An obsolete device family, a fault level that has climbed, or one feeder too few. Each turns an old board into a sourcing problem. Price matters less than how the switchgear suppliers and panel builders you shortlist handle the work around the new equipment.
Key takeaways
- Seven stages run from duty schedule to signed handover file. Each one changes what the job costs and who carries the risk.
- Quote from a duty schedule, never from the old nameplate. The frame size and the bar follow the five-year load.
- Build form and enclosure class are tender decisions. Leave them until after the order and the agreed price stops meaning anything.
- Ask switchgear suppliers for the verification route in writing: design verification, routine test record and spare parts horizon, all named.
- Score bids on capability and outage hours: the cheapest total usually carries the largest unstated assumption.
Freeze the duty before you freeze the equipment
The first stage is a duty schedule, not a shopping list. Record the present load on every way and the load you expect in five years.
Add the fault level at the electrical switch gear upstream and the ambient temperature in the switchroom. Those four numbers decide the frame size, the bar cross-section and the device rating.
Most buyers skip this and quote from the old nameplate. That works until a line is added. Then the bar becomes the bottleneck, not the devices.
Fix the interface before anyone quotes a price
The second stage lists what has to stay. A bidder who has not seen those items cannot price the fitting work.
- Cable sizes, and whether the existing lugs will reach the new terminals
- Floor footprint, and the aisle in front of the doors
- Earthing and bonding, which rarely matches the arrangement you are buying
- Capacity of the incoming supply, and the space left above the line-up
Footprint is where quotations drift apart. A like-for-like low voltage switchgear line-up often fits the same floor. A deeper frame can steal 200 mm from an aisle that is already tight.
Industrial electrical switchgear rarely fails on the electrical side. The room around it fails first, through a damp wall, a blocked aisle or a cable trench full of debris.
Everything downstream inherits your decisions. A power distribution board fed from this assembly loses discrimination when the new incomer settings move.
Decide the build form and the enclosure class early
The third stage fixes how each way is built. There are only two answers, and the duty tells you which one you want.
Where a drawer pays for itself
Withdrawable switchgear puts each feeder in a compartment that swaps without touching the bar.
A failed feeder changes over in about 15 minutes instead of a four-hour isolation. That premium is wasted on a board where nothing ever moves.
| Point of comparison | Drawer pattern | Fixed pattern |
|---|---|---|
| Responding to a device fault | Swap the compartment | Isolate the whole section |
| Outage per changeover | 15-30 minutes | 2-4 hours |
| Ways per metre of switchroom | Fewer | More |
| Cost per outgoing way | Higher | Roughly 15-30% lower |
| Spares you must hold | Drawer and chassis | Device only |
| Where it suits best | Feeders that trip or change often | Lighting, small power, steady loads |
A fixed switchgear frame bolts the devices in place and leaves them there. It suits industrial electrical switchgear where loads change slowly and floor space is short.
Enclosure class follows the same logic. Indoor boards are rarely the problem. Outdoor switchgear in a kiosk asks a harder question about the roof, the gaskets and the paint.
Write the verification requirement into the tender
The fourth stage asks how the finished assembly will be shown to comply. An assembly can be verified by design, by test, or by a combination of the two.
The tender should name which route you will accept and which records come with it. The low voltage electrical switchgear already on site carries a verification file. A structural change takes the work outside it.
Ask the bidder what the extended board will be verified against. Get that answer in writing. That is the point where a power distribution switchgear retrofit stops being a device change and becomes a new build.
Name the standard rather than the brand. Assembly design and verification sit under IEC 61439, which covers the whole assembly rather than the devices inside it.
Joints, supports and phase identification
Bar work is where a custom build separates from a device swap. Look for colour coded phase blocks and a support at every change of direction.
Every joint should carry a torque mark from the day it was tightened. A marked joint can be checked later without opening the whole section.
Score the bids on capability, not on the total
The fifth stage turns the returns from switchgear suppliers into a ranked list. The lowest number is rarely the best offer. The cheapest bid usually leaves out the survey, the temporary supply and the re-testing.
Four things a bidder should be able to show
| Criterion | Weight | What good looks like |
|---|---|---|
| Duty understood | 20% | They ask for the five-year load, not just the old nameplate |
| Verification route stated | 20% | Named before the price, not after the order |
| Outage hours per feeder | 20% | A figure per way, with the temporary supply included |
| Build evidence | 20% | Bar fabrication, test bay and torque records all in house |
| Spares and drawings | 10% | Years of availability, and a redrawn single-line diagram |
| Price | 10% | A total you can compare once the other five are level |
Capability shows up downstream as well. The sub main board fed from this assembly must be re-rated or re-set at the same time. Otherwise the discrimination you paid for disappears.
Custom switchgear manufacturers carry this capability in house. That is why they cost more per way than a stockist. A reseller can only pass the question back to whoever built the assembly.
Phase the changeover around the plant calendar
The sixth stage belongs to the plant, not the supplier. Retrofit work is sequenced by feeder rather than by board. Production can survive the loss of one section and rarely the loss of all.
Land the new incomer and transfer the load before you strip anything. Done in that order, every switchgear panel stays fed through the changeover. The plant keeps a live path at each step.
Budget the hours honestly. A three-way compartment swap takes four to six hours with the section isolated. Re-testing costs another half day.
Where the site has no spare feed at all, the work moves to the next planned shutdown. That is a planning problem. An low voltage distribution board that cannot be split into sections turns it into a production risk.
Demand keeps climbing across most of Africa, the Gulf and Southeast Asia. The International Energy Agency publishes that growth every year. A board already short of ways will not wait for a convenient shutdown.
Close the contract file before the last panel is energised
The seventh stage is paperwork, and it is the one most often left undone. Four records have to be produced while the board is open. None of them can be rebuilt six months later.
The as-built single-line diagram, the routine test report, the torque values used on every joint and the spare parts list. A supplier working to ISO 9001 files those records against a serial number.
Ask for the file format as well as the file. A drawing that exists only on paper will be redrawn by the next contractor, and every redraw introduces a mistake.
That is the difference between a finished project and a repair you repeat. A retrofit ends when the file is signed, not when the board is energised.
Frequently asked questions
How do I choose between switchgear suppliers for an old installation?
What should a retrofit tender document contain?
How many supplier visits should I expect before award?
Can a retrofit be priced from photographs alone?
Who owns the design verification after the board is extended?
How long should spare parts stay available for a new section?
What lead time is reasonable for a custom retrofit section?
Does a retrofit need a fresh short-circuit study?
Final thoughts
Fix the duty, the interface and the verification route before you ask for a price. Those three decisions are what make the returns comparable. Send Giantele the load schedule, the fault level and the existing pitch for a scoped proposal.
Writing a retrofit tender?
Send the load schedule, the fault level and the aisle width. Giantele engineers return a proposal that names the verification route before the price.
