The second component

In general, the fee for hot water supply is calculated using the following formula:

P i gv = Vi gv × T hv+ (V v cr × Vi gv/ ∑ Vi gv × T v cr)

Vi Guards- the volume of hot water consumed during the billing period (month) in an apartment or non-residential premises

T xv- tariff for cold water

V v cr- the amount of thermal energy used during the billing period for heating cold water during independent production of hot water management company

∑ Vi gv- the total volume of hot water consumed during the billing period in all rooms of the house

T v cr- tariff for thermal energy

Calculation example:

Let's assume that hot water consumption in an apartment for a month is 7 m3. Hot water consumption throughout the house is 465 m3. The amount of thermal energy spent on heating hot water according to a common house meter is 33.5 Gcal

7 m 3 * 33.3 rub. + (33.5 Gcal * 7 m 3 / 465 m 3 * 1331.1 rub.) = 233.1 + 671.3 = 904.4 rub.

Of which:

233.1 rub. - payment for actual water consumption (DHW line in the receipt)

671.3 - payment for thermal energy spent on heating water to the required temperature (DHW heating line in the receipt)

IN in this example To heat one cube of hot water, 0.072 gigacalories of thermal energy were spent.

IN the value showing how many gigacalories were required to heat 1 cubic meter of water in the calculation period is called coefficient DHW heating

The heating coefficient is not the same from month to month and largely depends on the following parameters:

Cold water supply temperature. IN different time During the year, the cold water temperature ranges from +2 to +20 degrees. Accordingly, in order to heat water to the required temperature, different amounts of thermal energy will have to be expended.

The total volume of water consumed per month in all areas of the house. This value is largely influenced by the number of apartments that submitted their testimony in the current month, recalculations, and, in general, the discipline of residents in submitting their testimony.

Thermal energy consumption for hot water circulation. Water circulation in the pipes occurs continuously, including during the hours of minimum water consumption. That is, for example, at night, hot water is practically not used by residents, but thermal energy for heating water is still spent to maintain the required temperature of hot water in heated towel rails and at the entrances to apartments. This figure is especially high in new, sparsely populated buildings and stabilizes as the number of residents increases.

The average values ​​of DHW heating coefficients for each block are given in the section “Tariffs and calculation coefficients”

With the arrival of cold weather, many Russians are concerned about how to pay for utilities. For example, To How to calculate hot water and how often you should pay for these services. To answer all these questions, you first need to clarify whether a water meter is installed in this home. If the meter is installed, then the calculation is made according to a certain scheme.

The first thing you need to do is look at the receipt for housing and communal services that came last month. In this document you should find a column that indicates the amount of water consumed for the last month; we will need figures with indicators at the end of the last reporting period.

The first thing you need to do is look at the receipt for housing and communal services that came last month

After these readings are written out, they should be entered into a new document. In this case, we are talking about a receipt for payment for housing and communal services for the next reporting period. As you can see, the answers to the questions of how to calculate the cost of hot water using a meter and how to determine its consumption are quite simple. It is necessary to take all water meter readings promptly and correctly.

By the way, many management companies themselves enter the above information into payment document. In this case, you won’t have to look for data in old receipts. You also need to remember that in situations where the water meter has just been installed and these are the first readings, the previous ones will be zeros.

The initial readings of some modern meters may contain some other numbers rather than zeros

I would also like to clarify that the initial readings of some modern meters may contain not zeros, but some other numbers. In this case, in the receipt in the column where you need to indicate the previous readings, you need to leave exactly these numbers.

The process of searching for previous meter readings is very important if you need to understand the question of how to calculate hot water according to the meter. Without this data, it will not be possible to correctly calculate how many cubic meters of water were used in a given reporting period.

So, before you start studying the question of how to calculate the cost of hot water, you should learn how to take water meter readings.

Symbols on the meter

Almost all modern meters have a scale with at least 8 digits. The first 5 of which are black, but the second 3 are red.

Important

It is important to understand that only the first 3 digits, which are black, are displayed on the receipt. Because these are cubic meters data, and it is based on them that the cost of water is calculated. But the data that is colored red is liters. They do not need to be indicated on receipts. Although these data make it possible to estimate how many liters of water a particular family consumes over a certain reporting period. In this way, you can understand whether it is worth saving on this benefit or whether the consumption is within normal limits. And of course, you can determine how much water is spent on bathing procedures, and how much on washing dishes, and so on.

It is important to understand that the receipt displays only the first 3 digits, which are black.

To correctly understand how to calculate the tariff for hot water, you should know on what day of the month the readings of this device are taken. Here, you need to remember that water meter data must be taken at the end of each reporting period, after which it must be transferred to the appropriate authority. This can be done through a phone call or via the Internet.

On a note! It should be remembered that the figures are always indicated at the beginning of the reporting period (that is, those that were taken last month) and at the end (these are those that are being taken now).

This regulation is prescribed in the Decree of the Government of the Russian Federation dated May 6, 2011, number 354.

How to calculate the service correctly?

It is no secret that the legislation of our country is constantly changing, and therefore citizens are beginning to worry about the question of how to calculate hot water or any other utility costs.

If we talk specifically about water, then we should take into account the fact that payment consists of certain components:

• indicators of a water meter, which is located in the room and controls the flow of cold water;
• indicators of the meter, which shows the consumption of hot water in a given apartment;
• indicators of a device that calculates the cold water consumption of all tenants;
• data from the meter that monitors the consumption of the residents of the house; it is installed in the basement of the house;
• the share of a specific apartment in the total expense;
• the share that corresponds to a specific apartment in this building.

The penultimate indicator is the most incomprehensible, although in fact everything is quite accessible. It is taken into account when determining the amount of resource that was spent on everyone. It is also called “general house needs”. This, by the way, also applies to the last indicator; it is calculated when general house needs are calculated.

Calculation of hot water consumption

As for the first two indicators, they are quite understandable. They depend on the residents themselves, because a person can choose for himself whether to save the consumption of a particular resource or not. But in other cases, it all depends on how often wet cleaning is done in the entrance of the house, on the number of riser leaks, and so on.

The worst thing about this calculation system is that almost the entire part of the general household needs is fictitious. After all, in every building there are residents who incorrectly indicate their individual indicators, or, for example, one person is registered in their apartment, but five live. Then the general house needs had to be calculated based on the fact that 3 people live in apartment No. 5, and not 1. In this case, everyone else would have to pay a little less. As you can see, the question of how to calculate hot water still needs careful research.

That is why our officials are still trying to figure out how to calculate the fee for hot water and which mechanism would be the most successful.

Do everyone have the same rates?

To save money, you should always turn on the tap if you don’t need to use water at the moment.

To do this, just go to the website of the management company or just call them. Also, similar information is contained on the receipt that comes to each resident.

After this data has been found, the cost of the consumed cubic meters of resource should be calculated. Next, calculating the payment for hot water is quite simple; this is done in the same way as in the case of all other resources. You should take the number of cubic meters spent and multiply by the specific tariff.

It should be noted that today there are many ways you can save hot water consumption, thereby reducing your costs for paying for it. To do this, you can use special nozzles on the faucet; they will help you not spray water so much and control the pressure power. You should also open the tap valve not at full strength, so the stream will flow under less pressure, but the water will not fly out in all directions. And of course, you should always turn on the tap if you don’t need to use water at the moment. For example, when a person brushes his teeth or washes his hair (while his head is being soaped or his toothbrush is being lubricated, the water tap can be closed).

All these tips will help reduce the cost of paying for hot or cold water, thereby helping to correctly calculate hot water consumption.

Difference between hot and cold water calculations

Of course, this formula, as well as the one that takes into account hot water consumption, has many flaws. Due to the fact that general house indicators are taken into account, it is difficult to control where the difference went between the individual indicators of all residents and the data that was taken from the water meter installed on the house. Perhaps this is really true, and all this water was used to clean the entrance. But this is hard to believe. Of course, there are residents who deceive the state and give incorrect data, but there are also errors in the operation of the pipeline system itself (the sewer pipes in most houses are old and can leak, so the water goes nowhere).

Hot water invoice

For a long time now, our government has been thinking about how to correctly calculate hot and cold water and how to improve the existing mechanism.

For example, in 2013, our authorities came to the conclusion that it was necessary to establish standard norms for general household needs and that this data should be taken into account when calculating the cost of one cubic meter water. This helped to slightly restrain the zeal of our management companies and help the citizens of the country. You can find out these numbers from the management company. But this only applies to those cases where residents have entered into an agreement with the management company. If we are talking about Vodokanal, then each locality will have its own separate fixed minimum payment. And, for example, an overpayment in a given reporting period may cover expenses in the next one.

As you can see, there is a whole diagram that makes it clear how to calculate hot water heating or how to calculate how much to pay for cold water consumption.

Calculation of the cost of thermal energy for heating 1 sq. meters of total area in 2017:

January-April 0.0366 Gcal/sq. m * 1197.50 rub/Gcal = 43.8285 rub/sq.m.

May 0.0122 Gcal/sq. m * 1197.50 rub./Gcal = 14.6095 rub./sq.m

October 0.0322 * 1211.33 rubles/Gcal = 39.0048 rubles/sq.m.

November-December 0.0366 Gcal/sq. m * 1211.33 rub./Gcal = 44.3347 rub./sq.m

Calculation of the cost of service for hot water supply per person in 2017:

January-June 0.2120 Gcal/per person. per month *1197.50 rub./Gcal = 253.87 rub./person.

July-December 0.2120 Gcal/per person. per month *1211.33 rub./Gcal = 256.80 rub./person.

Calculation of the cost of service for hot water supply using a domestic hot water meter in 2017:

January – June 0.0467 Gcal/cub. m * 1197.50 rub./Gcal = 55.9233 rub./cubic. m.

July-December 0.0467 Gcal/cu.m. m * 1211.33 rub./Gcal = 56.5691 rub./cubic. m

2016

Calculation of the cost of thermal energy for heating 1 sq. meters of total area in 2016:

January-April 0.0366 Gcal/sq. m * 1170.57 rub/Gcal = 42.8429 rub/sq.m.

May 0.0122 Gcal/sq. m * 1170.57 rub./Gcal = 14.2810 rub./sq.m

October 0.0322 * 1197.50 rubles/Gcal = 38.5595 rubles/sq.m.

November-December 0.0366 Gcal/sq. m * 1197.50 rub./Gcal = 43.8285 rub./sq.m

Calculation of the cost of hot water supply services per person in 2016:

January-June 0.2120 Gcal/per person. per month *1170.57 rub./Gcal = 248.16 rub./person.

July-December 0.2120 Gcal/per person. per month *1197.50 rub./Gcal = 253.87 rub./person.

Calculation of the cost of service for hot water supply using a domestic hot water meter in 2016:

January – June 0.0467 Gcal/cub. m * 1170.57 rub./Gcal = 54.6656 rub./cubic. m

July-December 0.0467 Gcal/cu.m. m * 1197.50 rub./Gcal = 55.9233 rub./cubic. m

2015

Calculation of the cost of thermal energy for heating 1 sq. meters of total area in 2015:

Heating consumption standard * Thermal energy tariff = cost of thermal energy for heating 1 sq. m:

January-April 0.0366 Gcal/sq. m * 990.50 rub./Gcal = 36.2523 rub./sq.m

May 0.0122 Gcal/sq. m * 990.50 rub./Gcal = 12.0841 rub./sq.m

October 0.0322 * 1170.57 rubles/Gcal = 37.6924 rubles/sq.m.

November-December 0.0366 Gcal/sq. m * 1170.57 rub./Gcal = 42.8429 rub./sq.m

Calculation of the cost of hot water supply services per person in 2015:

Standard DHW consumption* Heat tariff = cost DHW services for 1 person

An example of calculating the cost of a hot water supply service for 1 person with a fully equipped apartment (from 1 to 10 storeys, equipped with a sink, washbasin, bathtub 1500-1700 mm long with shower) in the absence of hot water meters:

January-June 0.2120 Gcal/per person. per month *990.50 rub./Gcal = 209.986 rub./person.

July-December 0.2120 Gcal/per person. per month *1170.57 rub./Gcal = 248.1608 rub./person.

Calculation of the cost of service for hot water supply using a domestic hot water meter in 2015:

The standard thermal energy consumption for heating is 1 cubic meter. m of water * Tariff for thermal energy = cost of service for heating 1 cubic meter. m

January – June 0.0467 Gcal/cub. m * 990.50 rub./Gcal = 46.2564 rub./cubic. m

July-December 0.0467 Gcal/cu.m. m * 1170.57 rub./Gcal = 54.6656 rub./cubic. m

year 2014

Calculation of the cost of thermal energy for heating 1 sq. meters of total area in 2014:

Heating consumption standard * Thermal energy tariff = cost of thermal energy for heating 1 sq. m:

January-April 0.0366 Gcal/sq. m * 934.43 rub./Gcal = 34.2001 rub./sq.m

May 0.0122 Gcal/sq. m * 934.43 rub./Gcal = 11.4000 rub./sq.m

October 0.0322 Gcal/sq. m * 990.50 rub./Gcal = 31.8941 rub./sq. m

November – December 0.0366 Gcal/sq. m * 990.50 rub./Gcal = 36.2523 rub./sq.m

Calculation of the cost of service for hot water supply per 1 person in 2014:

DHW consumption standard * Heat energy tariff = cost of DHW service per 1 person

An example of calculating the cost of a hot water supply service for 1 person with a fully equipped apartment (from 1 to 10 storeys, equipped with a sink, washbasin, bathtub 1500-1700 mm long with shower) in the absence of hot water meters:

January-June 0.2120 Gcal/per person. per month * 934.43 rub./Gcal = 198.0991 rub./person.

July – December 0.2120 Gcal/per person. per month * 990.50 rub./Gcal = 209.986 rub./person.

Calculation of the cost of service for hot water supply using a domestic hot water meter in 2014:

The standard thermal energy consumption for heating is 1 cubic meter. m of water * Tariff for thermal energy = cost of service for heating 1 cubic meter. m

January – June 0.0467 Gcal/cub. m * 934.43 rub./Gcal = 43.6378 rub./cubic. m

July – December 0.0467 Gcal/cubic. m * 990.50 rub./Gcal = 46.2564 rub./cubic. m

year 2013

Calculation of the cost of thermal energy for heating 1 sq. meters of total area in 2013:

Heating consumption standard

• January-April 0.0366 Gcal/sq. m * 851.03 rub./Gcal = 31.1477 rub./sq.m
• May 0.0122 Gcal/sq. m *851.03 rub./Gcal =10.3826 rub./sq.m
• October 0.0322 Gcal/sq. m * 934.43 rub./Gcal = 30.0886 rub./sq. m
• November – December 0.0366 Gcal/sq. m * 934.43 rub./Gcal = 34.2001 rub./sq.m

Calculation of the cost of service for hot water supply per 1 person in 2013:

DHW consumption standard

An example of calculating the cost of a hot water supply service for 1 person with a fully equipped apartment (from 1 to 10 storeys, equipped with a sink, washbasin, bathtub 1500-1700 mm long with shower) in the absence of hot water meters:

• January-June 0.2120 Gcal/per person. per month * 851.03 rub./Gcal = 180.4184 rub./person.
• July – December 0.2120 Gcal/per person. per month * 934.43 rub./Gcal = 198.0991 rub./person.

Calculation of the cost of service for hot water supply using a domestic hot water meter in 2013:

The standard thermal energy consumption for heating is 1 cubic meter. m of water

• January – June 0.0467 Gcal/cub. m * 851.03 rub./Gcal = 39.7431 rub./cubic. m
• July – December 0.0467 Gcal/cubic. m * 934.43 rub./Gcal = 43.6378 rub./cubic. m

year 2012

Calculation of the cost of thermal energy for heating 1 sq. meters of total area in 2012:

Heating consumption standard * Thermal energy tariff (supplier MUP "ChKTS" or Mechel-Energo LLC) = The cost of thermal energy for heating 1 sq. m

• January-April 0.0366 Gcal/sq. m * 747.48 rub./Gcal = 27.3578 rub./sq. m
• May 0.0122 Gcal/sq. m * 747.48 rub./Gcal = 9.1193 rub./sq. m
• October 0.0322 Gcal/sq. m * 851.03 rub./Gcal = 27.4032 rub./sq. m
• November - December 0.0366 Gcal/sq. m * 851.03 rub./Gcal = 31.1477 rub./sq. m

Calculation of the cost of hot water supply services per person in 2012:

DHW consumption standard * Heat energy tariff (supplier MUP "ChKTS" or Mechel-Energo LLC) = cost of DHW service per 1 person

An example of calculating the cost of a hot water supply service for 1 person with a fully equipped apartment (from 1 to 10 storeys, equipped with a sink, washbasin, bathtub 1500-1700 mm long with shower) in the absence of hot water meters:

• January - June 0.2120 Gcal/per 1 person. per month * 747.48 rub./Gcal = 158.47 rub./person.
• July - August 0.2120 Gcal/per person. per month * 792.47 rub./Gcal = 168.00 rub./person.
• September - December 0.2120 Gcal/per person. per month * 851.03 rub./Gcal = 180.42 rub./person.

Calculation of the cost of hot water supply services using a domestic hot water meter in 2012:

The standard thermal energy consumption for heating is 1 cubic meter. m of water * Tariff for thermal energy (supplier MUP "ChKTS" or LLC "Mechel-Energo") = cost of service for heating 1 cubic. m

• January – June 0.0467 Gcal/cub. m * 747.48 rub./Gcal = 34.9073 rub./cubic. m
• July – August 0.0467 Gcal/cubic. m * 792.47 rub./Gcal = 37.0083 rub./cubic. m
• September–December 0.0467 Gcal/cubic. m * 851.03 rub./Gcal = 39.7431 rub./cubic. m

The main parameters of residential buildings are water supply, sewer system and delivery electrical energy. Regardless of the number of residents ( a private house or multi-storey), the calculation of the main networks must be carried out according to certain rules, using the appropriate formulas. It does not take much time to create the correct electrical circuit; it is much more difficult to decide on the water supply. A particular difficulty is the design and calculation of hot water supply. In order to carry out all operations correctly, you need to know not only the technical side of the issue, but also the regulatory framework.

The most commonly chosen type of network is the circulation type. The principle of operation of such a system is the constant circulation of liquid. The only disadvantage of a circulating hot water supply system is that it is too expensive. The costs are only justified when the maximum number of users for a residential building is reached.

Also, in addition to the high pricing policy, constant circulation of water leads to significant heat losses, which entails additional costs. If there is a circulation system, designers try to reduce the length of the pipeline as much as possible. This option allows for additional savings on liquid transportation.

What is the waiting period and how is it calculated?

The waiting period is the time period that passes from the time the user opens the tap until hot water is supplied. They try to reduce this time as much as possible; for this purpose, the hot water supply system is optimized, adjustments are made, and if the indicators are poor, they are modernized.

To set the waiting period, generally accepted standards are used. To calculate it correctly, you should know the following:

• To reduce the waiting period, you should create high pressure water in the system. But setting too high pressure parameters can damage the pipeline.
• To reduce the waiting period, increase throughput device through which the user receives liquid.
• The waiting period increases in direct proportion to the internal diameter of the pipeline, as well as if there is a circuit at a large distance from the consumer.

The correct sequence for calculating the waiting period is:

• Determination of the number of consumers. After the exact figure, you should make a small reserve, since there are peak hot water consumption.
• Determination of the characteristics of the pipeline: length, internal diameter of the pipes, as well as the material from which they are made.
• Multiplying the length of the pipeline and its internal diameter by the specific volume of water, which is measured in l/s.
• Determination of the shortest and most convenient fluid path. This parameter also includes sections of the circuit located farthest from the water tap. All volumes of water are also added.
• The amount of liquid is divided by the water flow per second. When obtaining this parameter, the total fluid pressure in the system is also taken into account.

To achieve the most accurate results, you should correctly calculate the specific volume of the pipeline. The following formula is used for this:

Cs = 10 (F/100)2 3.14/4, where F is the internal diameter of the pipeline.

When determining the specific volume, you cannot use the value of both the external and nominal diameter of the pipes. This will significantly reduce the accuracy of calculations. There are tables in which the specific volume value is pre-calculated for certain materials (copper and steel).

Calculation of hot water consumption per day

The amount of hot water that the user needs per day is a parameter calculated in advance. Typically, such data is taken from tables, where they are divided by type of room and its square footage. European parameters should not be confused with those of other countries; they are strikingly different from each other.

On average, hot water consumption per person per day ranges from 25 to 50 liters. Compiling and calculating the amount of hot water per person is possible only after the status of the room or building is known.

How to calculate a pipeline

For long-term operation of a hot liquid transportation system, the pipeline should be calculated under peak load conditions. This allows you to make a certain reserve, which will eliminate the occurrence of malfunctions in the system with a sharp increase in pressure.

To calculate a pipeline, most often, ready-made diagrams and tables with relevant data are used. The material most often used is copper or galvanized steel. You should know that an important calculation parameter is the equivalent Fixture Unit. This device called a conditional element for a certain type of water folding mechanisms.

Pipeline calculation sequence:

• The calculation begins with determining the Fixture Unit parameter, which is mandatory for each water intake point.
• The main hot water transportation network is divided into separate sections (nodes). The principle is based on the design of the heating system.
• Find the total number of Fixture Units that will be located at different sites.
• Based on the total Fixture Unit amount and the type of building, the estimated flow rate for each section of the system is found.
• Design flow, also referred to as throughput volume, is an important component in determining the diameter of the pipeline. The internal diameter of the pipes is determined under the condition that the final figures will not exceed generally established limits.

When calculating the circulation network, you can use general position, that for each Fixture Unit element there is 3 l/s. A separate point is the calculation recirculation pump, which has a certain throughput capacity. To determine this parameter, it is necessary to know the exact number of water points.

To provide the circulation network with additional savings, a thermostat is installed on the pump. The thermostat ensures that the device turns on when the temperature of the transported liquid drops. When the water temperature on the return circuit reaches a value less than the nominal value by 5 degrees, the pump turns off.

What you need to have to start calculating hot water supply

It is impossible to start calculating a hot water supply system without having technical and design documentation for the house. At the same time, the size of the house is not important; a private plot requires the same plan as a multi-story building.

The calculation begins with a certified architectural plan, on which the selected correct location buildings, as well as the placement of sanitary fixtures. The location of the house will help you choose the water supply system along the shortest route.

It is necessary to know the number of people who will live in the building. Naturally, it is impossible to find out the exact number of residents, so it is better to carry out the calculation using the maximum data. Such figures will allow you to calculate the correct time of peak loads.

Determine the location where the hot water supply equipment will be placed. This area, must be indicated on the diagram.

Example 1. Calculate the hot water supply system for a five-story, two-section residential building. The network was designed based on the building plan given in appendix. 1, 2. The design diagram of the network is shown in Fig. 2.1 (similar to the cold water supply network diagram).

Superheated water from the heating network with parameters tn = 120 °C and tk = 70 °C is used as a coolant.

Data on cold water supply are taken from example 1 given in clause 1.7.

The hot water supply system is centralized with the preparation of hot water in a high-speed water heater with variable output using coolant from the heating network.

The hot water supply network diagram is adopted as a dead-end with lower mains routing (as is the cold water supply network).

Since the consumption of hot water is uneven, the network is adopted with circulation in the main and risers.

The estimated costs of hot water and heat are determined. Hot water consumption in network sections is determined by formula (2.1). Since the system serves identical consumers, the value P h is found according to formula (2.3).

Here the magnitude and are taken according to adj. 3 [1].

The value is determined by formula (2.7)

The value is taken according to adj. 3 [1].

The maximum hourly consumption of hot water is determined by formula (2.5)

The value is determined according to Table 2, appendix. 4 [1].

The average hourly consumption of hot water is determined by formula (2.8)

, m 3 / h

The maximum hourly heat consumption is determined by formula (2.11)

Rice. 2.1. Design diagram of the hot water supply network

Table 2.3

An example of calculating a hot water supply network in water withdrawal mode.

The heating surface of the heating tubes of the water heater is determined by formula (2.13). The calculated temperature difference is determined by formula (2.14). Let's take the coolant parameters t n = 120 °C, t to= 70 °C, parameters of heated water t h=60 C and t c=5 C.

°C

According to adj. 8 [2] accept high-speed water heater N 11 VTI - MosEnergo with a heating surface of one section of 5.89 m. The required number of sections will be determined by formula (2.16)

sections

Section length 2000 mm, outer diameter of the body 219 mm, number of tubes 64.

The calculation of the hot water supply system in water withdrawal mode is carried out in tabular form (Table 2.3).

Pressure losses in sections of the hot water supply network were determined using formula (2.19). Magnitude K l 0.2 was accepted for distribution pipelines and 0.1 for water risers without heated towel rails. (It is accepted to connect heated towel rails to the heating network.)

Total losses the pressure on line 1-input is 21125 mm or 21.1 m. Since the riser St TZ-2 has twice the hydraulic load than the riser St TZ-1, a diameter of 25 mm was adopted for it and the speeds and pressure losses on this riser were calculated. Since the pressure losses in sections 4 - 8 turned out to be greater than in sections 11 - 15, the riser St TZ-1 was taken as the design one.

The required pressure at the entrance to the building for the operation of the hot water supply system is determined by formula (2.20)

Here, the pressure loss in the water heater is determined by formula (2.17)

The calculation of the hot water supply system in circulation mode is carried out in tabular form (Table 2.4). The design diagram of the network is shown in Fig. 2.1.

Table 2.4.

Calculation of hot water supply network in circulation mode

The circulation flow in the sections was taken according to formula (2.23). The diameters of the circulation pipes in the risers were taken to be the same as the diameters of the distribution pipes; on highways they were accepted one size smaller.

The total head loss due to friction and local resistance in the network was 1340 mm. Here it is necessary to take into account the pressure loss in the water heater when the circulation flow is passed, which are determined by formula (2.17)

M = 7.9 mm = 8 mm

Thus, the pressure loss in the design circulation ring will be

Opportunity identified natural circulation. The natural circulation pressure is determined for a system with lower wiring according to formula (2.25)

13.2 (986.92 - 985.73) + 2(985.73 - 983.24) = 20.69 mm

The pressure loss in the circulation ring (1348 mm) significantly exceeds the natural circulation pressure (20.69 mm), so pump circulation is designed.

The performance of the circulation pump is determined by formula (2.26)

The required pump pressure is determined by formula (2.27)

According to adj. XIII [3] we accept the K50-32-125 (K8/18b) pump with a nominal capacity of 2.5 l/s and a head of 11.4 m. These values ​​​​exceed the calculated ones, therefore it is possible to replace the engine with a speed of 2860 rpm with 1480 rpm min. From formula (7.1) [3] we determine that

l/s; m.

In this case, the power on the pump shaft will become

kW

Here the quantities Q 1 , H 1 , N 1 correspond to the number of revolutions n 1=1480 rpm

3. DESIGN OF THE INTERNAL WATER WATER SYSTEM

The drainage system includes a set of engineering devices inside the building for receiving Wastewater and their discharge outside the building into the street drainage network. It consists of the following main elements:

Wastewater receivers - sanitary fixtures;

Hydraulic valves (siphons);

Branch lines;

Risers with exhaust pipes;

Issues.

A special place is occupied by the yard drainage network, which serves to drain wastewater from buildings into street sewers.

DHW calculations, BKN. We find the volume, power of the hot water supply, power of the BKN (snake), warm-up time, etc.

In this article we will consider practical problems for finding the volume of hot water accumulation and DHW heating power. Heating equipment power. Hot water readiness time for various equipment and the like.

Let's look at examples of tasks:

Task 1. Find power instantaneous water heater

Instantaneous water heater- This is a water heater, the volume of water in which can be so small that its existence is useless for storing water. Therefore, it is believed that an instantaneous water heater is not intended to accumulate hot water. And we do not take this into account in our calculations.

Given: Water consumption is 0.2 l/sec. Cold water temperature 15 degrees Celsius.

Find: The power of an instantaneous water heater, provided that it heats the water to 45 degrees.

Solution

Answer: The power of the instantaneous water heater will be 25120 W = 25 kW.

It is practically not advisable to consume a large number of electricity. Therefore, it is necessary to accumulate (accumulate hot water) and reduce the load on electrical wires.

Instantaneous water heaters have unstable heating of hot water. The hot water temperature will depend on the water flow through the instantaneous water heater. Power or temperature switching sensors do not allow for good temperature stabilization.

If you want to find the output temperature of an existing instantaneous water heater at a certain flow rate.

Task 2. Electric water heater (boiler) heating time

We have an electric water heater with a capacity of 200 liters. The power of electric heating elements is 3 kW. It is necessary to find the time for heating water from 10 degrees to 90 degrees Celsius.

Given:

Wt = 3 kW = 3000 W.

Find: The time it takes for the volume of water in the water heater tank to heat up from 10 to 90 degrees.

Solution

The power consumption of heating elements does not change depending on the temperature of the water in the tank. (We will consider how power changes in heat exchangers in another problem.)

It is necessary to find the power of heating elements, as for an instantaneous water heater. And this power will be enough to heat water in 1 hour.

If it is known that with a heating element power of 18.6 kW, the tank will heat water in 1 hour, then it is not difficult to calculate the time with a heating element power of 3 kW.

Answer: The time for heating water from 10 to 90 degrees with a capacity of 200 liters will be 6 hours 12 minutes.

Task 3. Indirect heating boiler heating time

Let's take an example of an indirect heating boiler: Buderus Logalux SU200

Rated power: 31.5 kW. It is not clear for what reasons this was found. But look at the table below.

Volume 200 liters

The snake is made from steel pipe DN25. Inner diameter 25 mm. Outer 32 mm.

Hydraulic losses in the snake pipe indicate 190 mbar at a flow rate of 2 m3/hour. Which corresponds to 4.6.

Of course, this resistance is high for water and new pipe. Most likely, there were risks associated with pipeline overgrowth, high-viscosity coolant and resistance at connections. It is better to indicate obviously large losses so that someone does not miscalculate.

Heat exchange area 0.9 m2.

Fits 6 liters of water in a snake pipe.

The length of this snake pipe is approximately 12 meters.

Warm-up time is written as 25 minutes. It is not clear how this was calculated. Let's look at the table.

BKN snake power table

Consider the table for determining the power of the snake

Consider the SU200 snake heat dissipation power of 32.8 kW

At the same time, in the circuit DHW consumption 805 l/hour. Flows in 10 degrees comes out 45 degrees

Another variant

Consider the SU200 snake heat dissipation power of 27.5 kW

A coolant with a temperature of 80 degrees flows into the snake at a flow rate of 2 m3/hour.

At the same time, the flow rate in the DHW circuit is 475 l/hour. Flows in 10 degrees comes out 60 degrees

Other characteristics

Unfortunately, I will not provide you with a calculation of the heating time for an indirect heating boiler. Because this is not one formula. There are many intertwined meanings here: Starting from the heat transfer coefficient formulas, correction factors for different heat exchangers (since water convection also introduces its own deviations), and this ends with an iteration of calculations based on changed temperatures over time. Here, most likely in the future I will make a calculation calculator.

You will have to be content with what the manufacturer of the BKN (Indirect Heating Boiler) tells us.

And the manufacturer tells us the following:

That the water will be ready in 25 minutes. Provided that the flow into the snake will be 80 degrees with a flow rate of 2 m3/hour. The power of the boiler producing heated coolant should not be lower than 31.5 kW. Ready-to-drink water is considered to be 45-60 degrees. 45 degrees wash in the shower. 60 is very hot water, for example for washing dishes.

Task 4. How much hot water does it take to take a 30-minute shower?

Let's calculate for example with electric water heater. Since the electric heating element has a constant output of thermal energy. The power of the heating elements is 3 kW.

Given:

Cold water 10 degrees

Minimum tap temperature 45 degrees

The maximum temperature of water heating in the tank is 80 degrees

Comfortable flow rate of flowing water from the tap is 0.25 l/sec.

Solution

First, let's find the power that will provide this water flow

Answer: 0.45 m3 = 450 liters of water will be needed to wash off the accumulated hot water. Provided that the heating elements do not heat the water at the time of hot water consumption.

It may seem to many that there is no accounting for the entry of cold water into the tank. How to calculate the loss of thermal energy when water temperature of 10 degrees enters water of 80 degrees. There will obviously be a loss of thermal energy.

This is proven as follows:

Energy spent on heating the tank from 10 to 80:

That is, a tank with a volume of 450 liters and a temperature of 80 degrees already contains 36 kW of thermal energy.

From this tank we take energy: 450 liters of water with a temperature of 45 degrees (through the tap). Thermal energy water volume of 450 liters with 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, they took 18 kW, leaving 18 kW. This 18 kW of energy contains water at a temperature of 45 degrees. That is, 70 degrees divided in half gives 35 degrees. 35 degrees + 10 degrees cold water we get a temperature of 45 degrees.

The main thing here is to understand what the law of conservation of energy is. This energy from the tank cannot escape to no one knows where! We know that 18 kW came out of the tap, and there was initially 36 kW in the tank. Taking 18 kW from the tank, we will lower the temperature in the tank to 45 degrees (to the average temperature (80+10)/2=45).

Let's now try to find the volume of the tank when the boiler is heated to 90 degrees.

Used energy consumption of hot water at the outlet of the tap 18317 W

Answer: Tank volume 350 liters. An increase of just 10 degrees reduced the tank volume by 100 liters.

This may seem unrealistic to many. This can be explained as follows: 100/450 = 0.22 is not that much. Stored temperature difference (80-45)

Let's prove that this is a valid formula in another way:

Of course this is a rough theoretical calculation! In the theoretical calculation, we take into account that the temperature in the tank between the upper and lower layers is instantly mixed. If we take into account the fact that the water is hotter at the top and colder at the bottom, then the volume of the tank can be reduced by the temperature difference. It is not for nothing that vertical tanks are considered more efficient in storing thermal energy. Since the greater the height of the tank, the higher the temperature difference between the top and bottom layers. When hot water is consumed quickly, this temperature difference is higher. When there is no water flow, very slowly the temperature in the tank becomes uniform.

We will simply lower 45 degrees to 10 degrees lower. For place 45 it will be 35 degrees.

Answer: Due to the temperature shift, we reduced the volume of the tank by another 0.35-0.286 = 64 liters.

We calculated on the condition that at the time of hot water consumption the heating elements were not working and did not heat the water.

Let's now calculate under the condition that the tank begins to heat the water at the moment of hot water consumption.

Let's add another power of 3 kW.

In 30 minutes of operation we will get half the power of 1.5 kW.

Then you need to subtract this power.

Answer: The tank volume will be 410 liters.

Task 5. Calculation of additional power for hot water supply

Consider a private house with an area of ​​200 m2. The maximum power consumption for heating the house is 15 kW.

4 people live in the house.

Find: Additional power for domestic hot water

That is, we need to find the boiler power taking into account: House heating power + hot water heating.

For this purpose it is better to use scheme No. 4:

Solution

It is necessary to find how many liters of hot water a person consumes per day:

SNiP 2.04.01-85* states that, according to statistics, 300 liters per day are consumed per person. Of these, 120 liters are for hot water at a temperature of 60 degrees. These city statistics are mixed with people who are not used to using so much water per day. I can offer my consumption statistics: If you like to take hot baths every day, you can spend 300-500 liters of hot water per day for just one person.

Volume of water per day for 4 people:

That is, to the heating power of a house of 15 kW, you need to add 930 W = 15930 W.

But if you take into account the fact that at night (from 23:00 to 7:00) you do not consume hot water, you get 16 hours when you consume hot water:

Answer: Boiler power = 15 kW + 1.4 kW for hot water supply. = 16.4 kW.

But in this calculation there is a risk that at the moment of high consumption of hot water at certain hours you will stop heating the house for a long time.

If you want to have a good flow of hot water for a private home, then choose a BKN of at least 30 kW. This will allow you to have an unlimited flow rate of 0.22 l/sec. with a temperature of at least 45 degrees. The boiler power should not be less than 30 kW.

In general, the objectives of this article were focused on energy conservation. We did not consider what was happening at a particular moment, but took a different route to calculate. We followed the undisputed method of energy conservation. The energy expended at the outlet of the tap will then be equal to the energy coming from the boiler equipment. Knowing the power in two different places, you can find the time spent.

Once we discussed the calculation of hot water supply on the forum: http://santeh-baza.ru/viewtopic.php?f=7&t=78

Calculation of hot water supply systems consists of determining the diameters of the supply and circulation pipelines, selecting water heaters (heat exchangers), generators and heat accumulators (if necessary), determining the required pressure at the inlet, selecting booster and circulation pumps, if they are necessary.

Calculation of a hot water supply system consists of the following sections:

The estimated costs of water and heat are determined and, on the basis of this, the power and dimensions of water heaters are determined.

The supply (distribution) network is calculated in water collection mode.

The hot water supply network is calculated in circulation mode; the possibilities of using natural circulation are determined, and if necessary, parameters are determined and circulation pumps are selected.

In accordance with the individual assignment for coursework and diploma design, calculations of storage tanks and coolant networks can be made.

2.2.1. Determination of estimated consumption of hot water and heat. Selection of water heaters

To determine the heating surface and further selection of water heaters, hourly consumption of hot water and heat is required; to calculate pipelines, second consumption of hot water is required.

In accordance with paragraph 3 of SNiP 2.04.01-85, the second and hourly consumption of hot water are determined using the same formulas as for cold water supply.

The maximum second consumption of hot water at any calculated section of the network is determined by the formula:

- second consumption of hot water by one device, which is determined by:

a separate device - in accordance with the mandatory Appendix 2;

different devices serving the same consumers - according to Appendix 3;

various devices serving different water consumers - according to the formula:

, (2.2)

- second consumption of hot water, l/s, by one water tap for each group of consumers: accepted according to Appendix 3;

N i – number of water taps for each type of water consumer;

- probability of operation of devices determined for each group of water consumers;

a is the coefficient determined according to Appendix 4 depending on the total number of devices N in the network section and the probability of their action P, which is determined by the formulas:

a) with identical water consumers in buildings or structures

, (2.3)

Where
- maximum hourly consumption of hot water of 1 liter by one water consumer, taken according to Appendix 3;

U – number of hot water consumers in a building or structure;

N – number of devices served by the hot water supply system;

b) with different groups of water consumers in buildings for various purposes

, (2.4)

and N i - values ​​​​related to each group of hot water consumers.

The maximum hourly consumption of hot water, m 3 / h, is determined by the formula:

, (2.5)

- hourly consumption of hot water by one device, which is determined by:

a) with identical consumers - according to Appendix 3;

b) for different consumers - according to the formula

, l/s (2.6)

And
- values ​​related to each type of hot water consumer;

magnitude determined by the formula:

, (2.7)

- coefficient determined according to Appendix 4 depending on the total number of devices N in the hot water supply system and the probability of their operation P.

Average hourly hot water consumption , m 3 / h, for the period (day, shift) of maximum water consumption, incl., is determined by the formula:

, (2.8)

- maximum daily hot water consumption of 1 liter by one water consumer, taken according to Appendix 3;

U – number of hot water consumers.

The amount of heat (heat flow) for the period (day, shift) of maximum water consumption for the needs of hot water supply, taking into account heat loss, is determined by the formulas:

a) within a maximum hour

b) during the average hour

And - maximum and average hourly consumption of hot water in m 3 / h, determined by formulas (2.5) and (2.8);

t s – design temperature cold water; in the absence of data in the building, t is taken equal to +5ºС;

Q ht – heat losses from supply and circulation pipelines, kW, which are determined by calculation depending on the lengths of pipeline sections, outer diameters of pipes, the difference in temperature of hot water and the environment surrounding the pipeline and the heat transfer coefficient through the walls of the pipes; In this case, the efficiency of pipe thermal insulation is taken into account. Depending on these values, heat loss is given in various reference books.

When calculating in course projects, heat loss Q ht by supply and circulation pipes can be taken in the amount of 0.2-0.3 of the amount of heat required for preparing hot water.

In this case, formulas (2.9) and (2.10) will take the form:

a) , kW (2.11)

b) , kW (2.12)

A smaller percentage of heat loss is accepted for systems without circulation. Most civil buildings use high-speed sectional water heaters with variable output, i.e. with adjustable coolant consumer. Such water heaters do not require heat storage tanks and are designed for maximum hourly heat flow
.

The selection of water heaters consists of determining the heating surface of the coils using the formula:

, m 3 (2.13)

K – heat transfer coefficient of the water heater, taken according to table 11.2; for high-speed water-water heaters with brass heating tubes, the value of k can be taken in the range of 1200-3000 W/m sq., ºC, with a smaller one accepted for devices with smaller section diameters;

µ - coefficient of reduction in heat transfer through the heat exchange surface due to deposits on the walls (µ = 0.7);

- calculated temperature difference between the coolant and heated water; for counterflow high-speed water heaters
º is determined by the formula:

, ºС (2.14)

Δt b and Δt m – greater and lesser temperature difference between the coolant and heated water at the ends of the water heater.

The parameters of the coolant during the winter calculation period, when the heating networks of buildings are operating, are assumed to be 110-130 ºC in the supply pipeline and -70 in the return pipeline, the parameters of the heated water during this period are t c = 5ºC and t c = 60...70 ºC. IN summer period the heating network only works for preparing hot water; The parameters of the coolant during this period in the supply pipeline are 70...80 ºC and in the return pipeline 30...40 ºC, the parameters of the heated water are t c = 10...20 ºC and t c = 60...70 ºC.

When calculating the heating surface of a water heater, it may happen that the determining period will be the summer period, when the temperature of the coolant is lower.

For cylinder water heaters, the calculation for the temperature difference is determined by the formula:

, ºC (2.15)

t n and t k – initial and final temperature of the coolant;

t h and t c – temperature of hot and cold water.

However, DHW water heaters are used for industrial buildings. They take up a lot of space and in these cases can be installed outdoors.

The heat transfer coefficient for such water heaters, according to table 11.2, is 348 W/m2 ºC.

The required number of standard sections of water heaters is determined:

, pcs (2.16)

F – design heating surface of the water heater, m2;

f – heating surface of one section of the water heater, adopted according to Appendix 8.

The pressure loss in a high-speed water heater can be determined by the formula:

, m (2.17)

n – coefficient taking into account the overgrowth of pipes, is taken according to experimental data: in their absence, with one cleaning of the water heater per year n=4;

m – coefficient of hydraulic resistance of one section of the water heater: with a section length of 4 m m=0.75, with a section length of 2 m m=0.4;

n in – number of sections of the water heater;

v is the speed of movement of heated water in the water heater tubes without taking into account their overgrowth.

, m/s (2.18)

q h – maximum second water flow through the water heater, m/s;

W total - the total open cross-sectional area of ​​the water heater tubes is determined by the number of tubes, taken according to Appendix 8, and the diameter of the tubes, taken as 14 mm.