How to Write an RFQ for a Complete Water Pump VFD Control Panel

A useful pump VFD control panel RFQ describes the operating system, not just “three pumps, 15 kW.” Suppliers need enough information to select drives and protection, understand the control sequence, size the enclosure, and state exclusions. Without it, quotations may cover very different responsibilities.

This guide focuses on the buyer's specification for a panel package. It complements, but is not the same as, an RFQ for loose VFDs. AUSENIST can evaluate YS620 or YS820 matching and OEM/ODM panel interfaces after the electrical, hydraulic, control, environmental, and documentation boundaries are clear.

Start with scope and responsibility

State whether the request covers loose VFDs, a populated enclosure, a complete pump skid panel, or engineering support only. Identify who supplies the pumps, motors, pressure vessel, sensors, PLC, HMI, remote telemetry, cables, isolators, and site commissioning. Define the physical and functional battery limits so essential items do not sit between two suppliers' assumptions.

List the quantity of panels and the number of pumps controlled by each. Explain whether all motors are variable-speed, one pump is variable with fixed-speed auxiliaries, or every pump has an individual coordinated drive. State duty/standby philosophy and whether the panel must continue service after a drive, sensor, or communication fault.

Give the installation country and site type. Local electrical rules, language, units, conductor practice, documentation, and site conditions affect design. Ask suppliers to identify information still required rather than silently pricing a default.

Provide supply and fault-level data

Specify nominal voltage, allowable range if known, phase, frequency, grounding system, transformer or generator source, and available short-circuit current at the panel. Include upstream protective device and feeder details. If power quality is a concern, describe voltage imbalance, capacitor banks, large switched loads, harmonics, or historical events with measurements where available.

State control-power requirements and whether an external source is available. Identify any required surge protection, isolation, line reactor, EMC treatment, or harmonic study, but allow the supplier to explain what each accessory addresses. An input reactor, output filter, and surge protective device are not interchangeable.

The panel designer must coordinate short-circuit rating, breakers or fuses, disconnects, contactors, conductors, earth bonding, and thermal design. Request device ratings and coordination information appropriate to the project rather than assuming the VFD alone determines panel safety.

Attach complete motor and pump data

For every motor, provide manufacturer, type, rated voltage, phase, frequency, current, power, speed, efficiency, power factor, duty, insulation information available, and connection. State whether it is induction or permanent magnet. If motors differ, identify each pump rather than presenting one average value.

Attach pump curves and the required flow/head operating points. Provide pump type, impeller information if relevant, suction conditions, minimum flow, maximum permitted pressure, and speed limits approved by the pump manufacturer. A panel supplier cannot responsibly set minimum frequency or overload behavior from kW alone.

Record motor-cable type and length from panel to each motor. Submersible or remote pumps may need an output-side cable review. State whether local isolators or contactors exist and how switching will be interlocked so a motor is not disconnected from an energized drive improperly.

Write the operating sequence in plain language

Describe what should happen from power-up through normal demand, staging, low demand, faults, and manual operation. For a constant-pressure booster, define the target pressure, how the lead pump starts, when an auxiliary pump joins, how it leaves, how rotation occurs, and what sleep/wake should achieve. Avoid specifying unexplained parameter numbers from a legacy panel.

Define local, remote, manual, automatic, and off modes. State which source owns start and setpoint in each mode and how conflicting commands are prevented. Explain what operators may change and what requires authorized access.

For standby logic, state whether a failed pump is skipped, how the next unit is selected, and whether loss of the primary controller must transfer control. If continuity is critical, describe the required degraded modes precisely. “Full redundancy” is too vague to quote or test.

Define instruments and interfaces

List each pressure transmitter, flowmeter, level transmitter, float switch, temperature contact, and external interlock. Provide range, signal type, supply requirement, process connection where in scope, cable length, and who supplies it. For 4–20 mA feedback, define engineering scaling and expected action for an open or out-of-range signal.

Create an I/O schedule for run commands, permissives, alarms, running indication, common fault, pump-specific fault, reset, valve status, and emergency or safety circuits. State whether contacts are volt-free and the electrical ratings expected. Safety-related functions require a project risk assessment and suitable architecture; ordinary VFD software or a general relay should not be presented as a certified safety function without evidence.

For BMS, SCADA, or PLC communication, specify protocol, physical interface, master/slave roles, required points, command permissions, update expectations, and loss-of-communication behavior. Request a register map and integration test, not merely “RS485 included.”

Specify enclosure and site conditions

Give indoor or outdoor location, ambient temperature range, altitude, humidity, dust, water, salt, chemicals, insects, vibration, solar exposure, and washdown conditions. State the required enclosure rating and the standard under which it is defined. The supplier still needs to address condensation, heat rejection, drains, sun shields, filters, heaters, or cooling as applicable.

Provide maximum dimensions, mounting method, cable-entry direction, gland or transit requirements, door clearance, access restrictions, and preferred segregation. Identify whether the panel will be installed in an electrical room, on a skid, beside a wet process, or in a public area.

Ask for a thermal design appropriate to the highest expected load and ambient. Fans and filters require maintenance access; sealed enclosures may need a different cooling strategy. Do not approve a layout solely from an attractive front view.

Request protection and alarm behavior

Define process protections such as high pressure, low pressure, water shortage, sensor failure, pipe leakage indication, low tank level, and minimum-flow permissive. For each, state the desired response, delay philosophy, reset method, alarm indication, and whether automatic restart is allowed. Thresholds may require commissioning, but their safe bounds should be known.

Electrical protections should be coordinated with the motor, supply, and drive. Ask for indication and fault history sufficient for service. The panel should distinguish an upstream trip, drive fault, motor issue, external interlock, and process alarm where practical, because a single red lamp creates expensive diagnosis.

Specify emergency stopping and isolation from the site risk assessment. Any bypass mode must be engineered around pressure control, motor starting current, protection, interlocks, and hydraulic risk; a bypass contactor is not automatically appropriate.

Define tests and deliverables before price comparison

List routine inspection and factory acceptance requirements. Typical checks include component identity, wiring continuity, insulation tests performed with VFD-sensitive equipment handled correctly, earth continuity, control-power operation, I/O simulation, motor rotation where feasible, sensor scaling, sequence demonstration, alarm behavior, communication, and parameter backup. State which tests require buyer witnessing.

Provide an acceptance matrix with requirement, method, and expected result. Hydraulic functions that cannot be reproduced at the panel factory should be identified for site commissioning. Do not demand unsafe simulations of short circuits, dry running, or overpressure; agree documentary or controlled alternatives.

Required documents may include approved drawings, single-line diagram, schematic, terminal plan, layout, bill of materials, I/O list, parameter list, software backup, manuals, certificates supported by evidence, inspection report, packing list, and recommended spares. Specify language, file format, review cycle, and final handover.

Compare quotations on the same basis

Create a compliance schedule so each bidder marks comply, deviation, option, or excluded against every requirement. Compare architecture, environmental design, tests, documents, commissioning, and exclusions—not only price. Resolve deviations in writing.

Information to send AUSENIST

For a panel or drive evaluation, send the supply voltage and phase, fault-level information available, each motor's rated current and power, pump type and curve, target pressure or other controlled variable, sensor ranges and signals, pump quantity, operating sequence, motor-cable lengths, site environment, country, and required interfaces.

Include drawings, enclosure limits, testing and documentation expectations, plus any OEM/ODM needs for labels, keypad, terminals, parameter defaults, communication, language, or packaging. AUSENIST can then assess YS620/YS820 matching and clarify which parts of the complete panel require a qualified panel designer or local engineering confirmation. A detailed RFQ produces comparable offers and a controllable project instead of a collection of hidden assumptions.