The HK(L)E variable speed multistage pump integrates a high-performance variable-frequency drive (VFD) directly into the pump motor assembly, delivering automatic constant-pressure water supply without the need for an external control panel. By continuously adjusting motor speed to match real-time demand, this pump achieves 20–40% energy savings compared with fixed-speed operation — making it the smart choice for any application where water consumption fluctuates throughout the day.
Built on the proven HK(L) hydraulic platform with an all-304-stainless-steel flow path and an IE3-rated motor, the HK(L)E adds a factory-installed VFD, a precision pressure sensor, and PID control logic inside a single compact housing. The result is a truly plug-and-play pressure-boosting solution.
How Built-In VFD Control Works
The HK(L)E monitors system pressure through an integrated pressure transducer. When demand drops — for example, at night in a residential building — the VFD reduces motor frequency proportionally, slowing the pump and maintaining the target pressure with minimal energy input. When demand spikes, the VFD ramps the motor up instantly to meet flow requirements.
This closed-loop PID (Proportional-Integral-Derivative) control eliminates the need for pressure relief valves, bypass lines, and oversized fixed-speed pumps that waste energy throttling excess flow.
Intelligent Protection Features
- Water Shortage Protection — The controller detects a drop in suction pressure and stops the pump automatically to prevent dry-running damage.
- Short Circuit & Overload Protection — Built-in electronic protection eliminates the need for external fuses or thermal relays.
- Low Voltage Alarm — The VFD warns and derates gracefully when supply voltage drops below acceptable thresholds, preventing unexpected shutdowns.
- Automatic Restart — After a power outage, the pump performs a soft restart to avoid water hammer and mechanical shock.
Energy Savings: Fixed-Speed vs. VFD Over 10 Years
The following comparison illustrates typical energy cost savings for a 7.5 kW pump operating 16 hours per day in a building water-supply application. Electricity rate: ¥0.85/kWh.
| Item | Fixed-Speed (DOL) | Variable Speed (VFD) |
|---|---|---|
| Rated power | 7.5 kW | 7.5 kW |
| Average load factor | 90% | 55% (speed-adjusted) |
| Daily energy use | 108 kWh | 63 kWh |
| Annual energy cost | ¥33,516 | ¥19,534 |
| 10-year energy cost | ¥335,160 | ¥195,340 |
| Energy savings (10 yr) | — | ¥139,820 (42%) |
| VFD premium (one-time) | — | ¥6,500 |
| Net 10-year benefit | — | ¥133,320 |
In most real-world installations with variable demand patterns, the HK(L)E pays for its VFD upgrade within 6–18 months through electricity savings alone.
Technical Specifications
| Parameter | Specification |
|---|---|
| Flow rate (Q) | 0.4 – 85 m³/h |
| Head (H) | Up to 245 m |
| Working pressure | Up to 2.5 MPa (25 bar) |
| Medium temperature | -15 °C to +120 °C |
| Motor efficiency class | IE3 (YE3) with built-in VFD |
| Frequency range | 30 – 60 Hz (standard) |
| Voltage | Three-phase 380 V, 50 Hz |
| Control mode | Closed-loop PID constant-pressure |
| Pressure setting range | 0.1 – 2.5 MPa (user-configurable) |
| Hydraulic material | SUS304 stainless steel |
| Mechanical seal | Silicon carbide / graphite |
| Connection types | F, N, T, K, L |
| Protection | IP55, built-in VFD protections |
| Display | LED digital (pressure, frequency, fault code) |
Applications
The HK(L)E variable speed multistage pump excels in scenarios where water demand varies significantly over time:
- Building Water Supply Boosting — Maintains constant tap pressure across all floors regardless of occupancy level, eliminating the morning/evening pressure swings common with fixed-speed systems.
- Irrigation with Variable Demand — Automatically adjusts flow to match seasonal and daily irrigation requirements for agricultural and landscape applications.
- Hotel & Residential Pressure Stabilization — Keeps guest-room shower pressure consistent even during peak check-in periods, improving occupant comfort and reducing complaints.
- Industrial Process Cooling — Modulates cooling-water flow in manufacturing plants where thermal loads change between production shifts.
- Municipal Booster Stations — Reduces peak-demand charges by smoothing the pump’s electrical load profile throughout the day.
Frequently Asked Questions
What is PID constant-pressure control?
PID stands for Proportional-Integral-Derivative. The built-in controller continuously compares the actual system pressure (measured by the pressure sensor) with your target setpoint. If actual pressure is too low, the PID algorithm increases motor frequency to raise flow. If pressure is too high, it decreases frequency. The “integral” and “derivative” terms eliminate steady-state error and prevent oscillation, resulting in rock-stable pressure that stays within ±0.02 MPa of the setpoint.
What is the pressure setting range?
The HK(L)E allows user-configurable setpoints from 0.1 MPa to 2.5 MPa (1–25 bar). The target pressure is adjusted on the LED panel during commissioning. Changing the setpoint at any time takes effect within seconds.
Can it replace my existing fixed-speed booster pump?
Yes. The HK(L)E is designed as a drop-in replacement for conventional fixed-speed booster pumps. The footprint and pipe connections (F, N, T, K, or L) are identical to the standard HK(L) series. Simply disconnect the old pump, bolt in the HK(L)E, set your desired pressure, and the system runs automatically — no external PLC or pressure tank is required.
Related Products
- HK(L) Vertical Multistage Water Pump — Fixed-speed standard version for constant-duty applications.
- HK(L)YE IE5 Permanent Magnet Pump — Ultra-efficient PM motor upgrade for maximum savings.
- HK(L) Vertical Multistage Pump — Full series overview and selection guide.
