The calculation of the area of air ducts and fittings is carried out before the installation of ventilation communications. The efficiency of the entire ventilation system depends on the correctness of their implementation. In practice, experienced craftsmen use two main methods of measurement: using a formula and using an online calculator. Calculation of the area of air ducts and fittings is a laborious and responsible business. The editors of the online magazine Homius.ru prepared a review on this topic specially for their readers, using all the modern capabilities and knowledge of experienced craftsmen. In this article, you will find useful guidelines for calculating data, as well as a handy online calculator.
There may be an error in calculating areas using formulas
1 Why do you need to calculate the area of the duct and fittings
2 What data are needed to calculate the parameters of the duct
4 Calculation of the area of the fittings of the duct
4.1 What programs exist for finding the parameters of the fittings of the duct
5 Calculation of square meters (cross-sectional area) of the duct
5.1 Calculator for calculating the required diameter of the duct
6 Calculation of the air velocity in the duct
7 Calculation of the resistance of the duct network
8 Pressure loss in straight sections
9 Pressure loss at local resistances
10 Calculation of materials for duct and fittings
11 Calculation of the power of the heater in the network
12 Conclusion
Why do you need to calculate the area of the duct and fittings
The ventilation complex consists of different elements. In order to select all the parts correctly, it is necessary to calculate their area, which is influenced by the following parameters:
volume and speed of air masses;
tightness of connections;
noise during operation of the ventilation system;
electricity consumption.
It is important! Thanks to correctly performed calculations, it is possible to determine the optimal number of fittings for organizing a ventilation system for a particular room. This will prevent unnecessary spending on the purchase of items that will not fit later.
Various designs and materials of the duct
What data is needed to calculate the parameters of the duct
To calculate the duct, two indicators should first be determined:
the norms established for the supply of fresh streams per 1 m² of the room per hour or the frequency of air exchange are taken from regulatory sources. Based on these data, knowing the volume of the room, you can easily determine the value of the ventilation system performance. Accordingly, the volume of air is calculated by multiplying the multiplicity by the volume of the room;
according to sanitary standards. In this case, 60 m³ should be taken for each person who is permanently in the room, and 20 m³ for a temporary person.
Air purification efficiency in production depends on correct calculations
The main task of the ventilation system is to improve the microclimate in the room and purify the air masses by removing the exhaust air to the outside. For high-quality performance, first of all, it is necessary to carry out design work and calculate the quadrature of the air ducts. During planning, the shape of the pipes, the number of elements required to connect the sections, the size of the section will also be determined.
Calculations can be done in two ways:
independently using formulas;
using an online calculator.
The first case is the most difficult option, it is important to understand all the values that are used in the calculations. For an online calculator, it is enough to enter the initial data, the software complex will independently perform all the calculations. One of the main parameters for designing an air duct and fittings is its design. You can choose pipes of rectangular or circular cross section. The throughput of round products is significantly higher than that of rectangular ones.
Maximum precision in counting
the smallest amount of transported air masses;
air transport speed.
And also a few more parameters directly depend on the size of the section:
the larger the cross-section, the less noise the flows move;
accordingly, the cost of electricity is reduced.
On the other hand, such a system will require more material, respectively, and the cost will be much higher. Thanks to the calculation formula, you can determine the actual cross-sectional area of the duct:
S = A × B / 100, where A and B are the height and width of the section, respectively.
The rectangular duct is almost invisible above the furniture
An air duct with a circular cross-section is easy to install and has excellent air flow capacity, since internal resistance is minimized. The choice of the form of communication follows from the personal preferences of consumers and the external design of the premises.
The actual area is calculated as follows:
S = π × D² / 400, where:
π is a constant equal to 3.14;
D is the length of the element.
Special techniques have been developed, for example, SNiPs, in which the calculated actual areas are compared with the required indicators. With their help, you can easily choose the optimal size of communication.
During the calculations, the following factors must be taken into account:
the cross-sectional area for straight sections of the duct should be calculated separately;
it is imperative to take into account the resistance that will be exerted on air masses during their transportation;
design should start from the central highway.
If the transport speed of the air flow exceeds the required values, and this directly affects the noise during operation, it is necessary to additionally purchase special silencers or increase the cross-section of the flange element of the central channel.
Product with a circular cross-section
Calculation of the area of the fittings of the duct
It will be difficult for a person who is not connected with mathematical formulas to make calculations correctly, an error in one indicator will affect the performance of the ventilation system, respectively, and the quality of air purification.
To simplify the process of calculating the surface area of the duct, you can use an online calculator and special programs that perform all the algorithms, for this you only need to enter the primary indicators.
Counting and selection program
What programs exist for finding the parameters of the fittings of the duct
To help engineering workers to eliminate errors associated with the human factor, as well as to speed up the process, special programs were created with which it is possible not only to perform competently calculations, but also 3D modeling of the future structure.
Program
Short description
The program calculates the cross-sectional area, thrust, resistance on different segments.
GIDRV 3.093 The program will perform a new and checkout duct data.
Ducter 2.5 In the program, you can select the elements of the ventilation system, calculate the cross-sectional areas of the structure.
This complex was created on the basis of AutoCAD, has the most detailed library of elements and capabilities.
Software calculation and design of ventilation
Calculation of square meters (cross-sectional area) of the duct
The size of the ventilation pipe is influenced by many factors: flow rate, pressure on the walls, air volume. If you perform calculations with an error, for example, reduce the cross-section of the trunk network, the speed of air masses will increase, noise will appear, pressure and electricity consumption will increase.
The calculation of the cross-sectional area of the duct is calculated using the following formula:
S = L × κ / ω, where:
L - air consumption, m³ / h;
ω — speed of movement of air flows, m / s;
κ is the calculated coefficient equal to 2.778.
Calculator for calculating the required diameter of the duct
Payment options Spam protection Enter the code from the picture Send the result to me by mail
Calculation of the air velocity in the duct
When calculating the ventilation system, one of the main indicators is the frequency of air exchange. In other words, how much air mass is needed to comfortably ventilate 1 m³ of a room in 1 hour. In this case, you can also refer to the development tables, but you should know that all indicators in them are rounded, therefore more accurate data are obtained by independent calculations. You can calculate the frequency of air exchange using the formula:
N = V / W, where V is the amount of fresh air masses that enter the room in 60 minutes (m³ / hour);
W is the volume of the room, m³.
To carry out aerodynamic calculations and calculate the speed of air movement, you can use the following formula:
ω = L / 3600 × S, where L is the volume of air used for 1 hour;
S is the cross-sectional area of the duct.
Air exchange rates for an apartment
Calculation of the resistance of the duct network
Air flows during transportation through pipes experience resistance, especially for pipes with a rectangular cross-section. To ensure normal system performance, you need to select a fan of the appropriate capacity. It is difficult to manually determine these parameters on your own; in the design team, all calculations are performed using the program.
The resistance is not affected by the number of rooms served by the ventilation system, the value of the coefficient depends on the structure and length of the communication.
Flow velocity in direct relation to resistance
Pressure loss in straight sections
To calculate the performance of ventilation equipment, you can simply add up the required amount of air masses and select a model that suits these parameters. However, the product passport does not include the duct network. Therefore, when it is connected to the system, the performance will drop significantly depending on the resistance parameter in the pipeline. To determine the pressure drop in the system, it is necessary to clarify its decrease on flat areas, pivoting and connecting elements. The pressure drop on flat areas is determined by the formula:
P = R × L + Ei × V2 × Y / 2, where R is the specific pressure loss caused by the frictional force during air movement, Pa / m;
L is the length of the straight section of the air duct, m;
ω — speed of air movement, m / s; Y — density of air masses, kg / m³;
Еi - the sum of head losses on local resistances (bends, transitions, grids, etc.), the data can be taken from the reference book.
Straight ventilation section
Pressure loss on local resistances
To calculate losses on rotary elements, it is first of all necessary to determine all areas that will interfere with the direct movement of flows. You can use the formula, but all data depending on the duct element and material of manufacture are already defined and are reference information. So, gradually section by section should be passed along its entire length, then add up all the indicators. We must not forget about the section that is located behind the fan, because there should also be enough pressure to divert the flows.
During the calculation, you need to take into account all curved connections.
Calculation of materials for duct and fittings
To select sizes and structural elements, for example, tees, elbows, transitions, there is no need to do it manually, especially since the nomenclature is quite large. Everything can be done in a special program, including the area of the air duct fittings, for this you just need to enter the primary data. The result will be ready in a few seconds. And also, if necessary, you can use the tabular form of equivalent cross-sections of round-diameter air ducts, in which the reduction in pressure due to friction is equal to the reduction in pressure in rectangular sections.
The calculation of materials was carried out using the program
Calculation of the power of the heater in the network
To calculate the supply ventilation system, it is first of all necessary to take into account the power of the heater that heats the incoming masses in the cool season. According to the approved standards, the temperature of the flow that enters the room must be at least 18 ° C, the outdoor air indicators depend on the location of the region. In modern equipment, it is possible to regulate the speed of circulation of air masses, thus, you can save electricity in the winter. Before choosing a model, the temperature of heating the air that comes from outside is calculated by the formula:
ΔТ = 2.98 × Р / L, where Р - equipment power, W;
L is the flow rate of air masses.
Correctly made calculations are the key to many years of equipment operation.
Conclusion
If necessary, you can understand all the calculations, however, with the help of the program, the possibility of an error is excluded, which will be quite expensive during operation. It is enough just to enter the primary parameters into the program and analyze the obtained indicators in fractions of seconds. And you can also ask for engineering assistance in calculating the area of air ducts in professional design workshops.
We tried to describe in as much detail as possible the entire process of self-calculation, and also talked about software products. In the comments, you can clarify incomprehensible points, the team of our magazine will be happy to answer them.
The principle of ventilation can be found in the video.
If ventilation in a house or apartment does not cope with its tasks, then this is fraught with very serious consequences. Yes, problems in the operation of this system manifest themselves as quickly and sensitively as, say, problems with heating, and not all owners give them adequate attention. But the results can be dire. This is stale, waterlogged indoor air, that is, an ideal environment for the development of pathogens. These are foggy windows and damp walls, on which pockets of mold can soon appear. Finally, this is simply a decrease in comfort due to odors spreading from the bathroom, bathroom, kitchen to the living area.
To avoid stagnation, air must be exchanged with a certain frequency in the premises over a period of time. The inflow is carried out through the living area of the apartment or house, the exhaust air - through the kitchen, bathroom, toilet. It is for this that the windows (vents) of the exhaust ventilation ducts are located there. Often, homeowners who are starting repairs ask if these vents can be repaired or reduced in size in order, for example, to install certain pieces of furniture on the walls. So - it is definitely impossible to completely overlap them, and transfer or change in size is possible, but not only on the condition that the required performance is ensured, that is, the ability to pass the required volume of air. How do you determine this? We hope the reader will be helped by the proposed calculators for calculating the cross-sectional area of the ventilation outlet.
Calculators will be accompanied by the necessary explanations for the calculations.
Calculation of normal air exchange for effective ventilation of an apartment or house
So, during normal operation of ventilation for an hour, the air in the premises must constantly change. The current governing documents (SNiP and SanPiN) establish norms for the flow of fresh air into each of the premises of the living area of the apartment, as well as the minimum volumes of its exhaust through the channels located in the kitchen, in the bathroom in the bathroom, and sometimes in some other special rooms.
| Room type | Minimum air exchange rates (rate per hour or cubic meters per hour) | |
|---|---|---|
| Inflow | EXTRACTOR | |
| Requirements for the Code of Rules SP 55.13330.2011 to SNiP 31-02-2001 "Single-family residential buildings" | ||
| Residential premises with permanent residence of people | At least one volume exchange within an hour | - |
| Kitchen | - | 60 m³ / hour |
| Bathroom, toilet | - | 25 m³ / hour |
| Other premises | Not less than 0.2 volume per hour | |
| Requirements for the Code of Rules SP 60.13330.2012 to SNiP 41-01-2003 "Heating, ventilation and air conditioning" | ||
| Minimum outdoor air consumption per person: living quarters with constant presence of people, in conditions of natural ventilation: | ||
| With a total living area of more than 20 m² per person | 30 m³ / hour, but at the same time not less than 0.35 of the total volume of apartment air exchange per hour | |
| With a total living space of less than 20 m² per person | 3 m³ / hour for each 1 m² of the area of the room | |
| Requirements for the Code of Rules SP 54.13330.2011 to SNiP 31-01-2003 "Multi-apartment residential buildings"
|
||
| Bedroom, nursery, living room | One-time volume exchange per hour | |
| Cabinet, library | 0.5 of the volume per hour | |
| Linen, pantry, dressing room | 0.2 of the volume per hour | |
| Home gym, billiard room | 80 m³ / hour | |
| Kitchen with electric stove | 60 m³ / hour | |
| Rooms with gas equipment | Single exchange + 100 m³ / hour for a gas stove | |
| Room with a solid fuel boiler or stove | Single exchange + 100 m³ / hour for a boiler or furnace | |
| Home laundry, dryer, ironing | 90 m³ / hour | |
| Shower, bath, toilet or combined bathroom | 25 m³ / hour | |
| Home sauna | 10 m³ / hour for each person | |
An inquisitive reader will surely notice that the standards for different documents are somewhat different. Moreover, in one case, the norms are established solely by the size (volume) of the room, and in the other - by the number of people constantly staying in this room. (Permanent stay means staying in a room for 2 hours or more).
Therefore, when calculating the calculation of the minimum volume of air exchange, it is advisable to carry out according to all available standards. And then - to choose the result with the maximum indicator - then there will definitely be no mistake.
The first proposed calculator will help to quickly and accurately calculate the air flow for all rooms of an apartment or house.
Calculator for calculating the required volumes of air flow for normal ventilation
The task of organized air exchange in the rooms of a residential building or apartment is to remove excess moisture and exhaust gases, replacing it with fresh air. Accordingly, for the exhaust and inflow device, it is necessary to determine the amount of removed air masses - to calculate the ventilation separately for each room. Calculation methods and air flow rates are adopted exclusively in accordance with SNiP.
Sanitary requirements of regulatory documents
The minimum amount of air supplied and removed from the rooms of the cottage by the ventilation system is regulated by two main documents:
- "Residential multi-apartment buildings" - SNiP 31-01-2003, paragraph 9.
- "Heating, ventilation and air conditioning" - SP 60.13330.2012, mandatory Appendix "K".
The first document sets out the sanitary and hygienic requirements for air exchange in residential premises of apartment buildings. The calculation of ventilation should be based on these data. Two types of dimension are used - air mass flow rate by volume per unit of time (m³ / h) and hourly frequency.
Ventilation is a primitive way to renew oxygen in a homeReference. The air exchange rate is expressed by a figure indicating how many times the air environment of the room will be completely renewed within 1 hour.
Depending on the purpose of the room, the supply and exhaust ventilation should provide the following flow rate or the number of air mixture updates (frequency ratio):
- living room, nursery, bedroom - once an hour;
- kitchen with electric stove - 60 m³ / h;
- bathroom, bathroom, toilet - 25 m³ / h;
- for a kitchen with a gas stove, a multiplicity of 1 plus 100 m³ / h is required during the period of operation of the equipment;
- burning natural gas - three times renewal plus the volume of air required for combustion;
- pantry, dressing room and other utility rooms - multiplicity 0.2;
- drying or laundry room - 90 m³ / h;
- library, office - 0.5 times per hour.
Note. SNiP provides for a decrease in the load on general ventilation when the equipment is not working or there are no people. In residential premises, the frequency ratio is reduced to 0.2, technical - to 0.5. The requirement for the rooms where gas-using installations are located remains unchanged - an hourly one-time renewal of the air environment.
The emission of harmful gases due to natural draft is the cheapest and easiest way to renew the air In clause 9 of the document, it is assumed that the volume of the exhaust is equal to the value of the inflow. The requirements of SP 60.13330.2012 are somewhat simpler and depend on the number of people staying in the room for 2 hours or more:
- If for 1 resident there is 20 m² or more of the area of the apartment, a fresh inflow of 30 m³ / h per person is provided to the rooms.
- The supply air volume is calculated by area, when there are less than 20 squares per 1 tenant. The ratio is as follows: for 1 m² of dwelling, 3 m³ of inflow is supplied.
- If ventilation is not provided in the apartment (there are no vents and opening windows), 60 m³ / h of pure mixture must be supplied for each resident, regardless of the quadrature.
The listed regulatory requirements of the two different documents do not contradict each other at all. Initially, the performance of the general ventilation system is calculated according to SNiP 31-01-2003 "Residential buildings".
The results are checked against the requirements of the Code of Practice "Ventilation and Air Conditioning" and, if necessary, adjusted. Below we will analyze the calculation algorithm using the example of a one-story house shown in the drawing.
Determination of air flow rate by frequency
This typical calculation of supply and exhaust ventilation is performed separately for each room in an apartment or country cottage. To find out the flow rate of air masses in the building as a whole, the results obtained are summed up. A fairly simple formula is used:
Explanation of designations:
- L is the required volume of supply and extract air, m³ / h;
- S is the square of the room where ventilation is calculated, m²;
- h - ceiling height, m;
- n is the number of updates to the air environment of the room within 1 hour (regulated by SNiP).
Calculation example. The living area of the one-storey building with a ceiling height of 3 m is 15.75 m². According to the requirements of SNiP 31-01-2003, the multiplicity n for residential premises is equal to one. Then the hourly consumption of the air mixture will be L = 15.75 x 3 x 1 = 47.25 m³ / h.
An important point. The determination of the volume of the air mixture removed from the kitchen with a gas stove depends on the installed ventilation equipment. A common scheme looks like this: a single exchange in accordance with the standards is provided by a natural ventilation system, and an additional 100 m³ / h is thrown out by household ventilation.
Similar calculations are made for all other rooms, a scheme for organizing air exchange (natural or forced) is being developed and the dimensions of the ventilation ducts are determined (see the example below). A calculation program will help automate and speed up the process.
Online calculator to help
The program calculates the required amount of air by the multiplicity, regulated by SNiP. Just select the type of room and enter its dimensions.
From the author: hello dear readers! The ventilation system is a very important component of any home furnishing. After all, it is thanks to her that you breathe fresh, and not stagnant air. This has a significant positive effect on both the health of the people living in the house and their level of comfort.
But all these advantages are relevant, of course, for those cases when it works correctly. In particular, its performance is very important, which should be sufficient for a particular building. To ensure the required indicator, it is important to choose the right equipment of the required power, as well as to calculate the cross-section of the ventilation duct.
The need for calculations
All calculations for arranging ventilation both in a private house and in an apartment must be performed as carefully as possible. This is due to the fact that poor-quality air exchange can lead to rather serious consequences. Among them are:
- discomfort of people living in the house. It's hard to be in a stuffy room. In addition, all unpleasant odors stagnate, because they simply do not have a chance to get out. As a result, both furniture and room decoration are impregnated with them. It is clear that such a dwelling does not evoke pleasant sensations;
- harm to health. The exhaust air contains a large amount of carbon dioxide. If you stay in such an atmosphere for a long time, then this does not affect the body in the best way. People get fatigued quickly, and headaches often begin. And the general state of health sooner or later deteriorates;
- high level of humidity. To regulate it, high-quality air exchange is necessary, and when there are problems with the latter, the result becomes obvious. The consequence of this state of affairs is unpleasant condensation on the windows, and it is harder to breathe in a room with a high level of humidity than usual. In addition, this situation will lead to the appearance of mold and mildew on the walls. Getting rid of such "neighbors" is very, very difficult. And you can not get rid of it - the spores released by the mold fall into the lungs of the people living in the house. This provokes the development of various infections, some of them are life-threatening.
Calculations
Now that you are convinced of the extreme necessity of calculations, you can talk about how they are made. But first of all, it is worth figuring out what factors affect the final indicator. Actually, they all belong to the type of the duct itself.
Varieties of air ducts
Air ducts differ in two ways. The first is the material from which this structural element is made. There are quite a few modern options. Air ducts can be:
- steel (from ferrous or stainless metal);
- plastic;
- aluminum;
- tissue;
- tin.
In this case, the structure of the material is of great importance. The rougher the surface inside the pipe, the more force the air has to exert to travel along the appropriate route, as the resistance increases. This factor directly affects the required cross-sectional index.
The second parameter is the shape of the duct. It can be round, square, oval or rectangular. Each form has certain advantages and disadvantages. For example, round varieties require less material to manufacture, which is beneficial from an economic point of view. Rectangular air ducts may not be too large both in height and width - all the same, their cross-sectional area will be maintained at the required level.
Payment methods
Strictly speaking, the calculations necessary for the arrangement and other types of ventilation should be carried out by specialized organizations that have the appropriate license. Professionals have a complete set of required knowledge and experience. It is often difficult for an ordinary person to understand how to correctly calculate this or that parameter.
But the desire for economy and love for independent work have not gone away, so many still prefer to understand this issue. If you belong precisely to this category of people, then please be patient and a notebook with a pen.
There are two ways to calculate the cross-section of a duct. One is based on allowable speeds, the other is based on constant pressure loss. both provide the required parameter, but the first is the simpler one. So it's better to start with him.
All buildings and premises are subdivided into different categories. Depending on the type of structure, a certain standardized value of the maximum permissible speed is provided for it, both for the main duct and for branches coming from it.
Accordingly, you will need these standard indicators for calculations. And you also need to have a plan on hand showing all the routes included in it and the types of equipment installed. It is on these blanks that the process of further work will be based.
As for the normalized indicators of the maximum permissible speed, they can be summarized in the following list:
- industrial premises - for the main highway, a speed of 6 to 11 meters per second is permissible, for branches from 4 to 9 meters per second;
- office premises - for the main highway from 3.5 to 6 m / s, for branches from 3 to 6.5 m / s;
- living quarters - for the main highway from 3.5 to 5 m / s, for branches from 3 to 5 m / s.
These standards are due to the fact that an air flow rate exceeding them will create a high level of noise, which will make it very uncomfortable for people to be in the room.
So, the calculation process comes down to the following steps.
- A diagram of the ventilation system is drawn up. It indicates each highway and branches coming from it. All equipment that is installed in the ducts is also indicated. This includes diffusers, valves, grilles and the like. All turns of the duct should also be marked.
- Next, you need to calculate how much air should flow into the room on an hourly basis. This parameter depends primarily on the number of people in the room for a long time. The volume of air for each person is approved by the SNiP standards. They indicate that in a room where natural ventilation is not performed, the air consumption per person is at least 60 m 3 / h. If we are talking about a bedroom, then the indicator there is less - only 30 m 3 / h. This is due to the fact that a person processes less oxygen during sleep. In general, for the calculation, it is necessary to take into account the number of people who stay in the house for a long time, and multiply this number by the indicator established by the norms. If you regularly meet large companies, then you do not need to be guided by them - the standards are relevant only for long stays. In such a case, you can get a VAV-system that will help regulate the air exchange processes between rooms during the reception of guests.
- After you have received both indicators - that is, the maximum allowable speed and the required volume of air entering the room - you can begin to calculate the estimated area of the duct. To do this, you can use a diagram called a nomogram. As a rule, it comes complete with a flexible duct pipe. If it is not in the paper version, then you can search on the website of the company that released this product. In addition to the nomogram, you can also calculate the required indicator manually. To do this, you need to substitute the available parameters in the formula: Sc = L * 2.778 / V. Sc means, in fact, the very same area of the duct. It will be expressed in square centimeters, since this is the most convenient value to work with. The letter L stands for the previously calculated required volume of air entering the room through the duct. The letter V is the air flow rate in a particular line. The number 2.778 is the factor required to reconcile different types of units of measure: m 3 / h, m / s and cm 2.
- Now you can start calculating the actual cross-sectional area of the duct. There are two formulas for this. Which one to use depends on the shape of the pipe. For a round duct: S = π * D² / 400. S stands for the calculated cross-sectional area, D stands for the pipe diameter. For a rectangular variant, the formula is as follows: S = A * B / 100. In this case, the letter A means the width of the pipe, and the letter B means the height. The dimensions of the sides of the rectangle and the diameter of the circle are indicated in millimeters.
Thus, it is necessary to calculate the corresponding indicator for each section of the ventilation system: both for the main highways and for additional routes. Based on these indicators, you can proceed to calculating the required power of the equipment installed for forced air inflow or outflow.
For the correct selection of the built-in fan, you will also need to know the pressure drop in the ventilation system. This parameter can be calculated all according to the same nomogram that you used to determine the volume of air.
Dear Readers! All the calculations required to equip any type of ventilation system, in principle, are not so complicated. But they require quite a lot of time, as well as careful attention. A miscalculation can lead to the fact that you install too narrow or wide air duct, or select ventilation equipment with a capacity that does not meet the needs of the room.
Therefore, if you are not confident in your abilities or firmly know about the existing problems with physics and mathematics, then it is better to turn to specialists. This will not hit the budget too hard, but in return will provide a guarantee that the ventilation system will work with the proper functionality.
If you are still determined to carry out the calculations yourself, then watch the video instruction, the link to which is left just below. Approach the matter carefully and carefully, then you will succeed perfectly. Good luck to you, comfort to your home! Until next time!