Cranborne THI 5-25c, Installation, Commissioning And Servicing Instructions

Page: 50 / 66

- 57 -
VII - GAS CONVERSION
Check that the boiler is properly adapted to the gas
used
1 - SERVICE PRESSURE CONTROL
P
i
= Network gas pressure
Natural gas H (G20): 20 mbar,
P
o
= Gas pressure at the gas valve regulator outlet.
PL = Servo-system air pressure (burner-gas valve)
Po
V
Pi
K
PL
THI-
82
-0
Fig. 60
V = Adjust the slope of the characteristic of the air/gas ratio only
when the burner is at high rate . This setting is carried out
in the factory for natural gas type H (G20) .
This means that the pressure P
o
can be changed to
obtain the required gas flow (section 3.2 - page 59).
K = Adjust the parallel shift of the characteristic only when the
burner is at low rate . This screw is pre-set in the factory.
Its setting must not be normally modified even for changing
gas. If however an adjustment is required, it may be carried
out with a low scale pressure gauge 0-10 mm
WG , and a
CO
2
, CO analyser.