When I have a lightning protection system installed on a building roof top , what is the best way to bond the electrical equipment on the roof? Is it ok to directly bond it to the down counductor of the LPS? or different measures should be taken?

Lets say I have multiple air-condition units on the roof, how can I safely bond them to the lightning protection system. With bonding here I mean bonding the metalic body of the units.

Lets say if I bond the body directly to the down conductor, in case of a lightning strike will current pass through the unit and destroy the electronics inside it or will it only follow to the down conductor and to the ground?


closed as off-topic by DoxyLover, pipe, Voltage Spike, Finbarr, Marla Nov 10 '18 at 18:23

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – DoxyLover, pipe, Voltage Spike, Finbarr, Marla
If this question can be reworded to fit the rules in the help center, please edit the question.


how can I safely bond them ...

Safely for what? For the units themselves against lightning? Or for humans operating or servicing the units? Or for the building, against fire risk?

You have no choice but to bond them correctly for humans and for the building, which means to the protective ground that's run with their power supply.

There may be other regulations in your area about cross-grounding of the electrical system protective ground and the LPS. Read that carefully before you do anything of that nature on the roof. It might be prohibited, it might be mandated. You must follow your local electrical code.

Why follow your local code, when the laws of physics are universal? Because the regulations are local, and if you don't follow them, the insurance company you thought were going to pay up when your building burns down are going to use any deviation from the local installation regulations to wriggle out of paying your claim. You may think you know better than the local regulations about lightning protection, and you may well do. But what matters, the survival of an AC unit against rare lightning, or your finances against rare building insurance claims? Not your building? The building owner may sue you if you've made his building non-compliant with local regulations.

  • \$\begingroup\$ Local electrical code? This statement im reading in many places and never failed to confuse me. Electricity and lightning always obeys the law of physics whether its on USA or planet xyz. As such why we have local codes goes specific for each country? \$\endgroup\$ – soosai steven Oct 24 '18 at 8:21
  • 1
    \$\begingroup\$ @soosaisteven Why do we have different vehicle operation laws in different countries? \$\endgroup\$ – R Drast Oct 24 '18 at 9:03
  • \$\begingroup\$ @RDrast In some country people drive on left and some other country they drive on right. But electricity always flows from high potential to lower potential in entire universe. \$\endgroup\$ – soosai steven Oct 24 '18 at 9:08
  • \$\begingroup\$ @soosaisteven Electricity and lighning obey the same physical laws. Unfortunately, lawyers obey local laws, and insurance companies use any means they can to avoid paying out money on a claim. Let's say your building burns down, with the fault starting in the AC units on the roof. If your wiring doesn't follow local regulations, for instance conductor diameter, or maximum link length, or whether you link them at all, then you may not get your claim paid out. \$\endgroup\$ – Neil_UK Oct 24 '18 at 9:18
  • \$\begingroup\$ The resistance and inductance of earth bonding varies widely from commercial to internal and external units , regional water levels and soil types. \$\endgroup\$ – Sunnyskyguy EE75 Oct 24 '18 at 18:56

Not the answer you're looking for? Browse other questions tagged or ask your own question.