Control And Safety Devices; Control Device; Gas Unit; Differential Pressure Switch - Accorroni MEC25-85 Technical Information

2. CONTROL AND SAFETY DEVICES

2.1 CONTROL DEVICE

This device is housed in a heat-resistant and
shockproof plastic enclosure and is mounted on
the air heater electric board, inside the service
door (fig. 11).
The control device operates on the ionisation
flame detection principle, using a special probe on
the burner.
The detection circuit must be fed with single-
phase 230 V ~ mains voltage. The circuit is
sensitive to the phase-neutral polarity and if
this is reversed, the device will lock out
within the safety time, even if the flame has
a regular shape.

CONTROL DEVICE

GAS UNIT - Models 25 - 30 - 35
Pressure set screw
Outlet pressure fitting
Electric connection
Inlet pressure fitting

2.2 GAS UNIT

The gas unit includes two, direct operation solenoid
valves with class B closing devices (maximum
pressure 60 mbar) and a pressure regulator. The
die-cast aluminium casing is equipped with 1/2
RP threaded gas inlet and outlet connections and
two inlet and outlet pressure measurement fittings.
The gas unit is also equipped with an inlet filter
(figures 12-13).

2.3 DIFFERENTIAL PRESSURE SWITCH

This device shuts off the burner if the flue gas
exhaust fan flow rate is insufficient, caused by fan
malfunction or an obstruction in the combustion
circuit.
Pressure set screw
Fig. 11

DIFFERENTIAL PRESSURE SWITCH

Gas
Fig. 12
page 19
GAS UNIT- Models 50 - 57 - 85
Inlet pressure fitting
Outlet pressure fitting
Electric connection
Sealed set screw
Gas
Fig. 13
Fig. 14