1. Set the boiler to full load.
2. Measure the gas inlet pressure via the measuring point P1 on the gas
pipe.
This gas inlet pressure should be at least 17 mbar.
3. Check the gas inlet pressure at measuring point 2 on the gas control
valve.
4. Compare the measured values with the values in the table.
Tab.126 Minimum gas inlet pressure values at gas control valve
measuring point 2
C 340
C 640
Minimum value
(mbar)
280
560
14
350
700
13
430
860
10
500
1000
10
570
1140
10
650
1300
10
5. If the measured value is lower than the minimum value, clean or
replace the gas filter.
11.3.4 Checking and cleaning the air supply hose
1. Disconnect the hose on the air box side by loosening the bayonet
fitting.
2. Check the hose for damage and pollution.
3. Remove the pollution from the hose with a cloth or soft brush.
4. Replace the hose if it is faulty and/or leaking.
11.3.5 Checking the air supply dirt trap
If necessary, disconnect the air supply pipe or air inlet filter from the boiler
to access the dirt trap.
1. Visually inspect the dirt trap on the air supply side for soiling.
2. Remove coarse soiling and clean the trap with a vacuum cleaner or a
cloth.
Fig.110 Gas control valve measuring points
AD-3001568-01
3
2
P
2
P1
Fig.111 Cleaning the air supply hose
AD-0000535-01
1
2
3
Fig.112 Dirt trap
1
2
AD-3001569-01
11 Maintenance
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C 340 / C 640
149
