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This rack's grounding reads 4.2 ohms to building steel

Datacenter Talk by MARIA3 3 replies 451 views
MARIA3

Member OP

#1

Hello, I need help with my rack in small datacenter. Electrician came to make a server up and he measured 4.2 ohms from my rack ground to building steel. He says this is too high but he is not sure what is acceptable for server rack. I read some guides but they say different numbers, some say 5 ohms is ok, some say must be 1 ohm or less. Can someone help me understand what is correct for this situation? I have 10 servers running and I don't want to make risk. Regards.

siesta first, deploy later
Lou1

Member

#2

  • 4.2 ohms is probably fine for most setups
  • NFPA and IEC standards differ on this
  • NEC allows 25 ohms for single electrode, but datacenter best practice is lower
  • Your electrician might be being cautious

That said I would want it under 3 for my own peace of mind. The building steel bond is what matters most here. If your rack is bonded to a good ground bus and that bus ties to building steel with low impedance youre probably not going to have issues with server good operation. How much cost to add another ground rod?

PU

Member

#3

Which standard is your electrician using, NFPA or IEC

AL

Member

#4

4.2 ohms is fine. Lou is being cautious.

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