Checking The Temperature; Dip; Ignition Gas Pressure Adjustment - Biasi GARDA M90F.24S Service Manual

Electronic starting control p.c.b.
12 D.h.w. temperature adjustment
13 Dip---switch selectors
14 Operation lamps
15 Ignition gas pressure adjustment (ACC.)
16 Maximum c.h. gas pressure adjustment (RISC.)
9.3

Checking the temperature

The Electronic starting control p.c.b. makes it possible
to separately adjust the c.h. water flow temperature and
d.h.w. outlet temperature.
The temperature of the water is converted into an elec-
tric signal by means of temperature probes.
The user, setting the desired temperature with the con-
trol panel knobs operates the variable elements (10 and
12 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
parison operates the modulation of the gas valve,
consequently changing the useful output of the boiler.
Fig. 29
16
). The result of such a com-
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
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
tion are illustrated in detail in sections 9.11 and 9.12.
9.4
Operation lights
The Electronic starting control p.c.b. is provided with
three lamps (L.E.D. indicators) 14 in Fig. 28 that give
optical information during the normal operation of the
boiler or for service purpose.
Normal operation
f
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.
The following table gives the relationship between the
visible lamp indication and its meaning.
).
75 ûC
function and in func-