PF X4-400, Installation And Operation Manual

Page: 12 / 22

Figure 6A Detail Pilot Assembly
C. Frequently the cause for pilot problems relates to gas pressures that are too high and/or
air dampers that are closed too far. Both conditions can cause a fuel rich mixture in the
pilot chamber which can substantially delay or totally prevent pilot ignition.
7.11 With the leak gas cock closed and pilot gas cock open (if provided); turn the burner switch ON. The
blower motor will purge the heat exchanger of
any accumulated combustibles . At the end of the purge
cycle, the pilot solenoid valve will energize and spark will be initiated. The pilot will attempt to light for 15
seconds. Adjust the pilot pressure at this time. If the pilot fails to light, power must be removed from the
control for 60 seconds to allow it to reset.
Note : If the leak test cock is not provided, remove the main
gas valve wire (MV) from the control to prevent the main valve from energizing during the pilot adjustment
period.
7.12 Pilot Adjustment and Main Flame Light Off Procedure
A. Set the air flow (see Table 3) and pilot gas pressure in order to provide instant pilot ignition, good
flame stability and a strong/steady signal reading. This can be accomplished as follows: Start
with the pilot pressure at the minimum adjustment on the regulator. When the pilot valve
energizes begin increasing the pilot pressure. Note the pressure where a signal is obtained or
the main valve energizes. This will be the minimum pilot pressure. Acceptable pilot and/or main
flame current reading is 1 – 5 microamp.
B. Raise the pilot gas pressure to the point where the signal and/or main valve drops out noting this
pressure. Reduce the pressure slightly and recycle the burner for an attempt to relight the pilot at
this pressure. If relight occurs this is the upper limit of the pilot pressure. Now set the pilot
pressure between the minimum and maximum pressure. This range is typically 1” w.c..
C. After attaining the proper pilot flame signal values, cycle the pilot off and on several times in order
to ensure reliability (with the gas leak test cock still closed).
Turn Burner Switch Off .
D. Having established pilot reliability, open gas leak test cock.
E. After burner has completed pre-purge and established a good pilot flame signal reading, the main
automatic fuel valve will be energized. The main flame should light immediately. If light off does
not occur, it is possible that air will need to be purged from the main gas line. Adjust main gas
pressure regulator (if used) or combination valve regulator to obtain the desired firing rate
pressure.
F. Adjust burner as necessary to provide smooth ignition of main flame. If pilot flame signal drops
significantly when main fuel valve opens, increase pilot gas pressure slightly to obtain a
reasonably stable flame signal value.
9