PART III: OPERATION
35
Setting air and gas pressure switches
The
air pressure switch
locks the control box if the air pressure is not the one requested. If it
happens, unlock the burner by means of the control box unlock pushbutton, placed on the bur-
ner control panel.
The
gas pressure switches
check the pressure to avoid the burner operate when the pressure
value is not in the requested pressure range.
Calibration of low gas pressure switch
As for the gas pressure switch calibration, proceed as follows:
z
Be sure that the filter is clean.
z
Remove the transparent plastic cap.
z
While the burner is operating at the maximum output, test the gas pressure on the pressure port of the minimum gas pressure
switch.
z
Slowly close the manual cutoff valve (placed upstream the pressure switch, see gas train installation diagram), until the detected
pressure is reduced by 50%. Pay attention that the CO value in the flue gas does not increase: if the CO values are higher than the
limits laid down by law, slowly open the cutoff valve as to get values lower than these limits.
z
Check that the burner is operating correctly.
z
Clockwise turn the pressure switch adjusting ring nut (as to increase the pressure value) until the burner stops.
z
Slowly fully open the manual cutoff valve.
z
Refit the transparent plastic cover on the pressure switch.
Adjusting the maximum gas pressure switch (when provided)
To calibrate the maximum pressure switch, proceed as follows according to its mounting position:
1
remove the pressure switch plastic cover;
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.
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.
PGCP Gas leakage pressure switch (witn Siemens LDU/LME7x burner control/Siemens LMV Burner
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.
Gas Proving System VPS504 (Option)
The VPS504 check the operation of the seal of the gas shut off valves. This check, carried out
as soon as the boiler thermostat gives a start signal to the burner, creates, by means of the
diaphragm pump inside it, a pressure in the test space of 20 mbar higher than the supply pres-
sure.
When wishing to monitor the test, install a pressure gauge ranged to that of the pressure sup-
ply point
PA
. If the test cycle is satisfactory, after a few seconds the consent light
LC
(yellow)
comes on. In the opposite case the lockout light
LB
(red) comes on. To restart it is necessary
to reset the appliance by pressing the illuminated pushbutton
LB
.
VR
LC
LB
PA
