TM 5-3895-374-24-2
HEATER OPERATIONAL SAFEGUARDS
CEI heaters are equipped with numerous safety controls to ensure a safe and reliable operating environment. A
brief discussion of each of these safeguards follows.
LOW LEVEL CONTROL-ensures that the circulating pump and the burner will not operate if the heat transfer fluid
level in the. expansion tank is too low. The LOW OIL light on the panel will also be lit.
PUMP PRESSURE SWITCH-ensures positive circulation of the heat transfer fluid before the burner will operate.
For example, if there is water in the heat transfer fluid, then as the temperature of the fluid approaches 2120F, the
water will be converted to steam and will expand. This is potentially an extremely dangerous situation. When the
steam reaches the pump, the pump will lose pressure and the safety switch will prevent the burner from operating.
FLAME SAFEGUARD SYSTEM-consists of the mini peeper, the flame amplifier module, program module and the
heater operation programmer. The main fuel supply is shut off and the FLAME FAILURE light on the panel box is
lit if burner ignition fails. Also, the normal operating cycle of the programmer includes a pre-purge and post-purge
phase to ensure that no combustible gases remain in the firebox when burner ignition is attempted.
PROOF-OF-CLOSURE SWITCH-on gas operation, ensures that the electric gas valve closed properly following the
last burner cycle. If the electric gas valve failed to close properly, the burner will not attempt to ignite.
AIR FLOW SWITCH-on gas operation, ensures that the burner blower is mixing air in the firebox with the gas being
supplied to the burner. If not, the burner will not ignite and the programmer will continue to cycle.
LOW FIRE START INTERLOCK-ensures that the burner is low-fire mode during ignition. If not, ignition will not be
attempted.
HIGH TEMPERATURE LIMIT SWITCH-shuts off the heater if the heat transfer fluid temperature reaches 450°F
(575°F for heaters set for high temperature operation). This switch works in conjunction with the temperature
controller which has a set point limit of 450°F programmed in it at the factory. The two devices provide a
temperature limit at two locations on the heater.
TEMPERATURE CONTROLLER-uses a thermocouple to indicate the heat transfer fluid temperature in the
circulating pump's pressure line. If a thermocouple failure was to occur, the temperature controller would read the
false signal as an infinite temperature and prevent operation of the heater.
BY-PASS VALVE-ensures that heat transfer fluid will continue to circulate through the heater even if all external
valves are closed. This valve must remain open when the heater is operating.
page 3-915
