Cal Spas OH Error — Overheat Shutdown Fix Guide

What Does This Error Mean?

OH means water has overheated past the safety limit (typically 110°F / 43°C) and the spa has shut down to prevent injury.
Don't enter the water — at OH temperatures it can burn within seconds.
Open the cover, power off at the breaker, wait at least an hour for water to cool.
Most causes: pumps running too long, sun-baked spa, or sensor failure causing overshoot.

Affected Models

Cal Spas Patio Series
Cal Spas Hawaii
Cal Spas Genesis
Cal Spas Atlantic Series

Common Causes

Pumps running too long (filter cycles too aggressive)
Sun and ambient heat pushing temp above setpoint
Sensor reading slightly low — heater overshoots
High limit sensor failed (no protection trip)
Cover insulating too well in hot weather

How to Fix It

Open the cover immediately.

Lift the spa cover.
Don't enter the water — burns can occur within seconds at OH temperatures.
Heat dissipates much faster with cover off.
Wait for water to drop below 104°F before considering use.
Power off at the breaker.

Switch the breaker off.
This stops any heating attempts.
Wait at least an hour for water to cool — longer if it's a hot day.
Don't try to run the spa with OH active.
Check ambient conditions.

Is the spa in direct sun?
Has the day been hot?
Cal Spas covers are well-insulated, which means heat doesn't escape easily on hot days.
If conditions are extreme, that's likely your OH cause — shade the spa or reduce filter cycles.
Reduce filter cycle frequency.

Cal Spas controllers let you adjust filter schedule.
If currently 2-4 cycles per day, reduce to 1-2 in summer.
Each cycle adds heat from pump operation.
Reducing prevents heat accumulation in hot weather.
Restart and monitor.

Once water has cooled below 100°F (use a thermometer), restore power.
Run a normal cycle.
Watch the temperature.
If it rises past set point and OH returns despite reduced cycles, the regulating sensor is failing — service needed.

Frequently Asked Questions

Is OH dangerous?

Yes — at 110°F+, water can cause severe burns within seconds, especially on children, elderly, or anyone with reduced sensitivity.
The shutdown is exactly the protection you want.
Don't attempt to bypass.
Wait for water to cool naturally.

Why does OH happen mostly in summer?

Summer combines sun heating the cover, warm ambient air, and pumps running for filtration — all push water temperature up.
If your OH events cluster in summer, run filter cycles overnight when it's cooler, and consider a reflective cover during peak summer.
Winter OH is uncommon.