Installation guide

COMMISSIONING SECTION 4
AIR/GAS
MIXTURE
ADJUSTMENT
The water heater gas/air mixture is adjusted at the factory for the proper mixture for
optimum combustion and ignition for the type of gas listed on the rating label. The water
heater should operate properly without requiring adjustment with the gas type shown on
the rating label. The following is a guide for the correct mixture adjustment settings in
case the gas content is different from the rating label or ignition is not satisfactory.
A combustion analyser is necessary for making gas/air mixture adjustments to determine
the correct setting.
The water heater cannot be converted from natural to L.P. gases or L.P. gas to natural gas,
without changing the gas valve/venturi assembly. Using L.P. gas on a water heater set up
for natural gases will result in rough ignitions and dangerous levels of carbon monoxide.
Do not attempt to adjust the venturi screws without a properly calibrated CO
2
/CO
combustion analyser. Making the mixture richer without an analyser to monitor the
adjustments can result in dangerous levels of carbon monoxide.
The venturi screw depth, when measured with a set of calipers, see fig.13, should be
approximately 13.0 - 13.5mm. The CO
2
range should be set as detailed in Table 1.
The CO content should be less than 50ppm.
If the CO
2
content is above the correct percentage then turn the venturi screw, see fig.14,
clockwise half a turn and recheck combustion. Repeat, if necessary until the correct
reading is achieved. Turn the venturi screw anti-clockwise if the CO
2
reading is less than the
stated figure or the ignitions are not smooth.
The burner assembly is factory adjusted for Propane Gas on LPG models. The nominal
venturi screw setting is the same as G20 Natural Gas, i.e. 13.0 - 13.5mm screw depth.
A gas inlet orifice is used on LPG models to use the same venturi screw setting. The CO
2
range for propane should be set as shown in Table 1, and adjustment carried out as
detailed above. The CO content should be less than 50ppm.
G20 (NATURAL
GAS, MOSTLY
METHANE) FAMILY
PROPANE GAS
MODELS
37
Fig.13