A useful specification gives every tenderer the same electrical, physical and commercial basis. Include the single-line diagram, schedules, supply conditions and agreed verification requirements, then make unresolved inputs and responsibilities explicit.
Define the board and the project
Start with the site, board designation, purpose and current document revisions. Identify whether you need an MSB, MCC, distribution board or control panel. State whether the project is new work, an addition or a replacement.
A specification should explain what is included in the supply: the assembly, protection devices, metering, control hardware, software, site installation, commissioning and handover documents. These are separate scope decisions. Do not assume that a manufacturing price includes all site or integration work.
The technical schedule
| Item | What to define |
|---|---|
| Supply | Voltage, frequency, phases, earthing arrangement and all possible sources. |
| Current | Design load, operating duty, diversity basis and planned growth. |
| Fault duty | Study reference, prospective fault conditions, required withstand and protection basis. |
| Circuits | Quantity, load, device, rating, cable details and motor starting method where applicable. |
| Internal layout | Required form, access, terminals, fixed or withdrawable equipment and spare ways. |
| Environment | IP requirement, ambient temperature, corrosion, contamination and cooling. |
| Controls | Metering, interlocks, I/O, communications, remote functions and responsibility boundaries. |
Treat fault rating, internal separation and IP protection as distinct requirements. A high value in one category does not establish performance in another.
Specify spare capacity in three separate ways
“Allow 20% spare” can produce very different quotations. One tenderer may allow empty space, another may fit unused breakers, and a third may increase the incoming current rating. Describe the intended future circuits so the allowance is useful.
| Allowance | Example wording for discussion |
|---|---|
| Physical space | Reserve defined space for the identified future feeder types, including cable access. |
| Equipped spare ways | List which spare devices are installed now, with their ratings and termination requirements. |
| Electrical capacity | State the future load scenario to be considered for busbars, incomer, supply and thermal design. |
These examples show how to frame the enquiry, not a recommended allowance for every board. A future motor feeder may need different space from a distribution feeder of the same current. The designer should establish the growth scenario and its effect on the wider installation.
Write the operating modes down
A single rating can hide several different duties. Identify normal supply, standby supply, bus-coupled operation, maintenance configurations and any other intended mode. Show which sources can run together and which combinations must be prevented.
This information affects interlocks, control supplies, protection and the load each section may have to carry. State whether transfers are manual or automatic and who provides the functional description. If the arrangement is still being developed, mark it as a design decision with an owner and required date.
Physical and site requirements
Include available footprint and height, front or rear access, cable-entry direction, termination sizes and transport splits. For a replacement, provide current photographs and verified dimensions. Doorways, corridors, stairs and lifting access can determine whether a complete board will reach its final position.
Nominate who supplies supports, plinths, seismic restraints and any building work. List shutdown constraints, temporary supplies and changeover interfaces. These details belong in the enquiry, before the board layout is fixed.
Standards and evidence
Nominate the applicable assembly standard, part, edition and project requirements. IEC publication updates, AS/NZS adoption and New Zealand regulatory citation are different matters. Our standards guide helps frame that discussion.
As at September 2026, New Zealand is in the transition described by WorkSafe following the November 2025 regulatory amendments. AS/NZS 3000:2018, including the cited amendments and New Zealand modifications, is part of that transition. Confirm the applicable basis for the project’s start date and scope with the responsible designer.
Agree the design-verification evidence, routine-verification records, functional tests and any witnessed factory acceptance test. Set a document register covering drawings, schedules, settings, manuals and outstanding items. A witnessed FAT does not replace the installation’s site testing or certification.
Review a tender response systematically
Compare the returned proposal against the specification by section. Ask for a departure schedule that identifies the original requirement, the proposed alternative and the effect on function, evidence, access, programme and price.
Do not approve a substitution only because the device has the same ampere rating. Its dimensions, breaking capacity, losses, terminals, trip functions or communications may differ. The assembly manufacturer needs to assess the effect on the proposed construction.
For a coordinated MSB and MCC package, check that the boundaries meet: supply feeders, controls, cable terminations and testing should not disappear between the two scopes. Use the MSB versus MCC comparison to clarify their different roles.
A real example of these scope boundaries is CWS’s Frimley and Eastbourne package. CWS supplied the MSBs, MCCs, distribution and control panels to ICE Electrical, including panel wiring, I/O termination and FAT. Software programming and site commissioning sat with the project’s control-system integrators. A specification should make that division explicit.
Commercial clarity before issue
Send the same schedule and scope boundaries with each tender enquiry. For the assembly itself, use the relevant MSB manufacturing or MCC manufacturing page. If the drawings still need developing, discuss a defined switchboard design and documentation scope before treating the brief as ready for manufacture.
- List assumptions and items still to be confirmed.
- Identify acceptable alternatives and the approval process for substitutions.
- Separate spare physical space, spare circuits and spare electrical capacity.
- Give required approval, FAT, dispatch and site dates.
- State packaging, delivery, unloading and storage responsibilities.
- Identify the person authorised to approve drawings and changes.
Send the same revision set to each tenderer and assess inclusions before comparing totals. CWS can discuss manufacturing requirements while the design is being developed. Start with the quotation information guide if you are assembling your first enquiry.
Questions we hear
Can I quote while some inputs are still open?
Yes, an indicative proposal may be possible if the assumptions and exclusions are clear. Resolve the outstanding design basis before manufacture.
How much spare capacity should I specify?
Base it on the expected additions. Spare space, spare ways and spare current capacity are different, and all may be needed.
Is a circuit schedule enough for a complete specification?
No. It identifies the circuits, but the supply basis, construction, environmental conditions, controls, verification and installation constraints still need to be defined.