baltur TBG 1200 MC, Installation, Use And Maintenance Instruction Manual

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MODULATION OPERATION DESCRIPTION
When the burner is on at minimum flow rate, if the modulation
probe allows it (set to a temperature or pressure value higher than
that in the boiler) the air/gas regulation servomotor starts turning;
• in a clockwise direction the air flow increases;
• anticlockwise rotation: the air flow decreases.
thus gradually increasing gas supply and combustion air until the
maximum supply level set for the burner is reached.
The burner remains in the maximum flow position until the tem-
perature or pressure is high enough to trip the modulation probe,
which reverses the rotation of the air adjustment servomotor.
The inverse rotation and therefore the air and gas supply reduc-
tion occurs shortly thereafter.
With this procedure, the modulation system attempts to balance
the amount of heat supplied to the boiler with respect to the
amount the boiler releases for use.
The modulation probe installed on the boiler measures any varia-
tion requests and automatically adjusts fuel and combustion air
supply, by starting the air/gas regulation servomotor and increa-
sing or reducing rotation as necessary.
If the limit value (temperature or pressure) at which the stop de-
vice is set (thermostat or pressure switch) is reached even with
gas supply at minimum level, the burner is shut down by the de-
vice.
When temperature or pressure returns below the shut-down de-
vice tripping value, the burner is activated once again according to
the program described in the previous section.