In a system of standard conventional heating, a central boiler delivery heat in the network of distribution of the heat.

For retrofitting a thermal system to pave, the system needs a warehouse storage additional intermediary in who the collectors and the conventional boiler can give heat.

The network of two-pipe is fed from the cover of the warehouse of storage intermediary.

The temperature of low return of the network enters the bottom of the warehouse and assures to point under the temperatures of return to the collectors and therefore to the above solar productions.