Rinnai 1500i Sensor Wiring Harness (P1500-724) The sensor wiring harness on a Rinnai HDC1500i commercial continuous flow water heater carries the temperature readings from the appliance's sensors back to the main control board. Accurate signal transmission here is essential — the appliance can only regulate combustion and temperature as well as the data it's receiving. Wiring harnesses are a wear item: repeated heat cycling and general use can degrade connections over time, leading to signal loss or intermittent readings. This genuine Rinnai harness, made to the original specification, restores a clean connection between the sensors and the control board, keeping combustion and temperature control accurate. ⚠ Important: This part must be installed by a Gas Safe registered engineer. Isolate the gas and electrical supplies