- Heat pumps
- Pool heat pump
LOW REFRIG
Pentair LOW REFRIG on pool heat pump: low refrigerant pressure
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
On the UltraTemp, LOW REFRIG means the refrigerant low pressure switch is open. If it is cold, wait for temperatures to rise; clear leaves or plants around the air coil.
Safety first
Stop and check this first
- Do not chip ice off with objects or use pressurized water: switch the unit off and let it thaw.
- Adding refrigerant without repairing the leak does not fix LOW REFRIG; in the EU only a technician certified for fluorinated gases may do it.
- Risk of electric shock: Pentair forbids internal adjustments by the user and asks for power to be turned off before any service.
Safe checks you can perform
- Air and water temperature
- Clear surroundings
- Fan turning
- Ice on the coil
- Pressures and low pressure switch
Leave these tasks to a qualified professional
- Do not attempt this professional task: Leak search and repair
- Do not attempt this professional task: Low pressure switch and TXV test
- Do not attempt this professional task: Fan check
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Leak search and repair
What they doThe technician locates the leak, repairs it, pulls a vacuum and recharges to the charge on the data plate.
They must show youthe leak point and the pressures after recharging.
In writingwhere the leak was, how it was repaired, the charge added and their fluorinated gas certificate.
Low pressure switch and TXV test
What they doWith a full charge, the technician checks the low pressure switch resistance and follows Pentair's procedure for a TXV stuck closed.
They must show youthe measured pressure and the switch resistance.
In writingthe diagnosis and the part replaced with its reference.
Fan check
What they doThe technician checks the fan capacitor and motor and that the blade is not slipping or broken, and replaces what fails.
They must show youthe capacitor reading and the fan turning after the repair.
In writingthe part replaced, its reference and the test done.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Air and water temperature
- Who:
- you, no tools.
- How:
- note the outdoor and water temperature when the alarm appears; Pentair says if they are too cold you should wait for them to rise.
- Result that matters:
- knowing whether the alarm matches cold weather.
- If it is cold and the unit runs again once it warms up:
- it was the temperature.
- If in mild weather the alarm stays:
- go to the airflow.
- Evidence to keep:
- a note of the temperatures and the time.
Evidence: ULTRATEMP Heat Pump Installation and User's Guide (P/N 474099 Rev. AA)
Clear surroundings
- Who:
- you, from outside without opening the unit.
- How:
- remove leaves, debris or branches around the air coil and check no plant blocks the air outlet and no sprinkler wets the unit.
- Result that matters:
- air flowing in and out freely.
- If there were obstructions and after removing them the alarm does not return:
- it was airflow.
- If the surroundings were clear:
- go to the fan.
- Evidence to keep:
- a photo of the surroundings before and after.
Evidence: ULTRATEMP Heat Pump Installation and User's Guide (P/N 474099 Rev. AA)
Fan turning
- Who:
- you, from outside.
- How:
- with the unit calling for heat, look through the top grille to see if the fan turns; keep hands and hair clear of the blades, as Pentair asks.
- Result that matters:
- whether the fan works.
- If it does not turn or turns poorly:
- tell the technician, it points to the fan.
- If it turns normally:
- the technician must measure pressures.
- Evidence to keep:
- a short video of the fan.
Evidence: ULTRATEMP Heat Pump Installation and User's Guide (P/N 474099 Rev. AA)
Ice on the coil
- Who:
- you.
- How:
- look for ice or frost on the outer air coil, usually at the bottom; if there is any, switch the heat pump off and let it thaw. Pentair allows water at low pressure with the unit off.
- Result that matters:
- the coil free of ice.
- If ice keeps forming:
- tell the technician, Pentair links it to a leak or the low pressure switch.
- If there is no ice:
- the technician checks the charge and the switch.
- Evidence to keep:
- a photo of the iced coil.
Evidence: ULTRATEMP Heat Pump Installation and User's Guide (P/N 474099 Rev. AA)
Pressures and low pressure switch
- Who:
- an authorized technician certified for fluorinated gases.
- How:
- fit gauges, check the charge, the TXV and the low pressure switch resistance with a full charge.
- Result that matters:
- telling leak, TXV or switch apart.
- If the charge is low:
- the leak must be found before recharging.
- If full charge and switch open:
- Pentair says to replace the switch.
- Evidence to keep:
- pressure and resistance readings.
Pressurized refrigerant circuit and mains powered unit. Only an authorized technician certified for fluorinated gases.
Evidence: ULTRATEMP Heat Pump Installation and User's Guide (P/N 474099 Rev. AA)
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Heat pumps
- Brand
- Pentair
- Product type
- Pool heat pump
Known code variants
- alarma baja presión bomba de calor Pentair
- LOW REFRIG
- Pentair heat pump low pressure
- Pentair LP alarm
- Pentair pool heat pump LOW REFRIG
- Pentair UltraTemp LOW REFRIG
- Pentair UltraTemp presión baja
- PRESIÓN BAJA
- UltraTemp low refrigerant pressure alarm
What it means
Pentair explains LOW REFRIG appears when the refrigerant low pressure switch is open. In the troubleshooting table causes are: low refrigerant from a leak, air and water too cold for the heat pump, a bad low pressure switch, a faulty fan (capacitor, motor or blade), a TXV stuck closed or insufficient airflow through the air coil. Pentair also links ice on the coil to this alarm. LOW REFRIG alone does not prove refrigerant is missing: in cold weather or without airflow, pressure drops even with a correct charge.
Warnings and stop conditions
- Mediumeditorial warning
Do not chip ice off with objects or use pressurized water: switch the unit off and let it thaw.
Evidence: ULTRATEMP Heat Pump Installation and User's Guide (P/N 474099 Rev. AA)
- Mediumeditorial warning
Adding refrigerant without repairing the leak does not fix LOW REFRIG; in the EU only a technician certified for fluorinated gases may do it.
Evidence: ULTRATEMP Heat Pump Installation and User's Guide (P/N 474099 Rev. AA)
- Highsource verified
Risk of electric shock: Pentair forbids internal adjustments by the user and asks for power to be turned off before any service.
Evidence: ULTRATEMP Heat Pump Installation and User's Guide (P/N 474099 Rev. AA)
Symptoms and causes
Probable causes · in order
- Air and water too coldPossible
The heat pump cannot work at those temperatures; Pentair says to wait for them to rise and see if the unit operates.
Evidence: ULTRATEMP Heat Pump Installation and User's Guide (P/N 474099 Rev. AA)
- Insufficient airflow through the coilPossible
Leaves, debris or shrubs next to the unit restrict air; visible from outside and fixed by clearing the surroundings.
Evidence: ULTRATEMP Heat Pump Installation and User's Guide (P/N 474099 Rev. AA)
- Refrigerant leakPossible
The circuit is short of refrigerant; it persists in mild weather with clear airflow, and needs the leak found, a vacuum and a recharge.
Evidence: ULTRATEMP Heat Pump Installation and User's Guide (P/N 474099 Rev. AA)
- Faulty fanPossible
Fan capacitor, motor or blade fails; the fan does not turn or turns poorly while the unit tries to heat.
Evidence: ULTRATEMP Heat Pump Installation and User's Guide (P/N 474099 Rev. AA)
- Low pressure switch or stuck TXVPossible
With a full charge the switch stays open, or the TXV is stuck closed; only gauges tell them apart.
Evidence: ULTRATEMP Heat Pump Installation and User's Guide (P/N 474099 Rev. AA)
Virtual technician
Does LOW REFRIG still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
ULTRATEMP Heat Pump Installation and User's Guide (P/N 474099 Rev. AA)
Pentair · 2023 · official_doc
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