750-96 (revised 2010)
Model CB Packaged Boiler Manual
4-5
4.5 — Firing Preparations for No. 2 Oil: Series 100-200
If the fuel oil supply originates from a pressurized loop, it is assumed that the pressure of the loop will be at a min-
imum of 75 psi. Boilers would not then have individual pumps furnished as standard equipment. Under these con-
ditions the relief valve at the terminal block should be adjusted to the point where it becomes inoperative.
A standard equipped boiler has a selector switch incorporated in the oil pump motor starter. Momentarily energize
the starter to check for proper pump rotation. With the rotation verified, operate the pump to determine that oil cir-
culation exists. Observe the oil burner pressure gauge for indication that flow is established. If no pressure shows
on this gauge after a few moments, stop the oil pump and re-prime. If the supply tank is lower than the pump, it is
possible that the initial priming of the suction line, followed by operation of the pump, will not establish oil flow.
This might be caused by obstruction in the suction line, excessive lift, inadequate priming, suction line leaks, etc.
If oil flow is not readily established, avoid prolonged operation of the pump to minimize risk of damage to internal
parts of the pump. If oil flow is not established after a second or third priming attempt, a full investigation is
required to determine the cause.
A vacuum (or a compound pressure-vacuum) gauge should be installed at the suction port of the pump and its
reading observed and recorded for future guidance. If a vacuum condition exists, this reading will reveal the tight-
ness of the system. It is advisable to maintain the vacuum reading at less than 10” W.C. A vacuum in excess of this
may allow oil to vaporize and cause cavitation, loss of prime, and unstable firing condition.
4.5.2 — Oil Pressure
Oil supply pressure is regulated by adjusting the pressure relief valve at the oil terminal block. A pressure gauge
should be installed in the terminal block and the relief valve adjusted to obtain a minimum reading of 75 psi when
the burner is firing at maximum rate.
When oil is supplied from a pressurized loop to a multiple boiler installation, the relief valve in the loop should be
properly adjusted to provide this reading. In this circumstance, the relief valve at the terminal block should be
adjusted to the point where it will be inoperative (or removed and openings plugged). To render inoperative, turn
adjusting screw in as far as possible.
Adjust the regulator in the fuel oil controller so that the burner oil gauge registers approximately 40 psi. The burner
pressure gauge will indicate a lower reading when main flame is ignited and pressure will decrease slightly as the
firing rate increases.
Final regulation of oil flow to the nozzle can be done later, if necessary, by adjusting the metering cam screws as
outlined in Chapter 5.
Suggested oil pressures at high fire operation:
4.5.3 — Starting
When all the conditions covered above and in Sections 4.1, 4.2, 4.3, and 4.4 are assured, the burner is ready for
firing. Refer to Section 4.8 of this chapter for further starting and operating information.
Oil Supply 75 psi
Oil Burner Pressure 40-50 psi
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