pre-ventilation phase.
•
The pressure switches for checking gas pressure (minimum and
maximum) prevent the burner from operating when gas pres-
sure is between the expected values. The specific function of
the pressure control switches clearly reveals that the pressure
switch for controlling minimum pressure must use the contact
which is closed when the pressure switch detects a pressure
value above the value it is set to; on the other hand, the pressure
switch for controlling maximum pressure must use the contact
that is closed when the pressure switch detects a pressure lower
than the value it is set to. The minimum and maximum gas pres-
sure switches must be set when testing the burner, on the basis
of the pressure measured in each case. Tripping of any of the
gas pressure switches (in the sense of opening the circuit) will
therefore prevent the equipment and therefore the burner from
working. When the burner is working (flame on), tripping of the
gas pressure switches (opening the circuit) will shut down the
burner immediately. When testing the burner, it is very important
to check that the pressure switches are working properly. With
appropriate regulation of the regulation components, we can be
sure that the pressure switch will be tripped (opening the circuit)
and shut down the burner.
•
Verify the flame detector operation as follows:
- disconnect the wire coming from the ionisation electrode,
- Start up the burner;
- The equipment will complete the control cycle and after two
seconds will lock the burner due to the lack of ignition flame;
- switch off the burner;
- Re-connect the wire to the ionisation electrode. This test
should also be conducted with the burner already on; the
equipment should "lock" immediately when the wire from the
ionisation electrode is disconnected.
•
Check the efficiency of the boiler pressure switches or thermo-
stats (they should shut down the burner when triggered).
Check that ignition occurs normally since if the mixer is not
positioned correctly, it may happen that the speed of the
delivery air is so high that ignition is difficult. If this happens,
the mixer must be shifted back by degrees until it is in a
position in which ignition occurs normally, and this new
position can be regarded as the final position.
Remember that for the ignition flame, it is better to limit the
amount of air to the amount strictly indispensable to ensure
safe ignition even in the most difficult cases.
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0006160035_201408
BT 3XX