Primary Circuit Flow Switch; Function; Checks; Removal - Biasi GARDA M90F.24S Service Manual

11

Primary circuit flow switch

11.1

Function

The Primary circuit flow switch (A in Fig. 46) function is
to detect water flowrate through the primary hydraulic
circuit of the boiler.
I
Fig. 46
This hydraulic/membrane operated electrical micro---
switch device will control the functioning of the ignition
control circuit, providing there is an adequate quantity
and flow of water in the primary circuit. Any failure of the
pump or obstructions in the primary circuit, whilst in
either c.h. or d.h.w. modes, will not allow the device to
operate.
This device is connected to the electronic control p.c.b.
and if, after the pump operates, it does not activate with-
in 20 seconds the control board will indicate that a fault
condition (see section 9.4 of this manual) has occurred.
C
D
Fig. 47
24
A
11.2

Checks

Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
Mechanical function
n
1 Remove the front panel of the case.
2 Start and stop the boiler either in d.h.w. or c.h.
mode.
3 Looking through the switch box verify the position
of the shaft B referring to Fig. 48.
Boiler OFF
Fig. 48
Electrical check
n
It is possible to verify the general operation of the switch
by measuring the electric resistance between the con-
tacts C. and N.O. of the switch.
1 Remove the switch as explained in section 11.3.
2 Measure the electrical resistance between the
tabs marked C. and N.O. (Fig. 49).
The contact must be normally open.
3 Operate the switch by hand and verify that the
contact is now closed.
C
N.O.
do not use
Fig. 49
11.3

Removal

Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
Removal of the switch
n
1 Remove the front and right hand side panels of
the case.
2 Remove the fork C (Fig. 47).
3 Open the box and disconnect the switch.
4 Re---assemble the parts in reverse order of re-
moval. Refer to Fig. 49 for the correct wiring con-
nectors on the switch
Removal of the membrane
n
1 Remove the front and right hand side panels of
the case, turn off the flow and return isolation
valves and empty the primary circuit.
2 Remove the fork C that holds the micro---switch
housing D (Fig. 47).
3 Unscrew the four screws E (see Fig. 50) open the
hydraulic operator and remove the membrane F.
Boiler ON
B