Every panel drawing shows an earth bar running the length of the assembly, and every panel has one. Far fewer have a protective circuit that is actually continuous everywhere it needs to be. The usual reason is something that was applied deliberately.

Earthing and bonding are not the same thing

Earthing connects the installation to the general mass of earth. Bonding connects exposed conductive parts to each other, so they cannot sit at different potentials while a fault is being cleared.

A panel can be properly earthed at the incomer and still have doors, gland plates and removable covers electrically floating, whatever its form separation.

Where continuity breaks

Powder coating is a dielectric. A 60 to 70 micron film is exactly what stops the enclosure corroding, and exactly what stops a bolted joint conducting. An earth stud tightened onto a coated surface can measure open circuit and look perfectly correct.

Hinges are not conductors. A hinge is a mechanical bearing. Its resistance under fault current is unpredictable and changes as it wears. A flexible braid between door and frame is a designed path; a hinge is an assumption.

Gland plates get removed. They are the part most likely to be taken off and refitted at site by someone who has no reason to think about the earth path.

What to check before energising

  • Paint masked or removed at every earthing point, with serrated washers
  • Flexible bonding braid on every door and hinged cover that carries equipment
  • Bonding strap across removable gland plates
  • Continuity measured from each exposed part to the main earth bar, not assumed
  • Protective conductor cross-section sized against prospective fault current, not habit

Continuity is cheap to verify on the shop floor and expensive to discover at site.

Frequently asked questions

If powder coating is an insulator, how does the panel get earthed?

Through metal to metal contact that is created deliberately. Paint is removed at the earthing points and at the joints between doors, gland plates and the frame, and serrated washers or earth straps hold the connection. The coating protects everything else.

Does scraping the paint at every joint weaken corrosion protection?

It would if the bare metal were left exposed. The cleaned area is kept small, the fastener covers it, and in corrosive environments the joint is made with a bonding strap and the bare area sealed. The alternative, trusting paint to conduct, fails a continuity test.

What coating thickness is right?

For an indoor panel, 60 to 80 microns is typical, and outdoor enclosures go higher. Too thin and coverage is uneven at the edges. Too thick and the coating chips at corners and around fasteners.

How is earth continuity actually verified?

With a low resistance ohmmeter between the main earth bar and every separately mounted metal part: each door, the gland plate, the mounting plate, the cable alley cover. A reading that drifts upward on a hinged door usually means the hinge is being relied on instead of a strap.