Constant-pressure water supply VFD panels
- Control method: PID closed-loop constant pressure, pressure transmitter 4–20 mA feedback, constant pressure accuracy up to ±0.01 MPa
- Pump configuration: one-pump, multi-pump (cyclic soft start), all-VFD multi-pump — selected by the range of water demand fluctuation
- Rotation logic: first-on first-off / first-on last-off selectable, VFD pump rotates automatically by cumulative running hours
- Sleep/wake: pump sleeps at low or zero flow to cut energy use, wakes automatically when pressure drops; pressure stabilization tank optional
- Protection and interfaces: dry-run protection, overpressure protection, automatic VFD-to-line-frequency transfer on VFD fault, running signal available for remote monitoring
Specifications
The table below covers 80% of factory distribution room cases. Anything outside it we can still build — those are engineered items, quoted separately, with an indicative price the same day.
| Type | Floor-standing constant pressure water supply control cabinet, standalone or integrated with the pump set |
|---|---|
| Standard sizes (W×D×H) | 800×600×1800 / 1000×600×2000 mm (multi-pump solutions widen with pump count) |
| Enclosure construction | 2.0 mm cold-rolled carbon steel, bent and welded with reinforcing ribs, electrostatic powder coated |
| Surface treatment | Degrease → derust → phosphating → electrostatic powder coating 60-80 μm, baked at 200 °C for 30 minutes |
| IP rating | IP54 standard / IP55 / IP65 optional (upgrade recommended for humid pump rooms) |
| Cooling | Top exhaust + bottom intake, with filter screens; separate air duct for the VFD section |
| Anti-condensation | Optional anti-condensation heater with thermostat for continuous operation |
| Installation | Floor mounting, leave ≥800 mm service access in front of the cabinet |
| Suitable power | Single pump ≤160 kW; total pump set power accumulates by pump count |
|---|---|
| Pump configuration | One-drive-one-pump (single pump on VFD), one-drive-multiple-pumps (one VFD plus multiple line-frequency pumps with soft-start sequencing), all-VFD multi-pump |
| Constant pressure accuracy | Steady-state pressure fluctuation ≤±0.01 MPa (depends on transmitter accuracy and piping network characteristics) |
| Feedback signal | Pressure transmitter 4–20 mA (hot-standby redundancy optional), or remote pressure gauge |
| PID parameters | Proportional / integral / derivative adjustable, preset to pump set characteristics before shipment, field-tunable |
| Sleep and wake | Zero-flow detection plus timed sleep; automatically wakes and soft-starts when pressure drops below the setpoint |
| Protection | Low-water (low-pressure) protection, overpressure protection, automatic transfer to line frequency on VFD fault, overload and phase-loss protection |
| Interfaces | Run / fault / frequency signal outputs; optional Modbus / Profinet connection to remote monitoring or a cloud platform |
| One-drive-one-pump constant pressure | One VFD drives one pump; suited to small water supply or booster applications, simplest configuration |
|---|---|
| One-drive-multiple-pumps with soft-start sequencing | One VFD serves as the variable-speed pump while the remaining pumps run at line frequency, staged on and off by demand and rotated |
| All-VFD multi-pump | Each pump has its own VFD and is fully variable speed; steadier pressure and less shock when pumps stage on and off |
| With pressure stabilization tank | At low flow, the air pressure tank holds pressure steady, reducing pump starts and stops and extending equipment life |
| Zoned water supply | One control cabinet serves multiple pressure zones, each regulated to its own pressure setpoint |
| With remote monitoring | Pressure, frequency and operating status are uploaded over communications and can be viewed and set from a control room or a phone |
| Reference standards | GB/T 7251.1 / IEC 61439-1 (assemblies); GB 12668.3 (EMC for adjustable-speed electrical drive systems) |
|---|---|
| Clearance & creepage | Meets pollution degree 3 and overvoltage category III requirements |
| Insulation resistance | ≥1 MΩ (500V megohmmeter, measured with the VFD disconnected) |
| Power frequency withstand voltage | Main circuit 2500V / 1 min, control circuit 1500V / 1 min |
| Constant pressure performance verification | Before shipment, the piping network is simulated on a pump test bench and steady-state fluctuation and pump staging transitions are measured |
| Routine tests (every unit) | Circuit checks, insulation and dielectric withstand, PID parameter presetting, sleep/wake operation, multi-pump rotation logic, on-load trial run |
| Documents with shipment | Electrical schematic, terminal wiring table, VFD and PID parameter table, BOM, test report, pre-shipment photos |
Five steps to specify your run
A configuration summary is generated as you go. It travels with your inquiry, saving a round of confirmation.
Build details
Systems have been in service for decades, and the failure points are always the same few: poor busbar contact, water ingress at the door seal, high temperature rise in the correction cabinet, and mis-phased outgoing feeders. The six hard rules below are written for exactly these points — every cabinet can be traced to them.
Steady-state fluctuation, MPa
Pressure stability comes down to three things working together: transmitter accuracy, PID parameters, and when pumps are added or dropped. We preset the parameters on the test bench to match the pump set's characteristics before shipment, so there is no tuning from scratch on site.
VFD pump rotation
In multi-pump systems, the VFD pump rotates based on cumulative run hours, so one pump does not run at high frequency for long periods while the others sit idle. Mechanical seal and bearing life is earned by rotation.
No spinning at low flow
At night with zero flow, the pump sleeps and wakes automatically when pressure drops below the setpoint. With an air pressure tank, pump starts and stops during low-flow periods drop noticeably.
No network shock when adding or dropping pumps
A new pump is soft-started before switching to line power, and a pump being taken offline is ramped down before it is disconnected. The pressure shock at the moment a pump is added or dropped is where networks fail most often.
VFD fault auto-switch to line power
If the VFD faults, the system automatically switches to line-power operation so water supply is never interrupted, and outputs an alarm signal. For a water supply system, lower efficiency is acceptable — stopping is not.
Bench-tested
Before shipment, the system is run on a pump test bench that simulates the pipe network for constant-pressure operation and pump staging, and the recorded pressure curve ships with the cabinet — that curve says more than any spec sheet.
Photos & enclosure construction
Below are photos taken in our own shop — from the complete unit down to the internal busbars and secondary wiring. Every build detail can be checked item by item.
Image key: 01–05 are shop photos (the numbers match the shot list). The line drawing shows the front elevation of the enclosure; dimensions match the specification table above.
Where these cabinets go
These are the routine applications — we can talk scheme and configuration directly. For the industry view, see the industry pages.
Residential secondary water supply
Constant-pressure domestic water supply for high-rise buildings, replacing elevated tanks and tankless supply schemes.
Hotels and commercial complexes
Constant-pressure control for chilled water, hot water circulation and domestic water supply.
Factory process water
Automatic speed control for process water and cooling loop water based on demand.
Water plants and booster pump stations
Pump group control for network boosting and zone water supply.
Agricultural irrigation and sprinkler systems
Automatic speed control based on line pressure, avoiding low pressure during daytime peak hours.
Energy-saving retrofit of existing pump rooms
Keep the existing pumps, replace the control cabinet and add VFDs — cutting power consumption and stabilizing pressure at the same time.
Commercial terms
Specification dated September 2026; quotations follow this.
| Drawings & design | Free |
| MOQ | 1 unit (5 or more recommended for production) |
| Production lead time | 15-25 days after drawing approval |
| on-time delivery | 98% |
| Warranty | 12 months |
| Loading port | Ningbo / Shanghai, China |
| Component brands | Schneider / ABB / Siemens / Chint |
| Factory visit & dispatch confirmation | Factory visits welcome; finished-cabinet photos and video before dispatch |
| Capacity | 5,800+ units / year |
Documents for your engineering team
Selection manual, outline dimensions and RFQ checklist — for the customer's electrical engineer. All three documents are being organized by product line; download links go live once complete.
Six questions procurement and electrical engineers ask most
How accurate is the constant-pressure control?
Steady-state fluctuation is typically held within ±0.01 MPa, though actual performance depends on pressure transmitter accuracy, pump characteristics and pipe network size. Fluctuation is larger during low-flow periods; adding an air tank or a small low-flow pressure-maintaining pump noticeably improves it.
Do I need an air tank?
We recommend one for nighttime or low-flow periods. Without an air tank, even a small draw-off causes the pump to start and stop frequently, which wastes power and wears the equipment. With a correctly sized air tank, pump start/stop cycles drop and pressure stays steadier.
How many pumps should I use?
It depends on how much the water demand fluctuates. For steady demand (such as industrial cooling water), one VFD pump plus one standby is enough. For residential complexes with large day/night demand swings, three pumps (two duty, one standby) or four pumps are common — pressure transitions during staging are smoothest. We can calculate it for you based on your water usage curve.
Can I draw water directly from the municipal main?
Direct draw-off competes with the municipal network for pressure and is not permitted in many areas. The usual approach is to install a storage tank or cistern and boost from there, or use pressure-superposed (non-negative-pressure) equipment. We supply the control cabinet portion; the specific intake method must be determined per local water authority requirements.
What about low flow at night?
Two options: sleep/wake mode, where the pump stops at zero flow and wakes when pressure drops; or an air tank plus a small low-flow pressure-maintaining pump, where the air tank holds pressure during low-flow periods. The former saves more energy; the latter holds pressure more steadily.
Can it connect to remote monitoring?
Yes. Pressure, frequency, pump status and faults can all be uploaded, with Modbus / Profinet interfaces for connection to a host system or cloud platform. You can also output dry contacts only, wired to an alarm light in the duty room.
Other cabinet types in the same main circuit
Related products use color-block placeholders for now (product photos not yet complete; they will be replaced together). Internal links will be filled in once live URLs are confirmed.
Retrofitting a pump room, or specifying a new project?
Send us your water demand, pump quantity and power, and line pressure requirements — we will provide a free constant-pressure scheme and energy-saving estimate · quotation within 24 hours. Direct from the source factory, MOQ 1 unit, 15–25 day delivery, 1-year warranty.
ISO 9001:2015 · CE(LVD+EMC) · CQC · IP65
When you write, include: single-line diagram or primary scheme, switch room layout, load list, and component brand requirements. You do not need complete drawings — capacity and cabinet type are enough to start.