Sensor protection against dry run lp 3. Cashless payment for legal entities. persons

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Pressure switch LP-3

In the "Accessories" section, we will consider the "dry running" relay LP3. The LP 3 relay is used as protection against "dry running" in autonomous water supply systems, irrigation and fire extinguishing installations, as well as in air conditioning systems. The operating medium of systems where the LP series relay is used must be water. The "dry running" mode is controlled according to the set pressure values ​​previously set on the relay. The opening of the contacts in the relay occurs when the pressure in the system becomes lower than the preset value. Contact closure occurs when the pressure in the system becomes higher than preset, or when the start button located at the top of the device cover is pressed. Dry running relayLP3 must be used in conjunction with pressure switches RM-5 and RM-12. On sale there are pressure switches LP3 and LP3 / 18 manufactured by an Italian company Italtecnica.

Specifications

Main technical characteristics dry run relay LP3 and LP3/18 are listed in Table 1.

Note:When using a dry-running relay to control pumping equipment, the maximum switching current is 10A.

Relay design

Structurally, the “dry running” relay is assembled in a plastic case and closed with a lid. On (Fig.1) the main elements are indicated.

On the basis of the relay (Pos. 7) all working elements are located. A flange is attached to the base (Pos. 8). We considered the design of the flange in detail in an article devoted to three-phase pressure switches. The flange has a nut with a 1/4″ female thread for connection to a water supply system. By means of a nut and a spring (Pos. 6) the switch-off pressure is adjusted. When the spring is compressed (we tighten the nut), the cut-off pressure will increase. When the spring is unclamped (the nut is unscrewed), the cut-off pressure will decrease. The button (Pos. 5) is used to force the dry running relay into operation. Terminals (Pos. 3 and 4) are used to connect electrical wires. At the same time, it does not matter which terminals are input (~220 V power is supplied) and which are output (motor is connected). For rigid fixation and fastening of the mains cable and the electric cable for connecting the motor, cable clamps (Pos. 1) are used. All working elements of the pressure switch are closed with a cover.

Equipment installation scheme

(Fig. 2) shows the installation diagram of an automatic pumping station using the LP relay.

A non-return valve with a mesh (Pos. 2) is mounted on the suction pipe (Pos. 3). A pressure switch (Pos. 5), a hydraulic accumulator (Pos. 6) and a dry-running switch (Pos. 9) are mounted on the pressure pipeline (Pos. 8). Mounted behind the dry run relay (Pos. 10). The sequence of electrical connections on (Fig. 2): mains plug (Pos. 4) - - dry-running relay and pump motor (Pos. 1). But this sequence can also be as follows: mains plug - dry running relay - pressure switch and pump motor. The basic principle of connecting these two relays is that they must be connected in series.

The principle of operation and adjustment of the "dry running" relay

The device is a two-contact switching relay. Initially, its contacts are in the open state. To start the device into operation, it is necessary to press and hold the red button down until the pressure in the system rises higher than set. When the pressure in the system drops below that set on the relay, the contacts open and the device turns off the pump in the "dry run" mode. The relays are sold with factory-set cut-in pressures (see Table 1). An adjusting nut and spring are used to change the factory settings of the switching pressure (Fig. 1). The more we compress the spring, the greater the switch-on pressure is set to the relay, and when the spring is weakened, the switch-on pressure decreases. It is necessary to control the value of the switch-on pressure on the pressure gauge.

Operation, maintenance and repair of the relay

Thank you for your attention.

Italtecnica LP3F14 (LP/3) low limit pressure switches are used to protect water systems (automatic pressure boosting stations, fire extinguishing systems), as well as in pneumatic systems (control of repetitive pressure cycles). The device opens the electrical connection between the power supply and the load when the pressure falls below the set value (switch-off pressure). In automatic water supply stations, it is connected to a relay to protect the pump from "dry running". The device restarts automatically when the pressure again becomes higher than the starting one.

Technical characteristics of the protection relay Italtecnica LP3F14

• application: pressure switch for water pumps, dry running protection;
• turn-off pressure setting range, bar: 0.1 - 0.4;
• switching pressure setting range, bar: 0.5 - 0.9;
• factory setting, bar: 0.1 - 0.5;
• Maximum temperature environment: 55°C.

• double electrical contact: normally open, Ag-Ni plated copper alloy;
• terminals with four M4 bolts and two clamping screws regulating pressure 8x8 mm;
• NBR rubber membrane with textile insert (material is safe for health);
• hydraulic connection (American type) with 1/4" female thread - made of galvanized steel;
• high-strength cable terminals.

Information about technical specifications, scope of delivery, country of manufacture and appearance product is for reference only and is based on the latest information available at the time of publication

Characteristics

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Dry running sensor LP-3 Unipump is offered by the group of Russian enterprises "Subline Service" and is used in automatic water supply systems, watering installations, fire extinguishing installations, air conditioning systems and other cases. This dry running sensor is designed to work with water. In the absence of water in the water supply system, it automatically turns off pumps (surface, borehole), automatic water supply stations, which prevents equipment breakdowns when working without water (“dry running” mode).

Technical characteristics of the dry-running relay LP-3

Device and principle of operation

The LP-3 dry running sensor is a two-contact relay for switching electrical circuits, triggered by water pressure. Initially, the group of relay contacts is open; in order to close the group, it is necessary to press and hold the button located on the relay cover at the first start. The relay contacts close. If the pressure drops to a level of 0.4-0.05 bar, then the relay contacts open. As a result, the dry-running sensor can be used as a dry-running safety device, for example for pumps.

Warranty - one year.