• High quality and performance star: solar thermal collector KA88/2002
    solar thermal collector KA88/2002
  • High quality and performance star: solar thermal collector KA88/2002
    solar thermal collector KA88/2002
  • High quality and performance star: solar thermal collector KA88/2002
    solar thermal collector KA88/2002

The flat plate collector KA88/2020

The most efficient collector in its class!

The solar thermal collector KA88/2020 is a high quality product that has been developed and improved over decades.

The result is an η-0 value of 84% tested and certified by the TÜV Rheinland (Germany).

These are the best results for any flate plate collector that has been tested in Europe.

Responsible for the extremely high efficiency is the WARO- flat pipe which was developed by Wallnöfer.

The main advantage of the WARO- flat pipe is the high contact surface between the tube and the absorber. Round pipes have a contact surface of about 2mm but with the flat tube, Wallnöfer managed to get 20 mm of surface which connects the tube to the absorber.

That means a higher heat transfer and a higher efficiency with a noticeably increased power output especially on days with bad weather.

The WARO- flat pipe is protected by an international patent.


Contact us for an offer, the pricelist or installation information!

Convincing advantages

  • Comfortable showering even on days with limited sunshine
  • 10 years warranty (stainless steel version)
  • Extremely short hot water heating times because of the unique absorber system
  • Longest lifetime and efficiency thanks to high build quality and premium materials
  • Hardened solar glass - hailproof and resistent to heavy snow loads

Technical data


1,8m² collector

2,5m² collector


88 mm

88 mm

Width :

920 mm

1050 mm


1940 mm

2350 mm


1,8 m²

2,51 m²

Absorber surface:

1,6 m²

2,3 m²

Fluid content in the absorber:

0,6 l/m²

0,6 l/m²

Dry weight/m²:

19,45 kg/m²

19,45 kg/m²

Dry weight:

35 kg

48 kg

Operating pressure:

2 - 4 bar

2 - 4 bar

Max. testing pressure:

8 bar

8 bar

Max. stagnation temp.:

250 °C


The connections:

The collector has 22mm copper tube exits, we use clamping ring connections to connect them

Glass type:

Hardened solar glass, hailproof with 92% transparancy


Mineral wool 55 mm

Heat loss:

~ 3,7 W/mk

Absorber coating:

sunselect α = 0,95  ε = 0,05

Collector case:

Stainless steel or aluminium

Flow rate:

On high flow: 50l/m², h 
  > means a pressure loss of about 10 mbar for a water / glycol mix at 45°C.
On low flow: 25 l/m², h

Heat transfer fluid:

Non toxic glycol


Frequently asked questions

How much water can a solar thermal collector heat in one day?

On a sunny day a panel with 1,8m² can heat around 150l of water while the 2,5m² model can heat up 200L.

How big does the storage tank need to be?

Fore every m² of solar thermal collectors you should have 80L of storage tank volume. If the solar plant is too big compared to the storage tank, it could overheat more easily. If you are on holiday and no one is at home using hot water, the solar controller can activate a cooling function. This will allow the solar pump to start at night, sending hot water from the storage tank to the solar plant to cool it down.

Combitank, puffertank or boiler?

The decision which storage tank to choose depends from a few factors. For domestic hot water production only, the boiler is the obvious choise, because in it, it contains the domestic hot water.  The size of a boiler would normally be 200-500L for a single-family home.

If the solar thermal plant is not only used to heat the domestic hot water, but also the heating water, a boiler is not ideal. you would either choose a puffer or a combi tank. A puffer tank contains the heating water, domestic hot water can only be produced by an external heat exchanger or a similar device. A combi tank like the Logix24 is a puffer tank with an integrated stainless steel coil for the domestic hot water production. The Logix24 also has a solar heat exchanger mode of copper inside.

Puffer and combi tanks are normally bigger than boilers, because they offer the possibility to connect multiple heating sources like for instance a wood stove.

What does stratification mean?

The Logix24 is a stratified solar combi tank, this means the heat of the solar thermal collectors is sent to the tank and the internal heat exchanger loads the heat to the exact spot where it´s needed. The top of the tank contains the hottest water and the bottom part contains the coldest water. The stratification heat exchanger charges the hot water into the hot area of the tank and avoids hot water getting mixed with colder water. So if the storage tank is completely cold and the solar thermal plant starts working, the hot water coming from the plant is loaded into the top part of the tank first, making it possible to heat domestic hot water relatively quickly, even if most of the storage tank is still cold.