- Heat pumps
- Pool heat pump
ER04
Poolex Er 04 on pool heat pump: antifreeze protection
Risk level
Low
Usually safe to check without specialist tools.
Urgency
Medium
Quick answer
On the Poolex Jetline Selection Fi, code 04 means the antifreeze protection has started with the unit on standby in cold weather. Poolex says no action is needed: keep the pump powered and the filtration available.
Safety first
Stop and check this first
- Poolex excludes frost damage from the titanium heat exchanger warranty. Do not cut the power in winter without winterising the heat pump first.
Safe checks you can perform
- Outdoor temperature and unit state
- Power and circulating pump available
- Status values and fault history
- Winterising if you will not use it
Leave these tasks to a qualified professional
- Do not attempt this professional task: Temperature sensor check
- Do not attempt this professional task: Circulating pump control 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.
Temperature sensor check
What they doIf the 04 shows in mild weather, the technician compares the water sensor reading (F3) and ambient reading (F6) with a reference thermometer.
They must show youthe F3 and F6 readings against the reference thermometer.
In writingthe measured values and whether any sensor was replaced, with its reference.
Circulating pump control check
What they doThe technician checks that the circulating pump wired to P1 and P2 starts when the heat pump calls for it (Pu status).
They must show youthe circulating pump starting with the Pu status active.
In writingthe test result and any wiring corrected.
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.
Outdoor temperature and unit state
- Who:
- you.
- How:
- check whether it is cold (near or below 2 °C) and whether the heat pump was on standby, not switched on.
- Result that matters:
- the 04 matching cold weather and a unit on standby.
- If it matches:
- it is the intended protection; do not cut the power.
- If it shows in mild weather or with the unit on:
- note it and raise it with a technician.
- Evidence to keep:
- time and approximate outdoor temperature.
Evidence: Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
Power and circulating pump available
- Who:
- you, without tools.
- How:
- confirm the heat pump has power and the circulating pump is switched on or wired to terminals P1 and P2 so the unit can start it, as Poolex requires for antifreeze.
- Result that matters:
- water flowing when the antifreeze programme calls for it.
- If the filtration was off:
- keep it available while frost is possible.
- If everything is powered and water flows:
- nothing more is needed.
- Evidence to keep:
- a photo of the filtration panel and timer.
Evidence: Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
Status values and fault history
- Who:
- you, from the heat pump controller.
- How:
- enter status check mode by holding for 3 seconds the button shown in section 5.9 of the manual; step through the parameters and note the inlet water temperature (F3) and ambient temperature (F6) and codes HE1 to HE4 (fault history).
- Result that matters:
- knowing whether the code repeats in the history and which values the unit showed.
- If the history shows the same code several times:
- it is not a one off; show it to the technician.
- If it is the first time and it clears once the water is corrected:
- watch it for a few days before calling.
- Evidence to keep:
- a photo of each value on the screen, with the date.
Evidence: Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
Winterising if you will not use it
- Who:
- you, following the 4 steps in the manual.
- How:
- if the heat pump will stay off in winter below 3 °C, Poolex asks you to winterise it: disconnect the power, open the by-pass valve and close the inlet and outlet valves, unscrew the water pipes to drain it, then plug the connections and cover the unit.
- Result that matters:
- a drained heat exchanger and a protected unit.
- If you drain it:
- antifreeze is no longer needed because no water is left inside.
- If you will keep using it:
- do not drain it, and keep power and filtration available.
- Evidence to keep:
- the winterising date and photos of the plugged connections.
Evidence: Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
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
- Poolex
- Product type
- Pool heat pump
Known code variants
- Er 04
- Poolex 04
- Poolex antifreeze protection
- Poolex E04
- Poolex error 04
- Poolex Jetline Selection Fi 04
- Poolex protección anticongelante
What it means
With the pump on standby, the controller watches the ambient and water temperatures. According to the Jetline Selection Fi manual, the antifreeze programme starts when either falls below 2 °C and the unit has been off for more than 120 minutes: it runs the compressor and the circulating pump until the water is above 2 °C. It ends by itself when ambient is 2 °C or more, or when you switch the unit on. The 04 is a protection, not a fault: it only works if the unit is powered and the circulating pump can start.
Warnings and stop conditions
- Mediumsource verified
Poolex excludes frost damage from the titanium heat exchanger warranty. Do not cut the power in winter without winterising the heat pump first.
Evidence: Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
Symptoms and causes
Probable causes · in order
- Cold weather with the unit on standbyCommon
Ambient or water below 2 °C and more than 120 minutes off. This is intended operation; Poolex says no intervention is required.
Evidence: Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
- Circulating pump unable to startPossible
If the filtration is off or unpowered, the protection cannot move water and the heat exchanger is exposed to frost. You tell by checking whether the pump runs.
Evidence: Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
Virtual technician
Does ER04 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
Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
Poolstar (Poolex) · 2025 · official_doc
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