Danfoss LLS 4000 Liquid level switch

Danfoss LLS 4000 Liquid level switch

 LLS 4000

The LLS 4000/4000U liquid level switch is designed to detect the state (gas or liquid) of the refrigerant in front of the sensing head, while installed in a wide range of refrigeration applications.

The LLS level switch comes in 2 variants, LLS 4000 and LLS 4000U. They are identical except for the connector thread interface to the system. The LLS 4000 is provided with G 3/4” thread, while the LLS 4000U is provided with NPT 3/4” thread.

The LLS 4000/4000U liquid level switch is based on the proven reflectometry measuring technology (microwave level measurement) adapted specifically for the new LLS 4000/4000U switch.

LLS 4000/4000U liquid level switches can be used to control the liquid level of many different refrigerants in vessels, accumulators, receivers, standpipes, etc.

The switches are normally installed in a pair of two, controlling the upper liquid level and the lower liquid level.

The level switch includes a relay that switches by change in refrigerant state. The on site configuration of the LLS allows the normally open/closed relay setting depending on the desired correlation.

For SIL applications a SIL2 version is available with blocked configuration (not configurable).

All configuration and readings from the LLS switch are performed through Bluetooth and a downloadable special Danfoss app.



  • Plug and play liquid level switch
  • Easy installation and minimum or no need for configuration
  • Convenient communication with all units via Bluetooth and a Danfoss app
  • SIL2 compliant version
  • Two commonly used connection variants
  • Maintenance free
  • Replacement of electronic part without removing mechanical part (no opening to refrigerant)
  • Applicable for ammonia and commonly used H(C)FCs
  • Well proven reflectometry measuring principle
  • Approvals:
    EAC (pending)
    CMIIT/TAC (pending)
  • Conforms to:
    Telecommunications Directive RED 2014/53 EU.
    Low voltage directive 2014/35/EU.
    EMC directive 2014/30/EU.
    ROHS 2011/65/EU


To control if a liquid level is within predefined allowed limits, two LLS 4000 are installed in an upper and a lower limit  position  respectively. By this setup the liquid level is between the two level switches and the lower switch will sense liquid, while the upper will sense gas. In case the liquid level moves outside the limits, one of the switches will sense opposite and switch the built-in relay. This relay switch function should be used for alarm settings. This is made easy when connected to the system PLC.

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Technical Data

Electrical data
24 V DC +/-25%, 80 mA
Standard power supply of type: SELV (Separated Extra Low Voltage) with current limit of max. 8A.
Relay (Solid state)
Max 30 V DC, 200 mA.
Same power supply as to supply can be used. Observe:
In applications with request for SIL2, another separate SELV power supply may be needed.
Max. cycles: 1.000.000
Maximum response time: 2 seconds
Overvoltage categoryCategory II for supply and output
Electrical connectionM12 (4 pins) male on the device
Measuring technologyMicrowave reflectometry
Communication optionBluetooth comply to ETSI EN 300 328
Mechanical Data
Max. medium viscosity5000 cps
Max. working pressure65 bar (943 psi)
Ambient temperature range-40 °C to +65 °C (-40 °F to +149 °F)
Medium temperature range-50 °C to +120 °C (-58 °F to +248 °F)
Operating environmentPollution degree 3, altitude 2000 max., outdoor use
Relative humidity RH4 to RH99 % (IEC 60721-3-4: 1995 Class 4K4)
Connection typeG 3/4” or NPT 3/4”
Weight350 g (0.77 lb)
Enclosure rating
IP 65 for Electronic part IP 67 for Mechanical part
IEC 60529: 1989 + A1: 1999 + A2: 2013
NEMA 250: 4X (~ IP 66)
Housing material (electronics)Transparent and UV resistant. Compliance with IEC 60695-11-10, UL 94 HB
Housing material (mechanics)Stainless Steel 316L
Approved media
RefrigerantsR717/NH₃ (Ammonia): -50 °C to +105 °C (-58 °F to +221 °F)
R22: -50 °C to +86 °C (-58 °F to +187 °F)
R404A: -50 °C to +63 °C (-58 °F to +145 °F)
R410A: -50 °C to +61 °C (-58 °F to +142 °F)
R134A: -50 °C to +91 °C (-58 °F to +196 °F)
EU conformity
Radio Equipment Directive (RED) 2014/53/EUEN 300 328 V2.1.1
EN 62311: 2008
Low voltage directive 2014/35/EUEN 61010-1 (edition III)
EMC directive 2014/30/EUEN 61326-1: 2013
PED2014/68/EU, A4P3.
ROHS 2011/65/EU2011/65/EU
ApprovalsCE: PED, EMC, RED, RoHS, LVD SIL2
EAC (pending) IC
CMIIT/TAC (pending)

Download Datasheet : Danfoss LLS 4000 Liquid level switch

Reference : danfoss.com