Expanzomat, or, as it is commonly called, an expansion tank, is the most important element of any autonomous heating system (CO). The purpose of this device is to compensate for thermal expansion and replenish minor coolant leaks. If the volume of this container is too large, it will be almost impossible to create the necessary pressure in CO. Too small a tank may not accept excess coolant. That is why it is so important to choose the right volume of the expansion tank for heating. The methods for calculating the expansion mat will be discussed in this publication.
The final result of computational operations is: determination of the volume of the tank; the minimum diameter of the supply pipe; the value of the initial pressure in the device and the working pressure in the system.
Today, there are three main methods for calculating the volume of an expansion tank for heating: calculators posted on specialized sites, software and self-calculation using formulas. When calculating using online calculators, sometimes a value with a high error is obtained. Specialized software, as a rule, is distributed on a paid basis, which is quite expensive. Next, consider the method of self-calculation.
Expanzomat calculation formula
At first glance, it is difficult and takes a lot of time. In fact, anyone who knows the multiplication table is able to perform these calculations.
Vbaka = (Vsyst * k) / N
Vsyst is the volume of total CO.
Kis the temperature coefficient of liquid in CO
N — the value of the efficiency of the expander.
Firstwhat you need to do is to calculate the volume of coolant in the system. You can do this:
- pumping it with water (glycol antifreeze), then draining and measuring the volume of liquid (using a flow meter or measuring container).
- by calculating the volume yourself.
The first method requires a lot of time and effort. The second method does not require labor. The total volume of CO is calculated based on the power of the heat generator.
Important! For 1 kW of power of the boiler plant, an expander with a capacity of 15 liters is required.
For example: the power of the boiler unit in CO is 30 kW. Based on this, the total volume of the system will be: 30 kW x 15 liters. u003d 450 l. So: the first value for calculating the volume of the expansion tank for heating (Vsyst) u003d 450 l.
Second meaning (K) is a constant value. Figure her out can be found in the reference literature.
Important! For water, the constant is 4%, for 10% ethylene glycol, 4.4%; for 20% 4.8%; The value is valid for CO, in which the coolant is heated up to 95°C.
The table shows the dependence of the thermal expansion of glycol antifreezes on the heating temperature and the percentage of the active substance in the aqueous solution.
Third value (N), most often, good manufacturers are indicated in the documents for the espanzomat. If there is no data, then we will calculate independently according to the formula:
N =(Pmax- Pn) / (Pmax + 1)
Pmax is the value of the maximum allowable pressure in CO.
Important! In autonomous CO of apartments and private houses, the upper pressure limits are in the range of 2.5–3 kg / cm2. In order to find out the exact maximum allowable pressure, you need to look at the setting of the safety valve in the safety group.
Pn is the initial pressure in the tank. The calculation is based on 0.5 kg/cm2 for every 5m height of CO.
For example: coolant — water; the height of the system is not more than 5m; allowable pressure 3 kg/cm2 then:
N = (3 — 0.5) / (3 + 0.5) = 0.71
Now, having the initial data in hand, you can start the calculations.
K = (450l x 0.04) / 0.71 = 25.35l
Tip: when calculating the volume of the expansion mat in CO with water as a heat carrier, increase the calculated values by 15–20%. If antifreeze will circulate in the CO, then increase the calculated expansion tank capacity by 50%.
Rules for choosing an expander
Most developers, especially those who are faced with the creation of autonomous COs for the first time, are interested in the question: “How to choose an expansion tank for a heating system?”
Competent selection of this device can be divided into four stages. The algorithm is the following:
- Determine the required type of expander. Everything is simple here: for open CO — an open tank; for closed — a membrane (balloon) tank.
- Calculate the required tank volume.
Pay attention to the quality of the product. Important points are: the quality of the body metal and color, which should protect the device from corrosion; the presence of an adjustable blast valve; membrane characteristics and the presence of an international quality certificate.
Tip: Today, tanks with a replaceable membrane are available in a wide range. If funds allow, we recommend choosing just such a model.
- Decide on the design, size and shape of the device.
On the European market of climatic equipment there are containers of various volumes, horizontal or vertical orientation, designed for different working and maximum pressures. Pay attention to the color of the device: blue — for the water system; red — for CO.
And the last. The selection of an expansion tank for heating is a rather responsible process, on which the stability of the CO operation depends. Entrust the choice to professionals.