Server rack grounding

Etanuye

Member
Location
Los Angeles
Occupation
Junior Engineer
Hi everyone,

I need some advice in grounding service rack.

if I am pulling a ground wire from panel that is approximately 90 feet away from the ground busbar, do I use #6 or #1 cable?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
It depends on the conductors feeding the equipment.

Generally, only made electrodes never need larger than #6.
 

Etanuye

Member
Location
Los Angeles
Occupation
Junior Engineer
It depends on the conductors feeding the equipment.

Generally, only made electrodes never need larger than #6.
What do you mean by “It depends on the conductors feeding the equipment.”

here Is my thought in the design;
Iam going to pull a #1AWG GND wire from existing panel and connect it to ground busbar. Then, connect #6 from busbar to the service rack.

why I used #1AWG? I sized 2kcmil per linear feet of conductor length. I found it In TIA-607-D. I might be wrong that’s why I am here to confirm.
 

suemarkp

Senior Member
Location
Kent, WA
Occupation
Engineer
What is a "service rack"? Are you grounding or bonding? Things in TIA documents aren't typically NEC requirements.

If it is for an electrical service (e.g. NEC 230 conductors), table 250.66 or 250.102 may apply. The values are based on the size of the conductors powering the service rack.

If it is just some rack powering equipment, then table 250.122 would apply and that is based on the size overcurrent device protecting the conductors powering the service rack.
 

Etanuye

Member
Location
Los Angeles
Occupation
Junior Engineer
What is a "service rack"? Are you grounding or bonding? Things in TIA documents aren't typically NEC requirements.

If it is for an electrical service (e.g. NEC 230 conductors), table 250.66 or 250.102 may apply. The values are based on the size of the conductors powering the service rack.

If it is just some rack powering equipment, then table 250.122 would apply and that is based on the size overcurrent device protecting the conductors powering the service rack.
Sorry, I meant server racks like computer room, I have server racks that are not grounded. I want to ground the rack

the main question is if the length of cable is 90-100ft can I still use #6 awg ground or do I need to upsize the ground conductor to make the ground effective
 

ActionDave

Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
wire pulling grunt
Sorry, I meant server racks like computer room, I have server racks that are not grounded. I want to ground the rack

the main question is if the length of cable is 90-100ft can I still use #6 awg ground or do I need to upsize the ground conductor to make the ground effective
What is this ground to the rack going to accomplish? Is it going to make the equipment safer? Will it improve the function of any of the gear in the room? Is it something that gets put into specs just because everybody else does it that way?
 

wyreman

Senior Member
Location
SF CA USA
Occupation
electrical contractor
california electric code requires the green wire even in the rigid pipe
but what about the choke? bonding bushing? and pvc pipe
but the inspector told me never to have a supplemental ground rod or offer at a remote subpanel 'cause parallel paths
but what about outbuildings?
soares book on grounding
 

Etanuye

Member
Location
Los Angeles
Occupation
Junior Engineer
What is this ground to the rack going to accomplish? Is it going to make the equipment safer? Will it improve the function of any of the gear in the room? Is it something that gets put into specs just because everybody else does it that way?
To make the equipment safer
 

Etanuye

Member
Location
Los Angeles
Occupation
Junior Engineer
california electric code requires the green wire even in the rigid pipe
but what about the choke? bonding bushing? and pvc pipe
but the inspector told me never to have a supplemental ground rod or offer at a remote subpanel 'cause parallel paths
but what about outbuildings?
soares book on grounding
There will be #6awg from busbar to the server rack,
Which pipe is preferable EMT or PVC pipe, I thought EMT in mind.
What do you mean by “what about outbuildings?” Do you mean like to bond it to steel structure
 

ActionDave

Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
wire pulling grunt
this server rack has been running without a ground. They installed the branch without ground wires, so I am pulling single ground in EMT
To make the equipment safer
I don't know about any California requirements but in the rest of the world the EMT is the equipment ground and it is perfectly safe and effective. If you are wanting to add a redundant green wire you would size it based on table 250.122 and 300.3(B) would require it to be inside the same EMT as the other circuit conductors.
 

tom baker

First Chief Moderator
Staff member
california electric code requires the green wire even in the rigid pipe
but what about the choke? bonding bushing? and pvc pipe
but the inspector told me never to have a supplemental ground rod or offer at a remote subpanel 'cause parallel paths
but what about outbuildings?
soares book on grounding
This is off topic can you repost in grounding and bonding?
Some or your comments are incorrect
 

tom baker

First Chief Moderator
Staff member
this server rack has been running without a ground. They installed the branch without ground wires, so I am pulling single ground in EMT
A single ground, in EMT, that is not run with the branch circuit conductors to the server rack is violation and will accomplish nothing.
In a ground fault, the magnetic fields of the ungrounded conductors and EGC (Green wire) cancel, keep in mind the high magnetic fields. It the EGC is seperate from the ungrounded conductors the impedance is greatly increased and little fault current returns to the source.
See section 300.5.
Pull the EGC with the circuit conductors. If the existing it uses EMT that qualifies as an EGC, but many specs require a wire type EGC.
 

Etanuye

Member
Location
Los Angeles
Occupation
Junior Engineer
A single ground, in EMT, that is not run with the branch circuit conductors to the server rack is violation and will accomplish nothing.
In a ground fault, the magnetic fields of the ungrounded conductors and EGC (Green wire) cancel, keep in mind the high magnetic fields. It the EGC is seperate from the ungrounded conductors the impedance is greatly increased and little fault current returns to the source.
See section 300.5.
Pull the EGC with the circuit conductors. If the existing it uses EMT that qualifies as an EGC, but many specs require a wire type EGC.
Thank you for clear explanation
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
We bond server racks, data racks, overhead cable tray and other equipment in IT rooms with a #6 copper jumper. We even bond the floor (not a raised floor) which has a metal tape under the tile.
 

Etanuye

Member
Location
Los Angeles
Occupation
Junior Engineer
We bond server racks, data racks, overhead cable tray and other equipment in IT rooms with a #6 copper jumper. We even bond the floor (not a raised floor) which has a metal tape under the tile.
You use #6 copper jumper from the busbar to the server racks, but What I am trying to figure out is how to bring a ground near to the server rack, if the panel is 100ft away how do I size that ground?
 

ron

Senior Member

suemarkp

Senior Member
Location
Kent, WA
Occupation
Engineer
Wow Ron, that document seems like much overkill to me. I don't know the reasoning behind all of this grounding and bonding in these other standards...

I have spec'd #6 AWG copper ground to cable trays and room ground bars myself. My thinking is that will cover bonding for circuits up to 200A and I should never have anything near that in the tray, and that copper grounding conductors exposed to physical damage should be at least #6 AWG (code specifically mentions this when running a separate conductor to ground receptacles in ungrounded circuits -- not sure it applies anywhere else but seems like good precidence). Most things that would need to connect to the ground bar are only required to be #10 to #14 (typically antenna downleads or coax ground blocks).
 
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