JUMO NESOS R01 LS Miniature Float Level Switch, Type 408301

A miniature magnetic float switch for tanks, sumps and skids

The JUMO NESOS R01 LS (type 408301) is a float switch in miniature form for point level measurement of liquids in storage tanks, containers, oil sumps and process tanks. Measurement follows Archimedes principle: a float with a magnet moves along a guide tube and operates reed contacts inside the tube, which can switch alarms, pumps, signal lamps, valves and horns, normally through a contact protection relay. Compact versions with a diameter from 27 mm suit low installation heights and small tank openings. The datasheet lists water and wastewater treatment, mechanical and plant engineering, shipbuilding, energy technology and tempering equipment, and offers versions with explosion protection, shipbuilding approval and a built-in Pt100 or Pt1000 temperature sensor.

Technical specifications

Contacts, floats and approvals

The number and positions of the contacts, the guide tube length and the float are set by the order details. A 29 mm spherical float in 316 stainless steel handles up to 35 bar, while the titanium float 729 suits media where titanium is the better chemical match, and each float needs a minimum medium density, so check the density table for the immersion depth. Intrinsically safe versions 408301/263, /362 and /662 and flameproof versions 408301/264, /462 and /962 carry the ATEX and IECEx certificates SEV 18 ATEX 0134 X and SEV 18 ATEX 0133 X. The datasheet says no isolating switch amplifier is required for the flameproof versions. DNV GL approval TAA00001VR applies to types /062, /662 and /962 and WHG approval Z-65.11-608 applies to /262, /263 and /264.

Installation and application notes

Fit the switch vertically within ±30° through a threaded or flanged connection and use a seal of at least 1.5 mm for G 1/8 to G 3/4 and at least 2 mm for G 1 and larger, as the datasheet recommends. The guide tube length, the contact positions and the extension tube length all depend on the process connection, and a diagram gives the maximum ambient temperature for each extension tube length at a given medium temperature, which matters on hot Gulf tanks. NAMUR versions may be used only with DC 15 V or less and can detect line break or short circuit in an evaluation unit. Typical jobs are minimum level protection of lubrication oil sumps, day tanks, condensate tanks and sump pumps.

For wiring, the datasheet shows terminal assignments for one to three contacts and for a Pt100 or Pt1000 element. Products with more than one contact must not mix hazardous network circuits and SELV circuits. The protection-class 3 versions are limited to AC 33 V or DC 70 V switching voltage. Spring-cage Push-In terminals shorten installation, and the maintenance-free design avoids moving seals or powered parts, which keeps running costs low on remote tanks.

Using the NESOS R01 LS in Oman and the GCC

Miniature float switches are used in the region on small water tanks, hydraulic and lubrication oil reservoirs, sumps on packaged equipment, chemical dosing tanks and the tanks of water treatment skids. They provide simple high and low level alarms, pump start and stop, and protection against dry running of pumps. Because the reed contacts have limited switching capacity, connecting them through a contact protection relay or to a PLC input is good practice, especially where pumps or solenoid valves are switched.

Check that the float material suits the liquid and its density, particularly for chemicals and oils. In outdoor tanks, the liquid can become much warmer than expected in summer, so check the temperature limits of the float and cable. Sludge or deposits can stop a float from moving, so the switch should be cleaned and tested during routine maintenance.

Where several switching points are needed in one tank, a multi-point version on one guide tube can replace several separate switches and reduce the number of tank openings. Send a sketch of the tank with the required switching heights.

Information to send with an enquiry

• Liquid, density, temperature and pressure
• Mounting thread and tank opening size
• Number of switching points and contact type
• Cable length and any approval needed

Related JUMO products: JUMO NESOS R04 LS Bent Float Level Switch, JUMO NESOS R20 LT Float Level Transmitter, JUMO ZELOS C01 LS Capacitive Level Switch, JUMO MAERA S29 SW Titanium Level Probe, JUMO MAERA F27 Ceramic Level Probe with PTFE or Steel Case and JUMO MAERA S25 Hydrostatic Level Probe.

Documents and quotation

The hosted document is JUMO data sheet 408301 (19 pages, English). It includes dimensions, wiring and order details. Confirm contact function, float, guide tube length, connection and approvals before ordering. Seven Star LLC is an independent supplier in Muscat; send the medium, density, temperature and switching points for a quotation.