# Bonding of data racks



## Kevin (Feb 14, 2017)

Hey Everyone,

I've been thinking about the bonding of data racks for rack mount equipment, as I have bid on a job in a residential building that will have a rack.

I've installed a couple of rack mount pieces before, and they have a screw on the back for "grounding" to the rack, even though it had a power cord with a ground/bonding pin (standard 5-15 plug). 

Should I be bonding the rack mount system to the ground in the panel? My understanding with this, is that it can cause parallel bonding/grounding paths? I can't wrap my head around how to avoid that without not bonding the rack. 

For residential is it even required?

Any input would be of help.


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## CoolWill (Jan 5, 2019)

I believe they should be bonded. And what does it matter if there is parallel grounding/bonding?


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## Kevin (Feb 14, 2017)

CoolWill said:


> I believe they should be bonded. And what does it matter if there is parallel grounding/bonding?


Ontario Electrical Code says to abandon a ground if there are parallel paths, hence my worries.

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## CoolWill (Jan 5, 2019)

Kevin_Essiambre said:


> Ontario Electrical Code says to abandon a ground if there are parallel paths, hence my worries.
> 
> Sent from my Samsung using Tapatalk


Does that mean parallel earth grounds, or parallel bonding paths? I could understand earth grounds being problematic, but bonding paths are often in parallel. Metal conduit, building steel, multiple circuits in a box, etc.


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## Kevin (Feb 14, 2017)

CoolWill said:


> Does that mean parallel earth grounds, or parallel bonding paths? I could understand earth grounds being problematic, but bonding paths are often in parallel. Metal conduit, building steel, multiple circuits in a box, etc.


I know grounds and bonds are not the same, however, if there's a shorter bond connection (say 3 feet) through the power cord with a 14 AWG ground, wouldn't the stray voltage try to take the 14 AWG before the longer 6 AWG? This is the reason why we had abandoned the bonding conductors in 14 AWG teck cable from a generator with a 3 AWG ground. If a short was caused, there's the risk of the 14 AWG melting from the current.

Granted, with networking equipment, we are only talking about small volts and amps... nothing to really worry about I guess. Just over thinking this I guess.

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## splatz (May 23, 2015)

I would bond it, even though it's very possible it will never matter. If there's a piece of equipment with power cord with a ground, and the metallic case of the equipment is bonded to cord ground, the rack will be grounded. However what if they swap out for equipment with a two prong plug in the future or etc., then the rack is floating. 

So the rack is floating, so what? Well, if there is any shielded cable terminated in a patch panel or etc., the patch panel will expect the rack to provide a ground path. For example, maybe you have just a cable modem / router (two wire power cord, no ground, plastic case) - if the rack is grounded, you can simply install a grounding block on the rack and run the coax through that and all is well. Especially important if you want to use a surge protector on the coax, most of those rely on the shield being grounded. 

Longshot, but if the cable shield ever comes in contact with line voltage, the shield gives you a path to clear the fault. 

Under normal circumstances, some communications equipment may bootleg the EGC for ground reference (I say bootleg because they should be using the signal ground, but this isn't always the case.) Some communications equipment will be more noise / interference resistant when the equipment is equipotentially bonded.


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## wcord (Jan 23, 2011)

If you mount a metal outlet box onto the metal of the rack then it is considered. If the the outlet is beside the rack and you just have the plug-in cords running over, then you have to run a number 6 from your outlet box to the metal of the rack


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## Navyguy (Mar 15, 2010)

Bonding the rack is just not for electrical bond, but for static bond. Often the datacenters are very dry and as you move across the raised floor if the rack is not bonded you will get zapped and depending on the equipment it may get zapped too.

Typically we would install a copper buss plate and bring separate tails for each rack and than connect that to the system ground. It could be as easy as installing it to building steel, a distribution panel for the server room, or a wire all they back to the system ground itself.

Some equipment, such as racks without equipment (patch panels) may not have any energized equipment on them, but still potentially be energized either through POE or other external sources. Video equipment seems to be the most vulnerable as the people installing that stuff do not understand the principle of potential difference and just start stringing cat6 all over and connecting cameras from separate power sources...

Cheers
John


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## Kevin (Feb 14, 2017)

wcord said:


> If you mount a metal outlet box onto the metal of the rack then it is considered. If the the outlet is beside the rack and you just have the plug-in cords running over, then you have to run a number 6 from your outlet box to the metal of the rack


So by mounting it on the rack,the 14 AWG bond wire in the AC90 cable would be a large enough bond wire?

I have no issues in running Flex and pulling a #6 bond and 2 #14 conductors.

Data racks is something you don't often find in a home set up (at least around here). This is a large custom home with NO smart home devices... the guy is paranoid about people gaining access yo his devices.

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## wcord (Jan 23, 2011)

Kevin_Essiambre said:


> So by mounting it on the rack,the 14 AWG bond wire in the AC90 cable would be a large enough bond wire?
> 
> I have no issues in running Flex and pulling a #6 bond and 2 #14 conductors.
> 
> ...


That's what one of my inspectors said was acceptable. I can't see any residential setup needing much more than that.
However, most commercial specs require a #6 bond wire. We've even had static disappating flooring to connect in some projects.


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## splatz (May 23, 2015)

There is a communications standard, TIA-607, if the specs are to that, grounding for racks etc. is really over the top, even after backing down a little in the last revision. 

The #6 certainly wouldn't hurt but I am not sure what it would ever do that a normal sized #14 conductor would not, other than being physically durable. Static dissipation, equipotential for signal reference, signal ground loops, etc, would probably be handled by #24. The slightly lower impedance of the big wire for the surge protection equipment would make some theoretical difference but I am skeptical it would ever be significant.


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## Incognito (Apr 14, 2019)

It must be bonded, but the bond only needs to be sized based on the ampacity of the largest ungrounded conductor carried by or connected to it, just like cable tray.

For electrical, the bonding conductor shall not be required to be larger than the current carrying conductors.

10-614


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