How to choose the boilers? There are several important criteria for the selection of boiler equipment, which you should draw a special attention:-power boiler, fuel type,-if you need the advantage of two-stage boilers, if you need a heating system "with a priority of hot water," and much more – for what should be the size of the chimney. So, we turn to the power power boiler is defined at the design stage at home. On the power boiler, at least, depends on the desired diameter of the chimney, etc. Power is calculated like this: a 10 m2 area with a ceiling height of 2.5 m requires 1 kW of power boiler. That is, a house of 300 m2 required boiler capacity of not less than 30 kW. On heating tap water leaves approximately 25% of its capacity. But this calculation is very approximate, in practice it is not always justified.
There are boilers that can run on multiple fuels. You can purchase Combination boilers (eg, boilers Viessmann), able to "digest" the electricity and gas, and fuel and firewood. Price combined boilers are often higher than the total value of two, three or even four separate boilers. Full power boiler requires about 15% of the heating season, and 85% of the time it is unnecessary. Therefore more economical to use the boiler with two power levels.
The main advantages of two-stage boiler (Viessmann) are: to increase the life of a gas boiler (by reducing the frequency of on / off burner) for about 70% work on a second stage with low power and reduced the number of on / off burner saves fuel, and, consequently, money, fewer exhaust gases and lower the amount of harmful substances emitted into the atmosphere. And, finally, turn to the question What is the heating system "with dhw priority "? At the very phrase is said that these systems have a priority of hot water (DHW) on heating. In other words, the heating circuit is turned off when you open the hot water tap. Since the system hot water usually works intermittently, but not all the time, when the average hot water use significantly lowering the room temperature is not observed.