Unigas RG91 Manual page 32

PART II: INSTALLATION
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.
CMF
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.

Minimum oil pressure switch (when provided)
The minimum oil pressure switch on the inlet line, checks that the pressure does not drop below a default value. The pressure switch
must be set, say, at 10% under the pressure at the nozzle.
Maximum oil pressure switch
The oil pressure switch on the return line, checks that the pressure does not exceed a default value. This value must not be higher
than the maximum acceptable pressure on the return line (this value is reported on the specification table). A pressure change on the
return line could affect the combustion parameters: for this reason, the pressure switch must be set, say, at 20% over the pressure
recorded during the combustion adjustment. The factory setting is 4 bar.
It is recommended to verify that the combustion parameters are within the range of acceptable values even against a pressure varia-
tion that gets close to the limit of the pressure switch.
This check should be carried out along the whole range of the burner output.
In case of inacceptable values, reduce from 20% to 15% the overpressure; later on, repeat the adjustments described above.
Oil pressure switch adjustment
Follow the below instruction, according to the pressure switch installed.
Trafag Picostat 9B4..
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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