7 Commissioning
7.4 Gas settings
7.4.1
Checking the working gas inlet pressure and gas rate
Note
If the pressure drops are greater than shown in the diagram
oppo-site, a problem with the pipework or connections is
indicated. Permissible pressure drop across system pipework
≤ 1 mbar. Carry out chimney sweep.
See
Activating the chimney sweep function, page 47.
Fig.44 Gas meter to valve
1.
2.
3.
With the boiler operating in the maximum rate condition check that
the operational (working) gas pressure at the inlet gas pressure test
point is in accordance with BS 6798 & BS 6891. This must be AT
LEAST 18 mb (Natural Gas) or 37 mb (LPG) !
Ensure that this inlet pressure can be obtained with all other gas ap
pliances in the property working. The pressure should be measured
at the gas test point on the gas inlet (A).
M
easure the gas rate— With any other appliances & pilot lights
turned OFF the gas rate can be measured. It should be:-
Tab.23 Natural gas
24
2.61 m
3
/h
30
3.26 m
3
/h
Fig.45 Gas inlet test point
7.4.2 Combustion parameters
The boiler has two dedicated sockets in order to measure the combustion
efficiency and cleanliness of the combustion exhaust gases during
operation. One socket is connected to the flue gas exhaust circuit (A)
which is used to detect the cleanliness of the combustion exhaust gases
and the combustion efficiency. The other is connected to the combustion
air intake circuit (B) which is used to check for the possible recirculation of
the combustion exhaust gases in the case of coaxial pipes. The following
parameters can be measured when using the socket connected to the flue
gas circuit:
temperature of the combustion exhaust gases;
concentration of oxygen O
2
or alternatively carbon dioxide CO
2
;
concentration of carbon monoxide CO.
The temperature of the combustion air must be measured using the socket
connected to the air intake circuit (B), inserting the measurement probe
approx. 7 cm.
In order to analyse the combustion exhaust gases, the chimney sweep
function must be activated, as described below.
Fig.46 Type of fittings — flue
gas measuring point
7 cm
A
B
A
36
3.90 m
3
/h
1.92 kg/h
2.40 kg/h
2.86 kg/h
LPG
46 600 Combi 2
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