Bonding Roof AC equipment to Lightning Protection System

[SAFI_GH]

Our Engineer is requesting to Bond Roof AC equipment to Lightning protection system i.e extending the copper tape that is installed around the roof parapet and connect it to the body of AC equipment (roof compressor for split unit system) on Roof.

I am trying to convince him that putting this equipment under coverage of air terminals is enough. In addition, I am not sure whether this is safe for equipment or even allowed in the code.

Can you advise whether this has been tackled anywhere in the code and do you support my statement that it is not advisable to do so?

Thank you

 

[augie47]

It appears from 250.106 that the answer may lie in NFPA 780. Reading between the lines on InfoNote2 I would say such a connection is prohibited but the real answer would be in the noted publication and I don't have that.

 

[don_resqcapt19]

There are requirements in 780 that require some equipment to be bonded to the lighting protection system conductors. It has been some time since I worked on a project where lighting protection was installed, but as I recall all of the equipment on the roof was bonded to the lighting protection system.

 

[LightningProtectionDesign]

Per the NFPA 780 all metal objects providing a path to ground that are within 6' of the lightning protection conductor must be bonded back to the system. It does not matter if the equipment is in the zone of protection, it will still need to be bonded back to the system.

 

[augie47]

Per the NFPA 780 all metal objects providing a path to ground that are within 6' of the lightning protection conductor must be bonded back to the system. It does not matter if the equipment is in the zone of protection, it will still need to be bonded back to the system.

Thanks !

 

[SAFI_GH]

Per the NFPA 780 all metal objects providing a path to ground that are within 6' of the lightning protection conductor must be bonded back to the system. It does not matter if the equipment is in the zone of protection, it will still need to be bonded back to the system.

After digging out more details about the project. I found the following information that I see as contradicting:


1-A note on the drawing stating: ALL METALLIC EQUIPMENTS AND EXPOSED METALLIC OBJECTS ARE TO BE BONDED TO THE SYSTEM

2- A section in the specs:

1. All metallic parts protruding outside the extended air termination network (e.g. balcony hand rails etc.) shall be connected to the air termination using suitable clamps at every floor wherever the horizontal conductor is applied.

B. The equipment on the roof shall be protected using vertical air terminals of suitable height so that it provides the zone of protection. This air terminal shall be installed at a suitable separation distance so that the partial lightning current doesn?t flow through the equipment. The cable from the equipment shall be protected using an over ? voltage protector. The equipment shall not be bonded to the air termination network. Specialist Lightning Protection Installer shall give the calculation of the suitable separation distance.



Any advice on solving this and which argument seems stronger?

Thank you

 

[mgookin]

After digging out more details about the project. I found the following information that I see as contradicting:


1-A note on the drawing stating: ALL METALLIC EQUIPMENTS AND EXPOSED METALLIC OBJECTS ARE TO BE BONDED TO THE SYSTEM

2- A section in the specs:

1. All metallic parts protruding outside the extended air termination network (e.g. balcony hand rails etc.) shall be connected to the air termination using suitable clamps at every floor wherever the horizontal conductor is applied.

B. The equipment on the roof shall be protected using vertical air terminals of suitable height so that it provides the zone of protection. This air terminal shall be installed at a suitable separation distance so that the partial lightning current doesn?t flow through the equipment. The cable from the equipment shall be protected using an over ? voltage protector. The equipment shall not be bonded to the air termination network. Specialist Lightning Protection Installer shall give the calculation of the suitable separation distance.



Any advice on solving this and which argument seems stronger?

Thank you

Sounds like the guy who designed it is saying find someone more qualified than him to do some calculations.

 

[LightningProtectionDesign]

It is kind of hard to say weather or not the equipment will need to be bonded without seeing the building. If they want a working system that can be inspected and certified, then they may have to have the lightning protection system attach to the mechanical equipment in one way or another, weather that be through bonding the equipment, or possibly even air terminals on the equipment in order to achieve a complete system.

The general code for bonding the equipment is that if it is within 6' of the main lightning protection conductor, it needs to be bonded, but this is only one part of the many factors that could require connections to the equipment.

 

[SAFI_GH]

It is kind of hard to say weather or not the equipment will need to be bonded without seeing the building. If they want a working system that can be inspected and certified, then they may have to have the lightning protection system attach to the mechanical equipment in one way or another, weather that be through bonding the equipment, or possibly even air terminals on the equipment in order to achieve a complete system.

The general code for bonding the equipment is that if it is within 6' of the main lightning protection conductor, it needs to be bonded, but this is only one part of the many factors that could require connections to the equipment.

Please find below drawing.

 

[LightningProtectionDesign]

I am not sure where you are located, or what codes you will be required to follow, but I noticed that your drawing would not meet the requirements for NFPA 780, UL 96A, or the LPI-175 code standards. There would need to be air terminals at every outside corner, and at no more than 20' intervals along the parapet wall (25' for air terminals 24" or taller in height. The "aluminum louvers" would also probably need air terminals on it depending on the height compared to the parapet wall, and possibly even some of the mechanical equipment that is closer to the outer parapet wall, again depending on the height of the units compared to the wall. Also it appears there is not enough down conductors on the building as you would need one for every 100' of perimeter if using full conductor, or one for every 60' of perimeter if using the steel as the down conductors.

As far as bonding goes, it looks as though the only units that would not need bonding would be the unit marked ACU-02 in the middle of the roof, and EF-1 just below it.