Unigas PN91 Manual Of Installation - Use - Maintenance page 23

Calibration of air pressure switch
To calibrate the air pressure switch, proceed as follows:
Remove the transparent plastic cap.

Once air and heavy oil 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 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.

Fully-modulating burners
To adjust the fully-modulating burners, use the CMF switch on the burner control panel (see next picture), instead of the TAB thermo-
stat as described on the previous paragraphs about the progressive burners. Go on adjusting the burner as described before, paying
attention to use the CMF switch intead of TAB.
The CMF position sets the oprating stages: to drive the burner to the high-flame stage, set CMF=1; to drive it to the low-flame stage, set
CMF=2.
To move the adjusting cam set CMF=1 or 2 and then CMF=0.
CMF
C.I.B. UNIGAS
(only for PN520 - PN525)
CMF = 0 stop at the current position
CMF = 1 high flame operation
CMF = 2 low flame operation
CMF = 3 automatic operation
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VR