Ventilation of the bathroom must be necessarily equipped to ensure comfortable conditions, prolong the service life of finishes and furniture.
An extractor hood for the bathroom is installed to ensure the efficiency of the ventilation system.
Classification of ventilation systems
Exhaust ventilation in the bathroom ensures correct air exchange. This eliminates the problem of unpleasant odors, the formation of mold and mildew, high humidity.
It is especially important to install the hood in combined bathrooms.
The main functions of the hood in the bathroom:
- ensuring air exchange;
- elimination of the likelihood of developing fungi;
- microclimate support.
In the photo of the bathroom hood, you can visually familiarize yourself with such structures, the features of their installation and operation.
But, there are different types of hoods that should be chosen based on the characteristics of the room.
If you have a question, how to calculate the hood power
It is a misconception that the efficiency of an exhaust system is to remove unpleasant odors from the air. Air fresheners work best for this task. Ventilation, on the other hand, should serve to rid the premises of suspended substances (such as fats, which would otherwise settle on the surface of furniture, walls and ceilings), as well as from combustion products and fumes. Often, the fundamental criterion for choosing a hood that is connected to a ventilation system is not power, but quiet operation.
.
Performance is also important, since it is expressed in how many times the air in the room is completely renewed in a given period of time. Yes, this concept is quite loose, since an open door excludes complete isolation of the kitchen from the hallway or living room. As a result, air masses move freely, drawn by drafts, movements of people and animals. In addition, as the room is ventilated during cooking in the kitchen or when the car engine in the garage is warming up, the air coming from outside becomes polluted. But we will rely on the recommendations of the SES, according to which, within an hour in the same kitchen, the entire volume of air should be changed at least 12 times. This thesis will serve as the basis for how to calculate the hood power.
Natural draft
Natural extraction involves the removal of air from the room through a ventilation duct. This ventilation system is developed at the stage of building design.
For the system to work efficiently, fresh air must be supplied to the room. For this, ventilation holes are made in the door or above it.
To check the efficiency of the system, you need to provide a draft in the room by opening a window or door.
Attach a piece of paper to the ventilation grill, if it is attracted to it, the system is working properly.
The most effective and simple way to make an extractor hood in the bathroom if the natural ventilation is not functioning properly is to provide forced air exchange.
For this, fans are used.
Standard hood
A wall-mounted hood helps to avoid such problems by providing sufficient ventilation in such a small space. But over time, the standard ventilation system begins to malfunction. This could be due to:
- the presence of debris in the ventilation shaft;
- location of the apartment on one of the top floors;
- high temperature and humidity.
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Fan types
In the shops where you can buy a hood for the bathroom, there is a fairly wide variety of forced fans.
They are divided into different types according to the following criteria:
Location: overhead and embedded. The first ones are mounted at the entrance to the ventilation duct. They are very easy to install and inexpensive.
Built-in fans are ways to serve several rooms, they are installed during the construction or overhaul of a building.
Installation location: ceiling, wall or roof. The former are usually channelized, the latter are overhead.
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Models for roofs are installed as part of integrated supply and exhaust ventilation, mounted under the roof.
By the technology of functioning: blade and centrifugal The first are axial and radial. Air is removed by vane rotation.
Centrifugals generate centrifugal force within their structure.
For additional functionality (with a check valve, timer, light, humidity, motion sensors, etc.).
Starting method: mechanical and automatic. The first ones need to be started manually with a separate button. Automatic ones start independently according to the specified settings.
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Always install a non-return valve. If it does not come with the fan, buy it separately. It will eliminate the possibility of air flow from the ventilation duct back into the room.
If you need a silent bathroom hood, choose the appropriate fan. All models emit noise, but the lower the level, the more comfortable it will be in the room.
This parameter is always indicated in the technical characteristics of the device.
We build the calculation of the hood for the kitchen
Somewhat earlier, such a factor influencing the choice as the noise emitted by the exhaust system was mentioned. We should not forget about this property of turbines built into kitchen ventilation, because it directly depends on the power, that is, the number of revolutions per minute, as well as on the diameter of the channel and the number of elbows in it, the distance to the ventilation shaft, the density of filters and other trifles. Therefore, you always need to find a compromise between the desire to buy more powerful equipment and the desire to spend evenings in the kitchen in a cozy atmosphere.
According to the facts, the comfortable threshold of noise in the room is no more than 30 decibels (dB), this is the so-called background noise - the distant rumble of engines of cars passing along the street, bird chirping outside the window, the murmur of water in pipes. At the lowest speed, a truly quiet hood emits no more than 35 dB, at the second speed - within 45, at the third - about 50 dB. Compared to household noise, this is tantamount to a whisper 5 meters away, a conversation 10 meters away and a quiet conversation 3 meters away, respectively. Accordingly, the noise threshold of 55 dB can be considered uncomfortable, given that there is always enough work in the kitchen.
If you do not pay attention to decibels, then the calculation of the hood is very simple. You have a certain volume of the room, the so-called cubic capacity, within these limits the air must be constantly renewed, preferably at least 12 times per hour. So we first calculate the volume of the room, multiplying its length, width (this will give us the area) and height V = S. H, and then multiply the result by those 12 complete air purifications. However, this number of airings is usually designed for the maximum load of the hood, that is, this will mean an outrageous noise in the kitchen during the same hour. Therefore, be sure to add at least 15% to the result of multiplications (ideally 30%) and get V. 12 . 15 = P, that is, the capacity, determined by cubic meters per hour (m3 / h).
The choice of hood is largely influenced by the type of hob, due to the different amounts of combustion products emitted into the air. So, in the electric panel they are completely absent, as well as in the induction one, and in the gas one they take place, along with soot. Therefore, for the first two in a 3x4 meter kitchen, a minimum capacity of 486 cubic meters per hour is sufficient, and for the third at least 650 cubic meters of air for the same time. Accordingly, the coefficient of air renewal in the room for electric hobs is taken as 15, and for gas 20 times per hour. It is logical that if the doorway is devoid of a closing sash and turned into an arch, the capacity should be increased due to the spread of odors and combustion products, and for the same surfaces it will already be in the range of 600 and 800 m3 / h, respectively.
Fan selection
When choosing an exhaust fan, be guided by the following criteria:
- performance. Depends on the size of the room. The larger the room, the more powerful the fan must be;
- noise level. It is better to choose a silent model that emits a noise level of no more than 25 dB;
- safety requirements. The fan must be designed to protect its electrical and electronic parts from moisture, which is inherent in the bathroom. Therefore, choose models designed specifically for bathrooms.
Main varieties
By design, forced exhaust devices in the bathroom are divided into certain types, namely, duct, and also radical. Moreover, they are divided into centrifugal and axial. To make the right choice, you need to know how to do it.
If the bathtub is combined with a bathroom, then hoods are used, with blades bent in different directions. Devices with backward curved blades save electricity, and forward - function almost silently.
Ventilation system maintenance
The hood in the bathroom needs to be serviced regularly. Clean the system from dust and other contaminants.
Inspect the condition of the fan periodically. When working with electrical appliances, always de-energize the room beforehand.
Disassemble the fan, clean all plastic elements from dirt. Dismantle and clean the propeller. Clean the motor with a brush and lubricate with engine oil.
Check the condition of the bearings, if they are worn, install new ones. After servicing, reassemble the fan and reinstall it.
The ventilation duct itself at the installation site of the fan also needs to be cleaned of dirt, since dust will collect here and various dirt will settle. This not only reduces the efficiency of the system, but also entails health risks.
Centrifugal system
These models belong to the channel type and have become in demand due to the efficiency of use in bathrooms of a sufficiently large area.
Devices are placed under the ceiling surface in a flow-through system, which makes it possible to hide with plasterboard panels.This type of appliance is suitable for installation directly above the shower in order to get rid of high degrees of humidity.
Photo of bathroom hoods
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The nuances of a competent choice of ventilation
Many people are faced with a question related to the choice of hoods with a check valve in the bathroom. When choosing a particular option, it is important to focus on a number of parameters that directly affect the functioning of the fan:
- operational safety;
- the degree of noise;
- functionality;
- high quality inexpensive.
The system is selected by measuring the quadrature of the room. Of no small importance is the design of the hood, on which regular maintenance directly depends.
Why doesn't the powerful hood "pull"?
First, you should check the condition of the ventilation channel in the hood itself, remove and wash (or replace) the filters. Make sure that the ventilation unit is in good working order and that there is power supply to it.
Drafts can also interfere with the operation of the hood, preventing the vertical movement of convection air flow from the stove.
If the problem of a "weak" hood is not detected, its source is outside the kitchen.
The performance of the hood depends on the section of the ventilation duct where the fumes from the stove go. And homeowners often install an unnecessarily powerful hood, or assign it an exaggerated operating mode.
Residential property owners follow an unpretentious logic - the more the fan pulls, the better volatile contamination is removed from the stove.
This is not true. The performance and operability of the kitchen hood system directly depend on the throughput characteristics of the ventilation duct.
For example, the ventilation duct of the supply and exhaust air exchange, which is available in the wall of the house, is not capable of removing more than 150 m3 / h of air.
Firstly, the cross-section of such ventilation ducts does not exceed 130-140 mm, which is insufficient for mechanical ventilation. Secondly, regular duct ventilation in high-rise buildings is long and contains multiple irregularities.
In the instructions for the ventilation unit, there is usually a diagram showing the relationship between the pressure in the ventilation duct and the performance. An increase in pressure causes a drop in the performance of the hood.
The ventilation ducts in the houses are assembled clumsily: uneven walls; solution drips; constrictions due to displaced blocks; many twists and turns.
Attempts to set the increased performance of the ventilation hood connected to the house ventilation duct have the opposite effect.
The stronger the air flow, the more intensively defects in the section of the ventilation duct prevent it. And if actively pumped air cannot move forward, it moves backward.
A simple example is a soccer ball. The more air you pump into such a ball, the more difficult it is to work with a pump. Pressure becomes an obstacle - there is a lot of air, it tends to go back through the tube, pushing the pump handle.
The situation is similar with the hood of increased power - the more intensively the air is supplied, the more its operation is blocked.
The ideal ventilation duct for a kitchen hood is short, with a minimum of bends. Therefore, it is required to remove air from the stove not through the supply and exhaust channel, but through a specially made for the exhaust hood.
Opening in the facade wall, rigid or flexible duct (ideally circular), non-return valve and grill inlet at the duct outlet. This is how the cooker hood should be equipped.
Calculation method
With general ventilation, the required air exchange is determined from the condition of removing excess heat and diluting harmful emissions with fresh air to permissible concentrations. The maximum permissible concentration of harmful substances in the air of the working area is set in accordance with GOST 12.1.005-88.
2.1.
The calculated value of the supply air temperature depends on the geographic location of the enterprise and is taken equal to 22.3 ° C.
The air temperature in the working area is taken 3 ... 5 ° C higher than the design temperature of the outside air. Density of air, kg / m3, entering the room,
.
(1)
The excess amount of heat to be removed from the production room is determined by the heat balance:
,(2)
Where
—Heat entering the room from various sources, kJ / h;
—Heat consumed (lost) by the walls of the building and leaving with heated materials, kJ / h.
The main sources of heat generation in industrial premises include:
- hot surfaces of equipment (ovens, drying chambers, pipelines, etc.);
- equipment driven by electric motors;
- solar radiation;
- indoor personnel;
- various cooling masses (metal, water, etc.).
Since the temperature difference between the air inside and outside the building during the warm period of the year is insignificant (3 ... 5 ° C), then when calculating the air exchange based on the excess heat release, heat losses through the building structures can be disregarded. At the same time, a slight increase in air exchange has a beneficial effect on the working conditions of workers on the hottest days of the warm season.
In view of the above, formula (2) takes the following form:
.
(3)
In this design assignment, the excess amount of heat is determined only taking into account the heat release of electrical equipment and working personnel:
,(4)
Where
, —Heat released during the operation of equipment electric motors, kJ / h;
, Is the heat generated by the working personnel, kJ / h.
The heat generated by the electric motors of the equipment
,
(5)
where β is a coefficient that takes into account the load of the equipment, the simultaneity of its operation, the operating mode; β = 0.25 ... 0.35; N — total installed power of electric motors, kW.
The heat generated by the working personnel
(6)
where n is the number of employees, people; Кр — heat generated by one person, KJ / h (taken equal to 300 kJ / h for light work; 400 kJ / h for moderate work; 500 kJ / h for heavy work).
2.2.
Supply air flow rate, m3 / h, required to remove excess heat,
(7)
where Qs6 is the excess amount of heat, kJ / h; from
- heat capacity of air, J / (kg-K);
c =
1.2 kJ / (kg K); ρ — air density, kg / m3;
t
beats - the temperature of the air removed from the room is taken equal to the air temperature in the working area, ° С;
t
pr - supply air temperature, ° С.
Supply air flow rate, m3 / h, required to maintain the concentration of harmful substances within the specified limits,
,(8)
where G is the amount of harmful substances emitted, mg / h (see table); q
beats — the concentration of harmful substances in the removed air, which should not exceed the maximum permissible, mg / m3, i.e.
q
oud
qpdc; qpr — concentration of harmful substances in the supply air, mg / m3.
(9)
2.3.
Determination of the required air exchange.
To determine the required air exchange L
it is necessary to compare the values
L1
and L2, calculated by formulas (1) and (8), and choose the largest of them.
2.4.
According to the nomogram (Fig. 1) select TsAGI fan series Ts4-70 No. 6 and determine its main characteristics: wheel circumferential speed
ω,
m / s
,
speed
n,
rpm, efficiency
η
, total pressure H kgf / m2 (mm water column)
2.5.
Air exchange rate, 1 / h,
(10)
Where L
—Required air exchange, m3 / h; Vc — internal free volume of the room, m3.
The air exchange rate in rooms is usually from 1 to 10 (large values for rooms with significant heat emission, harmful substances, or small in volume).
For machine and instrument-making shops, the recommended air exchange rate is 1 ... 3, for foundries, forging and pressing, heat treatment shops, chemical industries - 3 ... 10.
Exhaust device
In principle, they are all similar to a vacuum cleaner, but with different functions.Modern exhaust devices come in different designs, depending on the purpose - some only remove polluted air, while others filter it and return the already purified air back. According to the cleaning method, they are divided into flow, recirculation and combined, which combine both options.
- Flow hoods equipped with metal or plastic pipes (round, square, corrugated) for connection to the ventilation system, which can be rigid or flexible. The lower parts of the device consist of filters (grease traps) that trap soot and grease. They are disguised behind decorative panels. Fans and special motors are located inside. Behind them is an air duct connected to ventilation.
- Recirculating they work autonomously, without being connected to ventilation, therefore they do not have pipes, which makes them look more aesthetically pleasing. Inside their cases, after the fans, there are replaceable, very thin carbon filters. For coarse cleaning, the filters are made of durable aluminum, they can simply be washed with detergents. Outwardly, the principle of the structure of the cases is the same as that of the flow-through ones.
The exhaust system is powered by an electrical network. Everything is very simple - it plugs into the outlet, the button with the selected mode is pressed (denoted by numbers 1-3), the engine picks up speed. The most convenient hoods for connection are with touch displays or with remote control (using a remote control or voice commands).
