- Heat pumps
- Pool heat pump
FLO
Hayward FLO on pool heat pump: no water flow detected
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
FLO (or PS on round HeatPro units) means the water pressure switch is open: the heat pump sees no water flow. First check that the filter pump is running, the filter is clean and the bypass is closed.
Safety first
Stop and check this first
- Do not open the electrical box: the unit runs on 240 V next to water. Hayward reserves these tests for qualified service personnel.
- Never adjust or bypass the pressure switch so the heat pump runs without flow. Hayward asks to check after every adjustment that it stops when the pool pump is off.
Safe checks you can perform
- Filter pump running and time clock
- Heat pump valves and bypass
- Clean filter
- External control not calling for heat
- Water pressure switch continuity
Leave these tasks to a qualified professional
- Do not attempt this professional task: Wiring and board check
- Do not attempt this professional task: Water pressure switch test and adjustment
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.
Wiring and board check
What they doIf the switch closes and FLO stays, the technician checks the switch wiring and the connections to the display board before replacing the board.
They must show youthe damaged wire or connector, or the reading that rules out the wiring.
In writingthe cause found and, if the board was replaced, why.
Water pressure switch test and adjustment
What they doThe technician checks continuity through the switch with flow and the bypass closed; if it does not close, they adjust it as Hayward describes or replace it.
They must show youthe continuity reading with the pump running and, after any adjustment, the heat pump stopping when the pool pump is switched off.
In writingwhether the switch was adjusted or replaced, the part reference and the no-flow shutdown test.
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.
Filter pump running and time clock
- Who:
- you, no tools.
- How:
- see whether the filter pump is running and whether the timer or time clock is in its on period; Hayward notes the heat pump will not run with the pool pump off.
- Result that matters:
- the filter pump running while you call for heat.
- If it was off or outside its schedule and FLO clears when it starts:
- it was a normal lack of flow.
- If the pump runs and FLO stays:
- go to the valves.
- Evidence to keep:
- a photo of the timer and of the display with the time.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
Heat pump valves and bypass
- Who:
- you, no tools.
- How:
- check the heat pump inlet and outlet valves and the bypass valve; the bypass must be closed and the heat pump valves open so water passes through it.
- Result that matters:
- all the flow going through the heat pump.
- If the bypass was open and FLO clears once closed:
- it was the bypass.
- If the valves were already right:
- go to the filter.
- Evidence to keep:
- a photo of each valve position.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
Clean filter
- Who:
- you.
- How:
- clean or backwash the filter following your filter's instructions and restart the filter pump.
- Result that matters:
- more flow and the alert clearing.
- If FLO clears after cleaning:
- the dirty filter was restricting flow.
- If FLO stays with a clean filter, pump running and bypass closed:
- call a technician.
- Evidence to keep:
- the cleaning date and a photo of the filter gauge before and after, if it has one.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
External control not calling for heat
- Who:
- you.
- How:
- if an external control (for example a pool automation system) runs the heat pump, check whether it is calling for heat right now; Hayward says on square units from December 2016 FLo shows when the remote is not calling for heat.
- Result that matters:
- knowing whether FLO is only the external control's standby state.
- If the control was not calling for heat and the unit starts once it does:
- no fault.
- If the control calls for heat and FLO stays:
- tell the technician.
- Evidence to keep:
- a photo of the external control screen and of the heat pump display.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
Water pressure switch continuity
- Who:
- a pool or HVAC technician.
- How:
- with the filter pump running and the bypass closed, disconnect the switch wires and check continuity through the switch itself, not through the wires.
- Result that matters:
- whether the switch closes with flow.
- If there is no continuity with flow:
- Hayward allows one counterclockwise turn of adjustment; if still open, the switch is replaced.
- If there is continuity and FLO stays:
- the wires are checked and, if good, the board.
- Evidence to keep:
- the reading taken with the pump running.
Requires opening the electrical box of a 240 V unit next to water. Technician only, with power off before handling wires.
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
- error FLO bomba de calor piscina Hayward
- FLO
- Hayward FLO bomba de calor
- Hayward FLO heat pump
- Hayward HeatPro PS
- Hayward HeatPro PS error
- Hayward pool heat pump FLO code
- Hayward Summit FLo
- PS
What it means
Hayward explains that FLo (square display, Summit) or PS (round display, HeatPro) indicates an open water pressure switch: the control sees no water pressure in the heat exchanger and will not start the compressor. According to Hayward, most of these alerts are flow related: open bypass, pump time clock in its off cycle, pump off or dirty filter. The heat pump needs at least 30 gpm. FLO does not prove the pressure switch is faulty: Hayward asks you to confirm first that the pump runs and the filter is clean.
Warnings and stop conditions
- Mediumeditorial warning
Do not open the electrical box: the unit runs on 240 V next to water. Hayward reserves these tests for qualified service personnel.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
- Highsource verified
Never adjust or bypass the pressure switch so the heat pump runs without flow. Hayward asks to check after every adjustment that it stops when the pool pump is off.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
Symptoms and causes
Probable causes · in order
- Filter pump off or in its off periodCommon
The filter pump is off or the time clock is in its off cycle; the alert appears just as the pump stops and clears when it starts.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
- Open bypass or wrong valve positionsCommon
Water goes around the heat pump through the bypass instead of through the heat exchanger; the pump runs, but the switch sees no pressure.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
- Dirty filter and low flowCommon
The pump runs and the valves are right, but a dirty filter cuts flow below the minimum; the alert usually changes after cleaning the filter.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
- Remote control not calling for heatPossible
On square units from December 2016 wired to an external control, Hayward says FLo appears when the remote is not calling for heat; it is not a fault.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
- Pressure switch, wiring or boardPossible
With flow confirmed, the switch does not close, a wire is broken or the board does not read the signal; only continuity checks with the unit open tell them apart.
Evidence: Hayward/Summit Heat Pump Troubleshooting Guide (TSG-HTPMPa)
Virtual technician
Does FLO 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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