BT Series Electric Boilers – Installation, Operating and Maintenance Instructions
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6.2 CONTROLLER OPERATION
When the controller is powered-up, the green “Power” light will come on. If no sensor or high limit errors
are present, the controller enters the operating mode. Once in operating mode, the controller uses the
operating sensor to continuously monitor the boiler water temperature.
When the thermostat calls for heat, the controller will switch on the system pump and the yellow “Pump”
light. The control system will switch on the each stage(s) with yellow “Stage” light(s) in sequence followed
between each stage with an interstage delay as set by the Anti-Cycle Cube. When the yellow "Stage"
light for stage 2 or stage 3 switches on, the Anti-Cycle Cube will begin counting delay time to energize its
stage contactor(s) and will energize its stage contactor(s) only after the time delay has elapsed. This
feature prevents "short cycling", which can quickly wear out contactors and cause rapid temperature
fluctuations.
The elements will stay on until the supply water temperature reaches the temperature dial setting. When
the water temperature setpoint is reached, the control will automatically cycle the stage(s) of the boiler on
or off, as necessary, to maintain the supply water temperature. The required number of stages which are
activated is determined by the heating demand (difference between boiler water temperature and design
temperature setpoint). After the call for heat has been satisfied, the stage(s) of the boiler, along with the
"Stage" light(s), will switch off in sequence, followed by the pump.
All stage outputs will shut off within 15 seconds upon a sensor short circuit. The shut down sequence will
switch off one activated element at a time and then the pump. All stage outputs will shut off immediately
followed by the pump after a delay, if the high-limit temperature is reached or there is a sensor open
circuit. The controller has a built-in automatic reset function upon power interruption.
6.3 TEMPERATURE SETTING
The water temperature adjustment dial on the controller should always be set at the designed boiler water
temperature. A small screwdriver should be used to adjust the arrow on the temperature adjustment dial.
6.4 ANTI-CYCLE CUBE SETTING
The stage 1, stage 2, and stage 3 contactors are each connected in series with Anti-Cycle Cubes. Use a
small screwdriver to adjust the arrow on the Cube adjustment dial to the required stage time delay. The
recommended Anti-Cycle Cube settings are two minutes for stage 1, five minutes for stage 2 and eight
minutes for stage 3. Minimum Settings:
The stage 1 Cube should be set at a minimum of one
minute. The stage 2 Cube should always be set a minimum of two minutes longer than stage 1.
The stage 3 Cube should always be set a minimum of two minutes longer than stage 2.
6.5 CONTROLLER MOUNTING
The controller mounts on the boiler control panel using six #6 sheet metal screws and 1/2" high plastic
standoffs. The indicator LEDs are visible on the top of the boiler casing.
6.6 PROTECTION FROM LIQUIDS
The controller and other components located within the control panel are sensitive to water and other
liquids. Measures must be taken to fully protect components on the control panel from contact with
liquids. This especially applies to overhead pipes which may leak or condensate causing damage.
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