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Pahlén

Pahlén heat exchangers and flow switches for swimming pools

Here you will find Pahlén indirect pool heating components: tube heat exchangers in titanium and in stainless steel 316, each offered in three sizes, together with a flow switch for safe control of the heating circuit. A heat exchanger lets a boiler, heat pump or solar circuit warm the pool without the two water circuits ever mixing, which keeps treated pool water away from the heating system and keeps the heating water away from chlorine and salt.

What the range covers

The listing is built around two series in matching sizes, so the choice is mainly about material and about the size step you need.

  • Titanium series — T 28 (0891983), T 40 (0891984) and T 75 (0891985), all with male thread x female thread connections.
  • Stainless steel 316 series — HF 28 with 1½” connection (0891980), HF 40 (0891981) and HF 75 with 2″ secondary connection (0891982), also male thread x female thread.
  • Flow control — a Pahlén flow switch with ½” connection, used to confirm that water is actually circulating before the heat source is allowed to run.

Within each series the number separates the three sizes: 28 is the smallest body, 40 the middle one and 75 the largest. Pool-side and heating-side connections differ between the sizes, which is why the larger HF 75 is listed with a 2″ secondary connection while the HF 28 uses 1½”.

Titanium or stainless steel 316

The two materials exist for different water chemistries. Stainless steel 316 is the usual choice for conventional chlorinated freshwater pools where the water is balanced and the chloride level stays low. Titanium is specified where chlorides are high or aggressive — typically pools with salt electrolysis, brackish or seawater installations, and pools where the water is harder to keep in balance — because titanium is far less prone to pitting and crevice corrosion from chlorides than stainless steel.

If an earlier stainless exchanger has failed with pinholes in the coil or the tube bundle, that is a common sign that the water chemistry is too aggressive for the material, and the titanium equivalent in the same size is the straightforward replacement.

Choosing the right unit and planning the pipework

When comparing models, work through the practical points rather than the price:

  • Water type — salt-chlorinated or high-chloride water points to the T series; standard chlorinated water is normally served by the HF series.
  • Size step — 28, 40 or 75, chosen to suit the pool volume, the desired water temperature and the output available from the boiler or heat source.
  • Thread sizes — note both sides. The primary (heating) side and the secondary (pool) side are not the same, and the male x female arrangement determines which adaptors, unions or hoses you need.
  • Replacement of an existing unit — read the model designation and part number from the old body or its label, and measure the existing threads before ordering so the new unit drops into the same pipe run.
  • Mounting — allow space around the unit for the brackets and for later removal, and keep the connections accessible for descaling or inspection.

Flow switches and safe heating

A flow switch is a small but important safety device. Fitted in the pool circuit with its ½” connection, it closes a contact only while water is moving and interrupts the heating signal when the pump stops, the filter blocks or an air lock forms. Without that interlock, a heat source can keep firing into a static volume of water, which risks overheating, scaling inside the tubes and damage to pipework and fittings. If a heating system behaves erratically — heating cutting out when the filter is dirty, or refusing to start after a backwash — the flow switch and its wiring are among the first items worth checking.

Pahlén at PoolParthub.com

Here we list the Pahlén titanium T 28, T 40 and T 75 and the stainless steel 316 HF 28, HF 40 and HF 75 heat exchangers alongside the ½” flow switch, so a heating circuit can be built or repaired from one page rather than pieced together from several suppliers.

Each item is shown with its Pahlén part number, which is the quickest way to match a replacement to an existing installation. If the old unit is still in place, note the model designation, the part number and the thread sizes on both sides before ordering, and compare them with the description of the item you intend to buy.