Cranborne THI 10-50c, Installation, Commissioning And Servicing Instructions

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OPERATION
2.3 - Principle of air/gas servo-control system
The gas valve fitted on each boiler is controlled by
the air pressure supplied by the fan, thus guaran-
teeing a correct air-gas ratio over the whole modu-
lation range (constant CO
2
). This ratio remains
constant despite any pressure drop in the combus-
tion products outlet or the air intake. The air-gas link
is pneumatic.
2.4 - Air pressure variation procedure
Linear pressure modulation is carried out by a 230 V
variable-speed fan controlled by the LMU which cal-
culates the speed needed at any given time to pro-
duce the required pressure.
2.5 - Emission of pollutants
This air/gas control combined with high efficiency
pre-mixing burner enables CO and nitrogen oxide
(NOx) emissions to be obtained that lie within the
values laid down by the most demanding of quality
standards.
Fig. 9
Operating characteristics of the air/gas servo-system
0
1
2
3
4
5
6
7
0 1 2 3 4 5 6 7 PL mbar
P2 mbar GN
P2: gaz pressure at valve regulator outlet
PL: servo-system air pressure