PART III: OPERATION
27
2
if the maximum pressure switch is mounted upstreaam the gas valves: measure the gas pressure in the network, when flame is off;
by means of the adjusting ring nut
VR
, set the value read, increased by the 30%.
3
if the maximum pressure switch is mounted downstream the “gas governor-gas valves” group and upstream the butterfly valve:
light the burner, adjust it according to the procedure in the previous paragrph. Then, measure the gas pressure at the operating
flow rate, downstream the “gas governor-gas valves” group and upstream the butterfly valve; by means of the adjusting ring nut
VR
, set the value read on step 2, increased by the 30%;
4
replace the plastic cover.
5.8 Calibration of air pressure switch
To calibrate the air pressure switch, proceed as follows:
z
Remove the transparent plastic cap.
z
Once air and fuel setting have been accomplished, startup the burner.
z
During the pre-purge phase o the operation, turn slowly the adjusting ring nut
VR
in the clockwise direction (to increase the adju-
sting pressure) until the burner lockout, then read the value on the pressure switch scale and set it to a value reduced by 15%.
z
Repeat the ignition cycle of the burner and check it runs properly.
z
Refit the transparent plastic cover on the pressure switch.
5.9 PGCP Gas leakage pressure switch (witn Siemens LDU/LME7x burner control/Siemens LMV Bur-
ner Management System)
z
remove the pressure switch plastic cover;
z
adjust the PGCP pressure switch to the same value set for the minimum gas pressure switch;
z
replace the plastic cover.
5.10 Adjusting the combustion head
Only if necessary, change the combusiton head position: to let the burner operate at a lower output, loose the
VB
screw and move pro-
gressively back the combustion head towards the MIN position, by turning clockwise the
VRT
ring nut. Fasten
VB
screw when the
adjustment is accomplished.
Attention! if it is necessary to change the head position, repeat the air and gas adjustments described above.
VRT
VB
“MAX” head position
”MIN” head position
