Air Pressure Switch - Viessmann MatriX Service Instructions For Contractors

Air pressure switch

Fan pressure monitoring function (LDW1)
B A
Fig. 37
The switching threshold of air pressure switch 1
(LDW1) is monitored in all fan ramp-up phases and
checked in modulating burner operation. This ensures
a minimum pre-purge.
Combustion chamber pressure monitoring function (LDW2)
B
Fig. 38
To monitor the combustion chamber pressure, the
switching threshold of air pressure switch 2 (LDW2) is
monitored in all operating phases (except during safety
and stabilising time).
Air pressure switch triggers a fault shutdown at the
C
burner control unit under the following circumstances:
■ If the combustion chamber pressure is outside the
permissible range in the pre-purge phase, in control
mode or in the post-purge phase after 2 attempts
The fault shutdown is shown with fault indicator "F FB"
on the burner control unit display (see page 19) and
can be cleared by pressing reset button
C
B .
Air pressure switch triggers a fault shutdown at the
A
burner control unit under the following circumstances:
■ If the static pressure check was unsuccessful after
approx. 5 minutes
■ If the air pressure is outside the permissible range
during the pre-purge phase (tolerance time approx.
5 minutes)
■ If the air pressure switch fails in regular operation or
the air pressure lies outside the permissible range
The fault shutdown is shown with fault indicators
"F F5" and "F F7" on the burner control unit display
(see page 19) and can be cleared by pressing reset
button .
B
Burner output in kW
187
248
314
Burner output in kW
187
248
314
Air pressure switch
LDW1 setting
1.2 mbar (0.12 kPa)
↑
LDW2 setting
5 mbar (0.5 kPa)
↑
35