Unigas HR92A, Manual Of Installation - Use - Maintenance

Page: 41 / 140

PART III: OPERATION
41
Calibration 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 pres-
sure value is not in the requested pressure range.
Calibration of low gas pressure switch
As for the gas pressure switch calibration, proceed as follows:

Be sure that the filter is clean.

Remove the transparent plastic cap.

While the burner is operating at the maximum output, test the gas pressure on the pressure port of the minimum gas pressure
switch.

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.

Check that the burner is operating correctly.

Clockwise turn the pressure switch adjusting ring nut (as to increase the pressure value) until the burner stops.

Slowly fully open the manual cutoff valve.

Refit the transparent plastic cover on the pressure switch.
Calibration the maximum gas pressure switch (when provided)
To calibrate the maximum pressure switch, proceed as follows according to its mounting position:

remove the pressure switch plastic cover;

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%.

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%;

replace the plastic cover.
Calibration of air pressure switch
To calibrate the air pressure switch, proceed as follows:

Remove the transparent plastic cap.

Once air and fuel setting have been accomplished, startup the burner.

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%.

Repeat the ignition cycle of the burner and check it runs properly.

Refit the transparent plastic cover on the pressure switch.
Calibration gas leakage pressure switch (PGCP)

remove the pressure switch plastic cover;

adjust the PGCP pressure switch to the same value set for the minimum gas pressure switch;

replace the plastic cover.
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 fuel adjustments described above.
VR
VRT
VB
“MAX” head position
”MIN” head position