Direct Answer

Should the roof use a rod, a tape, or a mesh? The answer: the air-termination form follows the building outline — protruding parts (roof ridges, tower tops) use air-termination rods, flat roofs use air-termination tapes along the edges, and large or important roofs use air-termination meshes. The protection range is verified by the rolling-sphere method (taking the sphere radius by the lightning-protection class), ensuring protected objects do not fall outside the range — it is not "the higher the rod, the better".

At a plant, a high rod was erected at the center of the roof following a drawing, ignoring a large roof-mounted unit on the far side of the ridge: by the rolling-sphere calculation, that unit lay outside the protection range, and it was struck twice in the storm season. After adding a tape along the ridge plus local protection for the unit, the problem disappeared. The key distinction: air termination is not "the higher, the better" — the form is chosen by the building shape (rod/tape/mesh), the range is verified by the rolling sphere, and misses usually come from "copying the drawing without looking at the shape".

Why:

  • Three forms: the rod covers protrusions, the tape covers flat edges, the mesh covers large areas;
  • The rolling sphere: the radius is taken by the lightning-protection class;
  • Protected objects: must lie within the protection range;
  • Special treatment: protrusions/antennas/PV panels are verified separately.

Key insight: "Choose the air-termination form by the building outline and verify the range by the rolling sphere — being high does not mean being protected; misses come from ignoring the shape."

At a park, solar panels were added to the roof without re-verifying the air-termination coverage, and a strike damaged several modules. After re-calculating the rolling-sphere range for the panel positions and adding tapes, the damage did not recur. Lesson: adding roof protrusions (PV/antennas) requires re-verifying the protection range — the old scheme does not automatically cover new objects.

1. The Applicable Parts of the Three Air-Termination Forms

Step one: where the rod, tape and mesh go.

Air-termination rod (mast):

  • For protruding parts: roof ridges, tower tops, water towers;
  • Single-point protection; the coverage is set by the height;
  • Priority on the highest protrusions;
  • Free-standing masts also work.

Air-termination tape:

  • For flat roofs: along ridges, eaves, parapets;
  • Laid along edges; line-type protection;
  • Large coverage, fitting the building;
  • The most common roof form.

Air-termination mesh:

  • For large/important roofs;
  • Laid in a grid; full coverage;
  • The mesh size follows the class;
  • For important buildings/special places.

Key insight: "The rod covers protrusions, the tape covers edges, the mesh covers large areas — the form follows the building outline, not an arbitrary rod."

2. The Rolling-Sphere Method and the Radius by Class

Step two: how the protection range is calculated.

The rolling-sphere principle:

  • A sphere of the rolling radius rolls along the ground;
  • It is tangent to the air terminations and the ground;
  • The zone inside the sphere is the protection range;
  • The untouched zone is the blind area.

The radius by class:

  • Class I: rolling radius 30 m;
  • Class II: 45 m;
  • Class III: 60 m;
  • The higher the class, the smaller the radius, the stricter the protection.

The effect of the value:

  • A smaller radius → a narrower range;
  • Class I is the strictest;
  • The higher the rod, the wider the single coverage but the easier to miss at the edges;
  • Taking the radius by class is key.

Key insight: "The rolling sphere rolls along the ground and cuts out the protection range — the radius follows the class (I: 30 m, II: 45 m, III: 60 m); a higher class means stricter protection."

3. How Protected Objects Fall within the Range

Step three: how to confirm the protection holds.

The calculation steps:

  • Determine the building's class (connecting to KD-0179);
  • Take the corresponding rolling radius;
  • Roll the sphere along the building outline;
  • See whether the protected object is inside.

Common misses:

  • A protrusion outside the rod's range;
  • No tape at the roof edges;
  • Too large a mesh on a big roof;
  • New objects not re-verified.

How to confirm:

  • Calculate by the range diagram;
  • Check every protected object point by point;
  • Add air terminations where there are blind zones;
  • Double-verify with software/diagrams.

Key insight: "Every protected object must lie inside the sphere — check point by point and add where there are blind zones; 'roughly within range' is where misses happen."

4. Special Treatment of Protrusions, Antennas and Solar Panels

Step four: what to do about new things on the roof.

Types of protrusions:

  • Antennas/lightning arresters/exhaust pipes;
  • Solar panels/PV supports;
  • Cooling towers/water tanks/decorations;
  • Protrusions higher than the tape.

The treatment principles:

  • Higher than the tape → add separate protection;
  • Solar panels are conductors → bring them into the air-termination system;
  • Antennas need side-flash/equipotential protection;
  • New protrusions must be re-verified.

Common errors:

  • Adding PV without re-verifying the range;
  • Protruding metal not connected to the down-conductor;
  • Insufficient clearance between antennas and the tape;
  • Believing "a rod on the roof covers everything".

Key insight: "New roof protrusions (PV/antennas) must be re-verified and brought into the system — the old protection range does not automatically cover new objects."

5. The Connection Requirements between Air Terminations and Down-Conductors

Step five: the air-termination → down-conductor → earthing chain.

Connection requirements:

  • Reliable connection between the air terminations and the down-conductors;
  • Multiple down-conductors for shunting (connecting to KD-0182);
  • Welded/mechanical reliability at the joints;
  • Electrical continuity and low impedance.

Counterattack prevention:

  • Keep the clearance between the down-conductors and protected objects;
  • Use equipotential bonding when it cannot be met;
  • The down-conductor potential is high when carrying current;
  • The whole system is continuously connected.

Practice verification:

  • Verify the connections by continuity testing;
  • Monitor online with the FR Earth-Resistance Monitor;
  • Recheck the connections after strikes;
  • Repair abnormalities in time.

Key insight: "Air termination → down-conductor → earthing is one chain — reliable connection, electrical continuity, measurable continuity; a break in any link makes it all useless."

6. Product Implementation: Air Termination and Earthing as One

WeiWuLian products manage the air-termination system:

  • FR Earth-Resistance Monitor: online monitoring of the earthing system;
  • Continuity recheck: verifying the air-termination-down-conductor-earthing connections;
  • Strike-event correlation: rechecking the system after strikes;
  • Data loop: digitizing the range and the state.

The design principle in one sentence: "Form by the outline, range by the rolling sphere, connection by continuity — close the three and manage the air-termination system with data."

7. Common Misjudgments

  1. "The higher, the better": ignoring edge misses. Result: a protrusion outside the protection. Correct: choose the form by the shape and verify by the rolling sphere.
  2. "Copy the rod from the drawing": ignoring the building shape. Result: misses/waste. Correct: choose rod/tape/mesh by the outline.
  3. "Take any radius": ignoring the class. Result: insufficient protection. Correct: take the radius by the class.
  4. "No need to recheck after adding PV": ignoring new objects. Result: damaged modules. Correct: re-verify and add protection.
  5. "Connect it loosely": ignoring electrical continuity. Result: a broken chain, failed protection. Correct: verify by continuity testing.

Scope and Limitations

This article explains the applicable parts of the three air-termination forms (rod/tape/mesh), rolling-sphere range calculation, protected-object confirmation, special treatment of protrusions, and the connection requirements with down-conductors, applicable to air-termination selection and range calculation. The exact rolling radii and layouts follow GB 50057-2010 and its revisions; this article explains only the selection logic and calculation method. All cases are anonymized (a plant, a park) and do not refer to any specific customer.