Spa & Hot Tub Error Codes - OH, OHH, OHS

In our series on spa and hot tub error codes, today we turn our attention to the messages that your topside control may be trying to give you. There are many reasons why your spa or hot tub may be throwing error codes, so figuring out the cause quickly is crucial. In this article, we discuss spa and hot tub error codes, what they mean, and how to fix them.

Spa and Hot Tub Error Codes Decoded

Spa and Hot Tub Error Codes Decoded

OH, OHH, or OHS all mean that a temperature sensor has detected unsafe water temperatures of 108° - 118° F, and your spa is in an emergency cool down mode. The heater is shut off, and the circulation pumps and blower are turned on to help dissipate heat.

Open the spa cover to allow excess heat and steam to escape. The spa obviously should not be used when OH or OHH is flashing on the topside control; as the water could be scalding hot for several more minutes. After the water cools, the high limit switch may need to be reset on some spa packs. Press any topside button to reset a digital spa after the water has cooled to 100° F.

What Causes a Spa to Overheat?

What Causes a Spa to Overheat?

Low water flow (LF, FLO), is the usual cause of an overheating (OH, OHH) spa or hot tub. When water doesn't flow fast enough through the heater, the heater stays hotter, and the temperature of the water increases. Eventually, the temp sensors or high limit switches will detect the increased water temperature and shut everything down. Some causes of low water flow in a spa include:

  • A dirty spa filter cartridge.
  • Closed or partially closed valves or jets.
  • The pump has an air lock, or has lost prime.
  • Low water level in spa, and skimmer is sucking air.
  • The spa drain cover is obstructed or a pipe is blocked.

If your water flow is perfectly fine, then you could have a problem with the thermostat or high limit switches used on older spa packs. These can sometimes fall out of calibration or become too sensitive. Digital spas have electronic sensor circuits, which are more durable than mechanical switches. However, temperature sensors, high limit sensors, relays and circuit boards will still eventually fail on modern spas.

In most cases, for newer spas anyway, the water flow problem can be quickly remedied and the spa will cool, reset and start again on its own. Some panels need a prompt from you to restart. For spas without digital controls, you may need to manually reset the high limit switch near the heater housing.

Spa Troubleshooting Flow Chart

Here's a Cal Spa troubleshooting flow chart that has some other possible triggers of seeing OH, OHS, OHH or HH hot tub error codes blinking on your panel. Open the spa cover and let the spa cool down for 10 minutes, then touch the control panel to reset the circuits, or push a red reset button on air systems.

spa and hot tub error code troubleshooting chart

For OH, HH or HOT trouble codes, an overheating hot tub is not usually a heater problem. It is almost always a flow problem. When it's not a flow problem, it's usually a bad temp sensor, high limit switch or a stuck relay.

Here's another Cal Spa troubleshooting flowchart for spa error codes OH, including testing the spa heater element for excessive resistance. This type of testing should only be done with the spa heater and all systems powered OFF, and only performed by someone who is qualified to test safely.

spa and hot tub error code troubleshooting chart 2

So, the next time your spa throws you a OH, OHH or some other "overheat" error code, you know what to do. Clean or replace the spa filter, open all the jets and turn the pump on high. If you still have problems, check over your temp sensor and high limit circuits for wire, plug or sensor problems.

Essential Products

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Spa Parts

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Spa Jets

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Leslie’s makes every effort to provide accurate recommendations based upon current ANSI/APSP/ICC-5 2011 (R2022) standards, but codes and regulations change, and Leslie’s assumes no liability for any omissions or errors in this article or the outcome of any project. You must always exercise reasonable caution, carefully read the label on all products, follow all product directions, follow any current codes and regulations that may apply, and consult with a licensed professional if in doubt about any procedures. Leslie’s assumes no legal responsibility for your reliance or interpretation of the data contained herein, and makes no representations or warranties of any kind concerning the quality, safety, or suitability of the information, whether express or implied, including, without limitation, any implied warranties of merchantability or fitness for a particular purpose.