Combi-system warm water with heating support

Location: Nothern Germany, Bückelte

The installed 9.6 m² collector area (60 tubes) feeds into a 1,000 litre solar combi-reservoir.

An 8 KW wood stove, which supports the oil heating system with 25KW output, is additionally connected to the solar combi-reservoir. The warm water reservoir of the solar combi-reservoir is connected in series in front of the warm water reservoir of the oil heating system. This means that the cold drinking water is always pre-warmed by the combi-reservoir. Additionally, if the temperature in the solar combi-reservoir higher than the temperature in the drinking water reservoir of the oil heating system then the drinking water in both of the reservoirs is exchanged.

A temperature difference controller is connected to the oil condensing boiler return flow which monitors the temperature in the system return flow and in the solar combi-reservoir.

If the temperature in the solar combi-reservoir is higher than that in the system return flow then this is diverted through the solar combi-reservoir using a three way switching valve and the warmer water from the solar combi-reservoir is routed into the oil heating system.

The controller in the oil condensing boiler then decides how many degrees the heating-system water needs to be additionally heated, if at all.

The calculated amortisation period of the solar collector system is 6-7 years.

(With an oil price increase of 15% per year)