Building Custom Control Panels: From Design to Delivery

A control panel is not a complicated thing conceptually. It is a box containing the electrical and electronic components that control a machine or process. But building one properly, to standard, on time, and within budget, requires a process that is more involved than it might appear from the outside.

Here is how we approach it from initial enquiry to dispatch.

Schematic Design

Every panel build starts with a schematic. We design in AutoCAD Electrical, which provides library-based symbol insertion, automatic wire numbering, and cross-referencing between sheets. For larger projects or where the client uses EPlan, we can work in that environment as well.

The schematic defines every circuit, every component, every terminal, and every cable connection. It is the definitive engineering document for the panel. Getting the schematic right before starting the build avoids changes on the shop floor, which are always more expensive and time-consuming than changes on a drawing.

At this stage, we also produce the panel layout drawing showing the physical arrangement of components within the enclosure. This is where thermal calculations are done, clearances are verified, and cable routing is planned.

Component Selection and Procurement

Component selection is driven by the application requirements, the client's preferred brands (if any), and availability. We check availability before finalising the design and flag any long-lead items early.

For motor control, we predominantly use Siemens SIRIUS contactors and overloads or Allen-Bradley Bulletin 100/500 series, depending on the PLC platform. Circuit protection is typically Schneider or ABB. Terminal blocks are Weidmuller or Phoenix Contact. We maintain stock of commonly used items to avoid delays on standard builds.

Panel Build

The physical build follows a defined sequence. The enclosure is prepared: mounting plates are drilled and tapped (or fitted with DIN rail and trunking as the layout requires), gland plates are machined, and any enclosure modifications are completed before components are mounted.

Components are fitted according to the layout drawing. DIN rail mounted devices are straightforward. Larger items like drives, transformers, and main switches require specific mounting arrangements and thermal spacing.

Wiring follows the schematic exactly. We use ferrule-crimped conductors throughout, with wire colours conforming to BS 7671 and the applicable machinery standard (BS EN 60204-1). Cable trunking is sized for the conductor count with allowance for additional wiring if the panel may be modified in the future. Every conductor is labelled at both ends.

Testing

Before a panel leaves the workshop, it goes through a defined test procedure:

Visual inspection. Component placement matches the layout drawing. Wiring matches the schematic. Labels are correct and legible. Mechanical fixings are secure. Cable trunking lids close properly.

Continuity testing. Every circuit is verified end-to-end against the schematic. This confirms that the wiring is correct and all connections are made.

Insulation resistance. Tested at 500V DC between live conductors and earth. This verifies there are no insulation faults or inadvertent contact between circuits.

Functional testing. Where possible, the panel is powered up and functionally tested in the workshop. PLC programmes are loaded, HMI screens are verified, and basic I/O checks are performed.

All test results are recorded in the panel documentation pack.

Documentation and Dispatch

Every panel is delivered with a documentation pack containing the finalised schematic drawings, panel layout drawings, component data sheets, test certificates, and a declaration of conformity. For panels built to BS EN 61439, the design verification records are included.

Panels are packaged for transport with covers over all openings and cable entries sealed. Loose items (operator stations, pendant cables, external sensors) are packaged separately and clearly labelled.

The panel is one part of the system. But it is the part that everything else connects to, so getting it right matters.