Start with the panel line-up
Lay out the panels as they will stand, usually in one or two rows. The length of the room is the sum of the panel widths in the longest row, plus space at each end for access and future panels. Leaving room for one or two spare sections is simple at the design stage and very expensive later.
Group panels by function and cable direction so that incoming and outgoing cables do not cross unnecessarily, and so that the heaviest panels sit where the floor and foundation are designed for them.
- —List every panel with width, depth, height and weight.
- —Mark which panels need rear access or top clearance.
- —Show future panels as dotted sections at the end of each row.
- —Note any panels delivered later, so an equipment door is placed accordingly.
Width: panel depth plus clearances
Width is set by panel depth, the clearance in front for operation and withdrawal of breakers, and any clearance behind for rear access. Draw-out switchgear usually needs a generous front aisle for the breaker truck; panels with rear access need a rear aisle too.
| Layout | What sets the width | Typical use |
|---|---|---|
| Single row, front access only | Panel depth + front aisle | Compact PCC/MCC rooms, wall-standing panels |
| Single row, front and rear access | Rear aisle + panel depth + front aisle | Switchgear needing rear cable termination |
| Two rows facing each other | Two panel depths + shared central aisle | Larger line-ups in a wider module |
| Two rows back to back | Two panel depths + two front aisles | Where rear access is not needed |
Height: panels, cable trays and services
Internal height must clear the tallest panel plus any top-mounted items such as arc ducts, busbar chambers or cable trays, then leave room for lighting, fire detectors and HVAC ducting. If breakers or components are lifted out through the top, allow for that too.
Overall external height is then internal height plus the roof build-up, the floor or skid depth and any rooftop HVAC or canopy. That external figure, sitting on the trailer deck, is what must pass under bridges and wires on the way to site, so it should be checked before the design is frozen.
Cable trench, false floor or raised skid
- —Cable trench in the plinth below the panels: simple, but fixes the layout early and must be kept dry.
- —False floor within the enclosure: flexible cable routing, adds internal height to the overall envelope.
- —Raised skid on pedestals: cables enter from below through the skid, with space beneath for bending radius; common for relocatable units.
Whatever the method, the bending radius of the largest cables sets the minimum depth, and entry openings should be sealed after cabling.
Doors, exits and getting equipment in
Door positions are part of sizing, not an afterthought. A long panel room usually needs an exit at each end so that nobody is ever trapped behind a faulted panel, and the escape route should follow the requirements your project applies. At least one opening, often a double door or a removable panel, must be large enough to bring in the largest panel or transformer if equipment is installed or replaced on site.
- —Place main doors at the ends of aisles, not in the middle of a panel row.
- —Check door swing against aisle width so an open door does not block the escape route.
- —Allow a landing and steps or a ramp outside each door, sized for the plinth height.
- —Keep space outside the equipment door for a forklift or pallet truck.
Weight, floor and lifting
Panel weights shape the structure as much as their dimensions do. The skid and floor are designed for the heaviest panels and the point loads under their base frames, and for the forces during lifting and transport if panels travel installed. Lifting points are positioned around the loaded centre of gravity, which is rarely the centre of the room once panels are in place.
Send weights with the panel schedule, even if they are estimates. They determine skid sections, the trailer, the crane and the foundation, and a late increase in panel weight can ripple through all four.
The transport envelope
Everything above has to travel by road. Width is usually the hardest limit: past a certain width a load becomes over-dimensional, needing permits, escorts and restricted travel times. Height is limited by bridges, overhead lines and the trailer deck height. Weight is limited by the trailer, the route and the crane at site.
Check the route early with a transporter, including the last few kilometres to site. A module that fits the highway but not the village road is not a solution.
When to split into modules
When the room exceeds the transport envelope, it is built as two or more modules that are joined on site. Splits are best placed between panel sections, not through them, with a sealed joint, continuous earthing and planned cable interconnections across the joint. Each module is lifted separately, so the crane can be smaller too.
Share your panel schedule, GA drawings and site location, and we can propose a room size, module split and transport plan to match.