and more people in today’s world seek to install boilers (devices used to accumulate and heat water) Their presence allows residents to always have a hot water supply, even when not connected to the central system. These devices are common among owners of private houses and cottages, as well as apartments that do not have access to DHW.
Each storage device has the following main parts in its design: a tank made of metal, in which there are heating elements. special elements for heating water; special devices that provide automatic water heating and maintain a certain temperature.
There are two broad classes of heating devices:
Boilers are often installed near the places of common water supply (bath, toilet, kitchen). On today’s market there are many models that can be mounted on the wall or put on the floor. Models also differ in vertical or horizontal design.
Here it is on the whole, the boiler on 50 liters (on the average) at capacity THEN in 2,5 kw will heat water to a temperature in 55 degrees for 110 minutes. The same heating element boiler 80 liters of 100-110 minutes, a boiler of 100 liters will heat up for 230 minutes.
- T. time of water heating, hour
- V. volume of the water heating tank (l)
- tc. final water temperature, ° C (usually 60°C)
- Tn. initial temperature of water, ° C
- W. electric power of the heating element. heating element, kW
How to know if the kettle is full of water and can be connected to the mains
and more people have started to buy boilers. This allows you to always use hot water, even if the centralized supply is cut off. Or some people completely abandon the city hot water in favor of the boiler, which allows not to overpay on tariffs. You already know how easy it is to connect the equipment, but how to understand that the boiler is filled with water is also not difficult, as it may seem at first glance.
How to Get Hot Water Faster Upstairs, in Shower, and at Kitchen Sink
Boilers are gradually replacing the centralized hot water supply https://ultra-term.ru
Examples
Boiling water in an electric kettle
I usually fill the kettle with water at room temperature 20C to the 1 liter mark and always bring it to a boil (up to 100 degrees). Kettle capacity 2 kW. A simple calculation shows that boiling will consume about 0.1 kWh (kilowatt hours) of electricity, 3 minutes of time, and, according to Moscow tariffs, fifty kopecks of money.
So every tea party adds half a ruble to the electric bill, but that’s considerably less than the price of a cup of tea or coffee.
Heating water in a storage water heater
Every time I take a shower, I completely empty all the hot water from the storage heater, because at the end of the water becomes cold. The heater heats cold tap water from 5 to 45 degrees Celsius in winter. The tank volume is 80 liters. With 2 kW power of heaters, fresh water in the tank will be heated for 2 hours, and it will spend about 4 kW of electricity and 20 money to pay for it. In summer the water heats from 18 to 45.
So, each shower in winter costs the family coffers 20, and in summer 15 if you don’t count the cost of cold water.
How much does the water heater heat??
Many residents of urban apartments faced with a lack of hot water, disconnection of hot water or its low temperature. If such problems occur all the time, it is a logical decision to purchase a boiler. But, its operation is associated with some inconveniences. For example, the appliance needs to initially heat cold water. To use it comfortably, you should understand how much the water heater heats.
Let’s examine how long it takes to heat water in a water heater to a predetermined temperature, depending on its type. When using an accumulating device, you should take into account that this period is affected by several factors:
The optimal temperature is 60°C. This is not an accidental choice. Lower temperatures contribute to the formation of bacteria. As a result, the water will smell unpleasant. But, few people use water heated to 65 °C in the home. Usually, it is diluted to a comfortable state.
It is important to know that the amount of mixed water (the usual temperature for humans at 40 ° C) will be twice the internal volume of the heater. This means that the tub can be filled with a unit with half the volume.
The next important point. after using up all the water, remember that the next portion will heat much faster. It only takes a few minutes, and you can use the boiler again. This is explained by the fact that the hot water is taken from the top of the tank, where it rises during heating.
As for the flow-through heater, it heats water faster. As it passes through a powerful heating element. It is not hot water but warm water at the tap. But, when using it, it is impossible to turn on two taps at once.
Conclusion. On flow-through appliances, the water is heated immediately. Accumulation water heater is equipped with a thermostat, so it brings the liquid to the set temperature. If you have a water heater with a 50 gallon tank, it takes 2.5 hours., To heat the water to 50°C.
How long does it take to heat the water heater?
DHW calculations, BKN. We find the volume, DHW capacity, capacity of the BKN(snake), heating time and t.п.
In this article we will consider practical tasks for finding the amount of hot water storage, DHW heating capacity. Heating equipment capacity. Time of readiness of hot water for various equipment and the like.
Which diagrams to use for DHW? Answer here: Diagrams for obtaining DHW from a boiler.
| 1. Calculation of the flow heater capacity 2. Calculating the output temperature of a flow heater 3. Calculation of the heating time of the electric water heater (boiler) 4. Calculation of heating time of the indirect water heater 5. How much hot water must be accumulated in order to shower for 30 minutes? 6. Calculation of DHW tank volume 7. Calculation of additional capacity for DHW. Boiler capacity = DHW heating capacity |
Problem 1. Find the capacity of the flow heater
Flow heater. is a water heater the volume of water in which may be so small that its existence is useless to accumulate water. Therefore it is considered that the flow-through water heater is not designed to accumulate hot water. And we do not take that into account in the calculations.
Given: Water flow rate is 0.2 l/sec. The cold water temperature is 15 degrees Celsius.
Find: The capacity of the flow-through water heater, assuming that it heats water up to 45 degrees.
How to find the heat capacity at different water temperatures is described here: https://infobos.see here/str/576.html
Answer: The power of the flow-through water heater is 25120 W = 25 kW.
It is not practical to consume a large amount of electricity. Therefore, it is necessary to accumulate (accumulate hot water) and reduce the load on the electrical wires.
Flow-through water heaters have unstable heating of hot water. The temperature of hot water will depend on the flow of water through the flow heater. Power or temperature switching sensors do not stabilize the temperature well.
If you want to find the output temperature of an existing flow heater at a certain flow rate.
Problem 2. Electric water heater (boiler) heating time
We have an electric water heater of 200 liters. The power of the electric heaters is 3 kW. You need to find the time to heat water from 10 degrees to 90 degrees Celsius.
Find: The time it takes the volume of water in the tank of the water heater to heat from 10 to 90 degrees.
The power consumption of the coils does not change with the temperature of the water in the tank. (How the power changes in the heat exchangers, we will consider in another problem.)
You need to find the wattage of the heaters, as for a flow heater. And this power will be enough to heat the water in 1 hour time.
If we know that with the power of the heaters of 18,6 kW, the tank heats water in 1 hour, then it’s not difficult to calculate the time with the power of the heaters of 3 kW.
Answer: The time of heating water from 10 to 90 degrees with a capacity of 200 liters will be 6 hours and 12 minutes.
Next, let’s calculate the heating time of the indirect heating boiler.
Task 3. Time of heating of the indirect heating boiler
Let’s take for example an indirect heating boiler: Buderus Logalux SU200
Power rating: 31.5 kW. Here it is not clear, from what considerations it is found. But look at the table below.
The snake is made of DN25 steel pipe. Internal diameter 25 mm. Outer 32 mm.
The hydraulic loss in the snake pipe is 190 mbar at a flow rate of 2 m3/hour. Which corresponds to 4.6 Kvs.
Of course, this resistance is high for water and new pipe. Most likely the risks of the pipeline overgrowth were taken into account, as well as the high viscosity coolant and the resistance at the joints. It is better to specify knowingly high losses, so that someone does not miscalculate in the calculations.
6 liters of water can fit into the snake pipe.
The length of this snake pipe is approximately 12 meters.
Heating time is written 25 minutes. It’s not clear how it’s counted. Let’s look at the table.
Consider the table for determining the capacity of the coil
Consider the SU200 snake heat output 32.8 kW
Coolant with a temperature of 80 degrees with a flow of 2 m3/hour flows into the coil.
In this case, in the DHW circuit, the flow rate is 805 l / hr. Comes in 10 degrees comes out 45 degrees
How to Get Hot Water Instantly | Hot Water Heaters
Consider the SU200 coil heat output of 27.5 kW
Coolant with a temperature of 80 degrees with a flow of 2 m3/hour flows into the coil.
In this case, in the DHW circuit, the flow rate is 475 l/h. Coolant with a temperature of 10 degrees flows in and out at a flow rate of 60 degrees
Unfortunately, I will not give you a calculation of the heating time of the indirect heating boiler. Because it is not a formula. There are a lot of intertwined values here: starting from formulas for heat transfer coefficient, correction coefficients for different heat exchangers (since water convection also introduces its deviations), and ending with iterations of calculations for the changed temperatures over time. I will probably make a calculator for this in the future.
You have to be content with what the manufacturer tells us BCH (boiler indirect heating).)
That the water will be ready in 25 minutes. Assuming that the flow in the coil will be 80 degrees with a flow rate of 2 m3/hour. Power of the boiler, which gives the heated fluid must not be less than 31.5 kW. Ready to receive water is considered 45-60 degrees. 45 degrees in the shower. 60 is very hot water, for example to wash the dishes.
How Long Does it Take to Heat a Hot Tub?
Problem 4. How much hot water must be accumulated in order to wash for 30 minutes in the shower?
Let’s calculate for the example with an electric water heater. Since the electric heater has a constant output of heat energy. The power of the heaters 3 kW.
The minimum temperature from the faucet is 45 degrees
The maximum temperature for heating water in the tank of 80 degrees
Comfortable flow of water flowing from the faucet 0.25 l / sec.
First let’s find the power that will provide this flow of water
Answer: 0.45 m3 = 450 liters of water needed to wash with the accumulated hot water. Assuming that the heaters do not heat the water at the time of hot water consumption.
This is proved as follows:
The energy used to heat the tank from 10 to 80:
That is, a 450 liter tank with a temperature of 80 degrees already contains 36 kW of thermal energy.
From this tank we take the energy: 450 liters of water with a temperature of 45 degrees (through the faucet). The thermal energy of 450 liters of water at a temperature of 45 degrees = 18 kW.
This is proven by the law of conservation of energy. Initially there was 36 kW of energy in the tank, took 18 kW of energy left 18 kW. That 18 kW of energy contains water with a temperature of 45 degrees. That is 70 degrees divided in half is 35 degrees. 35 degrees 10 degrees of cold water get a temperature of 45 degrees.
Let’s now try to find the volume of the tank when the boiler is heated to 90 degrees.
Used energy of hot water consumption at the outlet of the faucet 18317 W
Answer: The tank volume of 350 liters. An increase of only 10 degrees reduced the volume of the tank by 100 liters.
one heater heats water twice as slowly The most common problem. is when the heating elements are covered with scale, because of this, the boiler heats water to the desired temperature much slower, t. к. Heating elements first heat up the thick, calcified layers of scale, and only then, from the scale heats the water.
- T. time of water heating, hour
- V. volume of the water heating tank (l)
- tc. the final temperature of water, ° C (usually 60 ° C)
- tn. the initial temperature of water, ° C
- W. electric power of the heating element, kVT
How much electricity does the boiler consume: time of water heating.
The following appliance specifications will be required for the necessary self-calculation:
- Boiler tank volume
- Power of the device is written in its passport
- Time during which the water heats up in the tank
- In most cases for modern boilers electricity consumption figures per day are already prescribed in the data sheet
How to calculate for how long the boiler heats up:
According to the formula T=0,00116V(T2. T1)/W V. volume of the source tank T2. heated water temperature (usually about 70 degrees) T1. water temperature at the inlet to the tank W. heating element power, kW (written in the documentation)
For example, let’s calculate the heating time for a 50 liter boiler. V. 50 l. T2. 70 degrees T1. 10 degrees Power (for example). 2 kW
Let’s substitute the values in formula Т= 0,0011650(70. 10)/2 = 1,74 hours or 104 minutes. (To convert hundredths of a percent into minutes (0.74 in our case) you need 60 min 74% / 100% = 44.4 min.) Next multiply obtained time and power of heating element 21,74 = 3,48 kWh. Thus we got the electric power consumption for one time heating of 50 liters. water. (3,48 kWh)
So, a 2 kW boiler with a capacity of 50 liters will heat up in 104 minutes. And will spend three.48 kWh electricity.
Further calculations will depend on how many liters of hot water per day the occupants consume. For 3 occupants, for example, an average of 200 litres of hot water is consumed. The average daily consumption of hot water. Therefore, if 50 liters of water are heated. If 3.48 kWh of water is consumed, then 200 liters of hot water are heated by 3.48 kWh. 3.484 = 13.92 kWh of water per day. To calculate the consumption in rubles, you need to multiply the energy consumption per day with the cost of 1 kW of energy.
Types of water heaters
The principle of operation of household water heating devices is to transfer the heat in the water heater from the heating elements through a metal shell of heating elements or combustion chambers and to keep a certain amount of water in a heated state for quite a long time. Water heaters can be of the flow type, in which water is heated in a stream, and storage type, having a tank of a certain capacity in an insulating shell.
In a flow heater water heating time is insignificant, but the flow is limited. This property proves useful when you need to quickly use a small amount of hot water, such as washing hands or dishes. This water heater does not even require a water pipe, you just lift the storage tank, fill it manually and gravity flow through the water heater. This model is better to use in the country house, where you need to quickly heat water for a short period of use.
By type of fuel used water heaters can be:
Factors affecting water heating time Water heating time depends:
The best, that is, faster, water is heated in a water heater that uses an open flame, as its capacity is limited only by the amount of solid fuel loaded or the consumption per unit time of liquid and gaseous fuel. The area of heat transfer can also be made large: you need to install a tube heat exchanger in the tank with as many tubes as will fit in the boiler. Water heats up very quickly, so it is better to install such appliances in places that require heating of large volumes, such as in the heating system of the house.
Electric boilers are limited by the capacity of electrical wiring, usually not more than 2.5 kW, and the area of heating elements. The water in them heats up much more slowly. To save time it is better to heat water in advance and store it in an insulated container. The temperature drop in modern boilers does not exceed 15 degrees a day, resulting in a slight loss of electricity.
It is very important to maintain the heating process without scale formation, as a build-up of scale creates a layer of thermal insulation. This leads to a significant difficulty in heating, power overruns and overheating of heating elements. For this you need to choose a boiler with a system of low-temperature heating elements of increased length. They quickly heat water due to a large area of heat transfer and do not overheat it to a scum formation. In addition, a system of automatic maintenance of the set temperature and protection against overheating of heating elements in case of insufficient amount of water in the boiler must be applied.
