to figure 59 and undo the securing nut on the top of the heat
exchanger and remove the retaining plate assembly.
Fig. 59 Securing nut
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.
CO/CO
2
values
CO/CO
2
should be measured after 10 minutes.
Gas type
CO
2
max.
CO
2
min.
Natural gas: 9 - 21kW outputs
9.6%
±
0.5
8.6%
±
0.5
Natural gas: 24kW output
9.55%
±
0.5
8.55%
±
0.5
LPG: All outputs
10.5%
±
0.5
10%
±
0.5
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)
Table 34 CO/CO
2
settings
6720643895-66.1Wo
2
1
MAX
MIN
2.5 mm
4 mm
NOTICE:
COMBUSTION TESTING
▶ Combustion testing 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.
NOTICE:
CO/CO
2
CHECKS
▶ If the joint between the Air/Gas manifold and heat
exchanger is disturbed, replace the sealing gasket.
▶ After completing the service of the appliance, the
CO/CO
2
must be checked and set to the limits shown
in “Setting the air/gas ratio” on page 47.
There is a special accessory kit available specifically
designed for cleaning the heat exchanger. If required
order 7 716 192 312.
If the plastic elbow can not be easily removed, undo the
nut to push the plastic elbow out of the fitting.
To prevent damage to the electrodes when removing the
air/gas manifold, disconnect the leads to the electrodes.
1.
2.
6720643895-72.1Wo
1.
6720643895-60.1W
o
Summary of Contents for Worcester GREENSTAR 12Ri ErP +
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