How to Prepare an RFQ for Custom Electrical Enclosures

1. Why RFQ preparation matters for custom enclosures

A “custom electrical enclosure” means an enclosure that is built to the buyer’s own specification, rather than selected from a manufacturer’s catalog. Custom enclosures include project-specific dimensions, project-specific cut-outs, project-specific internal layouts and project-specific materials. This shift from catalog to custom is where most procurement mistakes occur: catalog parts are pre-defined while custom parts need nearly every aspect specified by the buyer.

For a custom enclosure, the RFQ document is the technical baseline for everything that follows — the quotation, the production drawing review, the sample (if requested), the pre-production sample, the production run, the pre-shipment inspection and the final acceptance. Every item that is not specified in the RFQ will be interpreted by the supplier during quotation, and that interpretation is rarely aligned with the buyer’s actual project condition.

In practice this produces predictable failures:

• Quotations that miss the real cost. The supplier quotes what the RFQ literally says, not what the project needs. Cost increases later, after the supplier realises the work involved.
• Long clarification cycles. The supplier asks for drawings, environment and material details that should have been in the first message.
• Mid-production change orders. A missing detail is discovered during production drawing review. Schedule, cost and tooling are disrupted.
• Enclosures that do not fit. Cable entries, mounting footprints, door swing directions or thermal provisions are inconsistent with the site. The cabinets need rework on arrival.
• Acceptance disputes. It is unclear whether a visual defect or a dimensional deviation was specified as acceptable. Warranty discussions become difficult.

The reverse is also true. A well-prepared RFQ allows the selected manufacturing partner to return a commercially realistic response, because the requirement has been made unambiguous at the inquiry stage. The cost of clarity at this stage is minutes of writing; the cost of a missing detail later is days of clarification, and sometimes weeks of remediation.

2. Who this guide is for

This guide is written for procurement teams, project engineers and technical buyers who need to prepare an RFQ for custom electrical enclosures. The use cases covered include a single-project enclosure, a multi-site rollout with identical cabinets across several locations, and a multi-batch framework where the design is repeated over time.

The article assumes the buyer is working with Chinese manufacturing partners — either by introducing a new partner or by consolidating an existing relationship. For buyers who already have a confirmed sourcing partner and need a clean RFQ format, the structure below covers the items that should be present. For first-time buyers, the same structure supports internal review before the first RFQ is sent.

This guide is not intended for standard catalog enclosure purchases, where the RFQ typically reduces to a part number and a quantity. For catalog items, the procurement process is different and the cost of missing detail is much lower. For custom enclosures, every specification is project-dependent, and the items below are what the buyer should plan to address.

3. Project context to clarify before writing the RFQ

Before writing the RFQ document itself, several project-level decisions affect what the document needs to contain. These are not technical specifications — they are context items that allow the supplier to understand the project, propose the right manufacturing partner and prepare a realistic response.

Quantities, schedules and project totals are typically indicative at RFQ stage. They become contractual during quotation clarification, not before.

For inquiries routed through Anchor Matrix Global, this context is what the coordination team uses to identify which manufacturing partner in the network fits the requirement and what clarification is needed before the technical RFQ is consolidated.

4. Mechanical and dimensional requirements

Mechanical requirements describe the physical envelope and the way the enclosure is installed, accessed and assembled. These are the items that determine whether the enclosure will fit the site and whether the cables, components and maintenance crews can work inside it.

• Overall external dimensions. Height, width and depth in millimetres. Specify tolerances if known (for cabinets that fit into a designed footprint).
• Mounting arrangement. Floor-standing, wall-mounted, pole-mounted, free-standing on a base frame, or recessed into a structure. Drives the structural design of the cabinet.
• Footprint and installation clearances. Required space for door swing, cable bending radius behind the cabinet, ventilation clearance on the sides and rear.
• Internal usable space. Depth behind the mounting plate, working height above and below component rows, mounting-plate dimensions and load capacity.
• Access arrangement. Number of doors, door swing direction (left / right), removable panels, lift-off hinges, single-point or multi-point locking.
• Cable entry arrangement. Top entry, bottom entry, side entry, or a combination. Gland plate configuration: blank, pre-punched, or removable. Specify gland plate material and dimensions if they differ from the cabinet body.
• Mounting plate. Dimensions, material, thickness (a project-specific choice driven by weight of installed equipment), and grounding provisions.
• Internal metalwork. Sub-panels, dividers, component rails, cable management, DIN rails, earthing bars.

If the project drawings specify any of these items, send the drawings with the RFQ. If the dimensions are not yet fixed, list the available site envelope and the constraints, and let the supplier propose a workable solution.

5. Electrical and functional requirements

Electrical requirements describe what the enclosure is for — the function of the assembly inside. In custom enclosure projects, these items usually drive most of the design work and most of the supplier cost. Being clear here is more important than being clear anywhere else in the RFQ.

• Rated voltage, current and short-circuit withstand. The system parameters the assembly must handle. Drives busbar sizing, component selection and clearances.
• System earthing arrangement. TN-S, TN-C-S, TT, IT. Drives the configuration of the earthing bar and protective conductor provisions.
• Functional description. For example: “main incoming panel with one 800 A ACB and eight 250 A outgoing ways” or “PLC control cabinet for a pumping station with HMI and remote telemetry”. Functional descriptions let the supplier understand the intent without seeing the circuit first.
• Components to be installed. Switchgear, busbars, terminals, PLCs, VFDs, soft starters, instruments, protection relays, power supplies. Components may be buyer-supplied or supplier-sourced.
• Component-level specifications. If the buyer requires specific sub-suppliers (e.g. a particular switchgear brand), state this. If not, allow the supplier to propose equivalent options.
• Internal wiring standards. Wire colour code, wire type (e.g. PVC / XLPE / silicone), segregation between power and signal wiring, terminal block arrangement and labelling standard.
• Drawings to provide. Single-line diagram (SLD), general arrangement (GA), internal layout, wiring / termination diagram. The level of detail available at RFQ stage affects the accuracy of the quotation.

For projects where the electrical design is still in progress, sending the SLD and a description of the function is enough for a first-round budgetary quotation. Detailed component-level pricing is normally issued after the design is firmed up.

6. Environmental and ingress-protection requirements

Environmental requirements specify how the enclosure performs against the site it is installed in. The single most important item here is the IP rating — the level of protection against ingress of solid objects and water. IP ratings for enclosures are defined by the international standard IEC 60529, and the two-digit code determines the cabinet design, the gasket system, the cable-entry arrangement and the overall cost of the enclosure.

Buyers who are still choosing an IP rating, or who want to understand how IP54, IP55, IP65 and IP66 compare in cabinet procurement, should refer to the AMG technical reference What IP Ratings Mean for Outdoor Electrical Cabinets. That reference explains the two digits of the IP code under IEC 60529, compares the most commonly specified ratings and outlines the items that should appear in an outdoor-cabinet RFQ.

Apart from the IP rating, the environmental block should describe:

• Operating temperature range. Daily and seasonal extremes at the installation site. Drives derating of internal components and any thermal-management provisions.
• Ambient humidity and condensation profile. Tropical, temperate, desert, refrigerated. Affects condensation management, internal heating and ventilation design.
• Corrosion conditions. Coastal or salt-laden, industrial pollution, chemical exposure, or benign. Drives material selection and surface finish specification, which are separate from the IP rating.
• Sun and UV exposure. Direct sun, sheltered, indoor. Drives colour selection (light colours reflect heat), ventilation requirements and any sun-shade provisions.
• Mechanical exposure. Impact risk, vibration, foot traffic, vehicle proximity. Drives mechanical-strength provisions where required.

The IP rating is one item among these. Specifying the environment fully — not just the IP rating — lets the supplier propose a cabinet that performs in service, not just one that meets a single number.

7. Material selection

Material selection drives the enclosure cost, the cabinet weight, the corrosion behaviour, the fabrication complexity and the surface-finish system. The buyer should state the required material in the RFQ, or at minimum state the relevant constraint (indoor / outdoor, corrosion class, mechanical expectations). Material selection and surface-finish selection are separate decisions — both must be specified.

The currently verifiable material categories that may be relevant to a custom enclosure inquiry are listed below. AMG’s role is to coordinate enquiries and review availability with the selected manufacturing partner; specific grades, thicknesses and material specifications are confirmed per inquiry and are not represented as standard AMG offerings.

The four categories above reflect what may be reviewed in a custom-enclosure inquiry. Specific grades, thicknesses and material specifications are buyer-defined and confirmed per inquiry. Material and finish should be specified separately; specifying “stainless steel” or “aluminium” in the RFQ without specifying the grade, the surface finish or the thickness leaves an open question the supplier will fill with a default.

8. Surface finish and coating

The surface-finish specification determines the cabinet’s corrosion protection, its appearance, its colour and its compatibility with the installation environment. For most custom enclosures, the finish is part of the quotation — it is not optional and it is not the same as the material.

Buyers should specify the following surface-finish items in the RFQ where they have been defined:

• Required finish. Powder coating and other surface finishing are commonly considered. If the required finish has been defined, include it in the RFQ. If not, state the corrosion and environmental requirement so availability can be reviewed with the selected manufacturing partner.
• Colour reference, if defined. Where colour is specified, standardised colour references (such as RAL) are an example of how the colour requirement may be communicated. The colour reference itself comes from the buyer; the supplier confirms availability for the chosen finish system.
• Appearance or texture requirement, if relevant. Where the cabinet is visible in a finished installation, state any appearance or texture requirement (for example, a uniform finish, a specific texture family or a gloss level).
• Corrosion or environmental requirement. The installation environment (indoor, outdoor, coastal, chemical or wash-down) drives the corrosion requirement and is the basis for selecting a suitable finish system.

Any special surface-treatment or coating requirement should be stated in the RFQ and confirmed for availability with the selected manufacturing partner.

9. Tolerances and fabrication quality

Tolerances specify how much dimensional deviation the cabinet can have and still be considered acceptable. Tolerance specification is one of the places where RFQs most often go wrong — buyers either omit tolerances entirely, leaving suppliers to assume the loosest commercially available tolerance, or specify tolerances tighter than the application needs, increasing cost without benefit.

A practical approach is to specify by level rather than by numeric value, for example:

• General industrial. Suitable for most cabinet dimensions, mounting-plate cut-outs and standard fabrication. The widest tolerance band that does not interfere with installation.
• Architectural. Tighter straightness, flatness and angularity. Suitable where the cabinet is visible in a finished building or matches adjacent architectural elements.
• High-precision. Tightest tolerance band, requiring special tooling, fixturing and inspection. Reserved for interfaces where the project clearly demands it.

Specific numeric tolerances should be stated where they are functionally required and confirmed during technical clarification. Specifying tighter tolerances than the application requires drives cost without field benefit and is one of the most common inadvertent over-specifications in custom-enclosure RFQs.

Buyers should identify any critical dimensions and any project-specific tolerance requirements during RFQ preparation, rather than after production has started.

Welding requirements, surface roughness where relevant to function or appearance, and acceptance criteria for visual defects should be specified using the applicable project or industry requirements and confirmed during technical clarification.

10. Drawings and reference documents

Drawings and reference documents are how the RFQ is converted from a written description into something the supplier can quote against. The list below covers the typical drawing package for a custom-enclosure RFQ.

• General arrangement (GA). Overall dimensions, mounting arrangement, door configuration, gland plate positions. The drawing most useful at RFQ stage.
• Internal layout. Component positions inside the cabinet, mounting plate arrangement, earthing bar location.
• Single-line diagram (SLD). The electrical structure of the assembly — incomer, busbars, outgoing ways, instrument transformers, metering.
• Wiring / termination diagram. Wire numbers, terminal numbers, destination labels. Used during production and inspection.
• Component list (BOM). If specific components are required, the BOM is the cleanest way to communicate them.
• 3D models / STEP files. When available, 3D files make the supplier’s production drawing work faster. Optional at RFQ stage, very useful at sample stage.
• Reference standards. IEC 61439 series for low-voltage assemblies, IEC 60529 for IP ratings, applicable national standards, and any project-specific specifications the buyer maintains.
• Photographs of similar installations. Useful for context where the buyer wants the cabinet to match an existing look or where the site has unusual constraints not visible in drawings alone.

The drawings do not all need to be finalised at RFQ stage. Sending what is available — even a marked-up sketch with key dimensions — is enough for a first-round quotation; the detail is then firmed up during clarification.

11. Quantities, schedule and logistics

Quantities, schedule and logistics are the items that turn a technical RFQ into a project enquiry. For custom enclosures, these three items influence quotation structure and lead-time planning more than any technical specification.

• Order quantity. Number of identical cabinets (or assemblies) in the order.
• Total project quantity. Indicative total volume if the design will be repeated across batches or sites.
• Shipment arrangement. Single shipment, phased shipments, partial deliveries, or call-off from a buffer.
• Indicative target dates. Target month for RFQ response, sample approval, production start, and delivery. Indicative dates are fine at RFQ stage; firm dates are agreed during clarification.
• Incoterms. EXW, FOB, CIF, DAP, DDP. Determines the supplier’s scope and the buyer’s logistics responsibility.
• Destination port or site. Required for shipping quotation and any export-licence planning.
• Packing requirements. Standard export packing, sea-worthy packing, project-specific crating. Wooden crates, ISPM 15 marking, and shock indicators may be required.

Schedule and quantities that are indicative at RFQ stage become contractual during quotation clarification. Locking in dates before the RFQ is reviewed often leads to slippage when the actual production picture becomes clear.

12. Standards, certifications and compliance

Standards and certifications define the technical rules the enclosure must comply with. For custom enclosures sourced internationally, the RFQ should state which standards apply, so that the supplier’s quotation is built on the right design baseline.

• Applicable design standards. For low-voltage assemblies, the IEC 61439 series is the international reference. The buyer should identify applicable national standards, destination-market requirements, and any project-specific specifications, and state them in the RFQ.
• Industry-specific standards. Marine, food and beverage, pharmaceutical, hazardous area, rail, mining. Each industry has standards that affect the cabinet design beyond the general industrial baseline.
• Project specifications. Many buyers maintain internal procurement specifications that set additional requirements (preferred sub-suppliers, documentation format, inspection regime). Send these with the RFQ if they apply.
• Compliance scope. Whether the supplier must hold particular certifications, or whether specific testing or documentation is required, is normally clarified during quotation. Where certification scope is critical to the project, state this at RFQ stage rather than during production.

Where the RFQ covers a completed low-voltage assembly, assembly-level standards may apply in addition to the fabrication requirements for the enclosure itself. IEC 61439 relates to low-voltage assemblies and should not be interpreted as a default certification claim for a standalone fabricated enclosure.

Note that certification scope, testing arrangements and which party is responsible for documentation are typically confirmed per inquiry. Buyers should not assume specific certifications are included with the quotation unless they have been requested.

13. Inspection, testing and acceptance

Inspection and acceptance define how the finished enclosure is verified before shipment. For custom enclosures, the inspection regime is part of the RFQ scope — not an afterthought agreed during production. Clear acceptance criteria reduce post-shipment disputes and protect both parties.

• Pre-production. Material certificates, gauge reports, sample fabrications or sub-assemblies. Confirms that the agreed materials and tooling are being used.
• In-process. Dimensional checks, weld inspections, surface-finish acceptance. Confirms the cabinet matches the approved drawings during production.
• Pre-shipment. Function test (where the cabinet contains electrical assembly), insulation / continuity test (where applicable), Factory Acceptance Test (FAT), visual inspection against the approved sample.
• Documentation package. Test reports, material certificates, packing list, commercial invoice, certificate of origin, shipping marks. Often required for import clearance and warranty records.
• Inspection presence. Buyer on-site presence, independent third-party inspection, supplier self-certification. Each option has different cost and scheduling implications.

For most custom-enclosure projects, a clear pre-shipment inspection regime (with documentation retained on file) is the practical minimum. Where the project risk profile warrants it, a third-party inspection or buyer presence is added during quotation clarification.

14. Example RFQ — illustrative only

Project reference: EXAMPLE-ENCLOSURE-001

The purpose of the example is not to prescribe technical values. It shows how known requirements, buyer-defined requirements and parameters still requiring clarification can be separated clearly before the RFQ is submitted.

Frequently asked questions