Switchboard upgrades in NZ: retrofit or replacement?

Separate three possible scopes

A condition assessment and clear operating requirements help establish which approach is sensible. Do not assume that a new breaker can be fitted solely because its frame size or current rating looks similar.

CWS’s dairy-processing ACB retrofit work provides a practical example of retaining an existing main switchboard while replacing obsolete breakers. The work represented covers 800 A to 3200 A breaker positions using Masterpact MTZ equipment and retrofit arrangements, planned around shutdown windows. It does not establish that another existing board is suitable for the same approach.

Collect the existing information

• Board tag, manufacturer, serial number, drawings and available verification records.
• Current load schedule, supply configuration and fault-study information.
• Component references, protection settings and evidence of obsolescence.
• Dimensions, cable routes, cable-entry positions and termination details.
• Condition reports, previous faults and known alterations.
• Access routes, lifting constraints, switchroom layout and available working space.

Photographs help establish the initial scope, but internal checks require safe access planned by competent electrical personnel. Record which dimensions and circuits have been verified and which still rely on old drawings.

Build a short decision record

The purpose is to make assumptions visible. A lower initial modification price may be less attractive if the retained equipment cannot support the planned future duty. Equally, replacement should have a clear basis rather than being triggered by age alone.

Check replacement-device compatibility beyond size

A replacement protective device may differ in terminal position, heat dissipation, operating mechanism, protective characteristics or required clearances. Its presence can affect the original arrangement even if it fits inside the available opening.

Establish the manufacturer-supported replacement route where one exists. Otherwise agree how the proposed modification and affected assembly characteristics will be assessed. Record the equipment references, revised drawings and evidence supporting the change.

For a real example of a defined replacement scope, see the ACB retrofit project. A previous project illustrates an approach; it does not establish that the same device or method is suitable for another board.

Check the effect of the change

Adding load or a new supply can affect current, fault duty, protection settings and thermal performance. New equipment can also affect separation, ventilation, access and cable clearances. Changes need a suitable assessment of the retained and modified assembly.

WorkSafe’s current guidance distinguishes repairs and existing installations from additions and alterations. An older board does not automatically require replacement just because a newer standard exists. Confirm the applicable regulatory and technical basis for the actual scope with the responsible designer.

Plan the outage before manufacture

Nominate who owns isolation, temporary power, removal, installation, site testing and permission to energise. Agree the critical loads, shutdown duration, sequence and contingency arrangements with operations.

Factory testing can reduce the work left to discover on site, but it does not prove that every existing cable, field device or control interface is correct. Keep site commissioning and installation verification in the programme.

Prepare the changeover and handover together

Before the outage, confirm the new equipment is ready, the required parts and resources are available, and the installation team has the approved drawings. Review cable identification, access, lifting, temporary arrangements and the sequence for restoring the agreed loads.

Set hold points for inspections and tests that must be completed before the next stage. Agree who can authorise energisation and what happens if a check fails or an existing condition differs from the survey. The contingency must be realistic for the actual site, not simply a note saying “revert if needed”.

At handover, update the circuit schedules, drawings, settings records and operating information for the work completed. Close out outstanding items with an owner and due date. The owner should be able to distinguish the new equipment, retained equipment and limits of the work without reconstructing the project from emails.

Send a scope that can be priced

For an industrial or commercial MSB replacement, send the available information to our main switchboard manufacturing team. For work on a retained assembly, start with switchboard maintenance and retrofit services. The cold-storage MSB upgrade provides a manufactured replacement example alongside the retrofit work discussed above.

Provide the existing information, reason for the change, required new duty, shutdown constraints and documentation requirements. Mark exclusions and uncertainties. Where a site survey is needed, agree its scope and deliverables before relying on an installation price.

For the manufacturing side, see main switchboards and motor control centres. For planned remedial work, discuss the board and available records with the maintenance and retrofit team. Agree the assessment scope and its limits with the responsible project team.