CLEAN BURN CB-2800 Operator's Manual download pdf (Page 72)

Operator's Manual: Models CB-1500 & CB-2500 (230 V / 50 Hz)

7-2

The Blower/Fan Switch

The CB-1500/CB-2500 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 blower motor to turn ON the blower. When

the wall thermostat is satisfied and the burner shuts off, the blower continues to run until the switch senses that

the combustion chamber has cooled down. The switch then opens and shuts off the blower.

The Hi-Temp Limit Switches

The CB-1500/CB-2500 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 are both 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 blower 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.

• Improper ductwork is installed on the furnace (applicable only if your furnace is

operating as a central furnace). Ductwork must be installed by qualified HVAC personnel

according to industry standards and the specifications provided in Section 3.

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 blower has stopped running for any reason during furnace operation, the heat

in the furnace will cause the limit switches to open. Ensure that the blower 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.

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CLEAN BURN CB-2800 Operator's Manual Page 72