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The THR boiler’s gas valve is controlled by the air
pressure supplied by the fan, thus guaranteeing a
correct air/gas ratio over the whole range of opera-
tion (constant CO
2
). The ratio remains constant des-
pite any pressure drop in the combustion products
outlet or the air intake. The air-gas link is pneumatic.
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The THR boiler has a 24 volt variable-speed fan; it
is controlled by the regulator, which calculates the
speed needed at any given time to produce the re-
quired pressure.
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The THR boiler is fitted with a high performance pre-
mixed burner.
CO and NO
x
emissions are within the values laid
down by the most demanding quality standards.
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Manual adjustment of heating flow and domestic hot
water temperatures on the boiler control panel.
The heating regulator defines the heat output requi-
red to achieve the heating and hot water settings en-
tered by the user. These are set using temperature
knobs for the boiler flow and hot water settings. A
winter/summer switch can be used to switch from
hot water only (summer position) to heating and hot
water (winter position).
Whether the switch is set to winter or summer, the
boiler is protected against freezing when the tempe-
rature drops below 5 °C.
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Correction of flow temperature and adjustment of
hot water temperature on the boiler control panel.
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The hot water temperature setting is adjusted using
the hot water temperature control knob on the con-
trol panel.
Winter/summer switch set to the winter position:
- the regulator automatically switches between
winter and summer. The boiler provides only hot
water when the average outdoor temperature ex-
ceeds 19 °C. Otherwise, the boiler provides hea-
ting and hot water.
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0
1
2
3
4
5
6
0
2
4
6
8
PL mbar
PO mbar GN
PO: Gas valve output system
PL: Air pressure of air/gas servo-system
THR 5-25
THR 2-13
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1 : QAC 31 outside temperature sensor
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