Heater runs but water does not heat adequately or takes excessively long to reach set temperature.

Safety first: Turn off power and gas before opening panels or adjusting piping.

Steps to improve heating performance:

• Verify flow rate: Ensure valves are set so that adequate flow passes through the heater. Close any external bypass partially per Raypak guidelines.
• Check filter and pump: Clean filter and verify pump is operating at correct speed (for variable‑speed pumps, avoid very low speeds when heating).
• Inspect for scale: If the heater is older and used with hard water, the copper or cupronickel heat exchanger may be scaled, reducing heat transfer. A professional chemical descaling may be required.
• Gas input check: Have a licensed gas technician verify that the heater is receiving the correct gas pressure and that the gas orifices match the heater’s rating (natural gas vs LP).

Note: Compare actual temperature rise to Raypak’s performance tables to determine if output is within spec.