Bonding/Grounding Raised Floor Systems
- Thread starter KenEasley
- Start date
- Status
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
The only requirement in Art 250 is "if likely to become energized".
Its an AHJ call. Find out ahead of time.
Its an AHJ call. Find out ahead of time.
Hi Ken, Google up HP's Electrical and Environmental Guidelines for raised floor bonding systems. Scroll to the Raised Floor metal strip ground system for a detailed illustration. rbj
bonding a raised floor
bonding a raised floor
The raised floor is not powered equipment and it is not a grounding conductor for the protection of other equipment to be attached to it. Bonding the floor is correct but, as sometimes happens, bonding racks or other utilization equipment to the floor is imo wrong. The racks gets bonded to the copper strip signal reference grid in addition to the equipment ground coming in with the feed. Per NEC the racks may be bonded to the floor but not grounded to it (the floor is not a grounding conductor).
The floor gets bonded to the transformer secondary common grounding busbar where the GEC, EGC, and system neutral all connect. The floor gets another bonding jumper to the copper strip signal reference grid (if installed) and another bonding jumper to the local structural steel.
If you do not have a drawing showing all the wiring, I do not know if it's in the NEC since the floor is not powered and not used as (not suitable to be used as) a grounding conductor. It may be in the manufacturer's specs. I would be thinking change order.
IMO the floor wants an earth ground to be quieter and bonding interconnection to provide a low impedance path for any stray currents in the wrong place.
bonding a raised floor
The raised floor is not powered equipment and it is not a grounding conductor for the protection of other equipment to be attached to it. Bonding the floor is correct but, as sometimes happens, bonding racks or other utilization equipment to the floor is imo wrong. The racks gets bonded to the copper strip signal reference grid in addition to the equipment ground coming in with the feed. Per NEC the racks may be bonded to the floor but not grounded to it (the floor is not a grounding conductor).
The floor gets bonded to the transformer secondary common grounding busbar where the GEC, EGC, and system neutral all connect. The floor gets another bonding jumper to the copper strip signal reference grid (if installed) and another bonding jumper to the local structural steel.
If you do not have a drawing showing all the wiring, I do not know if it's in the NEC since the floor is not powered and not used as (not suitable to be used as) a grounding conductor. It may be in the manufacturer's specs. I would be thinking change order.
IMO the floor wants an earth ground to be quieter and bonding interconnection to provide a low impedance path for any stray currents in the wrong place.
DataCenterGuy
Member
- Location
- New York
Why a raised floor system in a Library where weight and floor loading are always substantial issues? If it's to provide a pathway for routing power, doesn't this then qualify it as "likely to become energized" under the intent of the Code? But other than then Grounding the raised floor as a safety issue, I see no reason for the complexity and expense of a true Signal Reference Grid in this situation (which is becoming a questionable expense anyway with the clock speeds of modern processors). A Ground Conductor, perhaps, to which metal book shelves could be grounded if that is necessary (so they are not considered "grounded" by simply sitting on or being bolted to the raised floor), but I would think that would be all that would be necessary.
nyhockey
Senior Member
- Location
- long island, ny
Just did a floor in the Empire State Building with a raised floor, No Bonding.
- Status