Bentone BF1 - Preheater

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Bentone BF1
General
7. Preheater
7.2.1 Function FPHE 5
When the boiler thermostat connects, the PTC element is energized and oil
begins to preheat. When the oil has reached the correct temperature, the
preheater thermostat closes and the burner receives the start signal.
During operations the PTC element compensates its output so that the
temperature does not become too high.
If the oil temperature is low and the oil flow high, the preheater thermostat
may open owing to the PTC element’s inability to maintain oil temperature. In
this case it is important to use oil burner controls with a preheater holding
circuit.
7.2.2 Function FPHE 5-LE
When the boiler thermostat connects, the PTC element is energized and oil
begins to preheat. When the oil has reached the correct temperature, the
preheater thermostat closes and the burner receives the start signal.
During operations the PTC element compensates its output so that the
temperature does not become too high. If the oil temperature is low and the
oil flow high, the preheater thermostat may open owing to the PTC element’s
inability to maintain oil temperature.
In this case it is important to use oil burner controls with a preheater holding
circuit.
7.2.2.1 LE-valve
FPHE 5-LE has an integrated shut-off valve which prevents oil drips at start
and stop. When a normal preheater is used before start, the oil
expands and a small quantity of oil flows out of the nozzle orifice and wets
the outside of the nozzle.
Also, when the burner stops, a small quantity of oil forces its way out after
the flame has gone out, especially when there are hot components which
radiate heat back to the nozzle.
The cut-off valve in the FPHE 5-LE is located immediately behind the nozzle.
It opens at ≈ 6.5 bar and closes at ≈ 2.5 bar.
In order to achieve the intended effect when the pressure of the trapped oil
increases, it must be evacuated back to the pump. This is made possible by
the pump solenoid valve’s return-valve function.
The cut-off valve can be pulled out of the preheater with the aid of an M5
screw as illustrated. When the valve is re-installed, oil pressure pushes it to a
position all the way forward behind the nozzle filter so that the volume in front
of the valve is as small as possible.