KAL-D Compact Thermal Flow Switch for Water-Based Liquids
The KOBOLD KAL-D is a compact insertion-style thermal flow switch that monitors non-viscous, water-based liquids with no moving parts. Sized for crowded equipment rooms and tight piping, its housing measures 1.75 inches (44.5 mm) in diameter with a maximum length of 3.75 inches (95 mm), and it detects flow velocities from 0.15 to 6.6 ft/sec (0.05 to 2 m/s).
The KAL-D is designed to bring microprocessor-based thermal flow monitoring to budget-conscious applications that previously relied on less reliable mechanical switches, pairing an economical price point with LED visual indication and solid-state switching.
How the Calorimetric Measuring Principle Works
The sensor tip is heated a few degrees above the liquid temperature; as liquid flows across the tip, it cools at a rate proportional to velocity. The electronics compare the measured velocity to a field-adjustable setpoint and activate a transistor switch when that setpoint is reached, according to specifications.
Microprocessor-based temperature compensation corrects each reading for changes in liquid temperature during the measuring cycle, with ±2% repeatability according to specifications, helping eliminate the drift and false switching seen in non-compensated thermal switches. A typical heating-and-measuring cycle completes in 5.6 to 12 seconds, and the smooth probe is insensitive to dirt and solids while producing minimal system pressure loss.
Stainless Steel Construction, Pressure, and Temperature Ratings
Wetted parts are 316L stainless steel and the housing is 304 stainless steel, according to specifications. The KAL-D is rated for a maximum pressure of 580 PSIG, operates from -4 to 176 °F (-20 to 80 °C), and tolerates clean-in-place cycles to 284 °F (140 °C) without switching function.
The 316L probe is designed to resist corrosion from water treatment additives, glycol solutions, and other water-based process liquids, while the NEMA 4/IP65-rated enclosure protects the electronics in washdown environments common to food processing, pharmaceutical manufacturing, and general industrial settings.
LED Display and Field-Adjustable Switch Point
An integrated 8-segment LED bargraph displays the actual flow level while a blinking LED marks the switch-point position, and a dual-color status LED shows green for flow and red for alarm. The setpoint is set with a potentiometer, with no external programming tools, PC software, or specialized equipment required.
Switching outputs are NPN or PNP open collector, wired normally open or normally closed depending on the ordering code, and rated 400 mA maximum at 24 VDC with short-circuit protection — enough to drive control relays, PLC inputs, or alarm indicators directly. Power requirements are 24 VDC ±10% at 150 mA maximum through a 4-pin male micro DC plug.
Insertion Installation and Model Options
The KAL-D installs through a single threaded connection — 1/4" NPT (KAL-D5408), 1/2" NPT (KAL-D5415), M12x1 (KAL-D0412), 1/4" BSP (KAL-D1408), or 1/2" BSP (KAL-D1415) — minimizing piping modifications and installation costs compared with in-line switches that require pipe cutting and flanged connections.
Approximate switching ranges span 0.02...1.0 GPM in 1/4" pipe up to 12...575 GPM in 6" pipe. Because flow in pipes is non-uniform across the cross-section, probe installation depth, internal pipe diameter, and flow profile can produce significant deviations from these calculated ranges. For best results, install with fully developed flow — five diameters of straight pipe before and after the sensor — in lines that remain completely filled; where liquids carry suspended solids, a horizontal side-mount lets particles settle below the probe.
Typical Applications for Water-Based Flow Monitoring
Designed for liquids containing at least 90% water, the KAL-D monitors process water distribution, cooling water circuits, water treatment systems, boiler feedwater, HVAC chilled water loops, industrial washdown systems, and general plant utilities. It is not suitable for oils or fuels, and its economical price suits multi-point monitoring installations.
Made in USA for Domestic Sourcing and Simplified Logistics
The KAL-D series is manufactured at KOBOLD's Pittsburgh, Pennsylvania facility, providing American-made instrumentation with responsive domestic support. United States manufacturing is designed to support consistent product availability without overseas shipping delays, simplified warranty service compared to imported alternatives, and supply-chain risk mitigation for engineering firms, contractors, and end users prioritizing American manufacturing.
Common Questions about KAL-D - Compact Thermal Flow Switch for Water-Based Liquids
Each measuring cycle records the ambient liquid temperature, heats the probe for 0.8 seconds, then evaluates how quickly the probe cools between fixed reading points. The electronics compare that result against stored cooling-rate data for the recorded temperature, and the reading is validated before the output updates, keeping switching accurate as liquid temperature changes.
Its velocity-based switching window spans 0.15–6.6 ft/sec (0.05–2 m/s). Expressed volumetrically, that corresponds to roughly 0.02...1.0 GPM for a 1/4-inch line and 12...575 GPM for a 6-inch line per the datasheet's pipe-size table; actual ranges vary with probe depth and flow profile.
It monitors non-viscous liquids whose water content is at least 90%, according to specifications — process water, cooling loops, treatment streams, and similar media. Oils and fuels are excluded, as are the medium-to-high viscosity and strongly temperature-absorbing media noted in the manual. When compatibility is uncertain, KOBOLD recommends contacting the manufacturer.
Maximum pressure is 580 PSIG. The operating temperature range spans -4 to 176 °F (-20 to 80 °C), while clean-in-place cycles up to 284 °F (140 °C) are tolerated with the switching function suspended during CIP, according to specifications — useful for hygienic cleaning regimes.
Ordering codes select NPN or PNP open-collector transistor switching in either N/O or N/C logic. The short-circuit-protected output handles up to 400 mA at 24 VDC, so it can drive PLC inputs, relays, or alarm indicators directly without external amplification. N/C logic gives a failsafe alarm state on power loss.
It runs on 24 VDC ±10% and draws 150 mA maximum, according to specifications. Electrical connection is made with the male 4-pin micro DC plug; a mating plug with a 6-foot (1.8 m) cable is available as accessory 807.037 for quick electrical hookup.
Unscrew the housing cover and turn the built-in potentiometer: a blinking LED travels along the 8-LED bargraph to mark the selected threshold while illuminated LEDs show live flow. Zero and span adjustments use the SET button, and the manual documents a factory span setting of 2 m/s.
Mount the sensor so the tip extends at least 5 mm (0.2 in) into the pipe and stays fully immersed, and keep the line completely full. The manual recommends straight runs of five pipe diameters upstream and downstream, plus a horizontal side-mount where the liquid carries settling solids.
Yes. KOBOLD builds the KAL-D series at its Pittsburgh, Pennsylvania facility, which shortens lead times, keeps warranty service domestic, and gives buyers direct access to applications engineers familiar with North American industrial practices — advantages for projects that prioritize domestic sourcing.
No routine maintenance is required — the manual describes the device as maintenance-free. With no parts moving in the flow stream, wear-related failures common to paddle-type devices are avoided; the only recommended check is inspecting the sensor tip for mineral deposits such as lime and cleaning it as needed.