Common Spa Heater Repair Parts

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How do you know when it’s time to replace specific parts of your Spa Heater? Spa water temperature will probably be your first clue!

When a hot tub becomes a cool tub, what should you look for, besides a clean spa filter, good water level and a running pump?

Today we will explore the different components that make up an electric spa or hot tub heater; those various spa heater parts that may be to blame when your hot tub is not heating up.

spa-and-hot-tub-flow-switch

Flow Switches tell the heater if there is enough water flow into the heater element and to safely power the heater element. It senses the flow of the water that passes through, and has two wires that connect into the control panel. A flow switch can get stuck; open when it should be closed or closed when it should be open.

Wire shorts and loose connections are prime examples of a common cause of problems with spa and hot tub heaters.

You can isolate the flow switch from the circuit to determine if the flow switch is to blame for any problems in the spa heater. This means that you can remove it from the circuit, or bypass the current that runs to the flow switch, to see if the spa heater will operate without the flow switch. If so, replace the switch.

spa-and-hot-tub-pressure-switch

Pressure Switches can have issues as well. If water flow or pressure proves to be insufficient to absorb enough heat from the heater element, a pressure switch will shut down the spa heater in an effort of self-preservation. If you need to replace a spa pressure switch, you’ll quickly note that there are over 40 pressure switches to select from.

You’ll need to be sure to replace your pressure switch with an exact duplicate, or adjust to match existing pressure settings.

spa-hot-tub-heater-elements

Heater elements are wire filaments that are wrapped in insulating powder and surrounded by a sheath, and are located in the heating chamber, usually a stainless steel cylinder. Power leads connect to the element, and when properly connected, power should heat up the element and warm the spa water.

Ohm meters are used for testing the heater element for a short circuit. Test on the lowest setting, and then measure the resistance of the terminals. An infinite reading on the meter means that there is no continuity to ground; a good thing. One helpful piece of advice is that there is NO in between – heater elements either are good or bad.

Exercise caution when any testing of spa elements is done. Spa heaters should be grounded and GFCI protected before connecting to the power. Spa elements can be tested for amperage using an amp meter, and the terminals can be tested for proper input voltage with a volt meter. If the heater element is leaking water from the terminals, it should be replaced to prevent electric shock.

spa-heater-unions

Speaking of leaking, Heater Unions can also have issues with leaks. If the spa heater leaks at either end of the union, inspect the internal o-ring and gently tighten the nut. If the union nut is cracked, it can be replaced fairly easily.

The Hi Limit switch is actually two high temperature sensors, mounted side by side on the heater manifold or cylinder. Their purpose is turn off the heater when it the water inside becomes too hot (over the limit). At times either high limit can go bad, and if that has happened, it could be an issue with the bypass valve leading to the heater, restricting water flow. Abnormal voltage can also cause a spa high limit to trip, or switch – causing the current to stop flowing to the heater.

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To find the Hi-Limit Switch, look for a red button. Once you find it – push it to see if you can feel or hear a click sound of the hi limit switch resetting. Nuisance tripping is not uncommon, but if you have to push the reset button often, the hi limit may be bad, or more likely, there is an issue causing the heater chamber to overheat, like excess voltage, or low water flow.

spa-heater-thermostat

Another important part is the Thermostat. This vital item comes manual in older spas. It can be turned on with the turn of a knob, while others may require the turn of an Allen key. A warning for turning the heat over 104 degrees is important to remember, however. Newer spas use electric  potentiometers to control the temperature from the circuit board.

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The Contactor confirms if the voltage is regular. If it is, the contactor will close and let the power through the heater element. Contactors can be loud and may be heard clicking into place when the power goes through to the element. The common problems that can occur with contactors include the occasional popping of springs as well as having bugs get inside the contactors.

Contactors must have power to the coil in order to close. The power can be come through the thermostat, hi-limit or the pressure switch. If any of those fail to transfer power, the contactor will not close.

Knowing what you now know from this basic information, you now have a starting point to troubleshoot a spa or hot tub heater. Or, perhaps you know just enough to be dangerous. Please don’t attempt an electric spa heater repair without proper electrical qualifications – more than just this skimpy blog post!

Visit our Spa & Hot Tub pages for spa heater parts, chemicals and hundreds of hot tub accessories to make your spa more enjoyable!

2 thoughts on “Common Spa Heater Repair Parts

  1. Terry Goebel

    My hot tub was not heating.I. checked the circuit board with a multimeter and am not getting power on heater terminals. I ran a direct line to heater wires and the heater started heating. What could be the problem?

    • Hi Terry, assuming the fuses on the board are good, check for any burned marks around the heater terminals on the board. Check the heater relay for any signs of warping, melting, etc, or a burnt smell.

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