Frequently asked questions

On this page we would like to answer your questions regarding technical terms, the functionality of our products or simply give you a short introduction into general solar thermal topics. Please choose the product application you are interested in:

What is the difference between the different types of solar thermal collectors?

How long does the vacuum in our evacuated tube collectors last?

How are the evacuated tube collectors of linuo ritter, manufactured in germany and china, constructed?

What is the vacuum value of the cpc collectors?

Why do tubes have different colors?


There are basically 3 different types of solar thermal collectors:

  • pool absorbers
  • flat plate collectors
  • evacuated tube collectors

Pool absorbers have no insulation and no selective coating.
Flat plate collectors are available with and without selective coating and normally are insulated in the back.
Evacuated tube collectors have a high selective coating and each single tube is evacuated which creates a perfect insulation all around the internal piping.

Thus the 3 different types have different application ranges. Since pool absorbers and flat plate collectors are barely insulated they have a very limited temperature range. Therefore pool absorbers are mainly used for outdoor pool heating in the summer where the target hot water temperature typically is lower than the ambient temperature. Moreover, flat plate collectors can also be used for DHW applications in temperate climates like the south-western states or where a minimum DHW temperature for legionella protection is not required.

Based on the principle of the thermos flask, the vacuum of our evacuated tube collectors lasts about 25 years and longer.

The coating process is affected by the undulation of voltage and air pressure. The more coating layers the tube has, the greater possibility it is that the color of the coating is difficult to control. Generally, it is natural that the color is a little different while it is abnormal that the color is varied.