32
SECTION E - SERVICE AND MAINTENANCE
8.1 FIRST START
The start-up of the heater shall be carried out by expert
operator, trained on the gas-fired heater function and
safety.
First check the data reported on the heater’s label
match with the gas and power supply data; check the
air combustion and exhaust ducts have been installed
in compliance with the local regulation and there isn’t
any obstacle to the air and exhaust flow along the duct
till the terminals;
check all the safety devices are correctly installed
along the gas supply line.
Once started the unit, check the static and dynamic
gas pressure, which shall be within the required range.
Then check the gas valve adjustment by means ofCO2
test, with reference to the table 16.
If the CO2 value isn’t within the required range,
the operator shall find the proper adjustment of the
valve.
The unit is delivered to run methane gas; if different
type of gas is supplied, the operator shall first
replace the gas nozzle with the proper one following
the procedure described in chapters 8.2
8.2 HOW TO ADJUST THE GAS VALVE (or the
combustion’s parameters)
Gas valve function
The gas valve installed in the MEC MIX heater is air/
gas 1:1 type, which maintains the gas delivery pressure
PINT equal to the sum of the detected air pressure
and the offset value adjusted by the screw:
PINT = Pa+Os
where Pa is the detected air pressure and Os is the
offset value. This relation is shown in the graphic in
picture 31.
The ratio Qa / Qg, where Qais the air flow rate and Qg
is the gas flow rate, is kept constant by the valve as
far as both the air and gas pressure drops versus the
relative flow rate follow the same fluctuation.
Technical features
Gas type: 2° - 3° family
Toutdoor: 0 - 60 °C
Max inlet gas pressure: 60 mbar
Inlet/outletgas connection: thread G3/4 B ISO228
Pressure sampling plug: diam. 9 mm
Airdetection plug: diam. 7 mm
Protection class: IP 40 with NAC connector
Protection class: IP 44 with NAC 504 connector and
gaske
GAS PRESSURE VS AIR PRESSURE
Fig. 30
Averagegas pressure Pint
Air signal Pa
