Spa water heater repair

All electrical resistance heaters work the same way: current is passed through a special element, which creates heat. When the current flow is interrupted or diverted, no heat is created.

Heater Element & Assembly

In hot tubs, the element coil is housed in a heater assembly housing, which exchanges heat produced by the element to the water, as it flows through the tube. The assembly may also incorporate sensors: hot tub high limit switch and thermostat. Heater assemblies come in various forms, a common type shown here.

Spa Heater Element Construction

Diagram shows construction of an electric heater element. Note the electrical connection terminal [1].

Inside is the heating coil [13], a filament encased in insulating powder [11]. It is surrounded by a sheath of Incoloy [12], a heat and corrosion resistant alloy which isolates the electrical coil and insulating filler from contact with water.

Reference this diagram when performing diagnostics below.

Common Symptoms & Causes of Heater Failure:

A heating element is similar to a light bulb in that its [13] is a heating coil which in time can break or burn out. Assuming that the heater's connection [1] are in good condition, it is properly energized by your hot tub's control system when it should be, and that the and are functioning properly, no heat can indicate a burned-out or broken heating coil, which results in an open circuit.

Note: Catastrophic failure of the heater element can be caused by a dry fire. This occurs when the heater is operated with little or no water present, or a greatly reduced water flow, which can cause the [13] and/or [12] to actually melt. The element will often have visible signs of damage when a dry fire occurs. Although properly functioning high limit switches, pressure/flow switches, and thermostats are designed to help prevent this condition, like all devices, these too can fail in hot tubs.