You will need
Select the capacity of your heating system. Practically, this exercise is quite difficult, so at a rough calculation based on the power system. At a power of 1 kW capacity of the system assuming 15 equal to L. Accordingly, if the capacity of the heating boiler is rated at 20 kW, the capacity of all components of the heating system are considered equal 300 l (20х15=300).
Determine the coefficient of expansion of the liquid used in your heating system. If you have a water heating system with a maximum temperature of 95°C., expansion ratio will be about 4%. If you use antifreeze, expansion of the system will increase: 10% solution is 1.1% for the 20% solution is 1.2 times, etc. Thus, system expansion, using a 20% solution of antifreeze, is 4.8% (4x1,2=4.8 V).
Calculate the efficiency of the expansion tank. To do this, the difference between the maximum working pressure and charging pressure of expansion tankand divide by the pressure of the charging, which add another 1 bar. Maximum working pressure of the heating system for the garden will take equal to 2 bars and the pressure of the charge will be equal to the static pressure (0.5 bar = 5 m). That is, for a height of 5 m the effectiveness of the surge tankand will be 0,5 (2-0,5)/(2+1)=0,25).
Calculate the capacity of the expansion tank. The capacity of the heating system multiply by the coefficient of expansion of the liquid used for heating, and divide by the efficiency of the expansion tank. If the volume of the storage tank 500 liters in the system, using for heating water, the calculated capacity of the tankand makes 128 liters (300+500)x0. 04/0,25=128).
Ethylene glycol (or antifreeze) is a toxic substance, its fumes are dangerous to humans. Therefore, when working with it be careful.
Capacity expansion tank choose with a margin of about 30% relative to the calculated value.