Compact 75 mm three-wire float switch for highly accurate and repeatable single point level sensing and control. Polypropylene float cell, hermetically sealed, with CPE rubber cable and no mercury or lead. Ideal for water, sea water, most acid and alkali solutions and effluent or sewage: the teardrop float has no shoulders or edges for solids to build on.
K Series
Float Switches
Features
- Low differential switching
- All-position tilt action (45° trips)
- S.P.D.T. three-wire single-point switch
- Polypropylene, SAN, fluorosilicone & CPE construction
- Wide range of cable lengths available (4 / 6 / 10 / 20 / 30 / 50 m)
- Stable, repeatable switching action
- No mercury or lead components
- Compact size, 75 mm diameter float
- IP68 rating
- 35 mm liquid level change to operate the switch
- 30 m maximum submergence (300 kPa static pressure)
- Optional KCW cable weight available
The K Series level regulator contains a heavy ball balanced on the actuating arm of a high precision switch. When a rising liquid level lifts and tilts the float, the ball’s centre of gravity moves away from the switch’s actuating axis and the switch de-actuates; when the level falls the float straightens up and the switch actuates again. The float only has to tilt 45° in any direction for the switch to operate. It is constructed from polypropylene and high compliance three-core CPE cable, with a double-moulded, hermetically sealed float chamber and a double-moulded barrier of solid polypropylene sealing the cable entry. The switch is a precision single pole double throw device rated from 5 to 500 VAC at up to 15 A resistive load (10 A at 500 VAC); load current is limited to 6 A by the 0.75 mm² cable. Use a separate KCW cable weight on the cable to set the switching pivot point. Rated for mains voltage, but Kelco recommends it is only ever operated at low voltage, preferably 24 to 48 VAC.
Select Model
Trade customers should contact sales@kelco.co.nz for account pricing.
Ordering — Available Models
| Model Number | Description |
|---|---|
| K10M | K Series float switch — 10 m of CPE cable (most common) |
| K20M | K Series float switch — 20 m of CPE cable |
| K30M | K Series float switch — 30 m of CPE cable |
| K4M | K Series float switch — 4 m of CPE cable |
| K50M | K Series float switch — 50 m of CPE cable |
| K6M | K Series float switch — 6 m of CPE cable |
| KCW |
Operating Limitations
| Maximum submergence | 30 m / 300 kPa static pressure |
|---|---|
| Maximum liquid temperature | 60 °C |
| Minimum liquid temperature | -20 °C |
| Liquid specific gravity | > 0.82 |
| Liquid pH range | 1 to 14 |
| Smallest well diameter | Within a 160 mm inside diameter vertically mounted pipe |
| Liquid level change for switch operation | 35 mm |
| Closest switching point to tank floor | 50 mm |
| Smallest opening through which the switch will fit | 75 mm |
| Minimum distance from float to closest tether/weight | 150 mm |
| Suitability — sodium hypochlorite | Fully compatible |
| Suitability — sea water | Fully compatible |
| Suitability — potable water | Fully compatible |
Electrical Data
| Switch type | Single pole double throw (S.P.D.T.), silver alloy contacts, 0.5 mm gap |
|---|---|
| Contact resistance | 15 milliohms maximum (initial) |
| Rated voltage (switch) | 125, 250 and 500 VAC; 8, 14, 30, 125 and 250 VDC |
| Operating voltage (safety note) | Rated for mains voltage operation, but only ever operate at low voltage, preferably 24 to 48 VAC. Where mains operation is unavoidable, install an earth leakage circuit breaker in the control circuit. |
| Resistive AC current rating | 15 A at 250 VAC, 15 A at 125 VAC (10 A at 500 VAC) |
| Motor load AC current rating | NO 2.5 A / NC 5 A at 125 VAC (⅛ HP); NO 1.5 A / NC 3 A at 250 VAC (¼ HP) |
| Resistive DC current rating | 15 A at 8 and 14 VDC, 6 A at 30 VDC, 0.5 A at 125 VDC, 0.25 A at 250 VDC |
| Maximum lamp load AC | NO 1.25 A / NC 2.5 A at 250 VAC |
| Maximum lamp load DC | NO 1.5 A / NC 3 A at 30 VDC |
| Minimum operating load | 160 mA at 5 VDC |
| Low-current inputs | The 160 mA at 5 VDC minimum is the microswitch manufacturer’s rating for guaranteed contact at very low currents. K Series switches are also used on PLC, BMS and 24 VDC control inputs. For a dedicated low-current signal input, the KP-10 reed probe and the L-L side-entry switch (gold contacts) are designed for that duty. |
| Maximum operating frequency, electrical | 20 operations per minute |
| Dielectric strength between contacts | 1000 VAC, 50/60 Hz for 1 minute |
| Dielectric strength to ground | 2000 VAC, 50/60 Hz for 1 minute |
| Insulation resistance | 100 megohms minimum (at 500 VDC) |
| Mechanical life expectancy | 10 000 000 operations minimum |
| Electrical life expectancy | 500 000 operations minimum |
| Approved standards | UL1054 E41515, CSA C22.2 No. 55 (File No. LR21642) |
| Product load current | 6 A maximum (limited by the 0.75 mm² cable) |
Dimensions
Typical Applications
Basic liquid level control; multi-point level control; sewage level control; chemical level control; high & low level alarms; self-powered signalling; pump protection; alarms, pump control (direct or through a contactor or relay), and PLC / BMS inputs.
KCW Cable Weight (separate accessory)
Heavy polypropylene cable weights are available to suit the K Series. Clamp the weight onto the cable using the screw provided and position it at least 150 mm above the float; several weights can be spaced along the cable if required. The KCW is a split-style polypropylene cable weight (with 316 stainless screw) that clamps to the K-series cable to act as the tether/pivot for the float’s tilt action. Use the KCW when the float is suspended down a deep tank or sump from above; without it, the cable must be tethered manually. For Q Series, order the matching QCW.
Safety — Low Voltage Recommended
The K Series is rated for mains voltage operation (5 to 500 VAC), but Kelco recommends it is only ever operated at low voltage, preferably 24 to 48 VAC, with the installation isolated by a low voltage transformer. Local regulations may require its use to be confined to low voltage control circuits. Where mains operation is unavoidable, an earth leakage circuit breaker should always be installed in the control circuit. Wiring must always be carried out by a qualified, licensed electrician in line with AS/NZS (or equivalent) standards and local wiring rules.
Hazardous Areas
The K Series is not certified for use in hazardous areas and must not be installed in any area classified as hazardous under AS/NZS 60079.10 (Zone 0, 1, 2, 20, 21 or 22).
Operating Environment
There are no metal parts in contact with the process liquid. The K Series can be used in water, sea water, acids, alkalis and a great variety of chemical solutions, including oil, oily waste, fats and effluents of many types. Do not use it in closed vessels above 300 kPa static pressure or in submerged applications deeper than 30 m. In liquids of low specific gravity the buoyancy of the float is reduced and a proportionally higher operating differential results.
Mounting and Wiring
Avoid turbulence and any place where the float or cable will abrade against tank walls, piping or pumps, and keep the cables of adjoining switches from rubbing or tangling. Suspend the switch at least 100 mm away from tank walls and stand pipes, and allow at least 150 mm of free cable between the float and the first tethering point or cable weight so the float can swing and tilt freely. Never tie the float against a pipe or the side of the tank. Keep exposed cable out of direct sunlight: terminate it in a junction box or run it in conduit rather than draping it over the tank rim. With the float hanging vertically the core colours are blue (common), black (normally closed) and brown (normally open); when the level rises and tilts the float 45°, blue to brown closes and blue to black opens. Most installations use only the blue common and one other wire; the unused wire is live when the switch actuates and must always be isolated. Two float switches controlling the high and low levels of a tank or pit normally use a latching circuit, for pumping out of or into the tank.
Cable Data
S05RN-F 3 × 0.75 mm² cable: three cores of 24/0.2 mm plain copper, EPR insulation, core colours blue, brown and black, black CPE (chlorinated polyethylene) outer sheath, 7.0 ± 0.2 mm diameter, voltage rating 300/500 V, test voltage 2000 V / 2500 V, minimum bending radius 6 × overall diameter (42 mm), conductor operating temperature -30 °C to +60 °C (85 °C max.), CENELEC HD 22.4 S4 & VDE 0282-4/2005, conductor resistance 26.7 Ω/km max. per core at 20 °C, cable current rating 6 A max. (cable limited), maximum suspended length approx. 45 m (cable only). Cable lengths available: 4, 6, 10, 20, 30 and 50 m.
Serviceability
Sealed unit — not user-serviceable internally. Spare cable lengths and KCW cable weights available from Kelco Engineering or your distributor.
