Wunder ALS Drain

Overview

Wunder ALS Drain is the drainback edition of the ALS flat plate collector, built so the absorber empties by gravity whenever the pump stops. That removes the freezing and stagnation risks associated with a pressurised glycol loop, allows plain water as the heat transfer medium and cuts maintenance in both cold winters and very hot summers. Two sizes are offered, ALS 2108 Drain and ALS 2510 Drain.

The absorber is highly selective aluminium with 95% absorptance and only 3% emittance, laser-welded to a copper harp of 8 mm risers on an 18 mm manifold. Low-iron tempered glass 3.2 mm thick and 40 mm of rock wool at 50 kg/m³ hold optical and thermal losses down, giving a thermal efficiency of 71% referred to gross area and 74% referred to absorber area.

Gross areas are 2.07 m² and 2.42 m², with absorber areas of 1.93 and 2.27 m² and empty weights of 29 and 33 kg. Both models withstand 10 bar and 130 °C at a design flow of 72 kg/h·m², and both are Solar Keymark certified with a ten-year warranty. A quick-mounting frame kit suits all standard roof types, on pitched roofs, flat roofs or ground frames.