TM 9-4940-342-14&P
Figure 4-2. Flame safeguard control.
(5) At the same time the pump control switch
is closed, the hourmeter will be energized and
begin recording unit operating time.
(6) After the motor has been started and water
flow, air flow and oil flow have been established,
the burner switch low may be closed.
(7) When the burner switch low is closed,
limit control circuit no. 3 is powered from control
circuit no. 1.
(a) Normally open air pressure switch
closes with 0.15-in WC air pressure.
(b) Normally open low water pressure
switch closes with 15 psig water pressure.
(c) Normally closed excess temperature
switch opens at 370°F.
NOTE
After the switch has opened, it requires manual
reset to close.
(d) Normally open low oil pressure switch
opens circuit with 45 psig oil pressure.
(8) When all of the above circuit switches
have been satisfied, terminal no. 7 of the flame
safeguard control will be powered through limit
control circuit. At this time the flame safeguard
should establish ignition with the combustion
chamber. If all the switches have been verified as
working properly, the flame safeguard has been
reset (depressed), and the unit fails to ignite, notify
the maintenance supervisor or higher maintenance
level.
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