Universal Pool & Spa Flow Switch - Heat Pumps, Chlorinators, Dosing Systems, etc - 3/4"

Universal Pool & Spa Flow Switch - Heat Pumps, Chlorinators, Dosing Systems, etc - 3/4"

Pool and spa water flow switch with a 3/4" thread (approx 25mm), used as the original equipment flow switch by most heat pump manufacturers. Also fitted to chlorinator cell housings, acid and chlorine dosing systems, and other pool and spa equipment. Normally Open, closes on flow.

• Physically Stocked, unlike most "drop-shipping" websites.
• Shipped from VIC, NSW, WA, QLD

Fault codes this part usually fixes

A failed flow switch is the most common cause of a flow fault on a heat pump that is otherwise plumbed and running correctly. Depending on the brand and controller, the same fault is displayed as:

• E3 / E03 / EE3 / ER3 / ERR 3 / ERR03 / Err 03 / Error 3 / Error 03 — water flow fault, the near-universal code across imported heat pumps
• E6 / E06 — used by some Madimack manuals for insufficient flow or excessive temperature differential
• "Low Flow", "No Flow", "Water Flow Fault", "Check Flow" — text-display controllers

Typical symptoms: the heater starts then shuts down after a minute or two, the unit will not start even though the filtration pump is running, heating cuts in and out, or the fault clears when you press on the paddle by hand. On a dosing system, the usual sign is that the pump will not dose at all even with the filtration running. More detail on our Error 3 for Pool & Spa Heat Pumps page.

Before replacing the switch, rule out a dirty filter, a closed or incorrectly set valve, a failing filtration pump, air in the line, or a bypass opened too far. A flow switch that tests fine on the bench will still fault if the flow is not there.

Used in

Aquark, AquaSolis, Aquatight, AstralPool, Australian Energy Systems (AES), CHR Heat Pumps, Chilli, Danfoss, Davey, Emaux, EvoHeat, Eziheat, Fairland, Fluidra, Garden PAC, Genesis, Grannus, Guardian, Hayward, HeatSeeker, Henden, Hurlcon, Hydro-Pro, Madimack, Midea, NCS, Neptune, Nova, Oasis, Pentair, PHNIX, Pool Set, Profacture, Raypak, Reltech, Rheem, SensaHeat, SpaNet, SpaPro, Sunlover, Sunrain, Swimmax, Theralux, Thermia, TiLab, Toyesi, Waterco, WWDG, Zealux, Zodiac, and many others.

Commonly seen on these model families: Hayward HeatPro (HP50A, HP50HA, HP65A, HP50A1, HP70A1, HP50AEE, HP70AEE), Hayward Trevinium HP55TR / HP75TR, Hayward HP31005T; Pentair UltraTemp HX, HXi, VX and VXi; Zodiac Z550iQ and ZS500; Madimack Elite V3 / V4, InverEco, Eco, InverTITAN, GT and GT Freedom; EvoHeat DHP, Fusion, Force, CS and Inver; Eziheat Infinity, Serenity and Aquamini; Aquark Mr. Perfect; Aquatight; AstralPool and Viron Eco heat pumps; Sunlover, Waterco and Davey heat pumps; and the many rebadged imported units built on the same platform.

Also used in dosing and sanitising equipment

On a dosing system the paddle switch acts as the flow interlock — it confirms water is actually circulating before the peristaltic pump is allowed to inject acid or chlorine. A failed switch stops dosing entirely, which is the safe failure mode but leaves your water drifting. Commonly fitted to:

• Profacture pHMate, pHMate Series 2, TuffChem and TuffChem TP100 dosing systems (Australian made)
• Pool Controls dosing systems, including those found in Endless® spas
• Davey / Henden Nipper chlorinator cell housings
• A wide range of other pool & spa equipment using a 3/4" threaded paddle switch

Specifications

• Type: Paddle / blade operated water flow switch
• Electrical action: Normally Open (NO) — contacts close when flow moves the paddle
• Wiring: Two-wire, unpolarised dry contact
• Switching voltage: 3V, 6V, 12V, 24V, 36V — rated range 3–100V
• Maximum current: 0.5A
• Minimum flow to actuate: 1 L/min
• Operating temperature: -10°C to 100°C
• Body material: Glass-filled nylon and POM (acetal)
• Thread: 3/4" BSP — at this size BSP and NPT are effectively interchangeable in moulded plastic fittings
• Measured thread diameter: approximately 25 mm across. Nominal spec is 26.4 mm, but moulded plastic threads read slightly under — this is normal and does not affect fitment
• Thread pitch: 14 TPI
• Mounting: Inline, direction-sensitive

Part numbers & cross references

Replaces the following manufacturer, distributor and OEM references where the thread, paddle length and electrical operation match:

Important: Manufacturers may use different plugs, wire lengths, paddle lengths or body revisions within the same equipment family. Compare against the original before ordering. As this is a two-wire unpolarised switch, the original plug can generally be transferred across.

Also searched as: 20000360005, 20000 360005, 2000-36005, JR B688, B688.

Notes

• Signal switch only — 0.5A maximum. This is a low-current control input to the heat pump or dosing controller board. It must never be wired to switch a pump, contactor, heating element or any other load directly. Doing so will weld or destroy the contacts immediately and is not covered by warranty.
• Universal style: each manufacturer uses different plugs, so you may need to cut and join the two wires. Polarity does not matter.
• The blue plastic shown in photos is only a thread protector and is not used in installation.
• Ensure correct orientation and water flow direction so the paddle engages properly.
• Most failures are caused by poor water balance, too much water flow, or bromine. The nylon and acetal body is chemically resistant to normal chlorinated pool water, but bromine and badly unbalanced water will attack it over time.
• Ensure heat pump water flow is restricted as per manufacturer's specs using a bypass valve setup like this.
• Test with a multimeter: Normally Open — should close when the paddle is engaged.
• Must be installed by a qualified person.

Warranty: 12 months. Excludes failures caused by excessive water flow or corrosive water.

Not sure if it's the right part? Send us a photo of what you're replacing and we'll confirm it before you order.