The Blower/Fan Switch; The High Temp Limit Switches - Saturn 125 Operator's Manual

The Blower/Fan Switch

The Saturn™ 140 & Saturn™ 230 furnaces feature an F-180 blower/fan switch (normally open) which is
surface mounted at the front of the combustion chamber (see Figure 7B). The blower/fan switch senses the
temperature of the combustion chamber as the burner is firing. When the combustion chamber reaches the
proper temperature, the blower/fan switch closes and sends power to the fan motor to turn ON the fan. When
the wall thermostat is satisfied and the burner shuts off, the fan continues to run until the switch senses that the
combustion chamber has cooled down. The switch then opens and shuts off the fan motor.
The Hi-Temp Limit Switches
These furnaces also feature two high temperature limit switches which are mounted on a bracket at the front of
the combustion chamber as shown in Figure 7B. The switches sense the build-up of heat within the combustion
chamber and are designed to protect the furnace from damage due to overheating. The limit switches are wired
in series, and both are auto-resetting.
Understanding the Function of the L-200 Hi-Temp Limit Switch
If the temperature of the combustion chamber is too hot, the L-200 hi-temp limit switch opens and shuts
off power to the primary control on the burner, and the burner shuts off. The fan continues to run to cool down
the furnace. After the combustion chamber has cooled down, the L-200 hi-temp limit switch will
automatically reset and allow the burner to restart.
ATTENTION: If the L-200 hi-temp limit switch is opening repeatedly, the burner MUST be readjusted
according to the instructions in Section 6 to correct the overheating problem, or serious damage to the
furnace may occur.
The L-200 hi-temp limit switch will open and shut down the burner if any of the following conditions exists:
• The furnace is over firing. Review the directions in Section 6 to properly adjust the burner.
• Ductwork is installed on the furnace. The Saturn™ 140 & Saturn™ 230 furnaces are not
designed for ductwork applications.
Understanding the Function of the L-290 Auxiliary Auto-Reset Hi-Temp Limit Switch
The L-290 auxiliary auto-reset high temperature limit switch is a back-up safety switch for the L-200 hi-temp
limit switch.
Both the L-200 and L-290 auxiliary hi-temp limit switches will open and shut down the burner if:
• the fan has stopped running for any reason during furnace operation, the heat
in the furnace will cause the limit switches to open. Ensure that the fan is functioning properly.
ATTENTION: It is very important to determine the reason for the opening of the limit switches and
take steps to correct the cause; failure to do so may result in serious overheating and damage to the
heat exchanger of the furnace. Additionally, if the burner is rapidly cycling on/off, contact your
Clean Burn Distributor immediately; failure to address this situation may result in serious damage to
the furnace.
Operator's Manual: Models Saturn™ 140 & Saturn™ 230
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