Multipoint Float Level Switch: Specify the Switching Points
Selection Guide / 4 min read
A multipoint float level switch detects several discrete liquid levels with one stem assembly. To specify it, define each switching position, the reference used to measure it, and the required contact action. Then check that the selected float, mounting and electrical arrangement can deliver those points. “Three levels” and an overall stem length are not a complete specification. BST configuration overview
What a multipoint switch measures
In a magnetic float design, the moving float actuates a reed contact inside the stem. Each contact reports a switching condition at a selected level. The KOBOLD NCM, for example, has up to four user-specified switching points on one stem. This is useful when several discrete signals are needed from the same tank. It does not supply a continuously changing level reading between those points. KOBOLD NCM
If the requirement is a continuous trend or level display, start with a level transmitter selection instead.
Define the points before choosing the stem
Create a point schedule. For each signal, record its function, distance from the agreed mounting reference, and whether its contact must open or close as the liquid rises or falls. Also record the controller input connected to it. Manufacturers can customize stem length, float positions, switch configuration, cable and mounting; specify these together. BST configuration overview
For example, a drawing might identify an upper alarm point and two separate control points. Naming those functions avoids treating all three contacts as interchangeable. Keep the required system response separate from the switch’s electrical designation: NO or NC needs a defined reference condition.
KOBOLD’s NCG/NCM instructions define the reed states in the dry position. They also state that the multilevel controls are not adjustable. Do not assume that moving a collar is an approved way to relocate the internal switching point. NCG/NCM instructions, sections 8–9
Check the dimensional reference and minimum spacing
The Gems LS-800PVC drawing measures actuation distances and overall length from the inner surface of the mounting plug or flange. For a top-mounted unit it specifies minimum distances of 38.1 mm to the highest point, 50.8 mm from the lowest point to the stem end, and 76.2 mm between points. These are LS-800PVC rules, not universal float-switch dimensions. Gems LS-800PVC documentation (catalog page 2)
As an illustrative screening check, two requested points 60 mm apart would fail that model’s 76.2 mm minimum. A long enough stem does not resolve the spacing conflict. Change the required positions or assess a different design.
The same Gems document uses descending water level for calibration unless otherwise specified, and bases its dimensions on liquid specific gravity 1.0. Identify the application liquid and required actuation direction when reviewing the drawing.
Match the wiring arrangement to the number of points
Do not select only by the largest advertised point count. For LS-800PVC, the available count depends on wiring: Group I supports up to seven points, while Group IV supports up to two. Confirm the actual contact and return arrangement on the selected configuration. Gems LS-800PVC documentation (catalog page 2)
Review installation and the receiving circuit
The KOBOLD instructions require compatible wetted materials and clearance between the probe end and tank bottom. They identify these reed switches as pilot-duty devices, not direct switches for motors or solenoid valves. The receiving circuit and contact protection must suit the selected switch. NCG/NCM instructions, sections 7–10
Float material and buoyancy also vary by configuration. The NCM product page lists multiple float materials and different minimum liquid specific gravities. Check the exact float option, rather than applying one series-level value to every build. KOBOLD NCM
Before final selection, reconcile the point schedule, manufacturer’s drawing and controller input list. For hot service, use the separate high-temperature float switch checks to review the process and electrical limits as well.