Accorroni MEC25-85 Technical Information page 35

d) the flue exhaust fan motor is malfunctioning
and the differential pressure switch does not
issue the enabling signal to start the cycle.
- Replace the fan making sure to re-assemble
the unit as reported in figures 38-39 (see point
8.9).
7.2.2 The control equipment is not in a block
condition, but the cycle remains in
continuous pre-ventilation.
a) the differential pressure switch does not issue
the enabling signal to continue the cycle
because the flue exhaust or air supply ducts
are obstructed.
- First eliminate any obstructions that may be
blocking the terminals and always check the
entire duct route to identify possible damage
or alterations.
b) the differential pressure switch does not issue
the enabling signal to continue the cycle
because the flue exhaust fan does not operate
correctly and does not exert an adequate
vacuum.
- Check for any friction problems regarding fan
motor rotation. Check that the fan is in the
correct position, that nothing interferes with
the rotation and that there are no deformations.
Replace the fan, if necessary, making sure to
re-assemble the unit as reported in figures 38-
39 (see point 8.9)
c) the differential pressure switch does not issue
the enabling signal to continue the cycle
because it is malfunctioning or its electrical
connection has been interrupted.
- Check for damage to the connection cable and
the relative terminals. Do not try to adjust the
pressure switch, removing the seal. Instead, it
should be replaced.
d) the differential pressure switch does not issue
the enabling signal to continue the cycle
because the pressure inlet tube is obstructed
or the silicon connection tube is detached or
broken.
- Check that the silicon tube is properly
connected and that there are no holes or cuts.
If it is undamaged, check the steel pressure
inlet tube and clear it by removing any
obstructions or deposits. To carry out this
entire operation, it will be necessary to access
the interior of the exchanger flue gas header.
Under particular temperature and humidity
conditions, condensate may form which, if
present inside the silicon tube, and even just
a few drops, might prevent the pressure switch
from performing the measurement.
7.2.3 At the end of the pre-ventilation phase,
the ignition electrode does not
discharge and the control equipment
blocks within the safety time.
a) the ignition transformer is malfunctioning.
- Replace the control equipment which contains
the transformer. Since these are electronic
components, it is recommended not to try to
replace just the transformer, nor to use
improper tools.
b) the ignition electrode is no longer connected to
the equipment connector.
- Restore the connection or replace the electrode
including the cable. Do not make joints to
avoid reducing the cable insulation level.
c) The ignition electrode is not correctly positioned
or its ceramic insulation is damaged, with a
subsequent leakage of the ignition discharge.
- Replace the electrode including the cable.
7.2.4 At the end of the pre-ventilation phase,
the ignition electrode discharges, but
the flame is not formed and the control
equipment blocks within the safety time.
a) No gas supply or there is air inside the piping.
- Determine why there is no gas supply first
checking the on-off components on the feed
line. Completely bleed off any residual air and
restart the appliance.
b) The gas solenoid valves do not open because
the coils are malfunctioning or their electrical
connection has been interrupted.
- Check if the connection cable and relative
terminals have been damaged. Use a special
tool to verify that the coils have failed and
replace them, if necessary (see point 8.3).
c) The safety thermostat is malfunctioning and
does not allow the solenoid valves to open.
- Replace the safety thermostat (see point 8.6).
7.2.5 At the end of the pre-ventilation phase,
the ignition electrode discharges, the
flame is formed correctly, but the control
equipment blocks within the safety time.
a) The phase-neutral electric power supply is not
correctly connected to the respective terminals,
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