Strebel S-CB Px 120, Руководство по установке, эксплуатации и техническому обслуживанию

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S-CB Px 120 Manual 87
Additional measurement at minimum load.
In the table, a CO
2
percentage is specified at which the gas valve must be set, with the boiler operating at mini-
mum load.
This setting of the gas valve is in general a good procedure to get a good gas/air ratio.
But to ensure a good setting at minimum load we also advice to check the pressure at measuring point 4 on the
gas valve, while the unit is firing at minimum load at the specified CO
2
setting, so after setting screw [1].
To do this, remove the screw on measuring point 4 from the gas valve and connect a pressure measuring device
(manometer) to it.
When the CO
2
has been set to the specified value at minimum load, one must measure a negative pressure: -10 ±
3 Pa . This measured pressure is valid for natural gas, propane and propane/butane mixtures.
If the measured pressure is not within this range, check the complete gas/air unit, consisting of the gas valve,
venturi, fan and burner plate, for defects and/or mounting errors. Also make sure that the measuring devices, both
CO
2
meter and manometer, are functioning well.
NOTICE : After the setting has been done at minimum load, go back to maximum load and check if it still gives
the right CO
2
level as specified for maximum load in the table; adjust the gas valve if necessary.
After readjustment go back to minimum load and check again the CO
2
level and gas valve pressure; adjust if nec-
essary.
Keep toggling between maximum load and minimum load up to the point that no adjustments are needed any-
more and the CO
2
levels and gas valve pressure are within the specified ranges.
After these adjustments, return to normal operation by pressing the [SERVICE] button.
IMPORTANT : Make sure that the screw(s) on the measuring points are mounted again, after the work on the gas
valve has been finished.