Jandy AquaPure High Temperature: Service Code 174
Quick Summary
- Code 174 = water temperature at the sensor exceeds 108°F (42°C). Cell shuts off automatically.
- This is normal protective behavior, not a malfunction. The cell will resume when temperature drops.
- Most commonly triggered during spa operation when the heater raises water temperature above 108°F.
- The AquaPure also has a low temperature cutoff: below 54°F (12.2°C), the display shows "Lo" and production stops.
What Code 174 Means
The flow/temp/salinity sensor includes a temperature probe that monitors pool water temperature at the equipment pad. When it reads above 108°F (42°C), the control board generates code 174 and shuts off the electrolytic cell. This is a safety feature to prevent damage to the cell electrodes and to avoid generating excessive chlorine in hot water.
Code 174 auto-clears when the water temperature drops below 108°F. No manual reset is required.
Common Causes
- Spa operation: On pool/spa combination systems, when the heater is running in spa mode and water passing through the cell exceeds 108°F. This is the most common trigger.
- Heater overshoot: The pool heater may temporarily push water past 108°F during startup or high-fire operation before the thermostat regulates.
- Sensor placement: If the sensor is installed too close to the heater outlet (upstream rather than downstream), it may read higher temperatures than the actual pool water.
What To Do
- If triggered during spa use, this is expected behavior. The cell will resume chlorine production when the system returns to pool mode and water temperature drops.
- If code 174 appears during normal pool operation (water should be well below 108°F), verify the temperature reading by pressing the POOL TEMP button (D) and comparing with an independent thermometer.
- If the reading is inaccurate, the temperature probe portion of the sensor may be faulty. Clean the sensor and power cycle. If the reading remains incorrect, the sensor may need replacement.
Temperature Range Summary
- Below 54°F (12.2°C): "Lo" displayed. Chlorine production stopped. Boost mode can override this for 24 hours.
- 54°F to 108°F: Normal operating range. Full chlorine production available.
- Above 108°F (42°C): Code 174. Cell shuts off. Auto-resumes when temperature drops.
Pool/Spa Plumbing Considerations
The manual recommends installing the cell and sensor in the common return line after the heater. On pool/spa combination systems (see manual Figure 4), the cell should be downstream of the heater and upstream of the pool/spa return diverter valve. This way, all water passing through the cell has been heated, and the sensor gets an accurate temperature reading.
If your system runs spa water through the cell at high temperatures regularly, code 174 is expected during spa use. The cell simply pauses and resumes after spa mode ends.
Frequently Asked Questions
Will my pool lose chlorine during spa mode?
During the time code 174 is active, no chlorine is being produced. For short spa sessions (1-2 hours), the chlorine loss is minimal. If you use the spa frequently, you may need to increase the production percentage or run time to compensate.
Can I override the 108°F cutoff?
No. This is a hard-coded safety limit that cannot be adjusted or overridden. It protects both the cell and the user.
What about the low temperature "Lo" cutoff?
Below 54°F, the AquaPure stops production to prevent over-chlorination in cold water. You can override this by activating Boost mode (press and hold POOL TEMP button for 10 seconds), which allows production for 24 hours of run time.