The simplest solution to this problem will be the design of an initially non-volatile autonomous heating system, in which there are no nodes connected to the power grid. As a boiler, you can use units for solid or liquid fuels, as well as gas. Most often, a model with an atmospheric gas burner and a mechanical control system is used. Such boilers with a capacity of several tens of kilowatts are available from many manufacturers. You can find something for every taste and budget, from domestic boilers worth 15–200 $. to imported ones worth 50–1000 $. These are mainly models for floor mounting; wall-mounted non-volatile gas boilers, such as IShMA-12.5 BSK (“Borinskoye”), are a rarity, and here’s why.
The fact is that as an alternative to a system with a circulation pump, a so-called gravity system with natural circulation is used. In it, the circulation of the coolant occurs due to the difference in the densities of the heated and cooled liquids. If we simply consider the closed circuit of the system, then the liquid heat carrier is heated in the boiler and is displaced by a colder and denser liquid coming from the radiators. The gravitational pressure in such a system is proportional to the vertical distance between the conditional heating center (boiler) and the cooling center (radiator) and the density difference between chilled and hot water.
The gravity system is structurally different not only in the absence of a circulation pump. It, for example, uses an open expansion tank located at the highest point of the system. Horizontal pipelines are recommended to be laid with a slope of 0.005 along the coolant (1 cm per 2 m of the pipeline). The entire circuit is designed so that the smallest possible hydraulic resistance occurs in it (from pipes of increased diameter).
In a gravity system with a single-tier arrangement of heating devices, the boiler must necessarily be located below the group of heating devices, and the greater the difference in the levels of their location, the better the circulation of the coolant.
The advantages of the gravitational system, in addition to energy independence, include its self-regulation. With more intensive cooling of the coolant in one of the radiators, the local flow of the coolant accelerates, and heat begins to be intensively supplied to the cooled radiator.
4 Rules for a Good Gravity Heating System
- The diameter of the inlet and outlet coolant pipelines should be as large as possible. In practice, metal pipes with a diameter of one to one and a half inches or similar plastic (or metal-plastic) pipes are used.
- Highways are laid with the least number of turns.
- The installation of shut-off valves is not recommended; in extreme cases, special ball valves with the lowest hydraulic resistance are used.
- It is recommended to use water as a heat carrier, as it has the lowest viscosity.
Structural diagram of the gravitational heating system