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12
PRIMARy CIRCUIT fLoW SWITCH
12.1 function
The Primary circuit flow switch (A in Figure 12.1) function is to
detect water flow rate through the primary hydraulic circuit of the
boiler.
B
figure 12.1
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 cir-
cuit. 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 within 20 seconds
the control board will indicate that a fault condition (see section
"Operation lights" page 19) has occurred.
12.2 Checks
Warning: isolate the boiler from the mains electrici-
ty supply before removing any covering or compo-
nent.
Mechanical function
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 lever
C referring to Figure 12.2.
Boiler OFF
figure 12.2
Electrical check
It is possible to verify the general operation of the switch by
measuring the electric resistance between the contacts D and
N.O. of the switch.
- 28 -
PRIMARy CIRCUIT fLoW SWITCH
A
C
Boiler ON
1 Remove the switch as explained in section "Removal" page
28.
2 Measure the electrical resistance between the tabs marked D
and N.O. (Figure 12.3).
The contact must close (resistance zero) with c.h. pressure of
0,35 bar or higher.
N.o.
figure 12.3
12.3 Removal
Warning: isolate the boiler from the mains electrici-
ty supply before removing any covering or compo-
nent.
Removal of the switch
1 Remove the front panel of the case.
2 Remove the fork E (Figure 12.4).
3 Open the box and disconnect the switch.
4 Re-assemble the parts in reverse order of removal. Refer to
Figure 12.3 for the correct wiring connectors on the switch
Removal of the membrane
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 E that holds the micro-switch housing F
(Figure 12.4).
E
f
figure 12.4
3 Unscrew the four screws G (Figure 12.5) open the hydraulic
operator and remove the membrane H.
J
figure 12.5
4 Reassemble the parts in reverse order of removal.
D
do not use
H
I
G
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