pumps and pumping systems  

LCS pressure connectors

Protection against dry running


LCS connectors are used to protect devices, mainly pumps, against operation at excessively low pressure in the installation. These connectors are typically used in hydrophore systems supplied from open tanks, wells and water supply networks, where protection against drop of pressure in a pipeline is required. Just like LCA connector it is a controlled contactor, in this case controlled by pressure drop.


  • in addition to 230 V motors of power up to 2.2 kW, LCS connectors may work with 400 V three-phase motors of power up to 4 kW,
  • durability (design based on proven pressure connector of LCA type, which has been present on the market for many years),
  • wide range of triggering and deactivating,
  • 24-months guarantee.

Example installation

Operating conditions

  • Connectors are intended for installation in closed rooms, free from dusts, gases and explosive or chemically active vapours.
  • Allowed installation height may not be greater than 2,000 m a.s.l.
  • Allowed ambient temperature is -5oC to 40oC .
  • The lowest relative humidity may reach up to 50% at temperature 40oC and up to 90% at temperature 20oC .
  • IP 43 protection class (provided that the connector is installed with its cover facing up).

Technical data:

Rated voltage of insulation [V] 230 V 400 V
Rated frequency [Hz] 50 Hz
Rated switching current [A] 16 A 10 A
Operating category AC-3
Insulation rated proof voltage [kV] 2,5 kV
Rated switching durability [switching cycles] 106 cycles
Normal rated switching frequency [switching cycles/hour] 120 cycles/h
Power of directly controlled motors [kW] 2,2 kW 4,0 kW
Propelling medium minimum temperature [oC] 0oC
Propelling medium maximum temperature [oC] 40oC
Propelling medium type water, air, machine oil, diesel fuel
Connecting cables cross-sections [mm2] min 1,5 mm2
max 4,0 mm2
Connector weight [kg]
- with G1/4” thread
- with G1/2” thread


Principle of operation, design

Their operation is reversed compared to LCA – LCS connectors, i.e. they deactivate the pump after pressure drops below set point. LCS connectors allow to set triggering pressure (in accordance with the graph below) without the change of pressure difference (delta, hysteresis), which is constant and is approximately 1 bar. They are three-way or single-way, low voltage, mechanised alternating current control switching devices. LCS type pressure connector is a normally open contactor (closes in case of pressure increase). Base, body, movable and immovable jaws are made of glass-fibre reinforced plastic. Copper contacts are equipped with tips made of cadmium-silver oxide. The connector’s housing is made of polycarbonate. It suspends operation of a system after detecting low pressure in LCS installation. The pump system will be activated again after physical pressing and holding RESET button until required operating pressure returns.

Possible set points



The pressure connector must be connected to pipelines by screwing it over G1/2” thread coupling of minimum length of 15 mm. The connection must be sealed using a rubber washer or hemp fibres. Before screwing the connector, carefully remove any burrs from the coupling. The coupling must not have any sharp edges, as these may damage the rubber washer.

NOTE! It is prohibited to tighten the connector beyond the cover. The connector should be tightened using 30 mm body wrench.
Before starting any works, disconnect power supply.

ELECTRICAL WIRING - The connector must be connected to the electricity network in accordance with the circuit diagram (Fig. 2) by appropriately qualified and authorised persons. The connecting cables must be selected in accordance with applicable regulations. The connector must be secured against effects of short-circuits. Warning signs must be visible and permanently affixed on the body of the connector. It is required to connect the protective cable to the safety terminal! The electrical cable must be attached to the installation in a way to not cause any strain on the terminals of the connector.

Rated operating parameters

Rated switching voltage Rated switching currents Operating category Rated switching durability Normal rated switching frequency Power of directly controlled motors Current flow relative time
V A - Switching cycles Switching cycles/hour kW %
230 (50Hz)
400 (50Hz)
AC-3 0,1*106 120 2,2


LCS connector setting

Factory setting – deactivation 0.5 bar; activation 1.5 bar.

The connector triggering pressure is set by adjusting PW nut. The pressure difference between triggering and deactivation (delta, hysteresis) may not be adjusted – it is fixed and is approximately 1 bar. In order to change settings, connect the connector to the hydraulic system, disconnect power supply and dismantle the cover. Turning PW nut clockwise increases the triggering pressure, and turning it anticlockwise lowers it. After completing adjustment, mount the cover of the connector.


The connector must be periodically inspected. The frequency of inspections depends on the operating conditions of the connector.
NOTE: Before starting inspection, activate the power line!
During inspection, carefully remove any dust from the connector. The axle of the movable jaw, the axle of the toggle lever and the ends of the toggle spring (inserted into the openings of the movable jaw) must be lubricated with several drops of machine oil. Redundant worn parts (contacts, springs etc.) must be replaced and screw connections must be checked for durability and tightened if they are loose.

Storage and transport

Connectors are packed in individual cardboard boxes. They should be stored in closed rooms (of temp. +5oC ÷ 35oC at air relative humidity up to 70%), free from chemically active vapours and gases. The connectors must be transported only via covered means of transport.

The connector will not deactivate the pump as long as pressure in the installation is above deactivation set point – such a situation will take place if a cause of dry run occurs and at the same time water consumption stops or is small during operation of the pump. In such a case the connector will not secure the pump against dry run because pressure will not drop to the value that triggers the connector.

Hydro-Vacuum S.A.
ul. Droga Jeziorna 8
86-303 Grudziądz
tel. 56 45 07 415
fax. 56 46 25 955
Copyright © Hydro-Vacuum S.A.

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