Hi-limit error
The electronic control is equipped with a second temperature probe located on the heater barrel called the hi-limit probe. This device can also be part of the sensing probe located inside the heater barrel. The hi-limit control works by stopping the heater when it senses the water has reached the highest acceptable temperature limit.
If the temperature increase was caused by a runaway heater (i.e. a heater that continues to heat the water even though it has already reached its appropriate temperature), this device will prevent the hot tub from reaching temperatures over 48.3 C (119 F).
If the cause of overheating is not a runaway heater, but a runaway pump, only a controller equipped with kinetic heating protection will prevent the hot tub water from overheating. Kinetic heating protection manages water temperature increase generated by pump heat dissipation and protects the hot tub’s equipment by automatically shutting down all accessories when the water temperature reaches high limits.
When troubleshooting a hi-limit problem the first thing to look for is the temperature of the water when the hi-limit warning appears. Is it close to 48.3 C?
If it is, only three things can increase the temperature of the hot tub water: outside temperature, a heater or a pump. If the outside temperature is higher than the hot tub’s water temperature, the water temperature will increase, as heat created by the pump or heater will not be lost to the environment.
If the exterior temperature is not an issue, then the heater or the pump is remaining on (runaway). This is easy to troubleshoot. First, the temperature on the heater barrel must be below 48.3 C, so gently feel the area of the probe to see if it is hot. If it is, cool down the area and reset the breaker to reset the error. When the error is clear, test the heater output to see if the connection still reads 240V when the heater icon is not displayed. If so, when the pump stops, the flow switch will not stop the heater and the technician will see and hear the heater overheat.
If the heater is not to blame, the pump is the culprit. When a pump runs, the heat created by the motor overheats the ambient air under the hot tub skirt, which is then transferred into the water. This is called kinetic heat.
In this case, it is important to first verify if the pump is running when is should be off. If it is running, the main board is defective, as it is allowing the pump to engage when it should be off.
If the temperature is nowhere near 48.3 C on the heater barrel, then either the controller or its probe is at fault. If either is defective, the error cannot be reset by simply turning the breaker on and off.
If the error can be reset but reoccurs after some time, there may be a blockage in the circulation system that is causing a local overheat. If this is the case, the pump and all plumbing—from the heater to the jets—should be checked for any restrictions.
Sophie Tremblay is the technical service department manager for Gecko Depot. She is an electrical engineer by trade and has been working with Gecko Alliance for 13 years. During this time she has conducted several educational seminars on troubleshooting electronic controls.
