Specify used medium-voltage switchgear as a complete assembly against the project's one-line, ratings and protection requirements. Identify every section, breaker, control component and installation interface. A matching voltage and current label is only an initial screen; the purchase needs documented assembly compatibility, condition evidence and an agreed acceptance scope before award.
A seller may quote a breaker, an empty section, a shipping group or an entire lineup. Those are different procurement objects. The most useful first step is to translate the project's electrical design into a schedule that makes the offered boundary unambiguous.
SecondWatt's switchgear catalogue supports equipment research. This guide addresses the detailed buying specification; the existing switchgear pricing guide provides the adjacent commercial context.
Key Takeaways
- Define the complete lineup and distinguish it from individual sections or breakers.
- Match assembly ratings and breaker compatibility to the receiving system.
- Include protection, instrument transformers and control power in the quoted scope.
- Verify arc-resistant construction and installation conditions for the actual assembly.
- Request drawings, condition evidence and acceptance responsibilities with the offer.
Translate the one-line into a lineup schedule#
Begin with the approved or current design one-line and identify its revision. List incoming sources, bus sections, ties, outgoing feeders and required future provisions. Ask the project engineer to identify the operating arrangements and interlocks that the supplied equipment must support.
Eaton's medium-voltage switchgear overview distinguishes equipment constructions and applications. Use the project specification to identify the required assembly type. Switchgear, switchboards, panelboards and transfer switches should not be treated as interchangeable descriptions in an RFQ.
Lineup schedule to accompany the enquiry#
| Position or function | Required content | Evidence requested |
|---|---|---|
| Incoming source | Required switching/protection arrangement | One-line and section drawing |
| Bus section | Continuous and fault-duty requirements | Assembly rating documentation |
| Bus tie | Breaker, controls and permitted operating logic | Schematics and interlock description |
| Outgoing feeder | Breaker and protection for the connected load | Feeder schedule and component details |
| Metering | Required current/voltage measurement arrangement | Instrument and wiring schedule |
| Auxiliary section | Control power and supporting equipment | Bill of materials and schematics |
| Future provision | Defined prepared or unprepared space | Drawings and included-parts schedule |
Make the meaning of spare explicit. It might mean an installed spare breaker, a prepared compartment without a breaker or space reserved for later construction. Those conditions have different acquisition and future-work implications.
Ask the seller to mark every offered section against the schedule. If the arrangement differs, request a proposed mapping and the engineering work needed to make it fit. Photographs help confirm physical identity, but they do not replace a one-line or the assembly's drawings.
Consider a project schedule that calls for two incoming functions, a bus tie and four outgoing feeders. That describes seven electrical functions, but it does not necessarily mean seven physical vertical sections. The assembly design determines how devices are arranged. Ask for both the functional schedule and the physical section drawing so neither the buyer nor seller prices an assumed layout.
A quotation covering the required functions can still omit a breaker from a prepared cell or leave metering to another section. Reconcile the devices and their locations individually. This is the point at which a shorter equipment description becomes a procurable assembly rather than a collection of promising photographs.
Reconcile voltage, current and fault-duty ratings#
Record nominal system voltage separately from the equipment's rated voltage. Review frequency, continuous current, insulation requirements and the applicable short-circuit duties with the responsible engineer. A familiar voltage-class description does not establish every rating needed for the installation.
The receiving system study should determine the required duty. Keep the study revision and assumptions with the procurement record, particularly where future sources or transformer changes may alter the available fault current. Do not select equipment from a guessed duty value based on facility size alone.
Rating comparison for the offered assembly#
| Rating or condition | Required project input | Offered evidence |
|---|---|---|
| System voltage and frequency | Receiving-system design | Assembly and component nameplates |
| Bus continuous current | Required operating case | Assembly rating record |
| Breaker continuous current | Feeder and source requirements | Breaker identification and ratings |
| Interrupting duty | Applicable system-study result | Breaker rating documentation |
| Withstand and duration | Required assembly duty | Assembly design evidence |
| Insulation level | Project specification | Applicable design documentation |
| Service environment | Indoor/outdoor and site conditions | Enclosure and installation documentation |
Keep ratings on their stated bases. The engineer should reconcile the relevant symmetrical, asymmetrical, peak and time-related quantities where applicable. A single short-circuit number copied from a listing may not represent the quantity the project needs to check.
If a seller proposes a component with a higher individual rating, confirm that the complete assembly remains suitable. One upgraded breaker does not automatically upgrade the bus, connections, instrument transformers or tested assembly. Require documentation for the final configuration rather than accepting the highest number on any one nameplate.
Verify breakers, cells and the bus arrangement#
Breaker interchangeability is a design-specific question. Confirm the manufacturer, family, type, frame, mechanism, control interfaces and relevant revision against the receiving cell. Matching current and voltage does not prove that a breaker is an acceptable replacement.
Siemens' GM-SG and GM-SG-AR technical brochure describes defined interchangeability boundaries, including limits involving older breaker designs. That is a useful example of why compatibility needs the actual product documentation rather than an industry-wide assumption.
Identify missing breakers and associated parts before normalizing the offer. A lineup photographed with open compartments may be complete for one project and incomplete for another. Ask for the required breaker complement, handling equipment and any supplied spares as separate bill-of-materials entries.
Assembly compatibility questions#
| Topic | Evidence to obtain |
|---|---|
| Breaker-to-cell fit | Documented compatible type and configuration |
| Primary connections | Correct interface and condition evidence |
| Secondary/control interfaces | Matching wiring and operating requirements |
| Interlocks | Documented arrangement and functional review |
| Bus joints and transitions | Complete supplied parts and assembly drawings |
| Extensions | Engineered interface to existing or future sections |
| Shipping splits | Reassembly scope, hardware and identification |
For an extension to an existing lineup, request the original assembly information and a documented transition design. Do not assume that the same product family guarantees a direct connection across different vintages or construction options.
Ask how the seller will preserve section identity through dismantling and shipment. The receiving installer needs to know which parts, bus connections and wiring belong together. A complete equipment schedule should survive removal rather than become a collection of unassigned components at the destination.
Include the removal and reassembly documentation in the delivery scope. Request identification of shipping splits, detached parts and any wiring disconnected for transport. If the lineup is split into multiple shipments, state what the receiving team can inspect at each delivery and when the full assembly can be checked. This keeps a partial shipment from being mistaken for completion of the equipment obligation.
Include protection, metering and control power#
A lineup's useful function depends on more than its primary current path. Specify the protection functions, instrument-transformer arrangement, control-power source, communications and required operating logic. Assign the settings study and configuration work to an identified party.
The SEL-751 product documentation illustrates how relay options, measurement inputs and communications can vary within a named product. A relay model on a photograph does not establish that the installed option set supports the receiving project's requirement.
Protection and control schedule#
| System element | What the RFQ should establish |
|---|---|
| Protective relays | Exact devices, options and required functions |
| Current transformers | Ratios, classes, burdens and wiring requirements |
| Voltage measurement | Required devices, connections and protection |
| Control power | Source, voltage and required behavior during supply loss |
| Trip and close circuits | Compatibility with breakers and control design |
| Communications | Protocols, ports and integration boundary |
| Settings and logic | Responsible engineer, revision and acceptance method |
Do not reuse the previous installation's settings without project review. The new source, transformer, load and protection arrangement may require different coordination. Ask for existing settings as historical configuration evidence, then develop and approve the receiving settings through the appropriate engineering process.
Agree the format of the settings and configuration handover. The owner should receive the editable files, associated drawings and a revision record that connects them to the installed devices. Identify any required software access or support entitlement. Without that handover, a relay that functions during commissioning can still leave the operating team unable to maintain its configuration effectively.
Keep the final protection study, settings files and functional test results aligned. If a design change occurs after testing, have the responsible engineer identify the affected settings and checks before closing acceptance.
Define any battery, charger, control transformer or external DC system boundary. If it is excluded, identify the buyer's corresponding procurement task. A switchgear offer can be physically complete while depending on a control-power system that nobody has included in the programme.
For data-center projects, align the lineup with the transformer design review. Changes in the upstream or downstream equipment should trigger a review of the affected ratings, interfaces and protection assumptions before the purchase specification is frozen.
Confirm enclosure, access and arc-resistant scope#
Obtain the actual outline and installation drawings, including clearances, cable entry, shipping groups and handling requirements. Compare these with the room or outdoor installation. A lineup that fits within the floor area may still lack the required service or cable access.
Eaton's VacClad product information provides an example of a named switchgear family with configuration choices. Those choices must be resolved for the offered assembly; a family-level product description cannot establish its exact dimensions or installation requirements.
Arc-resistant construction needs evidence for the actual assembly and its installed arrangement. Identify the classification, applicable documentation and required conditions, including any exhaust path or pressure-relief components. Do not treat an arc-detection relay or a general safety feature as proof that the assembly has an arc-resistant classification.
Physical installation review#
| Interface | Required confirmation |
|---|---|
| Room or enclosure | Dimensions, environment and required clearances |
| Cable entry | Direction, space and termination arrangement |
| Foundation | Loading, anchorage and installation tolerances |
| Access | Breaker handling, inspection and maintenance space |
| Arc exhaust, if applicable | Complete documented path and supplied components |
| Expansion | Space and engineered electrical/mechanical interface |
Schneider Electric's MCSeT pressure-relief duct guidance ties the arrangement to customer-specific switchgear documentation. The procurement implication is to obtain the correct installation evidence and include required components, not to apply another product's clearances to the proposed lineup.
Changes to the enclosure, vents, doors or pressure-relief arrangement need an appropriate review. A refurbishment should preserve or document the final assembly characteristics claimed in the offer. Repainting or replacing a component does not independently establish the original classification remains applicable.
Review condition and define acceptance evidence#
Request service history, known faults, maintenance records, storage conditions and any modifications. Identify what was inspected and tested, on which date and against which equipment schedule. A used lineup can contain components with different histories, so keep the evidence traceable to sections and devices.
The switchgear maintenance field guide provides context for maintenance planning. Purchase acceptance is a separate task: it must establish whether the offered equipment satisfies the agreed condition and project requirements at the relevant milestone.
Condition evidence to request#
| Evidence | Procurement purpose |
|---|---|
| Assembly and component inventory | Identify the equipment being accepted |
| Service and modification records | Explain changes and known issues |
| Inspection report | Document condition within the stated scope |
| Applicable electrical/mechanical tests | Support acceptance against agreed criteria |
| Protection and control checks | Confirm required configuration and functions |
| Corrective-work record | Show completion and any required retesting |
| Final drawings | Represent the supplied configuration |
The public ANSI/NETA ATS scope addresses acceptance testing before initial energization. Use the appropriate project specifications and manufacturer information to select procedures and criteria. This article does not reproduce paywalled test tables or prescribe universal pass thresholds.
Agree which evidence is required before shipment and which checks belong at the receiving site. Define the response to a missing component, failed test or drawing discrepancy. The buyer should know who performs corrective work, who pays for retesting and what event closes acceptance.
Request a complete offer with clear exclusions#
Send the lineup schedule, one-line and physical constraints together. Ask the supplier to return the offered assembly identification, bill of materials, drawings, ratings, condition evidence and a deviation list with the price. Keep unknown fields visible during the technical screen.
Minimum medium-voltage switchgear RFQ#
| Requirement | Information to provide |
|---|---|
| System | Nominal voltage, frequency and operating arrangement |
| Ratings | Bus current, fault duties and insulation requirements |
| Lineup | Section functions, breaker schedule and future provisions |
| Controls | Protection, metering, control power and communications |
| Installation | Environment, layout, cable interfaces and access |
| Condition | Accepted conditions and required evidence |
| Scope | Removal, transport, modifications and acceptance responsibilities |
| Programme | Review, delivery and energization targets |
Compare the complete scope after technical deviations have been resolved or priced. A lower initial quote may omit breakers, control power, an engineered transition or required installation components. Those omissions do not automatically disqualify it, but they belong in the total cost and schedule.
SecondWatt acts as an independent intermediary. To request switchgear sourcing, send the required voltage class, bus rating, fault-duty requirements, breaker schedule and target date. Include the one-line and accepted alternatives so candidate lineups can be evaluated against a defined receiving system.
FAQ: Buying used medium-voltage switchgear#
What counts as a complete lineup?#
The agreed equipment schedule defines completeness. It should identify sections, breakers, bus connections, protection, metering, controls and supplied accessories. State external dependencies separately. A seller's use of complete does not establish that every item required by the receiving project is included, configured or ready for acceptance.
Are breakers interchangeable when voltage and current match?#
Not on that evidence alone. Confirm the exact breaker and cell compatibility, control interfaces, interlocks and applicable assembly documentation. Different generations or configurations can have different requirements despite similar headline ratings. Proposed substitutions need an engineering review and documented acceptance before they become part of the supplied lineup.
Can I add used sections to an existing lineup?#
Possibly, with a documented compatibility and transition review. Obtain information for both assemblies, including their vintages, bus arrangements, interfaces and ratings. Identify the required mechanical, electrical and control work. A shared product-family name does not by itself establish that two sections can be directly joined.
Does an arc-flash relay make switchgear arc-resistant?#
No. Protection functions and an assembly's arc-resistant classification are different matters. Obtain the classification evidence and installation conditions for the actual assembly, including any required exhaust arrangement. The project should evaluate its protection strategy and equipment construction together without treating one feature as proof of the other.
Can existing relay settings be retained?#
They should be reviewed against the receiving system before use. Source characteristics, transformer data, loads and the protection arrangement may differ from the previous installation. Request the existing settings as configuration history, then assign the required study, revised settings and functional acceptance to the responsible engineering and commissioning parties.
What should accompany a sourcing request?#
Provide the one-line, ratings, lineup and breaker schedule, control requirements, physical constraints and target dates. State accepted condition and testing expectations. Ask each respondent for an identified assembly, supporting drawings, evidence and deviations. That allows the team to compare complete candidates rather than unrelated sections carrying similar voltage labels.