Biasi M90E.24S, Руководство по обслуживанию

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Electronic control p.c.b.
19
The user, setting the desired temperature with the con-
trol panel knobs operates the variable elements (5 and
6 in Fig. 28) of the electronic control p.c.b.
If the power requested is lower than 40% of the maxi-
mum power output then control is achieved by switch-
ing ON the burner at minimum power, then switching
OFF (ON/OFF function). If the power requested is
higher, then the burner is switched ON at maximum
power and will control by modulating to 40% of the
maximum power output.
During the c.h. operation (Fig. 29), the signal coming
from the c.h. temperature probe is compared to the sig-
nal given by the control panel through the adjustment
made by the user (knob ). The result of such a com-
parison operates the modulation of the gas valve,
consequently changing the useful output of the boiler.
Fig. 29
When the boiler functions in d.h.w. (Fig. 30), the signal
coming from the d.h.w. temperature probe is compared
with the signal given by the control panel through the
adjustment made by the user (knob
).
75
°
C
Fig. 30
Normally, the result of the comparison between these
two signals directly operates the adjustment elements
of the gas valve modulation device, adjusting the useful
output generated in order to stabilize the temperature
of the exiting water.
If during the d.h.w. mode operation, the temperature of
the primary circuit goes over 75
°
C, the useful output is
automatically reduced so that the primary circuit can-
not reach excessive temperatures.
The control sequences in function and in func-
tion are illustrated in detail in sections 9.11 and 9.12.
9.4
Operation/Service lamps
The Electronic control p.c.b. is provided with three
lamps (L.E.D. indicators) 7 in Fig. 28 that give optical in-
formation during the normal operation of the boiler or
for service purpose.
f
Normal operation
Only the green lamp on the left is directly visible on the
control panel fascia and it gives information during the
normal operation of the boiler. The other two lamps are
normally switched off.