My UPS source of power to 2 panels is located 70 feet away. The panels are inside Computer Room where there is a local grounding bus for grouning the raised floor. Where do I connect the local raised floor grounding bus, in the 2 new panels or in the source UPS?
RAISED FLOOR GROUNDING
- Thread starter J Medrana
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ron
Senior Member
- Location
- New York, 40.7514,-73.9925
The bus to bond the raised floor to the grounding electrode systems typically goes on the wall.
http://www.cooperindustries.com/content/dam/public/bline/Resources/Library/flyers/CDGRD-10.pdf
You might be asked to bond the panelboard enclosure to it or the floor or niether. Your panelboard must have a grounding electorde conductor in compliance with 250.118 as usual.
http://www.cooperindustries.com/content/dam/public/bline/Resources/Library/flyers/CDGRD-10.pdf
You might be asked to bond the panelboard enclosure to it or the floor or niether. Your panelboard must have a grounding electorde conductor in compliance with 250.118 as usual.
If you're in a 645 space, the floor grid structure connection would be a required grounding conductor. Outside of 645, it may be a bonding connection, (imo). You would also be complying with the manufacturer's literature for the UPS, and if the UPS was separately derived or not would make a difference (imo).
The cleanest way, what I would be looking for, the floor grid structure common grounding point would be connected by an insulated grounding conductor back to the origination point of the SDS at the same busbar where the SDS's GEC and system bonding jumper are also attached. I would probably also be looking to redundantly bond the subpanel EGC busbar in the raised floor space to the floor grounding point.
If you are also required to provide an "earth ground" to the attached equipment, I would not depend only on the load's EGC to bond back to the GEC. I would view that as a requirement to run a second dedicated grounding conductor to serve a second purpose (imo).
The cleanest way, what I would be looking for, the floor grid structure common grounding point would be connected by an insulated grounding conductor back to the origination point of the SDS at the same busbar where the SDS's GEC and system bonding jumper are also attached. I would probably also be looking to redundantly bond the subpanel EGC busbar in the raised floor space to the floor grounding point.
If you are also required to provide an "earth ground" to the attached equipment, I would not depend only on the load's EGC to bond back to the GEC. I would view that as a requirement to run a second dedicated grounding conductor to serve a second purpose (imo).
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I am curious where in the NEC it states to bond the raised floor. I know you must do it but I could not find it.
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
Dan,
I'm not sure that 645.15 requires bonding of the raised floor to the grounding system unless the pedestals are incorrectly identified as a signal reference structure. Everyone bonds the floor anyway as a good idea for other reasons like static electricity, etc, but it is not required since it is not likely to become energized (like metal studs in a wall).
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Probably because it's not directly required by the NEC.
I was reading 645.15 as, the floor grid is any exposed metal. I would not depend on it as a signal reference structure, but there is a haphazard metal to metal contact with the racks and everything else in the area. Better to have a bolted intended connection than just a rubbing intermittent surface contact. The definition of exposed includes behind removable panels (had to look it up).
Imo, the floor grid is not used for grounding (unless manufacturer listed for grounding). It is a structure that gets grounded and is haphazardly used for bonding.
If you put a Liebert PDU on the raised floor, their literature has a nice picture of the bonding jumper from the floor grid to the PDU common grounding and bonding busbar.
Imo, the floor grid is not used for grounding (unless manufacturer listed for grounding). It is a structure that gets grounded and is haphazardly used for bonding.
If you put a Liebert PDU on the raised floor, their literature has a nice picture of the bonding jumper from the floor grid to the PDU common grounding and bonding busbar.
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