How servos and three-way valves work
In this article I will tell you how to understand the operation of three-way valves and servos (electric actuators).
What is a valve?
Valve - this is a mechanism that serves to skip or not to skip a liquid or gas from one space to another. Moreover, the valve can be opened or closed by a certain percentage. That is, the valves can serve to control the passage of liquids or gas. The movement of liquid or gas is due to the pressure difference between the sides of the valve.
In the heating system, there are two of the most common types of valves:
Saddle (saddle) type - has a sleeve and directly surround the body, which blocks the passage.
Ball (or rotational) type - has a body, which due to its rotation leads to the opening or closing of the passage.
Ball valves have the highest flow capacity with respect to the seat type of valve. That is, in the ball valves less hydraulic resistance is achieved.
Valves are:
Two way valves - have two connections on opposite sides of the valve. For example, they are used to pass liquid or gas on one circuit. That is, they close or open one branch of a water supply or heating system.
Three way valves - They have three connections. Mainly used for mixing or separating the flow of liquid or gas. The main work of a three-way valve is necessary either to obtain a certain temperature or to redirect flows. In heating systems, temperature control is needed in order to regulate the indoor climate. Redirection of flows usually serves to redirect the heated coolant from the heating system to the indirect heating boiler. There are also many other tasks ...
Four way valves - They have four connections. Do the same job as three-way valves. But there may be other tasks.
Communication between servos and valves
In the heating system, there are several ways of the relationship between the valves and valve control elements (servo and thermomechanics):
1. Thermostatic mixer - usually called a mechanism that has immediately in itself a valve and a device that changes the position of the valve in automatic mode. Varies depending on the temperature of the liquid or gas. This device has a mechanism that, under the influence of temperature, changes the force of elasticity and because of this, the valve moves. Depending on the actuator, such a valve does not require electricity. The temperature is regulated by turning the handle. Typically, some valves are designed for a small temperature range. Maximum to 60 degrees. There may be exceptions from other manufacturers.
2. Ways to use individual elements without resorting to servos. For example, a thermostatic valve with a thermal head. There are thermal heads that have a remote sensor.
3. Valves and actuators are separate elements. The servo is attached to the valve and regulates the valve.
What is a servo drive?
Servo - This is a device that carries out the movement of the valve. The valve in turn either passes or does not pass liquid or gas. Or passes it in a certain amount, depending on pressure, valve position and hydraulic resistance.
What are the servos?
There are also thermal drives, which are also called servo drives.
But in this article we will analyze only electric drives (servos)
Electric drives come in two directions:
A complete package (set) is when a complete set of functions is already embedded in the device. For example, the kit already has a temperature controller, an electric thermal sensor. It is possible to immediately adjust it to the desired temperature. Setting test time for valve movement. It is connected directly to the 220 V AC network with a frequency of 50 Hz. Standard for Russia. It is possible to adjust it in various directions of movement of a ball-type valve. It is possible to adjust it to rotate 90 or 180 degrees. You can set any value, even 49 degrees or 125 degrees. And this is done inside the black box. Look for details in the instructions.
I told you one of the options. Of course, there are a dozen other options ... Servo drives also vary in speed of closing and opening valves. This example serves to smoothly adjust the valve to mix flows of different temperatures to obtain a control temperature.
This option serves to redirect the flow of coolant.
This option is used to redirect the flow of coolant from the boiler either to the direction of radiator heating or to the heating of an indirect heating boiler. The specified servo needs a 220 volt signal. Moreover, there are three contacts. One is common, and the other two are for redirecting traffic. The easiest option when you need to redirect the flows in the heating system on demand from the indirect thermal boiler relay.
Servos are of the type of movement to the seat type of valve or ball (rotary) type of valve.
If you will choose a servo to the valve, be sure to specify the type of movement of the servo. Also, the seat type servo drive is not always the same as all types of seat valves. With rotary ball valves there seems to be a universal standard, but with globe valves it's not so simple. There is no one standard.
Electric drive as a separate link in automation.
Consider an analog servo from Valtec art. VT.M106.R.024
Such a servo drive requires 24 V continuous supply and a control signal from 0 to 10 Volts.
That is, if the voltage is 0 Volts, then the rotary mechanism is in the 0 degree position. If 5 volts then 45 degrees. If 10 Volts then 90 Degrees.
Such a servo drive receives a signal from a special controller, on which there is a 0-10 Volt signal supply function. Depending on the temperature and the controller’s temperature settings, the controller supplies different voltages from 0 to 10 volts. There is a rotation setting: Hourly and counterclockwise. Of course, in order to find more detailed information about the signals and the connection diagram, ask the manufacturer for a passport with a detailed signal management diagram.
I repeat ... As indicated in this article, not all signals are described. There are many other signals ...
What is a controller?
Controller - This device is designed to control signals for various logical tasks. The controller is the brain of an automatic system. It determines, depending on the program, which signals need to be given at one time or another.
There are many different controllers that perform various tasks.
For a heating system, the following tasks are usually performed:
The most common task is to get the adjusting temperature of the coolant.
Depending on the temperature, receive a signal (for example, turn off the boiler or pump). The controller may comprise a contact relay. That is dry contact. This contact relay can be set to receive any voltage. For example, 220 Volts turn the pump on or off or send a signal to a servo drive to redirect flows.
You can also use the controller to turn off the boiler in case of critical temperatures. The signal from the controller is sent to power the powerful contactors, and they, in turn, feed the powerful electric boilers.
Cheapest TPM Series Controller
Sells ARIES they have a lot of interesting things you can get. owen.ru
The logic of work is very extensive ... In the future I plan to write and develop useful material on automation systems of heating and water supply systems. Record your emails to receive notifications of new articles.
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Private home video tutorial series
Part 1. Where to drill a well?
Part 2. Development of a well for water
Part 3. Laying the pipeline from the well to the house
Part 4. Automatic water supply
Water supply
Water supply of a private house. Principle of operation. Wiring diagram
Self-priming surface pumps. Principle of operation. Wiring diagram
Calculation of a self-priming pump
Calculation of diameters from central water supply
Water pumping station
How to choose a pump for a well?
Pressure switch setting
Pressure switch circuit
The principle of operation of the accumulator
Slope of the sewerage on 1 meter of SNIP
Heating schemes
Hydraulic calculation of a two-pipe heating system
Hydraulic calculation of a two-pipe associated heating system Tichelman's loop
Hydraulic calculation of a single pipe heating system
Hydraulic calculation of the radial distribution of the heating system
The scheme with a heat pump and a solid fuel boiler - the logic of work
Valtec 3-way valve + thermal head with remote sensor
Why the radiator in an apartment building is not warming well
How to connect the boiler to the boiler? Connection options and schemes
DHW recirculation. Principle of work and calculation
You are not correctly calculating the water spouts and collectors
Manual hydraulic calculation of heating
Calculation of warm water floor and mixing units
Three-way valve with servo for domestic hot water
Calculations of hot water, BKN. We find the volume, power of the snake, warm-up time, etc.
Water and heating constructor
Bernoulli equation
Calculation of water supply for apartment buildings
Automation
How servos and three-way valves work
Three-way valve for redirecting coolant movement
Heating
Calculation of the thermal power of heating radiators
Radiator section
Overgrowing and deposits in the pipes impair the functioning of the water supply and heating system
New pumps work differently ...
Differential pressure calculation
Calculation of temperature in an unheated room
Heat regulators
Room thermostat - principle of operation
Mixing unit
What is a mixing unit?
Types of mixing units for heating
System characteristics and parameters
Local hydraulic resistance. What is GDN?
Kvs bandwidth. What it is?
Boiling water under pressure - what will happen?
What is hysteresis in temperature and pressure?
What is infiltration?
Two-way valve with a servo-drive - a mandatory attribute of an automation system when using a boiler with any energy source or central heating circuit (when using meters).
A two-way valve with a servomotor is used in space heating systems based on Volcano VR and Volcano Mini water heaters. The valve is controlled by a thermostat or a programmable temperature controller and allows you to adjust the heat transfer of heating units. Typically, the valve is installed in the return water pipe. When the temperature set by the user is reached, the thermostat gives a signal to the servo drive and the valve switches to the closed position, thereby interrupting the movement of the heat carrier through the Volcano heater heat exchanger. As a result of this, the heat transfer decreases and the room temperature begins to fall, after which the thermostat gives the command to open the valve again. In this way, the set temperature is maintained.
- Use with VOLCANO fan heaters
A two-way valve with a servo drive is controlled by a Thermostat or a Programmed controller. The control elements supply power to the servo to open the valve.
Fast response time allows you to smoothly control the air temperature without differences. The valve also serves to maintain a stable and accurate temperature. And prevents overspending of energy.
- Use with WING and DEFENDER thermal curtains
A two-way valve with a servo drive is used, similar to the Volkano fan heater, it is controlled using the DX panel. The control elements supply power to the servo to open the valve.
Caution if there is no power, the valve will close provide mechanical opening of the valve to prevent freezing of the heat exchanger in the curtain.
QUESTION - Do I need a two-way valve with a servo actuator?
This can only be decided by the client. The valve is recommended in systems where there is a gas or electric boiler. When the valve is closed, they are automatically turned off, thereby saving. Also, with the help of a clan and a thermostat, you can more accurately control the temperature in the room.
Without a two-way valve, the coolant will pass through the VOLCANO fan heater, regardless of whether the fan heater is on or off.
It is not recommended to install a two-way valve in systems with a wood boiler, where heat removal is necessary, in order to avoid overheating of the boiler. And in rooms where the temperature can drop below zero, which will cause the freezing of the heat exchanger apparatus VOLCANO.
- Diameter of branch pipes: 3/4 ";
- Operating mode: on-off;
- Maximum pressure drop: 100 kPa;
- Pressure Class: PN 16;
- Kvs flow coefficient: 3.5 m3 / h;
- Maximum heat carrier temperature: 105 ° C;
- Environmental parameters: 2 ... 40 ° C;
- It is recommended to install a two-way valve on the return pipe.
- Supply voltage: 230V AC +/- 10%;
- Closing / Opening Time: 5/11 s;
- De-energized position: closed;
- Protection class IP: 44;
- Environmental parameters: 2 ... 40 ° C;
- It is recommended to connect the power cable min. 2 x 0.75 mm2.
Hello to all readers of this blog! This article will discuss three-way valves and actuators. An article was written at the level of educational program, so I’ll ask experts not to laugh out loud at the issues discussed here. We start the discussion with three-way valves, and then move on to servos. Let's get down to business.
What is a three-way valve and why is it needed?
From the name of the three-way valve it is clear that it has three threaded or flange connections. There are two types of valves:
If you are interested, then there is a separate one. Read and expand your horizons.
The internal arrangement of three-way valves.
Now let's look at the technical structure of three-way valves. Let's start in order with the device of the heat mixing valve. In order to have a visual representation of its internal structure, look at the following figure:
The temperature sensitive element expands or contracts depending on the temperature. This allows you to withstand a certain temperature at the outlet of the mixture (4). Temperature fluctuations usually lie within two or three degrees, depending on the difference in pressure between hot and cold water. The presence of scale in the mixing valve also reduces the accuracy of its adjustment. The water temperature at the outlet of the valve can be set rigidly during the manufacture of the valve, or may vary within certain limits. This is done by rotating the adjusting wheel.
Now we turn to the consideration of another type of valves - flow direction switches. Actually, such valves can also work as mixing ones, but they are controlled using manual adjustment or a servo drive. For clarity, see the figure below:
In essence, such a valve is a ball valve, in which the holes in the ball are not on the same line, but are made at right angles to each other. To completely switch the flow, a ball rotation of 90 ° is necessary. Let's see the top view of such a valve:
An angular scale indicates the position of the ball inside the valve. As I already said, most often such valves are used to connect an indirect heating boiler to the boiler. The connection diagram will look like this:
In this scheme, the coolant will circulate either through the boiler heat exchanger or through heating radiators. The valve servo will be controlled by the boiler thermostat. Now let's talk about the most important technical characteristics of such valves:
- Connection diameter - thread diameter in inches.
- Operating temperature - the temperature of the coolant at which the valve will work out its entire life.
- The material of the body and seals - most often, such valves are made of brass, and EPDM elastomer (rubber) can be used as seals.
- Nominal flow - measured in cubic meters per hour and determines the valve capacity limit. The nominal flow is directly proportional to the diameter of the valve connection.
- Work environment - this parameter determines in which environment this node can work. For example, it can only be water, or glycol solutions ().
What is a servo drive and how is it arranged?
Let's start with the definition. A servo drive is an electric motor driven through negative feedback. In this case, the negative feedback will be the shaft angle sensor, which stops the shaft moving when the desired angle is reached. To visualize the servo drive, look at the picture below:
Internal servo device.
As usual, for clarity, consider the servo device according to the figure:
As you can see, the following components are located inside the servo drive:
- Electric motor.
- Gearbox consisting of several gears.
- The output shaft by which the actuator rotates the valve or other device.
- Potentiometer - this is the very negative feedback that controls the angle of rotation of the shaft.
- Control electronics located on a printed circuit board.
- The wire through which the supply voltage (220 or 24 V) and the control signal are supplied.
Servo control signal.
Let us now dwell in detail on the control signal. The servo drive is controlled by a pulse signal with a variable pulse width. For those who do not know what they are talking about, I bring one more picture:
That is, the pulse width (in time) determines the value of the angle of rotation of the shaft. Setting up such control signals is not trivial and depends on the specific drive. The number of control signals depends on how many positions the output shaft can occupy. The servo drive can be two-position (2 control signals), three-position (3 control signals) and so on.
The conclusion of the article.
In this article, I reviewed (very briefly) three-way valves and servos. The main thing why they are needed is automation of the management of utility networks (water supply, heating, and so on). They are expensive and in many cases you can do without them, but there are still cases when you can not do without them, for example, with the boiler connection diagram described above. That's all, write your questions in the comments and press the buttons of social networks.
The valves are equipped with a servo actuator and have two positions, depending on whether the actuator is powered or not. Upon request, one or two auxiliary microswitches can be installed, which are valve position indicators. The valves are equipped with a manual override for the forced opening of a two-way valve; in a three-way valve, a handwheel takes the locking ball to the position where all three holes are connected.
- Specifications
- Charts
- Dimensions
- Order
Main characteristics
- Supply voltage: 230, 24, 110 VAC
- Power Consumption: 5 - 6 W
- Degree of protection: IP22
- Additional contacts: 3A, 250 VAC
- Nominal pressure: 10 bar
- Working environment temperature: + 5..110С
- Opening time: 10 seconds (two-way valve); 20 sec (three-way valve)
- Closing time: 4sec (two-way valve); 6 sec (three way valve)
- Standard cable length: 1000 mm
Valve Materials
- Body: Brass
- Locking Ball: Brass
- Return spring: stainless steel
- Drive Cover: Flame Retardant Plastic
Hydraulic characteristics
Two way valveThree-way valve
Principle of operation (two-way valve)
diagram: valve closed. When the valve is energized, the actuator acts on the spring and moves the ball from position A to average for 10 seconds and holds it in this position until the supply voltage is removed. When the power is removed, the spring returns the ball to position A within 4 seconds.
Principle of operation (three-way valve)
Without supply voltage, the valve is in the state in the diagram: the valve is closed. When the valve is energized, the servomotor acts on the spring and moves the ball from position A to position B for 20 seconds and holds it in this position until the supply voltage is removed. When the power is removed, the spring returns the ball to position A within 6 seconds.
Using a handwheel
The backup is located on the side of the servo. It is used to force open a two-way valve; in a three-way valve, a handwheel takes the locking ball to the position in which all three holes are connected (circuit). This is useful when filling or emptying the heating system. The reset of the switch to the “automatic” state from the “manual” state occurs automatically whenever the valve is energized.
Additional microswitches
All versions can be equipped with a single-position or two-position microswitch. There is a special kit for installing the on-off switch on valves that were not originally equipped with it. A kit with an on / off switch cannot be installed on a valve that did not have one. See the circuit diagram of the switches.
| A type | Dn | A | B | C | D | E |
| SF3-15 | G1 / 2 | 92 | 46 | 46 | 84 | 130 |
| SF3-15C | tube F15 | 106 | 53 | 53 | 84 | 137 |
| SF3-16C | tube F16 | 106 | 53 | 53 | 84 | 137 |
| SF3-20A | G3 / 4 | 92 | 46 | 46 | 84 | 130 |
| SF3-20B | G3 / 4 | 92 | 46 | 46 | 84 | 130 |
| SF3-20C | tube F22 | 106 | 53 | 53 | 84 | 139 |
| SF3-25A | G1 | 92 | 46 | 46 | 84 | 130 |
| SF3-25B | G1 | 92 | 46 | 46 | 84 | 130 |
| SF3-25C | tube F25 | 120 | 60 | 60 | 88 | 148 |