Danfoss 031E020066 CS Pressure Switch 2-6 bar 3-Pole

CS pressure switch with three-pole contact for compressors and pump sets

The 031E020066 is the Danfoss CS, a pressure switch whose built-in three-pole contact can start and stop a small motor without a separate contactor. The data sheet positions it for automatic start and stop of air compressors and water boosters. This code is set 2 to 6 bar with a G 1/4 female connection, a diaphragm element and an IP43 cover, which fits the pressures of a domestic or light-commercial booster or a workshop compressor.

A manual switch on the cover locks the contact system open independently of the pressure, so the pump can be taken out of service for maintenance without touching the wiring. Relief valves are available as accessories for compressors that need pressure relief on the piston before start.

Technical specifications

Sizing the contact and the differential

The contact ratings of 12 A at 220-415 V (AC3) and 9 A at 600 V mean the switch can take a three-phase motor of a few kilowatts directly; above that, drive a contactor. The differential is adjustable from 0.72 to 2 bar depending on where the range spindle sits, which is what controls the number of starts per hour. A booster set with a small pressure vessel needs a wider differential than one with a large vessel.

The maximum working pressure of 6 bar equals the top of the range, so the CS is intended for low-pressure systems. For higher air pressure the data sheet offers other CS types with ranges up to 20 bar. Do not set the cut-out within a few tenths of a bar of the 6 bar working limit.

Mounting and what to check

Fit the G 1/4 female connection to a clean tapping and keep the switch upright. The Pg 16 cable entry takes a standard motor cable; an optional Pg 16 gland is available as an accessory. For drinking water, Danfoss lists special versions with polyacetal pressure connections, which are different code numbers.

Before ordering, confirm supply voltage and motor power against the contact rating, check that a manual switch version is what you need and decide whether a pressure relief valve is required. Seven Star LLC is an independent supplier in Muscat; send 031E020066 and the quantity for a quotation.

Our quotation for 031E020066 will state what is included, such as the document set and the packing, and what is not, for instance accessories or commissioning. Read these lines against your specification, and ask us to adjust the scope if your project requires something extra.

Where the switch sits in a booster or compressor system

In a typical water booster set, the switch senses discharge pressure close to the pressure vessel. When demand draws the pressure down to the cut-in point, the contact closes and the pump starts; when the vessel refills to the cut-out point, the contact opens and the pump stops. In a small air compressor the logic is the same, with the receiver taking the place of the vessel. Because the CS switches the motor directly, the control circuit can be very simple, though motor overload protection must still be provided separately in line with local wiring rules.

The tapping point matters. A connection on a turbulent section of pipe, or one exposed to pressure surges from a check valve closing, can cause chattering or early wear. A short, steady branch close to the vessel or receiver gives cleaner switching.

Setting cut-in and cut-out in practice

The range spindle sets the cut-out and the differential spindle sets the gap to the cut-in. A practical approach is to choose the lowest pressure the users can accept, add the differential needed to keep motor starts within the motor maker’s limit, and then confirm that the resulting cut-out sits comfortably below the working pressure limit. Settings should be checked against a calibrated gauge during commissioning rather than relying on the scale alone.

Installation and commissioning practice

Before connecting the switch, the system should be flushed so that sand, scale or thread sealant does not reach the diaphragm. Thread sealing should be applied sparingly on the male fitting only. The supply must be isolated during wiring, and the cable gland tightened so that the cover seal can do its job. After wiring, a few test cycles with the gauge in view confirm that the pump or compressor starts and stops at the intended pressures, and that the manual switch locks the contact open as expected.

Service in GCC climate conditions

Booster sets on rooftops and compressors in workshops across Oman and the Gulf often operate in direct sun, dust and humid coastal air. The ambient temperature limit in the table should be compared with the real surface temperature of the switch location, which can be much hotter than the shade air temperature on an exposed roof. Shading the switch, or mounting it inside a ventilated pump-room, reduces heat stress. The IP43 cover offers basic protection, so a position away from direct water spray and blowing sand is preferable.

Maintenance checks

Periodic checks should look for drift in the switching points, pitting or burning signs reported by unusual motor behaviour, loose terminals and damaged cable entries. Frequent short cycling usually points to a waterlogged pressure vessel or a leaking check valve rather than a faulty switch, so the system should be examined before replacing the unit. In compressors, condensate and oil carry-over in the sensing line should also be watched.

Documents and quotation

We attach the Danfoss CS pressure switch data sheet AI547816451399 with applications and wiring examples. See also pressure instrumentation.