What’s a Thermocouple? A thermocouple is a device made up of two distinct metal wires joined at both ends. When exposed to heat at its tip, energy diverges along the two wires, producing a subtle electric signal when they reconnect. This electric output is typically measured in millivolts.
What’s a control box? The control box is an electronic box that controls the speed and flow of the pellet drop. It’s the electronic ‘brain’ of the unit.
Per the user manual for a Quadrafire 1200 (the same control box is used in CB1200, 1200I, Castile FS & Insert, Contour, Santa Fe & Santa Fe Insert)
The control box is located under a small cover in
the right rear corner of the inside of the hopper.
b. There is a light located inside of the control box.
The internal light will turn green when the appliance
has reached a temperature of 200°F (93°C) in the
fire pot and will turn red when it reaches 600°F
(315°C).
c. There is also an internal blue light located in the
upper left corner of the control box. When you plug
in the appliance the blue light will automatically
start blinking 1 blink every 10 seconds for the first
60 seconds and then will stop.
A flashing yellow light on the control box indicates a problem
with the thermocouple.
Thermocouple’s Role in a Quadra-Fire Pellet Stove: The thermocouple in a Quadra-Fire pellet stove functions as a flame-detection sensor in the firepot. Upon ignition, the stove’s control box initiates an 18-minute start-up procedure. After this, the stove uses the thermocouple to gauge the firepot’s temperature. Depending on the temperature, the thermocouple communicates with the control box to regulate the pellet supply. Correct positioning of the thermocouple and its ceramic shield is crucial for precise temperature readings. Ideally, the ceramic shield should protrude 1 3/4 inches into the firepot, touching the thermocouple’s tip. Misalignment can potentially lead to an unplanned stove shutdown.
Identifying a Malfunctioning Thermocouple: With constant heat exposure, the thermocouple’s wires may wear out over time. Here are some signs to watch for:
- A flashing yellow indicator on the control box
- The red alert light on the junction box remains active, but the firepot flame extinguishes.
- The stove ceases pellet supply roughly 18 minutes after ignition.
Quadra-Fire Thermocouple Troubleshooting Guide: For a basic thermocouple examination, determine its voltage output. For this, you’ll need a DC multimeter and a BBQ lighter. Always disconnect the stove before meddling with any wires.
Expert Tip: For a more advanced assessment, craft an adapter wire equipped with spade connectors. This setup enables voltage measurement with the thermocouple still linked to the control box, facilitating a check on the control box lights’ response to thermocouple signals. Typically, the green light activates around 2.7 mV (±0.5mV) and the red one at approximately 12.0 mV (±1mV).
To perform the test:
- Set your meter to detect 30 mV of DC power.
- Attach your meter’s probes to both ends of the thermocouple wire.
- Heat the thermocouple’s tip in the firepot. If your thermocouple is functioning it should generate 12-30 mV as it warms up.
A reading below 12 mV indicates the thermocouple needs replacement. If the reading is as expected, inspect for any bad connections between the wiring assembly and the thermocouple. If everything seems in order and the yellow light is not flashing, the control box might require a swap.
