- Heat pumps
- Pool heat pump
deF
Hayward deF on pool heat pump: defrost cycle in progress
Risk level
Low
Usually safe to check without specialist tools.
Urgency
Low
Quick answer
deF (FS on square models) means the Hayward heat pump is defrosting. With outdoor air below the mid 50s °F it is normal operation; it only needs a check if it appears in warmer weather.
Safety first
Stop and check this first
- Water dripping under the unit is usually condensation from the coil, which Hayward calls normal; do not switch the heat pump off halfway through a defrost.
- Hayward's guide reserves service for trained personnel because of 240 volts at the terminals: do not remove panels to look at the sensor or the ice on the coil.
Safe checks you can perform
- Measure the air temperature next to the unit
- Let the cycle finish without touching anything
- Log whether deF shows on mild days
Leave these tasks to a qualified professional
- Do not attempt this professional task: Testing the Hayward defrost sensor
- Do not attempt this professional task: Control board if the sensor tests good
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.
Testing the Hayward defrost sensor
What they doIf deF shows in mild air, a technician measures the defrost sensor, fitted on the suction line near the TXV bulb, and compares it with the guide's chart.
They must show youthe measured sensor resistance and the chart value for that temperature.
In writingthe reading obtained, whether the sensor was replaced and the warranty on the part.
Control board if the sensor tests good
What they doWhen the defrost sensor reads the correct resistance and the problem continues, the guide says to replace the control board.
They must show youthe correct sensor reading that justifies the board change.
In writingthe part number of the board fitted, the cost and the warranty.
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.
Measure the air temperature next to the unit
- Who:
- you, with a shaded thermometer.
- How:
- measure the air temperature near the heat pump when you see deF or FS. Hayward's guide says that with outdoor air in the low to mid 50s °F or below, defrost is part of normal operation.
- Result that matters:
- knowing whether the code matches cold air, which is what you would expect.
- If the air is below that range:
- it is a normal defrost, let it finish on its own.
- If it is clearly warmer and the code still shows:
- keep a record for service.
- Evidence to keep:
- the air temperature, the time and a photo of the display.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
Let the cycle finish without touching anything
- Who:
- you, being patient.
- How:
- on round models the compressor stops and the fan keeps running for about 15 minutes per cycle, up to three cycles; if that fails, the unit rests for two hours. On square models the compressor restarts when the sensor reaches 42 °F. Do not switch off or reset the unit to speed things up.
- Result that matters:
- confirming the heat pump goes back to heating by itself after defrost.
- If it heats again:
- nothing else is needed.
- If it stays off with deF for many hours although the air has warmed:
- ask for service.
- Evidence to keep:
- how long the code lasted and whether the unit restarted.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
Log whether deF shows on mild days
- Who:
- you, over several days.
- How:
- keep a simple note of the days you see deF or FS and the air temperature at that moment. The guide only treats the code as suspicious when it shows with outdoor temperatures above the mid 50s °F.
- Result that matters:
- a clear pattern that separates normal defrosts from a possible sensor fault.
- If it only appears in cold weather:
- the unit works as Hayward describes.
- If it also appears in mild air:
- hand the log to the technician.
- Evidence to keep:
- the list of dates, times and temperatures.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
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
- Hayward
- Product type
- Pool heat pump
Known code variants
- deF
- desescarche Hayward bomba de calor piscina
- FS
- FS/deF
- Hayward deF bomba de calor
- Hayward deF heat pump
- Hayward HeatPro deF
- Hayward pool heat pump defrost code
- Hayward Summit FS
What it means
Hayward's TSG-HTPMPa guide explains that FS or deF on the display means the heat pump is in defrost mode, which is normal when outdoor air is in the low to mid 50s °F (about 10 to 13 °C) or below. On round models, if the coil has not reached 50 °F after three 15 minute cycles, the unit shuts down for two hours showing deF. deF is not a fault in itself: only if it appears in warmer weather may it point to a failing defrost sensor, and that has to be measured.
Warnings and stop conditions
- Loweditorial warning
Water dripping under the unit is usually condensation from the coil, which Hayward calls normal; do not switch the heat pump off halfway through a defrost.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
- Highsource verified
Hayward's guide reserves service for trained personnel because of 240 volts at the terminals: do not remove panels to look at the sensor or the ice on the coil.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
Symptoms and causes
Probable causes · in order
- Normal defrost in cold airCommon
Hayward treats defrost as normal whenever outdoor air drops to the low to mid 50s °F or below; the coil gets cold and collects frost.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
- Defrost not finishing in timePossible
On round units, if the sensor is still below 50 °F after the third 15 minute cycle, the unit stops for two hours and shows deF.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
- Defrost sensor failingLess common
If FS or deF shows with outdoor air above the mid 50s °F, the guide points to a defrost temperature sensor that is starting to fail.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
Virtual technician
Does deF 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
Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
Hayward · 2018 · official_doc
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