Can Multiple Pump VFDs Share One Pressure Sensor?

Multiple VFD-controlled pumps can regulate one common header from one pressure sensor, but the sensor signal and PID authority must be distributed deliberately. The safest design is not to wire one transmitter casually into every analog input and let every drive regulate independently. That approach can overload the signal, create ground loops and make several PID loops compete.

Start with the hydraulic measurement point

The pressure sensor should represent the header or remote point that the system is intended to control. A sensor placed too close to one pump can read local turbulence rather than the pressure supplied to users. A sensor across a closed valve can cause the controller to increase speed while the actual network is already pressurized.

One process sensor does not mean many PID masters

If several VFDs each receive the same pressure signal and run separate PID loops, small differences in scaling, tuning and sampling can make them respond differently. One drive may accelerate as another decelerates. The result can be frequency hunting, repeated staging and pressure oscillation.

Use one controller as the active authority. It can command auxiliary drives through the documented multi-pump logic or communications. The auxiliary pumps then follow the coordinated system state rather than independently chasing the same analog value.

The documented YS620 architecture supports two master-capable drives and up to four auxiliary pumps, for as many as six pumps. It includes standby master takeover, failed-pump skipping and timed pump rotation with an eight-hour default. The project should state which unit owns PID after every normal and fault transition.

Do not parallel analog inputs without checking the circuit

A 4–20 mA transmitter is a current-loop device with a permitted load and supply requirement. Several receiver inputs in series may exceed the available loop voltage, while wiring inputs in an unplanned parallel arrangement may not produce the intended current in each device. Voltage-output sensors have their own input-impedance and grounding constraints.

Confirm sensor signal, supply, range, connector and every receiving input. If more than one device needs an analog copy, use an approved signal distributor, isolator, controller output or communication method. Do not infer compatibility from the fact that all terminals are labeled “analog input.”

Decide how the backup master receives pressure

A system with two master-capable drives must define the backup's information source. One option is a single transmitter connected through an appropriate distribution method to both master inputs. Another is two independent transmitters, each associated with a master or voted by a controller. Each choice has different fault behavior.

One shared transmitter is simple and measures one point consistently, but it is a single point of failure. A second master cannot maintain valid pressure control if the only sensor has failed. Two sensors improve diagnostic possibilities, yet disagreement between them requires a rule: which value is trusted, when control transfers and how an alarm is raised.

Design sensor-failure behavior before tuning PID

Define how the system detects an open circuit, short circuit, out-of-range signal, frozen value or implausible pressure change. Not every sensor failure produces a clean zero. A blocked pressure port can provide a valid electrical signal that no longer represents the pipe.

Choose the safe response for the water system. It may be a controlled stop, a limited fallback speed, transfer to a validated secondary sensor or an alarm requiring operator action. Avoid an unlimited high-speed fallback that can overpressurize the network.

YS620 water-pump functions include sensor-related protection, high- and low-pressure alarms and pipe-burst shutdown. These functions require thresholds, delays and reset conditions matched to the installation. A function name is not evidence that every failure mode has been covered.

Separate sensor failure from communication failure

If the master reads an analog sensor and sends commands to auxiliary drives over RS485, a communication fault and a pressure-sensor fault are different events. The sequence should identify each one and avoid transferring control repeatedly between unhealthy units.

The YS620 provides dual RS485 throughout its documented 0.75–7.5 kW range. YS820 hardware differs: documented 220 V 0.75 and 2.2 kW versions have single RS485, while documented 380 V versions provide dual RS485. Verify the exact drive before assigning one port to multi-pump control and another to BMS or SCADA.

Prevent ground loops and electrical noise

Pressure signals are often routed through a cabinet containing VFD input and output conductors. Keep low-level signal wiring separated from motor power. Follow the approved shield and grounding practice, and avoid inconsistent terminations that create circulating current.

A shared sensor can link the ground reference of several devices. Signal isolation may be necessary when drives, controllers or power supplies do not share a suitable reference. Noise symptoms can include pressure fluctuation related to output frequency, intermittent sensor alarms and unstable PID response.

Configure scaling identically where more than one device reads it

Every receiving device must use the same transmitter range and engineering units. A 0–10 bar sensor interpreted as 0–16 bar can create a serious disagreement even though the 4–20 mA current is valid. Record zero, span, units and display decimal position.

If two master drives can take control, compare their displayed pressure at several real values. Confirm that the active setpoint, PID direction, alarm thresholds and sleep logic transfer with the intended parameter set. A standby master that reads pressure differently is not a true standby.

Coordinate staging with pressure feedback

The active controller should add a pump only after demand remains beyond the useful capacity of the running combination for a defined condition. It should remove a pump without forcing the remaining unit into immediate saturation. Frequency, pressure deviation and time can all inform staging, depending on the approved logic.

Use delays and hysteresis to prevent rapid add/remove cycling, but do not mask a pump that is too large for the minimum demand. Verify the pump curves and operating points. When pumps have different sizes, define the intended contribution of each rather than trying to make current equal.

Match each drive to its own motor

One common pressure sensor does not make the pump motors identical. Select every drive from its motor voltage, rated current, frequency, connection and duty. The documented YS620 range is 0.75–7.5 kW; YS820 covers 0.75–22 kW.

AUSENIST solutions can be matched to asynchronous induction and permanent-magnet synchronous motors. Each drive needs the correct motor-specific data. A multi-pump station can include different pump sizes if the hydraulic sequence is designed for them, but settings must not be copied blindly between PMSM and induction units.

Standard 220 V and 380 V solutions and confirmed custom 440 V or 460 V projects can be evaluated. State actual supply, input phase and motor output requirements for each branch.

Include installation and environmental requirements

Drive arrangements can be cabinet-mounted, wall-mounted or directly integrated with compatible vertical and horizontal pumps. The sensor wiring route should be considered with the physical arrangement. A universal mounting plate can support varied pump packages, while actual screws depend on the pump.

At high altitude, apply the documented YS620 capacity rule: no derating below 1,000 m and 1% for each additional 100 m. Altitude does not change the sensor pressure range directly, but it can affect drive capacity and enclosure cooling.

IP54 does not remove the need to protect sensor connections, cable glands and electronics from unsuitable exposure. Condensation or water in a transmitter connector can defeat an otherwise correct control design.

Commission normal and failure paths

Calibrate the pressure display against a reference, confirm PID direction, and run from low to high demand. Record pressure, frequency and motor current for each staging state. Then test lead rotation and master transfer under a controlled procedure.

Simulate permitted sensor and communication faults using safe methods. Confirm the alarm, fallback, stop and restart behavior. Test what happens if the sensor isolation valve is closed or the sensing port becomes slow, not only an electrical open circuit.

For OEM packages, AUSENIST customization can define sensor interfaces, parameters, communication mapping, multi-pump logic, labels, localized documentation and wiring drawings. The goal is that installers know exactly where one sensor signal goes and which controller owns it.

Multiple pump VFDs can share one pressure measurement successfully when there is one active control authority, a validated signal-distribution method and a defined failure response. The number of sensors should be chosen from reliability requirements, not from habit. One sensor can simplify control; a second sensor can add resilience only when disagreement and transfer logic are engineered as carefully as the hardware.