Reliance tankless water heater cycles on and off rapidly (temperature swings at fixtures)

Safety first: For gas units, ensure adequate ventilation and follow all gas safety precautions. Turn OFF power before opening covers.

Steps to check:

• 1. Increase flow: Open the hot water tap further to increase flow. Tankless units require a minimum flow to stay lit.
• 2. Clean aerators: Remove and clean faucet aerators and showerheads to restore proper flow.
• 3. Descale heat exchanger: Use the service valves, pump, and descaling solution to remove scale that can restrict flow and cause overheating.
• 4. Check gas supply: Ensure gas shutoff is fully open and that other gas appliances operate normally. Low gas pressure can cause flame instability.
• 5. Adjust temperature setting: Lowering the set temperature can reduce cycling by requiring less modulation.

Note: If cycling persists despite adequate flow and descaling, a technician should check sensors and gas valve modulation.