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Water pressure switch for a pump: device and principle of operation, do-it-yourself troubleshooting

The water pressure switch is one of the most important parts that make up the household pumping station.

It provides pressure control in the system and serves to timely turn on and off the motor in automatic mode without human intervention.

It is the relay that is the part that significantly distinguishes the stations from simple submersible pumps.

Executable function

The device of the pumping station. (Click to enlarge) To understand how the water pressure switch works, you should take a closer look at the device of the pumping station itself.

It includes in its composition:

  • pump;
  • electric motor;
  • hydraulic accumulator;
  • relay;
  • water dispensing system with pressure indicator (pressure gauge).

The accumulator is an expansion tank of a certain volume. Inside it contains another container (pear), usually made of rubber. The pear is constantly filled with air.

It is the differential change in air and water pressure that leads to the operation of the relay and the cessation of the operation of the engine and pump. Having the simplest device, the relay performs a very important function.

It includes:

  • two pairs of contacts providing power to the electric motor;
  • a membrane representing a sensor that creates a mechanical effect on the contacts;
  • adjusting bolts and springs.

Operating principle

The work is done as follows. Initially, the accumulator tank is empty. The relay contacts are in the closed position.

When power is applied, the motor starts to run, driving the pump. Water filling the tank creates pressure.

The difference between this indicator and the same in a pear sets in motion a membrane that opens the contacts. The entire unit is de-energized and goes into standby mode.

Now, the operation of the relay depends solely on the pressure difference between the pear and the water in the tank. Usually, water pressure is limited to a limit of 2.5 atm, and air - 1.5.

When a tap is opened in the system, the water pressure in the accumulator will begin to decrease. The pear with air, expanding, acts on the membrane and leads to the closure of the contacts. The station will start working again and turn off only after reaching the set limit.

Adjustment

Pressure switch adjustment. (Press to enlarge) As a rule, the relay supplied with the station has factory settings, prepared in advance for certain conditions.

But, it happens that the device needs to be replaced. In this case, you have to adjust the parameters yourself.

To start the procedure, it is necessary to release the relay from the decorative case, which is also the protection of the internal parts.

Two clamping nuts located on the rods with springs are responsible for adjusting the relay. They are labeled accordingly. One is responsible for high pressure, the second for low.

Adjustment sequence:

  1. First, you need to make sure that the expansion tank is empty. After, the air pressure in the pear is measured. To do this, use the spool located on the accumulator housing.

    Measurement and pumping is carried out using a pump equipped with a pressure gauge. The minimum pressure should be in the range of 1.5–1.8 atm. If this indicator is lower, then swapping is performed. Above, the air is bled through the spool.

  2. The station is powered. The pump starts pumping water. The pressure can be observed on the pressure gauge, which is part of the entire unit.

    Having reached the upper limit, which should be between 2.5 and 3 atm, the pressure acts on the relay and turns off the motor. If necessary, adjustment is made with the upper limit nut.

  3. The lower limit is determined by opening the taps in the system. Gradually lowering, the water pressure in the tank will cause the bulb to expand, and it will again press on the relay membrane, starting the motor.

    To ensure optimal operation of the station, the minimum pressure on the accumulator pressure gauge should not fall below 0.8–0.9 atm. Adjustment is made with the corresponding nut.

  4. After setting the required parameters, several complete cycles should be performed to check the entire system.

Possible problems

Water pressure switch device. (Click to enlarge) The electronic pressure switch has a minimum number of parts and works according to the simplest scheme. However, it is a very finicky mechanism.

The main problems are most often associated with the constant operation of the device and environmental conditions. Sometimes the cause of a malfunction may be a manufacturing defect or mechanical damage.

Electrical part:

  1. The motor is not running. It is necessary to check the presence of current in the network, the condition of the wiring before entering the pumping station. Having opened the cover, inspect the relay contacts (if necessary, clean with fine emery).

    The destruction of the contact group will require a complete replacement of the entire relay. A more serious malfunction may be a blown motor winding. In this case, it must also be replaced.

  2. The station often turns on and off, the work is uneven, with disruptions. The reason is soot on the contacts.