Solar Hot Water Controllers | Senztek, RESOL, Aestiva

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Replacement Solar Hot Water Controllers

The controller is the brain of your solar hot water system. It reads the roof and tank sensors, decides when to run the circulating pump, and manages the electric or heat pump booster. When it fails, nothing else in the system works properly — even if the pump, sensors and collectors are all fine.

We stock over 80 controllers and replacement boards across the Senztek, RESOL, Aestiva and Reclaim ranges, covering most Australian systems built in the last 25 years.

✔ Signs your controller has failed

No hot water and the pump never runs
Pump runs constantly, including at night
Blank, flickering or partially dead display
Error codes that persist after sensors have been replaced
Burnt smell, scorch marks, or audible relay chattering
System overheating or repeatedly shutting down

✔ Choosing a replacement

Controllers are specified by how many sensors your system uses, and the count must match. A controller cannot be set up on site to run with fewer sensors than it is built for.

1-2 controller — 2 sensors: roof + one tank sensor. For tanks with a single sensor port.
1-3 controller — 3 sensors: roof + tank (upper) + inlet (bottom of the tank). All three must be connected, so the tank needs two sensor ports.
2-3 controller — the same 3 sensors as the 1-3, plus a second output to control the electric booster element. All three sensors must be connected.

The easiest check is to match your existing controller, or count the sensor ports on your tank.

Then match the family: Senztek SolaStat / SolaStat Plus / SolaStat ST Plus (solar circulation), Senztek AlphaStat Plus (electric booster control), Senztek SolaSmart, RESOL DeltaSol BS/4, BS/2, SLL, AL and AX, Aestiva 2 and 3 sensor, and Reclaim heat pump controllers.

Note: RESOL's DeltaSol BS/4 has been superseded by the DeltaSol SLL — we list the direct replacement alongside the original.