Pump station pressure switch: principle of operation and adjustment


To make an autonomous water supply system in a small private house, a conventional pump, borehole or surface, with suitable performance characteristics will be enough. But for a house in which more than 4 people live, or for a 2-3-storey dwelling, you will need to install a pumping station. This equipment already has factory pressure settings, but sometimes they need to be adjusted. When adjustment of the pumping station is required, and how to do it, will be described below.

Pumping station device

In order to properly adjust this pumping equipment, you must have at least a minimal idea of ​​​​how it works and on what principle it works. The main purpose of pumping stations consisting of several modules is to provide drinking water to all water intake points in the house. Also, these units are able to automatically increase and maintain the pressure in the system at the required level.

Below is a diagram of a pumping station with a hydraulic accumulator.

Scheme of a pumping station with a hydraulic accumulator

The pumping station includes the following elements (see the figure above).

  1. Hydraulic accumulator. It is made in the form of a sealed tank, inside of which there is an elastic membrane. In some containers, a rubber bulb is installed instead of a membrane. Thanks to the membrane (pear), the hydraulic tank is divided into 2 compartments: for air and for water. The latter is pumped into a pear or into a part of the tank intended for liquid. The accumulator is connected in the section between the pump and the pipe leading to the water intake points.
  2. Pump. It can be surface or borehole. The pump type must be either centrifugal or vortex. The vibration pump for the station cannot be used.
  3. Pressure switch. The pressure sensor automates the entire process by which water is supplied from the well to the expansion tank. The relay is responsible for turning the pump motor on and off when the required compression force is reached in the tank.
  4. check valve. Prevents leakage of fluid from the accumulator when the pump is turned off.
  5. Power supply. To connect the equipment to the electrical network, it is required to stretch a separate wiring with a cross section corresponding to the power of the unit. Also, a protection system in the form of automatic machines should be installed in the electrical circuit.

This equipment works according to the following principle. After opening the tap at the water intake point, water from the accumulator begins to flow into the system. At the same time, compression is reduced in the tank. When the compression force drops to the value set on the sensor, its contacts close and the pump motor starts to work. After the cessation of water consumption at the water intake point, or when the compression force in the accumulator rises to the required level, the relay is activated to turn off the pump.

Pump station pressure switch

The sensor automatically regulates the process of pumping water in the system. It is the pressure switch that is responsible for turning the pumping equipment on and off. It also controls the level of water pressure. There are mechanical and electronic elements.

Mechanical relays

Devices of this kind are distinguished by a simple and at the same time reliable design. They are much less likely to fail than electronic counterparts, because there is simply nothing to burn out in mechanical relays. Adjustment occurs by changing the tension of the springs.

mechanical pressure switch

Mechanical pressure switch adjustable by spring tension

The mechanical relay includes a metal plate where the contact group is fixed. There are also terminals for connecting the device and springs for adjustment. The lower part of the relay is reserved for the membrane and piston. The design of the sensor is quite simple, so there should be no serious problems with self-disassembly and damage analysis.

Electronic relays

Such devices attract primarily by ease of use and their accuracy. The step of the electronic relay is noticeably smaller than the mechanical one, which means that there are more adjustment options here. But electronics, especially budget ones, often break down. Therefore, excessive savings in this case is impractical.

electronic pressure switch

Electronic water pressure switch

Another clear advantage of an electronic relay is protection of equipment from idling. When the water pressure in the line is minimal, the element will continue to work for some time. This approach allows you to protect the main nodes of the station. Repairing an electronic relay on your own is much more difficult: in addition to technical knowledge, you need a specific tool. Therefore, it is better to leave the diagnostics and maintenance of the sensor to professionals.

Device specifications

Depending on the model of the station and its type, the device can be located both inside the case and mounted outside. That is, if the equipment comes without a relay, or its functionality does not suit the user, then it is always possible to select the element in a separate order.

The sensors are also different according to the maximum allowable pressure. A good half of the classic relays are set to 1.5 atm to start the system and 2.5 atm to deactivate it. Powerful household models have a threshold of 5 atm.

When it comes to an external element, it is extremely important to consider characteristics of the pumping station. If the pressure is too high, the system may not withstand, and as a result, leaks, ruptures and early wear of the membrane will appear. Therefore, it is so important to adjust the relay with an eye to the critical indicators of the station.

Features of work

Consider the principle of operation of the device using the example of one of the most common relays for pumping stations — RM-5. On sale you can also find foreign analogues and more advanced solutions. Such models are equipped with additional protection and offer advanced functionality.

pressure switch rm-5

PM-5 includes a movable metal base and a pair of springs on both sides. The membrane moves the plate depending on the pressure. By means of a clamping bolt, you can adjust the minimum and maximum indicators at which the equipment turns on or off. RM-5 equipped check valvetherefore, when the pumping station is deactivated, the water does not drain back into the well or well.

On the market, you can also find factory and amateur modifications of the RM-5. Relays are reinforced, supplemented with some protective elements and functionality.

Step-by-step analysis of the pressure sensor:

  1. When the faucet is opened, water begins to flow from the tank.
  2. As the liquid in the pumping station decreases, the pressure gradually decreases.
  3. The membrane acts on the piston, and it, in turn, closes the contacts, including the equipment.
  4. When the tap is closed, the tank is filled with water.
  5. As soon as the pressure indicator reaches its maximum values, the equipment turns off.

The available settings determine the frequency of the pump: how often it will turn on and off, as well as the pressure level. The shorter the interval between the start-up and deactivation of the equipment, the longer the main components of the system and all the equipment as a whole will last. Therefore, competent adjustment of the pressure switch is so important.

But not only the sensor affects the operation of the equipment. It happens that the device is configured correctly, but other elements of the station nullify the operation of the entire system. For example, the problem may be due to faulty engine or clogged communications. Therefore, it is worth approaching the inspection of the relay after diagnosing the main elements, especially when it comes to mechanical sensors. In a good half of the cases, to eliminate problems with pressure spread, it is enough to clean the relay from accumulated dirt: springs, plates and contact groups.

When to Adjust the Relay

As mentioned above, the relay automates the process of pumping fluid into the plumbing system and into the expansion tank. Most often, pumping equipment purchased ready-made already has basic relay settings. But there are situations when urgent adjustment of the pressure of the pumping station is required. You will need to perform these steps if:

  • after starting the pump motor, it immediately turns off;
  • after the station is turned off, there is a weak pressure in the system;
  • during the operation of the station, an excessive compression force is created in the hydraulic tank, as evidenced by the readings of the pressure gauge, but the device does not turn off;
  • the pressure switch does not work, and the pump does not turn on.

Most often, if the unit has the above symptoms, then relay repair is not required. You just need to properly configure this module.

Tank preparation and adjustment

Before the accumulators go on sale, air is pumped into them at a certain pressure at the factory. Air is pumped through the spool installed on this container.

On average, the pressure in the pumping station should be as follows: in hydraulic tanks up to 150 liters. — 1.5 bar, in expansion tanks from 200 to 500 l. — 2 bar.

Under what pressure is the air in the hydraulic tank, you can find out from the label glued to it. In the following figure, the red arrow indicates the line in which the air pressure in the accumulator is indicated.


Also, these measurements of the compression force in the tank can be made using car pressure gauge. The measuring device is connected to the spool of the tank.

Automotive monometer

To start adjusting the compression force in the hydraulic tank, you need to prepare it:

  1. Disconnect the equipment from the mains.
  2. Open any faucet installed in the system and wait until the liquid stops flowing from it. Of course, it will be better if the crane is located near the drive or on the same floor with it.
  3. Next, measure the compression force in the container using a pressure gauge and note this value. For small volume drives, the indicator should be about 1.5 bar.

In order to properly adjust the accumulator, the rule should be taken into account: the pressure that causes the relay to turn on the unit must exceed the compression force in the accumulator by 10%. For example, the pump relay turns on the motor at 1.6 bar. This means that it is necessary to create an appropriate air compression force in the drive, namely 1.4-1.5 bar. By the way, the coincidence with the factory settings is not accidental here.

If the sensor is configured to start the engine of the station with a compression force greater than 1.6 bar, then, accordingly, the settings of the drive change. You can increase the pressure in the latter, that is, pump air, if you use car tire pump.

Tire inflation compressor

Advice! Correction of the air compression force in the accumulator is recommended to be carried out at least once a year, since during the winter it can decrease by several tenths of a bar.

Setting the pressure switch

There are times when the default sensor settings do not suit users of pumping equipment. For example, if you open a tap on any floor of a building, you will notice that the water pressure in it is rapidly decreasing. Also, the installation of some water purification systems is not possible if the compression force in the system is less than 2.5 bar. If the station is set to turn on at 1.6-1.8 bar, then the filters will not work in this case.

The design of the pumping station

Usually, setting up a pressure switch with your own hands is not difficult and is performed according to the following algorithm.

  1. Write down the readings on the pressure gauge when turning the unit on and off.
  2. Unplug the station’s power cord from the socket or turn off the machines.
  3. Remove the cover from the sensor. Usually it is fixed with 1 screw. Under the lid you can see 2 screws with springs. The one that is larger is responsible for the pressure at which the station engine starts. Usually, next to it there is a marking in the form of the letter “P” and arrows are drawn with the signs “+” and “-” applied next to them.
  4. To increase grip strength, turn the nut towards the “+” sign. And vice versa, to reduce it, you need to turn the screw to the “-” sign. Turn the nut one turn in the desired direction and start the machine.
  5. Wait until the station turns off. If the pressure gauge readings do not suit you, then continue to turn the nut and turn on the device until the pressure in the accumulator reaches the required value.
  6. The next step should set the time to turn off the station. A smaller screw with a spring around is designed for this. Near it is the marking “ΔP”, as well as arrows with the signs “+” and “-”. Setting the pressure regulator to turn on the device is carried out in the same way as to turn off the device.

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On average, the interval between the compression force at which the sensor turns on the engine of the station, and the value of the compression force when the unit stops, is in the range of 1-1.5 bar. In this case, the interval may increase if the shutdown occurs at large values.

For example, the unit is factory set to Pon = 1.6 bar, and Poff = 2.6 bar. It follows from this that the difference does not go beyond the standard value and is equal to 1 bar. If it is required for any reason to increase Poff up to 4 bar, then the interval should also be increased to 1.5 bar. That is, Ron should be around 2.5 bar.

But as this interval increases, so will differential pressure in the water supply system. Sometimes this can cause discomfort, since you have to use more water from the tank in order for the station to turn on. But due to the large interval between Ron and Roff the pump will turn on less frequently, which will increase its resource.

The above-described manipulations with the compression force settings are only possible with equipment of the appropriate power. For example, in those the passport to the device states that it can give out no more than 3.5 bar. So, set up R on itoff = 4 bar does not make sense, since the station will work without stopping, and the pressure in the tank will not be able to rise to the required value. Therefore, in order to obtain a pressure in the receiver of 4 bar and above, it is necessary to purchase a pump of the appropriate capacity.

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