Lightning protection on a building has three parts: an air terminal on top to receive the strike, down conductors to carry it, and an earthing system to disperse it into the ground. The choice that causes most debate is the air terminal: a conventional rod, or an Early Streamer Emission (ESE) device. Here is how they differ and how to choose.
Conventional air terminals
Conventional terminals are rods or multi-spike heads, such as our copper bonded, brass copper coated and pure copper arresters. They are placed so that the whole structure falls within their protected zone, which the designer works out using the methods in IEC 62305, adopted in India as IS/IEC 62305. On a large roof this can mean many terminals linked by roof conductors.
ESE air terminals
An ESE terminal is designed to send up a connecting leader earlier than a plain rod. Its makers rate each model for a larger protection radius, so a single terminal on a mast can cover a wide area. ESE systems are designed to the French standard NF C 17-102.
The honest picture
ESE terminals are widely used in India, especially on large flat roofs, open plants and solar fields, because one terminal replaces many rods. However, IEC 62305 does not give ESE devices any larger protection zone than a conventional rod, and some consultants and approving authorities specify conventional systems only. Neither choice is wrong in itself; what matters is that the system is designed to a recognised standard and accepted by whoever approves your project.
Comparing the two
| Conventional | ESE | |
|---|---|---|
| Design standard | IEC 62305 (IS/IEC 62305) | NF C 17-102 |
| Terminals needed on a large roof | Several, with roof conductors | Often one or a few |
| Visual impact | Several small rods | One taller mast |
| Acceptance | Universal | Check with your consultant or authority |
| Cost | Rises with roof size | Higher per terminal, fewer terminals |
How to decide
- Check the specification first. If the project or authority names a standard, follow it.
- Small or tall, narrow buildings: conventional rods are usually simple and economical.
- Large flat roofs, open yards and solar plants: compare a conventional design with an ESE design, including conductors and labour, not just the terminal price.
- Either way, the earthing matters as much as the terminal. Each down conductor needs a low-resistance earth, and the earths should be bonded together.
The parts people forget
- Down conductors sized and fixed properly, following the shortest practical route.
- A test joint on each down conductor, so the earth can be checked without breaking anything.
- Earth pits with covers, so they can be tested. Chemical earthing keeps the resistance steady, as our guide on choosing an earthing method explains.
- A lightning strike counter, so you know when the system has been hit and should be inspected.
- Surge protection on incoming power and data lines, because a direct strike on the building also sends surges into its wiring.
Frequently asked questions
How high should a lightning arrester be mounted?
The height comes from the protection design for the building. Our G.I masts come in 3 m, 5 m and 6 m heights to raise the air terminal to the designed level.
Does an ESE system still need earth pits?
Yes. Every lightning protection system, ESE or conventional, needs down conductors and a low-resistance earthing system to carry the strike into the ground.
Is ESE accepted in India?
ESE terminals are widely used in India, but acceptance depends on the project specification, the consultant and the approving authority. Check with them before choosing.
We supply both types of air terminal with masts, accessories, down conductor material and earthing, and we install complete systems. Send us your building drawings for a design and quotation.