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If a Pentair MasterTemp 250 will not fire, first check the pool system conditions you can verify safely: pump operation, water circulation, valve positions, timer operation, and whether the thermostat is set above the water temperature. Then use the displayed code to identify the issue. Do not bypass a switch or open the heater; Pentair says only qualified, trained technicians with appropriate test equipment should service it.
Start with these safe checks
Before treating the heater itself as the cause, confirm the equipment around it is operating as expected. Pentair’s MasterTemp guide recommends checking the pump, water flow, valves, and time clock. These external checks may help identify a circulation or control-setting issue without opening the heater.
- Confirm the pool pump is running correctly.
- Check for an obvious blockage in the water system.
- Verify valves are set to allow water to circulate through the heater.
- Make sure the time clock is set correctly and running.
- Set the heater temperature above the current pool-water temperature.
If these checks do not resolve the problem, note the exact display before turning to the fault descriptions below. A code is a diagnostic clue, not permission to defeat a safety control.
What the MasterTemp 250 error codes mean
The following descriptions are from Pentair’s MasterTemp Installation and User’s Guide. Use them to orient your next step, not as a substitute for the guide’s complete troubleshooting procedures.
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| Display | Manufacturer-described condition | Safe next step |
|---|---|---|
| ERR PS | Water-pressure switch open; the guide’s troubleshooting direction is no water flow through the heater. | Recheck pump operation, circulation blockage, and valve positions from outside the heater. If flow appears normal but the code remains, arrange qualified service. |
| ERR HLS | High-temperature limit switch open; the guide associates this with water over 135°F after the first pass through the exchanger. | Do not bypass the limit. Have the cause of the temperature or flow condition diagnosed. |
| ERR AFS | Airflow switch open; the blower may not be on or airflow may be restricted. If adequate airflow is not established within 60 seconds, the guide says to turn the heater off. | If the fault remains, turn off the heater as directed. Leave internal inspection to a qualified technician. |
| ERR IGN | The ignition control module was unable to ignite the heater. | Press HEATER OFF to clear the error as the guide directs. If it returns, do not make repeated repair attempts or work on the gas system; contact a qualified technician. |
| ERR AGS | Automatic gas shutoff; the guide associates this with water over 140°F after the second pass through the exchanger. | Treat it as a safety fault and have the cause professionally diagnosed. |
| ERR SFS | Excessive stack-flue temperature; the guide lists more than 480°F. | Stop internal troubleshooting and contact a qualified pool-heater professional. |
| E05 / E06 | Stack-flue sensor open / shorted, respectively. | Follow the manufacturer’s sensor diagnostic guidance; use professional service for a stack-flue alarm. |
| E01 / 126 | Water-temperature sensor open / shorted, respectively. | Use the guide’s sensor diagnostic procedure. Do not order a replacement based only on a code. |
When to stop and call a technician
Pentair’s guide states: “Only qualified, trained service technicians with appropriate test equipment should service the heater.” This is especially important when the fault involves ignition, gas, electrical components, airflow inside the unit, or a high-limit, gas-shutoff, stack-flue, or sensor condition. Do not jumper a switch, defeat an interlock, or work on gas or energized electrical parts.
The heater operates on 120 V or 240 V AC, and the guide warns that the control-box voltage plug must match the heater circuit. Leave electrical checks and repairs to a qualified technician; an incorrect voltage selection can damage components.
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- MasterTemp Pool Heatar.
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- Master Temp Pool Heater Natural Gas
- Compatible With Pentair Natural Gas
For a stack-flue alarm, Pentair’s support FAQ, published May 4, 2023, asks: “What do I do when the MasterTemp experiences a Stack Flue Sensor Error Alarm in the IntelliCenter?” Its guidance recommends contacting a local licensed pool professional.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Identify the exact heater before ordering parts
Pentair lists MasterTemp 250 natural-gas model 460732 and propane model 460733, as well as separately identified 250 ASME variants, on its MasterTemp product page. The page also lists replacement-part families, including burner, electrical, and water-system components.
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- 400K BTU propane gas high performance heater
- Heats up fast so no long waits before enjoying your pool or spa
- Best-in-class energy efficiency
- Manual gas shut-off when service is required
- MasterTemp is certified for low NOx emission and outperforms industry standards; Measures 36-inch length by 30-inch height by 25-inch width
Before buying a part, check the heater nameplate, fuel type, exact part number, and manufacturer compatibility for your unit. A displayed code alone does not confirm which component has failed, and the existence of a listed parts family does not establish that any particular listing fits your heater revision.
Quick Recap
Best Value
- MasterTemp 250K BTU Pool Heatar Liquid Propane.
- Smart Digital Display: Rotating digital control panel offers easy viewing and user-friendly menu navigation for simple operation and diagnostics.
- Compatible With Pentair 250K BTU Liquid Propane.
- Master Temp Pool Heater 250K BTU Liquid Propane.
- Compatible With Pentair 250 000 Liquid Propane.
Rank #4
- Cupro-Nickel Heat Exchanger: Offers superior resistance to corrosion and scale buildup.
- High Heating Capacity: Delivers 250,000 BTUS for quick heating of pools and spas.
- For Pentair Mastertemp 250 000 BTU HD 460806
- Energy Efficiency: Certified for low NOx emissions, meeting eco-friendly standards.
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