Display shows OH or OHH and spa shuts down; water may feel very hot.

Safety: Turn off power at the GFCI. Do not use the spa until the cause is corrected.

• Remove cover and let spa cool: Open the spa cover to allow heat to escape. Wait until water temperature drops below 40°C (104°F).
• Check water level: Ensure water is above all jets and suction fittings. Low water can cause poor flow and localized overheating at the heater.
• Inspect filters: Remove the Canadian Spa Company filter cartridges and rinse thoroughly with a garden hose from inside out. Severely clogged filters can cause OH errors.
• Check for closed valves: At the equipment bay, verify that all slice valves or ball valves on the pump and heater plumbing are fully open.
• Bleed air locks: Loosen the pump union slightly (with power OFF) until water seeps out and air escapes, then retighten. This helps restore full flow through the heater.
• Restore power and test circulation: Turn GFCI back on, run the circulation pump and jets. Confirm strong flow from heater return jets.
• Monitor temperature rise: If temperature climbs rapidly with poor flow, shut power off and inspect the circulation pump for failure. If flow is good but OH recurs at normal temperatures, suspect a faulty hi-limit sensor or heater relay stuck on.

If OH persists after ensuring proper flow and cleaning filters, contact a spa technician to test the heater relay and hi-limit sensor on the Canadian Spa Company spa pack.