1. One-Duty/One-Standby Pump Control Cabinet Photos (Dual-Pump Alternating Operation)
The photo shows aOne-duty/one-standby pump control cabinet(2×15kW pumps): The cabinet interior is split into upper and lower tiers, each with its own independent control unit — circuit breaker (NSX40F 32A) + contactor (LC1D18) + thermal overload relay (LRD14). Between the two unitselectrical interlocking, only one pump runs at any given time. The cabinet door is fitted with amanual/auto selector switch + start/stop pushbuttons + run indicator lights.
2. Two-Duty/One-Standby Pump Control Cabinet Photos (Three-Pump Rotation)
The photo shows aTwo-duty/one-standby pump control cabinet(3×22kW pumps, VFD constant pressure water supply): The cabinet houses one 22kW VFD (Siemens G120) that controls the lead pump, while the other two pumps start directly via soft starters or contactors. A PLC handles the rotation logic to keep cumulative run time balanced across all three pumps. Internal layout — VFD + braking resistor on the left, three sets of circuit breakers + contactors in the center, PLC + relays + terminal blocks on the right.
3. Constant Pressure Water Supply System Configuration Photos (VFD + Pressure Tank + Sensors)
The photos show the completeconstant pressure water supply systemcontrol cabinet interior:
- VFD: Siemens G120 22kW, with built-in PID that reads the 4-20mA pressure sensor signal directly for closed-loop control.
- PLC: Siemens S7-1200, controlling the rotation logic for three pumps (lead pump on VFD, assist pump on line frequency for supplemental flow, standby pump idle).
- Pressure sensor: submersible level transmitter (0-1.6MPa 4-20mA), mounted on the main discharge pipe.
- Pressure tank: diaphragm-type pressure tank (100L/0.6MPa), absorbing water hammer and reducing frequent pump starts and stops.
- Touchscreen: 7-inch HMI, displaying each pump's operating status, real-time pressure curves, and fault alarm history.
4. Pump control cabinet ingress protection (IP) rating (required for damp environments)
Pump rooms are damp, so the control cabinet IP rating≥IP54(splash-proof); for outdoor pump rooms, specify IP65. Photo shows:
| Installation environment | Recommended IP rating | Enclosure requirements | Cooling method |
|---|---|---|---|
| Indoor, dry | IP30 | Painted steel | Natural convection |
| Indoor, damp | IP54 | Stainless steel / galvanized sheet | Sealed + roof-mounted fan |
| Outdoor, rain-exposed | IP65 | stainless steel 304 | Sealed + cabinet air conditioner |
| Underground pump room | IP54 + anti-condensation | Sealed + heater | 50W heater for moisture protection |
5. Pump control cabinet visual inspection standard (5 quality checks)
① Reliable interlock: main and standby pump contactors interlocked through normally closed auxiliary contacts; pressing both start buttons manually starts only one pump; ② Manual/auto switching: in manual mode each pump can be started and stopped individually; in auto mode the PLC controls rotation; ③ IP rating: incoming and outgoing cable glands sealed; door gasket complete and undamaged; ④ Grounding: separate PE bar, grounding resistance ≤4Ω, VFD PE wired separately; ⑤ Marking: each pump circuit has its own nameplate (pump number, power, current) matching the drawing.
FAQ FAQ
Does a pump control cabinet have to be fitted with a VFD?
Not necessarily. Small pump rooms (≤7.5kW) can use direct-on-line starting plus a pressure tank. Variable frequency constant pressure water supply suits≥11kWor applications with high pressure stability requirements. A VFD can save 20-40% energy, but costs more and has a higher failure rate than direct-on-line starting.
How do I choose between one duty / one standby and two duty / one standby?
It depends on how much water demand fluctuates. For stable demand, chooseduty/standby(the standby pump runs only if the duty pump fails); for highly variable demand, chooseTwo duty / one standby(two pumps run in parallel to meet peak demand, one stops at low demand). Systems with three or more pumps suit large water supply systems.
What should I watch out for when installing a pump control cabinet outdoors?
IP rating ≥IP65, 304 stainless steel enclosure, sealed cable glands, and ananti-condensation heaterinside the cabinet (50W, temperature-controlled start at 5°C) to prevent temperature differential condensation from causing electrical short circuits. In high summer temperatures, add a cooling fan or air conditioner.
What does the pressure tank in a constant pressure water supply system do?
It absorbs pressure fluctuations in the piping network (water hammer) and reduces frequent pump starts and stops. Pressure tank volume is selected based on pump flow rate and piping network volume — too small and the pump cycles frequently (more than 6 times per minute), too large and it takes up space. Rule of thumb: a 22 kW pump pairs with a 100 L pressure tank.
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