flow sensor- a device that generates an output signal in the presence of a liquid or gas flow. They are installed in pipelines and air ducts, where the presence of the flow of the working fluid is a critical parameter.

This sensor is also called flow switch, because its principle of operation is similar to the one with the only difference that its operation is caused not by the appearance of a control voltage on the coil, but by the presence of a liquid or gas flow. But the result of the operation of the flow sensor, as well as a conventional relay, is a change in the state of the output contacts to the opposite ones.

As a rule, the sensor has a normally closed (NC) and normally open (NO) contact. When a flow of the working medium appears, the NC contact opens, and the NO contact closes.

There are several types of flow sensors:

Petal flow switch

The figure shows a diagram of the petal-type duct sensor.

As the name implies, the main working element of this type of flow sensor is a flexible petal that contacts the working medium and deviates from the vertical position in case of flow. The petal is mechanically connected to the output contacts and changes their state when it bends itself.

Leaf switches Caleffi (left) and Danfoss (right)

Turbine flow sensor

The figure shows a diagram of a turbine-type flow sensor.

Such sensors are a small turbine, the rotor of which is equipped with a magnet. When the flow of the working substance passes through the device, the turbine begins to rotate, resulting in a magnetic field that is converted into electrical impulses that enter the electronic circuit of the sensor. The electronics cause the output contacts to change state when flow is present, just as in a lobe sensor.

Thus, such flow sensors have two types of outputs: output contacts (NO and NC) and a pulse output. The latter is used to determine the flow rate: the higher the pulse repetition rate, the greater the flow rate.

Flow sensor (turbine) for Ariston boiler

An example of this type of sensor is the Ariston gas boiler flow switch. When a flow appears (when the user opens a hot water tap), the sensor generates an output signal and switches the boiler to the DHW heating mode.

Using flow sensors

Flow sensors most often perform protective, informational or control functions.

The protective function is associated with the detection of the presence of flow in systems where its absence can lead to emergencies or equipment breakdowns. So, for example, they protect pumps, because when working in the absence of water flow, they overheat and fail. You can also determine the lack of air flow in ventilation systems when the filter is clogged, the damper is closed, or the fan breaks down. With the help of a flow switch, you can detect leaks in water supply systems, determine the lack of water in the storage tank, etc.

The information function of the flow switch is spoken of when the presence or absence of a flow is not associated with an emergency, but is a significant event in the system that the user needs to know about. In such cases, the sensor operation is used to turn on a light or sound indication, or to generate a message on the operator panel.

The flow switch performs the control function when other equipment is turned on or off at its signal. For example, in DHW systems, when the user opens a hot water tap, the gas boiler must turn on the pump and switch to DHW heating mode. This happens just when the flow sensor is triggered after the tap is opened.

Flow switch connection diagram

The following figure shows a typical connection diagram for a flow sensor for a pump.

In the absence of flow, the NO contact 1-2 is open, and the NC contact 1-3 is closed, the power circuit is open, the pump is stopped. When water flows through the relay, its contacts change their state, the pump power circuit closes and it turns on.

Hydraulic water flow sensor - also simply detects the presence of a flow, regardless of the amount of passing fluid, ranging from 1.7 to 30 l / min. The sensor is triggered by pressing the switch button under the influence of the pressure of the passing water. The water flow acts on the boiler membrane, moving the rod with the plate pressing the button of the DHW flow sensor. After the water movement stops, the pressure on both sides of the membrane equalizes and the rod drives back, releasing the flow sensor button to its original position - the contact opens. The use of such a principle for determining the flow has faded into the background with the start of the use of reed flow switches, which have proven to be more reliable, simple and durable.

Water flow switch- allows you to instantly determine the flow of water that has appeared. Structurally, it includes a float of an original design with a built-in magnet and a reed switch. Under the influence of the water flow, the float moves to the upper position, it approaches the sensor. At the same time, the built-in magnet acts with its magnetic field on the micro-reed switch switch, which leads to a contact closure. The design feature is that the float does not float up, but moves relative to the axis by the pressure of water. The minimum flow is 1.7 l / min., which can be fixed by the flow switch, a flow limiter is installed at the outlet up to 15 l / min. bandwidth. It helps to avoid the situation when the flow through the heat exchanger exceeds the DHW capacity of the boiler. Insufficient heating may occur due to too high a flow rate in the hot water circuit. Often, in our conditions, we are faced with the opposite situation, when the pressure and water flow are very low, the boiler therefore does not start or overheats the water when operating in column mode, as a way out of the situation - the dismantling of the flow restrictor.

Hall Sensor- when the magnet in the turbine rotates, a rotating magnetic field arises. The rotation speed of this field completely coincides with the amount of water passing through the flow sensor. The Hall sensor under the influence of this field generates electrical impulses that are read by the boiler board. The frequency of these pulses is used to calculate the water flow rate of the boiler. Thanks to the Hall sensor at the outlet, we get water with a stable temperature, which does not depend on the amount of flow. The use of such a sensor is due to the constant desire of gas equipment manufacturers to achieve maximum comfort in the operation of boilers and columns. The water temperature error when working with such a flow sensor is reduced to a minimum of 1-2 degrees.

The water flow sensor is a device that regulates the pressure inside the water supply system. It is connected to the pumps through pipes. The main parameters of devices should include not only the limiting pressure, but also the output voltage. Manufacturers also indicate the throughput without fail. Today there are many types of modifications. To understand the issue in more detail, it is worth first of all to study the device of the water flow sensor.

Model device

The standard water flow sensor circuit includes a relay and a set of plates. Inside the modification there is a wide chamber. The flask is always in a stationary state. Inside it is a small float. There is a feeding channel at the output. Many modifications are made with an adjusting tap, which is installed at the outlet. Models with valves are equipped with movable fittings. They use magnetic force to work.

Sensor: DIY

Making a water flow sensor with your own hands is quite simple. First of all, it is recommended to install the camera. A small plastic container is suitable for this. Then you will have to cut three plates that are installed in a horizontal position. The flask as a result should not come into contact with them. If we consider a simple model, then one float is enough. It is more expedient to install the fitting on two adapters. The valve must withstand a pressure of at least 5 Pa.

Types of modifications

By design, only relay and fitting devices are distinguished. Additionally, modifications are separated according to the pressure level. Devices for circulation pumps are allocated in a separate subcategory.

Relay models

The relay water flow sensor for a gas boiler is suitable for small power pumps. As a rule, models are produced with one chamber. Many experts say that they have low conductivity. However, it is worth noting that there are devices with a vertical arrangement of plates. Their limiting pressure is at least 5 Pa. Protection systems are quite often used by the P48 series. All this suggests that water leaks are rarely observed. Modifications are characterized by excellent stability. Their suction power is at least 3 N. Very rarely, models have faucets.

Union devices

The most common devices for pumps are choke modifications, which are produced with one chamber. Their plates are usually located in a horizontal position. Some modifications are equipped with two valves. And their limiting pressure parameter is approximately 5 Pa. Protection systems are quite often used class P58. In this case, the conductivity depends on the size of the fitting. Some modifications are capable of boasting a high pumping speed. Their connections are quite often threaded. There are also clip-on sensors on the market, which are not very popular.

Low pressure devices

Low pressure versions are well suited for centrifugal pumps up to 4 kW. Their conductivity depends on the size of the chamber. The most common on the market is a water flow sensor for a two-float pump. In this case, the pumping force is on average 5 N. Protection systems are used in different classes. Many sensors are installed through pads. Output contacts are designed for wire adapters. It is also worth noting that there are many inexpensive models on the market.

High pressure modifications

High pressure models are usually manufactured with one oblong fitting. The plates on the water flow sensor for the pump are most often installed in a horizontal position. If you believe the reviews of experts, then the models are great for centrifugal pumps. When choosing a modification, it is important to pay attention to the throughput of devices. The dimensions of the devices are also taken into account. Many models are made with two cameras. However, they only use one valve. If we consider the standard model, then the limiting pressure averages no more than 6 Pa. The protection system in the devices is applied class P70. It is very rare to find models with a crane. Basically, ordinary switches are installed.

Devices for circulation pumps

Sensors for circulation pumps are very popular. A distinctive feature of the modifications is considered to be low reducibility. The limiting pressure is on average 3.3 Pa. Protection systems are used in various classes. It is very rare to find devices with two cameras. When choosing a model, it is important to pay attention to the shape of the fitting. It should have a wide head and a narrow channel. Otherwise, leaks will often occur. In addition, it is worth noting that devices on floats are on the market. Their contacts are designed for adapters.

Features of models for two cameras

Sensors for two chambers, as a rule, are distinguished by large dimensions and a high pressure parameter. There are many models on the market for two valves. They have a suction force of 4 N. Protection systems are used in the P88 series. The plates of the sensors are always installed in a horizontal position. If we talk about the shortcomings of the devices, it is important to note that they use very large output channels. For pumps with a power of up to 8 kW, models are not uniquely suitable. There are devices on the market with and without taps. Additionally, there are modifications based on contactor switches.

Devices with three cameras

Sensors for three chambers are connected for centrifugal pumps. Their compressive strength is very high. It is also worth noting that the models are produced with short channels. Valves they use rotary type. They are protected by a special membrane. According to experts, the conductivity depends on the size of the chamber. If we talk about designs, it is worth noting that there are models on the market with oblong fittings. They have extremely low suction power. However, they can last a long time. In stores, devices with switches are very rare. As a rule, three-chamber models are made with small cranes.

Models for small pumps

The water flow sensor for pumps of low power should be selected only among fitting modifications. The limiting pressure indicator should be about 5 Pa. The protection system is welcome class P48. Many experts praise devices based on two cameras. Their suction force is approximately 4 N. Relay modifications for low-power pumps are not suitable in the best way.

Modifications with a vertical arrangement of plates

Devices of this type perform well on centrifugal pumps. They have good conductivity and there are no problems with high pressure. However, do not forget about the disadvantages of modifications. First of all, they often clog the channel. If we consider an inexpensive water flow sensor, then it may have problems with the valve. For the normal operation of the system, it is more expedient to select devices with output contacts for 12 V. The protection system must be installed class P55. Experts also say that the water flow sensor should be with a contactor switch.

Devices with a horizontal arrangement of plates

The water flow sensor for this type of boiler is suitable for a wide variety of pumps. The conductivity of the models depends on the dimensions of the chamber itself, as well as the channel. Additionally, the diameter of the fitting is taken into account. Many experts recommend installing two-chamber modifications. Their pumping force, as a rule, does not fall below 5 N. The protection system is quite often used by the P50 series. All this suggests that the manufacturer guarantees a high degree of sealing and overall reliability.

When choosing a device, it is important to evaluate the parameters of the valve. If it is made of ordinary plastic, then it is not able to last for a long time. Copper counterparts perform well, but are expensive. The main flask of the sensors is made of plastic. Very rarely there are modifications with transitional contacts. Relay modifications boast high conductivity. They are not afraid of overload. And they use high-quality protection systems.

The water supply system of a private house is impossible without a pump. But it must somehow be turned on and off, to ensure that it does not work in the absence of water. The water pressure switch is responsible for turning the pump on and off, and protection against dry running of the pump should monitor the presence of water. How to implement this protection in different situations and consider further.

What is a dry running pump

Wherever the pump pumps water, sometimes a situation arises that the water is over - with a small flow rate of a well or well, you can simply pump out all the water. If water is pumped from a centralized water supply, its supply can simply be stopped. The operation of the pump in the absence of water is called dry running. Sometimes the term "idling" is used, although this is not entirely correct.

In order for the water supply at home to work normally, you need not only a pump, but also a dry water protection system, automatic on-off

What's wrong with dry running, besides wasting electricity? If the pump runs without water, it will overheat and burn out - the pumped water is used to cool it. No water, no cooling. The engine will overheat and burn out. Therefore, protection against the dry running of the pump is one of the components of automation that will have to be purchased. There are, however, models with built-in protection, but they are expensive. Cheaper to buy automation.

How can the pump be protected from running dry?

There are several different devices that will turn off the pump in the absence of water:

• dry run protection relay;
• water flow control devices;
• water level sensors (float switch and level control relay).

All these devices are designed for one thing - turn off the pump in the absence of water. They just work differently and have different applications. Next, we will understand the features of their work and when they are most effective.

Dry run protection relay

A simple electromechanical device controls the presence of pressure in the system. As soon as the pressure drops below the threshold, the power circuit breaks, the pump stops working.

The relay consists of a membrane that reacts to pressure and a contact group that is normally open. When the pressure drops, the membrane presses on the contacts, they close, turning off the power.

This is what dry running protection looks like.

When is it effective?

The pressure to which the device responds is from 0.1 atm to 0.6 atm (depending on factory settings). This situation is possible when there is little or no water at all, the filter is clogged, the self-priming part is too high. In any case, this is a dry running condition and the pump must be turned off, which is what happens.

An idle protection relay is installed on the surface, although there are models in a sealed housing. It works normally in an irrigation scheme or any system without a hydraulic accumulator. Works more effectively with surface pumps when a check valve is installed downstream of the pump.

When it does not guarantee shutdown in the absence of water

You can put it in a system with GA, but you will not get 100% protection against dry running of the pump. It's all about the features of the structure and operation of such a system. They put a protective relay in front of the water pressure switch and the accumulator. In this case, there is usually a check valve between the pump and the protection, that is, the membrane is under pressure created by the accumulator. This is the usual pattern. But with this method of switching on, a situation is possible when a running pump, in the absence of water, does not turn off and burns out.

For example, a dry run situation has been created: the pump has turned on, there is no water in the well / well / tank, there is some water in the accumulator. Since the lower pressure threshold is usually set on the order of 1.4-1.6 atm, the protective relay membrane will not work. After all, there is pressure in the system. In this position, the membrane is pressed out, the pump will run dry.

It will stop either when it burns out or when most of the water supply is used up from the accumulator. Only then will the pressure drop to critical and the relay will be able to work. If such a situation arose during the active use of water, nothing terrible will happen in principle - a few tens of liters will run out quickly and everything will be fine. But if it happened at night, they let the water out of the tank, washed their hands and went to bed. The pump has turned on, there is no signal to turn off. By the morning, when the analysis of water begins, it will be inoperative. That is why in systems with hydraulic accumulators or pumping stations it is better to use other devices to protect against the dry running of the water pump.

Water flow control devices

In any situation that causes the pump to run dry, there is insufficient or no water flow. There are devices that monitor this situation - relays and water flow controllers. Relays or flow sensors are electromechanical devices, controllers are electronic.

Relay (sensors) of the flow

There are two types of flow sensors - petal and turbine. Flap has a flexible plate that is in the pipeline. In the absence of water flow, the plate deviates from the normal state, contacts are activated that turn off the power to the pump.

Turbine flow sensors are somewhat more complicated. The basis of the device is a small turbine with an electromagnet in the rotor. In the presence of a flow of water or gas, the turbine rotates, an electromagnetic field is created, which is converted into electromagnetic pulses read by the sensor. This sensor, depending on the number of pulses, turns on / off the power to the pump.

flow controllers

Basically, these are devices that combine two functions: protection against dry running and a water pressure switch. Some models, in addition to these features, may have a built-in pressure gauge and check valve. These devices are also called electronic pressure switches. These devices cannot be called cheap, but they provide high-quality protection, serving several parameters at once, providing the pressure required in the system, turning off the equipment when there is insufficient water flow.

In the case of using an automation unit, a hydraulic accumulator is an extra device. The system works perfectly on the appearance of a flow - the opening of a tap, the operation of household appliances, etc. But this is if the headroom is small. If the gap is large, both a GA and a pressure switch are needed. The fact is that the pump shutdown limit in the automation unit is not adjustable. The pump will only turn off when it reaches maximum pressure. If it is taken with a large headroom, it can create excess pressure (optimal - no more than 3-4 atm, anything higher leads to premature wear of the system). Therefore, after the automation unit and the accumulator. This scheme makes it possible to regulate the pressure at which the pump is turned off.

Water level sensors

These sensors are installed in a well, borehole, tank. It is advisable to use them with submersible pumps, although they are compatible with surface pumps. There are two types of sensors - float and electronic.

float

There are two types of water level sensors - for filling the tank (protection against overflows) and for emptying - just protection against dry running. The second option is ours, the first is needed when filling out. There are also models that can work this way and that, and the principle of operation depends on the connection scheme (included in the instructions).

The principle of operation when used to protect against dry running is simple: as long as there is water, the float sensor is pulled up, the pump can work as soon as the water level has dropped so much that the sensor has dropped, the contactor opens the pump power circuit, it cannot turn on until until the water level rises. To protect the pump from idling, the float cable is connected to a break in the phase wire.

Level control relay

These devices can be used not only to control the minimum water level and dry running in a well, well or storage tank. They can also control overflow (overflow), which is often necessary when there is a storage tank in the system, from which water is then pumped into the house or when organizing water supply to the pool.

Electrodes are lowered into the water. Their number depends on the parameters they track. If you only need to monitor the presence of a sufficient amount of water, two sensors are enough. One - falls to the level of the minimum possible level, the second - the base - is located a little lower. The work uses the electrical conductivity of water: while both sensors are immersed in water, small currents flow between them. This means that there is enough water in the well / well / tank. If there is no current, it means that the water has dropped below the minimum level sensor. This command opens the power supply circuit of the pump and it stops working.

These are the main ways in which protection against dry running of the pump is organized in the water supply systems of a private house. There are also frequency converters, but they are expensive, so it is advisable to use them in large systems with powerful pumps. There they quickly pay off due to energy savings.

The introduction of a water flow sensor for the boiler into the heating and hot water supply system makes it possible to secure communications from such a phenomenon as “dry running”. This is what experts call emergency activation of the pump in conditions where there is no water in the circuit, there is a high probability of engine overheating and failure of connecting components.

The water flow sensor for a gas boiler is a device combined with a pump through pipes, it controls the pressure indicators in the water supply system. The standard package of the node in question includes:

• relay;
• wide inner chamber;
• feed output channel;
• a set of plates;
• a compact float inserted into a fixed flask;
• a small control valve mounted at the outlet.

The sensor operates as follows: if there is no working fluid flow in the system, the device automatically turns off the pumping station so that the circuit does not run dry, when water appears, the units start up again.

Through the branch pipe, the liquid enters the apparatus; a petal or valve is provided on its inner wall. The reed switch is isolated from other components, it is responsible for connecting to the power supply. The design also includes multi-caliber springs.

When the valve is affected by water pressure, it shifts relative to its axis, and the opposite magnet approaches the switch. Such a movement causes the contact to close, as a result, the pump is connected. When the flow of fluid stops, when the pressure decreases, due to the weakening compression, the valve returns to its original position. Beckoning is displaced, the contact is disconnected, the pump stops working.

Devices that monitor the flow of water are often built into circuits that need constant and comprehensive monitoring of the performance of a life support system, into equipment operating in a complex automatic mode. Typically, such a sensor is used in tandem with a gas boiler and a pump; improved bundles are equally effective for both hot water supply and heating in the private sector.

The flow sensor is installed on the pipeline through which fluid is supplied from the water supply. When water enters the system, the device sends a signal received by the boiler board, as a result, the operation of the circulation pump is suspended. The boiler control board activates the nozzles that provide heating of running water, due to which the temperature of the liquid in the heat exchanger begins to rise. When the tap is closed, the sensor notifies the system that the water supply has stopped.

Modern communication systems are based on autonomous water supply - in this case, the most comfortable living conditions are created. Here, the entire functionality of the flow sensor comes down to the fact that when any of the devices embedded in the water supply system is activated, the pump is connected and water flows. Therefore, when choosing a model, it is important to consider its size and throughput.

Varieties of the model range

According to the type of execution, the nodes are classified into choke and relay, they are also typified in terms of working pressure.

Relay devices are installed on pumps that do not have high power. As a rule, relay sensors serve as a rational addition to single-chamber devices. Experts warn that this class of devices exhibits low conductivity. In the profile market, there are models characterized by vertical placement of plates. The upper limit of their working pressure is 5 Pa. Representatives of the P48 series are often introduced into protective systems, they minimize the likelihood of leaks, attract with stability and reliable operation.

Choke devices that functionally complement pumps have become widespread. They can be distinguished by the characteristic horizontal placement of the plates, in samples with improved technology, two valves can be seen. Here, too, the maximum pressure in the system should not exceed 5 Pa, but the protection class differs from the previous version - P58. The level of patency of the node is directly dependent on the dimensions of the fitting.

If we consider the device triggering mechanism, one of two scenarios can be used:

• a model that functions on the principle of a Hall sensor - it gives signals both about the presence of a water flow and about the parameters of its supply (that is, speed);
• reed sensors operate on the principle of a magnet - a magnetic float is provided in their body, it moves along the internal cavity in proportion to the increase in fluid pressure, thereby affecting the location of the reed switch.

Low pressure devices are rational for installation on pumps whose power does not exceed 4 kW. Camera parameters have a direct impact on the degree of passability of the device. The profile market is filled with two float models of sensors for pumps. A rich assortment range and loyal cost contribute to their widespread use.

The design of high-pressure devices provides for a single elongated fitting, in which the plates are placed in a horizontal direction. It is recommended to use such samples in tandem with centrifugal pumps. It provides protection class P70, the maximum pressure mark is at the level of 6 Pa.

Instrument selection criteria

• the level of electricity consumption;
• maximum pressure;
• priority method of mounting the boiler, pump, directly the sensor;
• weight range of attachments that will not damage the performance of the boiler;
• requirements for the quality of the passed water;
• device performance.

The marking of the nodes usually indicates the models and full characteristics of the equipment, in tandem with which a particular device will fully function. The cost of production is influenced by factors such as body material, type of fixation, weight, power consumption and operating head.

Strengths of the units:

• simple installation - installation can be done on your own;
• the possibility of coordinating all parameters of the flow of water or working fluid;
• the ability to automatically turn off the pump in case of emergency;
• rich assortment and flexible price range.

When choosing, it should be borne in mind that when the springs are weakened, the correct operation of the assembly will be called into question. Not every heating system can be implemented with such a component, here you need to delve into the specification.

Overview of products from the best manufacturers

Companies whose range includes double-circuit boilers offer highly specialized additional equipment to the attention of users, among which flow sensors occupy a special niche.

Electrolux products are compatible with the GCB 24 X FI and GCB 24 XI series, their weight is only 150 g, the maximum working pressure is 1.5 Pa. The dimensions of the devices are compact - 40x115x45 mm, the pressure range does not exceed 3 bar, the upper mark of the permissible humidity of the environment is 70%.

Viessmann Vitopend WH1D

The Wismann flow sensor is installed in the gas boiler on the left side of the hydroblock. This element is necessary to control the parameters and performance of the hot water flow. Model designed for the Vitopend and Vitopend 100 series.

Ariston GENUS CLAS B 24

The Genus Ariston sensor is necessary for coordinating the heating of water by a gas boiler. During the flow, a signal is received on the electronic board of the latter, as a result, the equipment switches to the operating mode. A magnetic float is enclosed in a composite plastic case, it acts on the reed switch, the contacts of which close (the boiler starts producing hot water) or open (heating is provided).

Grundfos UPA 120

The device protects the pump from idling, is being introduced into individual water supply systems. The functionality of automation needs to ensure a steady flow of fluid of at least 90-120 l / h. The protection class of the device is IP65, the power consumption of this budget model does not exceed 2.2 kW. The operating temperature limits are kept in the positive range - from 5 to 60 ° C, 8 A - an indicator of the maximum current consumption.

It is widely used in domestic water supply systems, the basis for its activity is the actual water consumption. The sensor is able to monitor the level of pressure in the water supply. The pump starts only when the water flow reaches 1.5 liters per minute. The degree of protection of the unit is IP65, the operating voltage is used in the range of 220-240 V. The power consumption is kept at around 2.4 kW.

Immergas 1.028570

Initially, the model was designed for use with boilers of the same brand, it is compatible with double-circuit gas equipment of the Victrix 26, Mini 24 3 E, Major Eolo 24 4E series. The device can be used with boilers of turbocharged and chimney versions. The sensor is enclosed in a plastic housing, equipped with a threaded element for implementation in the system. An additional option is the possibility of obtaining hot water with a stable temperature at the outlet.

A significant segment of the water flow sensors for the boiler is supplied complete with heating equipment, so the need for their installation arises only in the event of a breakdown, when you have to think about a proportional replacement. A rare case when a separate installation of the device is planned is the need to increase the pressure of the liquid supplied to the system. A similar situation occurs if the central water supply is characterized by low pressure, barely reaching the needs of the boiler. In order for a gas appliance to be able to provide the proper quality of hot water supply, it must deal with good pressure.

To solve this problem, an additional circulation pump is mounted and equipped with a water flow sensor (the components must be introduced into the system in this order). With the beginning of the flow of water, the device activates the pump, which leads to an increase in pressure.

Homemade models are made from a chamber that will be used in conjunction with three horizontally mounted plates. It is important that the latter do not come into contact with each other and do not touch the flask.

For the simplest modifications, the introduction of one float is sufficient. The fitting should be mounted in tandem with two adapters, the maximum allowable pressure of the valve is 5 Pa.