Frost or icing is an indication of an LP leak, although it is possible for a leak to occur without such
evidence. Although the LP supply is, initially, in a liquid state, as it is vaporized it becomes heavier
than air and accumulates near the ground and dissipates relatively slowly, becoming highly
flammable. Extreme care should be exercised with LP fuels and systems.
Adjustment of LP supply pressure:
Close the ball valve downstream of the backpressure regulator to temporarily take the regulator out of the
system (see fig. 13).
Adjust the pump bypass valve value for an initial setting for your burner 100 psi above the maximum
expected tank pressure. Refer to fig. 13.
To adjust the backpressure regulator, open the ball valve downstream of the backpressure regulator and
adjust the regulator to an initial setting of 50 psig above the maximum expected tank pressure (see fig. 13)
and table 2.
The low pressure switch setting should be approximately 15 psig below the backpressure regulator setting.
Check with your LP supplier for exact maximum expected tank pressure for the fuel being used.
These settings are initial settings only. Settings will have to be readjusted for changes in
temperature and operation.
a. Be sure the metering valve is in the low fire position. This valve is factory set to travel approximately 90
degrees starting at position 1 to position 10. These positions can be modified to adjust to a higher or lower
firing rate. If adjusting high fire, low fire must be reset.
b. Read and record valve settings and flow rates using the in line flow meter (gal/min LP gas) provided with the
Check rotation of the combustion blower. The impeller should rotate toward the blower discharge.
Inspect and operate the plant exhaust damper control. The exhaust damper should be capable of maintaining a
consistent negative drum front bulkhead pressure of negative 0.2 to negative 0.5 inches wc from low to high firing
rates for most applications.
Burner flame spin vanes adjustment can be set at 35 to 60 degrees. Thirty-five degrees narrows the flame. Sixty
degrees widens the flame. Forty-five degrees is a nominal starting point.
Burner air adjustments: (See Section C - Operation)
Install a gas sampling probe in the dryer drum rear (see Application Sheet GJ73).
Connect a flue gas analyzer to the gas sampling probe (see Application Sheet GJ73).