DIY Error Codes

Pentair MasterTemp gas pool heater Error ERR HLS

High temperature limit switch open. Water temperature after the first pass through the heat exchanger is more than 135 °F.

Turn the heater off and have a qualified service technician check it, as Pentair's manual directs for ERR HLS.

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Full answer & models

Pentair MasterTemp ERR HLS means high temperature limit switch open. Turn the heater off and call a qualified technician.

Applies to: MasterTemp 175K (460792, 460793)MasterTemp 200K (460730, 460731, 461000, 461001, 461032)MasterTemp 250K (460732, 460733, 460771, 460772, 460806, 461020)MasterTemp 300K (460734, 460735)MasterTemp 400K (460736, 460737, 460775, 460776, 460805, 461021)
Also searched as: Pentair heater HLS, MasterTemp ERR HLS, Pentair pool heater high limit

Gas appliance. Do not keep operating the heater with this code; shut it down and call a technician.
Why
Pentair, what to do if you smell gas: do not try to light any appliance; do not touch any electrical switch and do not use any phone in your building; immediately call your gas supplier from a neighbor's phone. Pentair: this product must be installed and serviced by authorized personnel qualified in pool/spa heater installation; improper installation or operation can create carbon monoxide and flue gases that can cause serious injury or death. Pentair warning: risk of explosion or fire causing burns or death if safety interlocks are disabled. Do not operate the heater when ERR HLS, ERR AFS, ERR IGN, ERR AGS, ERR SFS, E01, E05, E06 or 126 is displayed; shut down the heater ("To turn off gas to appliance", page 43) and have a qualified service technician check the system.

What HLS means

High temperature limit switch open. Water temperature after the first pass through the heat exchanger is more than 135 °F.

More detail
Pentair's MasterTemp Installation and User's Guide (Table 8, Heater Error and Fault Codes, page 48) lists ERR HLS as "Hi temperature limit switch open". Water temperature after the first pass through the heat exchanger is more than 135 °F. Pentair: when the temperature falls below 135 °F the error clears and normal operation resumes.

5-minute checks

Fix it step by step

Step 1 of 2

  1. Shut the heater down

    • 2 min
    • None
    • DIY

    Safety: Gas appliance. Do not keep operating the heater with this code; shut it down and call a technician.

    Pentair: do not keep running the heater with this code.

    More detail

    Shut the heater down.

    Pentair's "To turn off gas to appliance" (page 43): press the OFF button on the operating control and switch off all electric power to the unit. Pentair's remaining steps (removing the access panels to close the gas valve) can be left to your technician.

    Did the code clear?

  2. Call a qualified service company

    • Decision
    • None
    • Pro decision

    Stop here and book a qualified technician.

    More detail

    Call a qualified service company.

    Pentair's manual says only qualified, trained service technicians with appropriate test equipment should service the heater. For ERR HLS, Pentair's troubleshooting chart (page 53) has the technician verify water flow is above the heater's minimum and inlet water is below 104 °F, then check the high limit switch, thermistor, control board, internal bypass valve, thermal governor and heat exchanger.

    Still showing HLS?Need a pro → call a pro

Code cleared. Nice work.

Watch the display for a day to make sure it stays clear.

Back to top

Fixed after any step? Watch the display for a day to make sure it stays clear. Still HLS after step 2? call a pro.

Call a pro if…

  • You smell gas (leave first, then call your gas supplier from a neighbor's phone).
  • ERR HLS is displayed and does not clear, or keeps returning.
  • Anything inside the heater cabinet, wiring, or the gas valve.

FAQ

What does ERR HLS mean on a Pentair MasterTemp?

"Hi temperature limit switch open", per Table 8 of the MasterTemp manual. Water temperature after the first pass through the heat exchanger is more than 135 °F.

Why does a MasterTemp show HLS?

Pentair's sequence of operation says the high limit switch opens if the heat exchanger outlet temperature goes above 135 °F (57 °C).

Source: Pentair MasterTemp Pool and Spa Heater Installation and User's Guide, Table 8 Heater Error and Fault Codes and Troubleshooting, pp. 45, 48 and 53. Written by the DIY Error Codes team. Updated 2026-10-16. DIY Error Codes is independent and not affiliated with or endorsed by Pentair.