Adjustments
4-6
750-204
Profire D/LND
2. That all oil valves between the burner and the tank are open.
3. That the suction line is not airbound.
4. That the low fire setting has not been disturbed.
5. That there is pressure at the integral metering unit, but not to exceed 15 psi (20 psi on a separate metering
unit).
6. That the pump turns freely.
7. Check for a clogged strainer at the suction side of the circulating pump.
8. Check for a dirty burner strainer.
9. Check for a plugged or carboned nozzle. This will show up as excessive primary air pressure.
10. That the oil bypass valve is not bypassing the metered fuel oil.
Internal wear of the pump may take place due to the presence of dirt in the oil and in time, this will result in
excessive clearances which reduces the pump capacity.
If the oil metering pump fails to deliver capacity or meters erratically, replace the oil and air pump as a unit and
return the old pump for repair or exchange (where allowed).
4.5.2 — Atomizing Air Pressure
Atomizing air in the air/oil tank is regulated by adjusting the valve in the return air line on integral metering units
or in the air inlet on air compressor module burners. The air pressure is indicated by the pressure gauge at the
air/oil tank.
A minimum of 10 psi air pressure in low fire is suggested. As the firing rate increases, the air pressure also
increases. Air pressure will be less with light oils. If any change in atomizing air pressure is made, check ignition
several times for reliable light off. Adjustments should be set to obtain reliable ignition with best low and high fire
combustion results.
If the required atomizing air pressure cannot be maintained, a lack of lubricating oil may be the cause or the
intake filter may be dirty.
4.5.3 — Atomizing Air Proving Switch
The knurled nut between the switch and bellows is turned in to raise the pressure setting. The minimum amount
of atomizing air is during pre- and post-purge. during pre-purge, adjust the switch until it breaks the circuit.
Readjust the switch above this circuit break point to actuate under a condition of minimum pressure, but not so
close as to cause nuisance shutdowns. Since the pressure of the atomizing air is at minimum when no fuel is
present at the nozzle, adjustment of the switch should be made while the unit is purging, but not firing.
4.5.4 — Low Oil Pressure Switch
The low oil pressure switch is adjusted at the minimum setting of 4 psi. Turning the knob clockwise will increase
pressure, counterclockwise will decrease pressure.
4.5.5 — High Oil Temperature Switch
The temperature switch is set slightly below the maximum of 260º F. To adjust, remove cover and turn the screw
located on top. Clockwise will increase temperature, counterclockwise will decrease temperature.
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