Installation, Operation and Maintenance Manual– Ed.07/2005
19
EVOLUZIONE series natural gas/LPG heaters
3.3.5 PROCEDURE FOR CHECKING & ADJUSTING CALIBRATION OF THE NOVAMIX VALVE SIT 822
These operations must be carried out by
qualified personnel
. Wrong or careless assembly or fitting of the
gas circuit can cause dangerous gas leaks and in particular in areas that are tampered with. Use, too,
adequate sealants on all connections.
Each heater is tested and approved in the factory for operation with G20 natural gas.
The calibration of the valve must be carried out
ONLY
if the gas valve is replaced.
After calibration is completed, the valve’s adjusting screws, A and B, must be sealed. After calibration, check
the sealing of the screws of the pressure intakes with soapy water or other suitable means.
A) Completely unscrew the air/gas ratio adjustment screw A (Figure 15), turning it anticlockwise.
B) Tighten screw B (Figure 15) until flush, turning it clockwise.
C) Connect a differential manometer, with a resolution of at least 5 Pascal, in the following way:
-
the positive connector (+) to the blower gas pressure intake D (Figure 15) on the gas valve;
-
The negative connector (-) in parallel to the silicon tube that connects the blower (connector “G”,
Figure 18) to the open valve signal input F (this operation is made possible by inserting a “T”
connector between the silicon tube and the input (connector “F”) to the valve as indicated in Figure 17.
D) Start the heater and select minimum operating power.
E) Check that the difference in pressure read on the differential manometer corresponds to the OFFSET
value (pressure at the burner – pressure at the blower) indicated in Table 5.
F) If the OFFSET value detected is more than +/- 0,1 mbar off of the valued indicated in Table 5, adjust the
valve by turning OFFSET adjustment screw C.
If the readout of the differential manometer is not sufficiently stable to carry out a correct calibration of the
offset, we suggest inserting a damping nozzle (ROBUR optional accessory Code B-GLL103) in the silicone
tube connected to the positive connector (pressure at the burner).
G) Switch operation of the heater to maximum power and check that the offset value does not change from
that indicated at minimum power (tol/- 0.1 mbar).
H) Visually check that the burner does not show signs of reddening at either minimum or maximum power.
I) Switch the heater off and on, and check the offset calibration again at minimum and maximum power.
J) Switch off the heater, disconnect the differential manometer from the valve’s gas pressure intake “F” and
the burner’s “G”, restore the connection of the silicone tube to the gas valve’s connector “F” and tighten
until flush screw “D” (Figure 15) of the gas pressure intake.
Figure 15 –
Novamix SIT 822 gas valve
WARNING
WARNING
A)
Air-gas ratio adjustment screw
B)
Pilot gas flow adjustment screw
C) OFFSET adjustment screw
D) Burner pressure intake
E)
Pressure intake at valve entrance