Display shows Er15 and furnace will not respond to thermostat calls.

Safety first: Turn off power before working on thermostat wiring.

Steps:

• 1. Verify thermostat type: Ensure you are using a thermostat compatible with your US Stove furnace (typically a low-voltage, dry-contact thermostat unless otherwise specified).
• 2. Inspect thermostat cable: Check the cable from the thermostat to the furnace for cuts, staples through the wire, or melted sections. Repair or replace as needed.
• 3. Test thermostat operation: Remove the thermostat from its base and temporarily jumper the appropriate terminals (e.g., R to W) to call for heat. If the furnace responds, the thermostat may be faulty and should be replaced.
• 4. Check furnace terminals: At the furnace control board, ensure thermostat wires are firmly attached to the correct terminals and not shorted to ground or each other.
• 5. Board input test: If jumpering the thermostat terminals at the board does not clear Er15 or start the furnace, the thermostat input circuit on the control board may be defective and require replacement.