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In the “Accessories” section we will consider a pressure switch that controls the operation of automatic pumping stations, as well as superficial , or if they are used in conjunction with. By using pressure switch you can configure an autonomous water supply system, irrigation or fire extinguishing system for the required tasks.Available for sale pressure switch RM-5, RM-5G, RM-12 produced by an Italian companyItaltecnica.The main difference of the product RM-5 differs from RM-5G in that the latter uses a union nut with a connection size of 1/4″. The PM-5G relay is more convenient for installation.
The main characteristics of RM-5 and RM-12 are shown in Table 1.
| Characteristics | RM-5 | RM-12 |
| 1. Working pressure range (bar) | 1-5 | 3-12 |
| 2. Factory settings for switch-on and switch-off pressure (bar) | 1,4-2,8 | 5-7 |
| 3. Minimum pressure drop (bar) | 0,6 | 1,5 |
| 4. Temperature working environment to (°C) | 55 | 55 |
| 5. Maximum operating current (amps) | 16 (10) | 16 (10) |
| 6. Voltage (volts) | 250 | 250 |
| 7. Connection internal thread(inch) | 1/4 | 1/4 |
Table 1
Note: When using a pressure switch to control pumping equipment, the maximum switching current is 10 A.
IN Lately The product PM-5G (25 A) with maximum switching current for controlling pumping equipment components 16 A.
Relay design
Structurally, the relay is assembled in a plastic case and closed with a lid. Figure 1 shows the main elements. To remove the top cover from the product, use a slotted screwdriver to unscrew plastic stopper at its end.
Pressure switch device
1. Housing – all elements of the pressure switch are located on it;
2. Connecting flange, used to connect the automation to the water supply system. The connecting flange size is 1/4″ internal thread. The flange contains the working chamber and membrane. The flange and diaphragm are attached to the relay body using four screws;
3. Nut for adjusting the pressure difference ΔР between the on and off pressure. The more we compress the spring (tighten the nut), the greater this difference will be;
4. Relay shutdown pressure adjustment nut. When tightening the nut, the shut-off pressure will increase, and when loosening, it will decrease. The top cover is also attached to this rod using a plastic plug;
5, 6. Terminals for connecting electrical wires;
7. Terminals for connecting ground wires from the power supply and the engine;
8. Cable clamps are used to firmly fix the mains power cable and motor connection cable.
Electrical diagram for connecting a pressure switch
In Fig. 2 shows a diagram of the electrical connection of the relay RM-5, RM-5G, RM-12.
Connection diagram for pressure switch PM-5, PM-5G, PM-12.
The diagram for connecting a relay to an electrical network is very simple. Wires are connected to terminals 5, 6 (see Fig. 1). Moreover, it does not matter which pair of terminals is input (connection ~220 V) and which pair is output (connection to the engine). After connecting the wires, you need to make sure that they are in reliable contact with the relay terminals; if necessary, you need to tighten the contacts.
Relay operation, maintenance and adjustment
Pressure switch RM-5, RM-5G, RM-12 are very simple and reliable control devices autonomous system water supply Subject to operating conditions, they operate without interruptions and failures for a long time and reliably. However, given the quality of our water, voltage fluctuations or high humidity, malfunctions occur. Incorrect operation of the automation usually leads to pump failure.
Let's look at the most common cases.
Hard water. In hard water or in water with a high iron content, during operation the passage to the working chamber gradually becomes overgrown, or the chamber itself becomes overgrown. The diameter of the passage is small, 5–5.5 mm. There may come a time when the relay does not turn on or, on the contrary, does not turn off. To eliminate this defect, you need to clean the passage or the chamber itself by following these steps:
High humidity. Very often the station or automation is located in a pit. Lack of proper ventilation leads to high humidity, and humidity leads to oxidation and burning of contacts in the pressure switch. In this case, the automation begins to work unstably, turns on with a delay, or turns on when you lightly tap on the body. If there is moisture on the surface of the product when you remove the cover, and there are marks on the metal parts white plaque, then there is a high probability that the contacts are burnt. To repair such defects, you must contact your nearest service center, or call a service technician to the installation site of the station or automation.
Unstable operation of the pressure switch is also caused by fluctuations in the voltage of the electrical network and the entry of air into the water supply system.
Pressure adjustment. To adjust the pressure, two adjusting nuts and springs are used (Fig. 1). Using nut 4 and a large spring, you can adjust the shutdown pressure of the system. The more we compress the spring, the higher pressure Automation in the system will turn off. One of the most common causes of non-stop pump operation is incorrect setting of the pressure switch. Before setting up the automation, you need to look at the operating parameters of the pump, namely, what maximum pressure it produces. For example: the pump produces a maximum pressure of 40 meters of water column or 4 bar (atmosphere). Theoretically, the maximum pressure setting of the relay can be 4 bar, but taking into account fluctuations in the mains voltage and the gradual wear of equipment, the maximum pressure for which we can set the automation is no more than 3.4–3.5 bar. Using nut 3 and a small spring, we adjust the difference ΔP between the pump on and off pressure. The more we compress the spring, the greater the difference between turning the pump on and off. The minimum difference between the pump on and off pressure is 0.6 bar for the PM-5 and 1.5 bar for the PM-12 relay - this is when the small spring is completely released. On the one hand, the difference between the switch-on and switch-off pressures must be adjusted as small as possible in order to reduce pressure drops. On the other hand, with a minimum range, the number of pump starts and stops increases, this problem is solved by increasing the volume of the hydraulic accumulator. For optimal performance pumping equipment and autonomous plumbing system it is necessary to choose the golden mean between the pressure to turn the pump on and off and the volume of the accumulator. Additionally, you can see how to configure and adjust the pressure switch. If you have any questions, please write in the comments.
Thank you for your attention.
To find out which is stronger - water hose, pipes or pump, you can assemble a water supply system without a pressure switch. In all other cases, when supplying water to a house, a device is built into the system that replaces manually turning on and off the supply voltage of the deep-well pump.
It is impossible to imagine individual water supply at home without a relay that allows you to automatically turn off the pump as the water supply system fills with water and turn it on after the water is consumed.
Fig.1 Design pressure switchStructurally, a standard pressure switch for controlling a pump looks like this. The plastic case contains terminal blocks for connecting the power cable and a mechanical device control system with adjustable spring struts; a 4-inch diameter pipe is located outside for connection to the water main. The power cable enters and leaves the pressure switch through two wide inlets; the wires are clamped using a nut with a plastic ferrule.
In the normal state, the contacts are normally closed and the connected device powers the pump motor. When the pressure in the system increases, water acts on a rubber membrane with a piston installed at the inlet of the water pipe of the device. In turn, the membrane piston presses on a movable metal platform, hinged inside the device body at one point. The platform plate rises and opens electrical contacts, when the pressure decreases, it returns to its original state, closing the contacts.
A screw with a spring and a nut is installed in the center of the device, which sets the distance of the contact plate to the membrane piston - if it is smaller, the device operates at lower pressure, an increased distance will require greater movement of the piston with the membrane to act on the contact pad, which is equivalent to increasing the pressure in the system.
At some distance from the main adjusting screw there is a second adjusting screw with a smaller spring. It sets the range of movement of the contact metal pad, establishing the difference between the pressure that turns the contacts on and off. Thus, the large adjusting screw sets the lower response threshold of the device (the pressure for turning it on), the small one regulates the range of operation of the device for shutdown (adjustment depth).
Rice. 2 Connection diagram When purchased, the relay is configured for a specific switching mode, standard values are 1.4 and 2.8 atm, that is, at 2.8 atm. the pump will be turned off and turned on if the pressure is less than 1.4 atm. Usually, when installing a device into a system, you need to select a response threshold - for this you need to know what pressure the pump in the well provides.
If the pressure well pump 2 atm., and the standard value of 2.8 atm. remains in the relay, then the pump will never turn off (it physically cannot create a pressure that reaches the response threshold) and after intensive work will go to eternal rest. A less tragic situation is when the pump can produce a pressure of 5 atm, and the relay turns it off at 2.8 atm. In this case, the system does not work efficiently and it is advisable to install a device that matches the pressure of the well water pump.
To take measurements when adjusting the relay, you need a pressure gauge; the work consists of the following steps.
When installing a relay in a water intake system, the following rules must be observed.
Rice. 3 Connection diagram of a submersible pump to a hydraulic accumulator Connecting a pressure switch to a submersible pump can be done in two ways:
There are two types of pressure switches: mechanical and electronic, the latter are much more expensive and are rarely used. The market offers a wide range of devices from domestic and foreign manufacturer, making it easier to select the required model.
RDM-5 Gilex (15 USD) - the most popular high quality model from a domestic manufacturer.
Fig.4 RDM-5 Characteristics
Genebre 3781 1/4″ (10 c.u.) — budget model Spanish made.
Rice. 5 Genebre 3781 1/4″ Characteristics
Italtecnica PM/5-3W (13 USD) - inexpensive device Italian manufacturer with built-in pressure gauge.
Rice. 6 Italtecnica PM/5-3W Characteristics
Pressure switch - essential element in the water intake system, providing automatic individual water supply to the house. It is located next to the hydraulic accumulator, the operating mode is set using adjusting screws inside the housing.
More details electrical diagram Connecting the pressure switch and everything connected with it has been reviewed by us.
So, as can be seen from the diagram, A three-wire power cable is connected to the pressure switch single-phase network (phase, zero and ground), and a similar cable already comes out of the relay to the pump that pumps water into the system. There are, of course, three-phase devices and a water pressure switch is used accordingly, but in everyday life a single-phase one is usually sufficient.
In the water supply of a private home, single-phase surface or submersible pumps are most often used, pumping water from a well or well. Electric power pumps vary greatly depending on the required performance of a particular device under specific operating conditions.
Usually, the power of such a household pump does not exceed 1.5-2 kW, accordingly, to connect it, a cable with a core cross-section of 1.5 sq. mm is required. and a 10 Amp line circuit breaker.
Connecting a pressure switch to the electrical network is usually accepted in one of two ways:, each of which has its own strengths and weaknesses:
1. Mounted near the installation site of the pressure switch, on the wall electric outlet, for him. A cable with an electrical plug at the end is connected to the relay itself.
This is a universal, and often the most convenient, connection option. The main disadvantage of this method is the need extra costs on the socket device itself, as well as possible problems at the connection point, in the vicinity of the water supply system of the house.
2. The second option is the simplest and, accordingly, the most reliable. At the location where the pressure switch is installed, a power cable is pulled out of the wall, which connects the relay to the network. In this way, maximum connection reliability is achieved, because The pressure switch housing, as well as the cable entry into it, are usually sealed and they reliably protect the contact point from possible adverse influences.
The main disadvantages of this method include increased requirements for the accuracy of choosing the output location and cable length, as well as some possible complexity in subsequent maintenance. It is always easier to unplug the device from the outlet than to disassemble and disconnect the wires.
In our installation example, the second option was chosen - a cable coming out of the wall. Maintenance problem solved by installing a separate circuit breaker for a pressure switch in the electrical panel of a boiler room.
Before connecting the power cable to the relay, be sure to ensure that there is no voltage at the installation location!
We proceed directly to connecting the pressure switch to the network, using the example of the Italtecnica TYPE PM/5G model.
First of all remove the protective plastic casing, to do this you need to use a straight screwdriver (slotted) to unscrew the fasteners, as shown in the image below
Then In the pressure switch, the supply cable and the cable going to the pump are laid through the cable entries.
This model uses standard sealed cable glands that are familiar to many. To fix the cable in them, you must first unscrew the plastic nut, then insert the cable first into it, and then through the input, into the relay and finally tighten the nut until it stops.
Then, having previously prepared - removing the protective insulation, connect the cable cores to the relay terminals pressure according to the following diagram.
Do not pay attention that one of the connected cables in the diagram ends with an electrical plug; in our case, instead of it, a power cable is connected that runs continuously to the electrical panel.
After connecting the wires and testing all the terminals, you should get something like this:
This completes the connection, all that remains is to carefully put it back on protective cover and secure.
Now, by turning on the electricity supply, you can check the operation of the water pressure switch and adjust its operation.
As you can see, there is nothing difficult in installing a relay, especially if you clearly understand the principle of its operation.
If you still have any questions about connecting the pressure relay to the power supply, for example, you have a more powerful pump or it is three-phase, or just a different relay model, or you don’t know how to connect and what cable and socket to use - be sure to leave them in comments on the article, I will try to answer everyone promptly.
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