Constant pressure
The set point is held while the household uses water, instead of rising and falling between cut-in and cut-out points.
Variable Frequency Drive · Constant Pressure
Inverter water pumps that hold constant pressure
An inverter (VFD) pump changes motor speed to match demand instead of switching on and off at full speed. The pressure at the tap stays steady whether one outlet or five are open.
How it works
Speed follows demand, pressure stays put
A pressure sensor reads the line, the controller adjusts motor speed, and the pump delivers only the flow the site is using at that moment. Open another tap and the pump speeds up; close it and the pump slows down.
Soft start
The pump starts softly and ramps up, instead of drawing a hard current surge at every start.
Energy follows load
At low demand the motor runs slowly and draws less power, instead of running flat out or stopping.
Quieter running
Lower speed at low demand means less noise — the SPS-90 holds 40 dB or less at 1 m when sized for the duty.
Inverter vs fixed speed
An honest comparison, with the test conditions
A fixed speed pump has two states: running at full speed, or off. An inverter pump matches speed to demand. The difference shows up where demand changes through the day — multi-storey homes, small hotels at peak hours, and irrigation lines opened tap by tap.
Fixed speed pump
- Starts at full speed, fills the pressure vessel, then stops.
- Pressure rises and falls between the cut-in and cut-out points.
- Each start draws a current surge.
- Works acceptably in single-storey houses with steady mains supply.
Inverter (VFD) pump
- Starts softly, then matches speed to the outlets in use.
- Holds the pressure set point while water is being used.
- Speed falls as demand falls, so running cost follows load.
- Suits multi-storey homes, villas, guesthouses and irrigation lines.
Energy saving, measured on the same basis: a permanent magnet VFD pump saves 60% or more against a conventional fixed-speed pump of the same power, at the same flow and head duty point, under constant-pressure conditions. The outdoor PB320EA saves 42% or more on the same basis. Both types still need correct flow and head selection, a clean water supply and a properly sized inlet.
The range
Inverter models for every household duty
Every AC pump in the Calliope range runs on the same permanent magnet VFD platform. Choose the hydraulic body by duty — single-stage for flow, multistage for height.
SPS-90
Five power stages in one model, 47–60 L/min, up to 32 m head, at or below 40 dB at 1 m.
View SPS-90SCS100P-3
Stainless multistage, 115–165 L/min, up to 75 m head — the highest head in the range.
View SCS100P-3ICP100F
Self-priming VFD booster, 86 L/min, 38 m head, 8 m suction lift for tank and well supply.
View ICP100FSG95
Pipeline pump family in five models, 0.55–1.5 kW, 42–73 m head for mains and tank duty.
View SG95ICP102-50
High-flow centrifugal with 2-inch ports, up to 500 L/min for large properties.
View ICP102-50Browse both groups
Nine single-stage models and five stainless multistage models, all on the same VFD platform.
Questions
Inverter water pumps, answered
Do I need a pressure vessel with an inverter pump?
No large one. A VFD booster controls pressure by changing speed, so it does not rely on a large pressure vessel to hold the set point the way a fixed speed pump does. A small vessel is sometimes used to smooth pressure on very low flow.
Is the pressure setting adjustable after installation?
Yes. The pressure set point can be set on the controller to match the site, and the local installer can adjust it on site.
What power supply do inverter pumps need?
All models are single-phase. Most of the range runs on 170–250 V or 170–260 V at 50/60 Hz, the outdoor PB320EA covers 160–265 V, and the PYS-E and PYPZ-E families offer 110 V / 60 Hz builds for the Americas.
Are inverter pumps noisy?
A pump running near its design duty is quieter than one throttled far from the curve. The SPS-90 runs at or below 40 dB at 1 m when it is sized for the duty, and other models run at or below 55 dB.
The full technical comparison sits on the technology page , and the constant pressure vs fixed speed article explains the difference in plain language.
Sizing an inverter pump for a project?
Send the flow, head, voltage and water source for the site. Our export team confirms the model and replies with a quotation.
Request a Quote
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