Hot tub and spas can have many different error codes that help you diagnose and rectify problems occurring in your spa. OH, OHH and OHS are all common codes that are associated with a "too hot" reading in your hot tub. When the temperature sensors detect unsafe water temperatures, these overheat codes will be generated on your topside control. Unsafe water temperatures are when the sensors detect water temperatures of 108 – 120 F and your spa goes into emergency cool down mode. The heater will be shut off and, if available, your circulation pump and/or blower will turn on to help release the heat.
If you see the OH or OHH flashing on your topside control, the spa should not be used as the water could be scalding hot. Open the spa cover to allow the heat and steam to escape and once the water has cooled, the high limit switch may need to to be reset on some spa packs.
One common cause for an overheating hot tub is low water flow. When your heater does not receive a fast enough water flow over the element, the water within the heating tube can become over heated, and the water temperature will increase. Once this happens the temperature sensors or high limit switches will sense the water temperature is too high and turn the heating unit down or off. Some causes for low water flow are: closed jets or valves, a clogged or dirty filter cartridge, the pump has lost its' prime, or has an air lock, a pipe blockage or the drain cover is blocked.
If low water flow is not what is causing the OH error, then the problem could be with the thermostat or high limit sensors themselves. Sensors and switches can become oversensitive and fall out of adjustment over time. Newer spas usually have electronic sensors, which are more long-lasting than mechanical switches. However even the new technology does wear over time and will eventually need to be replaced.
An overheat code such as OH or OHH can be alarming, but usually can be fixed with some simple steps. Determining what is causing the overheat code, whether it be low water flow through the system or a problem with the heat sensors will help you to decide on your next step. Sometimes it can be as simple as turning the spa off and letting it cool down. So hopefully doing a little detective work when you get an error will have you back soaking in your backyard haven in no time.