Three contracts meet at one cabinet

Switchboard installation reads as one line on a quotation. In practice three separate contracts meet at the same cabinet. They often meet for the first time on the morning the crate is opened.

The first contract builds and tests the cabinet. It ends when the unit is closed, labelled and packed.

The second contract bolts it down, pulls the cables and makes the joints. That firm is almost always local, because nobody sends a crew across a border to tighten bolts.

The third contract belongs to whoever supplies the generator or the transfer switch. It touches the cabinet at one terminal block and nowhere else.

That split appears in any industrial power system installation, whatever the size of the lineup.

Each contract is sound on its own. The joint between them is nobody's product, which is where the argument starts three weeks later.

An electrical panel builder can describe the whole chain and still be responsible for the first link only. Ask which links are in the price.

Bolted lugs

Every lug on this bar is a joint someone made.

Each one is a place where responsibility changes hands.

Who is standing on the floor when the crate opens

Three arrangements cover most projects. They differ in who carries the risk, not in who carries the spanner.

Supply only is the cheapest line and the largest risk. It also suits a plant with its own electrical department, which a later section covers.

Supervision sounds like the safe middle. It works when the supervisor arrives before the crate, not after the first gland is drilled.

The local partner model fails in one specific way. The partner is named in the offer and unnamed in the warranty. Nobody then owns a leak at the cable entry.

Pack the joints, not just the cabinet

The crate is the only part of the installation the works still controls. Anything left out becomes a purchase in your country, at your price, on your critical path.

Start with the jointing kit. Section bolts, shims and insulating barriers are made for one cabinet and cannot be bought locally.

Add a gland plate, undrilled, plus one spare. Add the torque schedule for every terminal, printed in newton metres, and a second copy inside the door pocket.

Keys and door retainers go in too, along with spare gaskets, touch-up paint and a fuse chart. Small items, and each one stops work when it is missing.

The paperwork travels with the metal. That means the as-built drawing and the routine test record required by IEC 61439. Add a wiring diagram in the language of the installing crew.

A crate is a transport decision before it is a packing decision. Splitting a lineup into sections changes what the crew has to reassemble. It also decides how many joints arrive open, so read transport of electrical equipment as a scope line.

Where it stands decides the enclosure

The enclosure is usually chosen before anyone has measured the room. That order is backwards, and the site pays for it.

Buyers arrive with a phrase instead of a question. One asks for a waterproof power enclosure, meaning a box that survives rain and a hose. The phrase describes a performance, not a material.

Another asks for a nema 4 cabinet. In the IEC scheme that is close to IP 66, dust-tight and protected against water jets from any direction.

A third asks for a nema 12 cabinet, which is the indoor version, close to IP 52. It keeps dust out and will not take a hose.

The two schemes do not map exactly. The number that crosses a border without argument is the IP code plus the test behind it.

Then there is the plainest phrase of all. An electric box cabinet can mean a wall-mounted board or a floor-standing lineup. Ask for dimensions and a rating instead of a noun.

For a site that is genuinely wet, an nema 4 outdoor enclosure is the search that finds the right pages. The installation still decides whether the rating survives.

Busbar taps

Rows of taps on one bar.

Each tap is a clamp someone has to torque.

The transfer switch has two owners

A generator power transfer switch is the only point where two suppliers' products share a terminal. That is why it is the joint that fails a commissioning test most often.

The switch needs a two-wire start signal from the generator controller. The generator needs to know when the mains is acceptable again. Neither signal appears on the other supplier's drawing by default.

Ask three questions before the order. Who supplies the control cable between the two cabinets. Whose diagram shows the interlock. Who tests the transfer with a real load.

In a hospital the window is short. A transfer in two to ten seconds is normal, and a mis-sequenced parallel connection is not survivable for the equipment.

Neutral and earth treatment decides more than the controller settings. Two sources bonded at two points create a loop that no test in the factory will reveal.

A page on the electrical transfer switch for generator is worth reading before the layout is frozen. Order the two cabinets together when you can.

When the plant brings its own electricians

Some buyers do not need a crew. They need a package that their own team can work from, and they judge a supplier on exactly that.

A plant that runs its own electrical department buys switchgear in power plant work differently. It asks for the single-line diagram, the isolation points and the switching schedule before it asks about price.

The reason is ownership. Inside a plant, electric power distribution is usually a ring or a mesh with a switching authority. That authority will not accept a cabinet without an approved schedule.

Most switchgear manufacturing companies are set up to answer labour questions. A plant asks document questions, and the two lists barely overlap.

This is the cheapest route when the team is strong. It is also the route that punishes a thin drawing set hardest, because nobody on site is paid to interpret.

Some plants want the sequence managed rather than the labour supplied. For those, project management services is the scope that fits. It buys coordination, not hands.

Electricity use is shifting the calculation as well. The IEA tracks industrial demand as a share of national load. A plant that installs for today's load usually reopens the board within a decade.

Inside the panel

Every conductor in the crate has to arrive with a number

1

The drawing is only half the map.A number sleeve on the wire is the other half, and it travels with the crate.

2

Ferrules survive a language change.A local crew reads numbers faster than it reads your prose.

3

Spare cores belong in the kit.One extra core per cable costs little and saves a week.

The money you hold until site acceptance

Retention is the only lever a buyer has when the works is not on site. Use it, and name the event that releases it.

Delivery is not that event. A cabinet in a wet room is not installed, and a signed delivery note proves only that a lorry arrived.

Site acceptance is a separate test. Check insulation resistance on every section and phase sequence at the incomer. Spot-check torque on a sample of joints, and photograph every sealed gland.

Add the settings as left, the interlock test and one real transfer with load on it. Those four items catch almost everything the factory could not.

A site acceptance sheet written before the work starts is a different document from one written afterwards. Draft it with the scope.

Two percentages are enough in most contracts. Release eighty percent at delivery and the rest at acceptance. Tie the second payment to documents rather than to opinion.

Nine lines that decide who owns each joint

A switchboard installation scope is one page, written by the buyer. It closes most of the gaps, and it is shorter than the specification behind it.

• Who supplies the gland plates, and in what material.
• Who owns the cable ladder between the wall and the cabinet.
• Which torque values are recorded, on how many joints.
• Who pays for a second visit when a part is missing.
• Which language the drawings and labels are written in.
• Who witnesses the insulation and interlock tests.
• What happens to packaging, pallets and transport frames.
• Which spare parts ship inside the crate rather than later.
• Whose signature releases the final payment.

The list costs nothing to write and settles most disputes before they exist. Send it with the enquiry, not with the complaint.

A quality system certified to ISO 9001 tells you a process is audited. The scope line tells you whether installation documents fall inside that process.

Frequently asked questions

Final thoughts

A cabinet is bought as a product and commissioned as an interface. The supplier controls the crate, the drawing and the labels, and very little else. Decide the joints before you order, and the installation stops being a surprise.