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How do you ground a cabinet?

Posted on 2006-07-22
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Last Modified: 2009-07-29
I have a BlackBox SP090A cable modem surge protector, and I need to know how to connect the grounding wire.  I contacted BlackBox, and they told me to connect the surge protector's grounding wire to my RM335A-R2 network cabinet, then connect the cabinet to my building ground.  They said "safety ground has to go to the building ground", how should I do this?

Cable TV/Cable Modem Protector
https://www.blackbox.com/Catalog/Detail.aspx?cid=45,75,1426&mid=3633

RM335A-R2 Wallmount Cabinet
http://www.blackbox.com/Catalog/Detail.aspx?cid=111,1335,1358&mid=159
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Question by:Crash2100
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Rob Williams earned 400 total points
ID: 17161278
As simple as it sounds it is really a job for an electrician if you want to make sure the grounding/bonding is done properly.
In most of the racks and cabinets there is a grounding "post" which is a bolt or machine screw with a corrugated washer to make sure it has a good connection. You can recognize them, as they are usually painted green. If not you can put the grounding lug from your adapter under any screw in the cabinet that is solidly fastened to the cabinet itself. You then need a wire, most often 14 or 12 gage green insulated, that goes to something you are certain is grounded and bonded, to the building ground, not a handy water pipe. Though not an accepted practice, often folks use the screw that holds the cover on an electrical plate. If the plug is grounded this should be connected to the appropriate ground. However, you really should have an electrician ground the cabinet, or install an appropriate grounding bar, for all sensitive components. Once you have a proper grounding bar, you can connect any of your own equipment as necessary.
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by:scrathcyboy
ID: 17161525
Every outlet in a properly wired office has a GROUND WIRE as part of the outlet --

3 prong outlet -

neutral       live
round ground

So where the ground wire comes into the cabinet, find any screw in the metal part of the cabinet, and tie a 14 ga. copper wire from this screw to the ground wire coming into the appliance.  YOu will find that any well built cabinet already has done this, and I doubt you will need to do it again.  They are just being overcautious.  As long as the wall outlet, the surge unit and the cabinet all have 3 pronged outlets or plugs, it is already grounded.  Just make sure there is a good ground from the service entrance on the building into a ground rod in the ground, below the electricity box.
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by:giltjr
ID: 17161955
scrathcyboy, go look at the SP090A and you will see that they are not being overcautious.  It is an in-line cable surge protector.  No 3 prong plug: cable "in", cable "out", and ground wire hanging out the side.

I agree with RobWill, as simple as grounding may seem, it is not.  If done improperly you can damage more equipment that if not done at all.  You can also injury people and start fires.



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by:scrathcyboy
ID: 17161998
Any surge supressor without a 3 prong grounded plug should be thrown in the trash.  You simply cannot stop surges unless the ENTIRE CHAIN from the wall outlet to the final box has a ground line independent of neutral, that runs directly back to the service entrance ground via a copper cable.  I dont have to look at some 1/2 baked specs, I am telling the questioner the CORRECT grounding principles of what is correct electric wiring.  If you are talking about the cable input, dont you know the outside shielding of the cable MUST be grounded at both ends, before it even comes into the building?  I mean this is basic cable and electrical wiring specs, anyone not adhering to the correct wiring should not be in the business.
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by:giltjr
giltjr earned 100 total points
ID: 17162758
scratcyboy, what?  Once again you show that you obviously have not worked in BIG IT.  HE IS NOT TRYING TO GROUND the electrical system he is trying to ground the Cable, as in Cable T.V., connection.  So that if there is a lighting strike on the cable, it does not damage his cable modem.  I don't NOT need, nor want to waist, a electrical outlet for that.  Just like you can ground a Ethernet or phone line without one either.

I assume in that your experience you have a 19.95 surge protector from K-Mart or Target protecting each of your servers that have a Cable and or phone line surge protector built into it.  Well real data centers DON'T.   I could not image having 40, 50, 1,000 of these little K-Mart/Target surge protectors to protect my servers.  I have big PDU's (with surge protection) going to 30 and 60 AMP power strips that  also have surge protection. Neither of which have Cable/phone/RJ45 surge protectors in built in them.  Because in a real data center you do not use the little K-Mart/Target surge protectors.
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by:Rob Williams
Rob Williams earned 400 total points
ID: 17163218
giltjr, agree 100%. Your basic equipment should have the standard grounded plug, but most commercial equipment requires an isolated ground going right back to the main building ground. Proper grounding and bonding is a huge area of study for electricians, which is controlled by electrical codes, and always inspected very carefully during electrical inspections. Any communications room will usually have a minimum of a 6 gage wire connected to a grounding bar, with numerous connection points, specifically for grounding sensitive electrical equipment and cabinets. Here, even a single 'U' rack has to have a separatee ground.
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by:Rob Williams
ID: 17163735
Thanks Crash2100,
--Rob
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by:Crash2100
ID: 17163738
I wish I had realized connecting this equipment was going to be this complicated.  Because, ironically, I just had an electrician come out and put an electrical outlet in the closet where I have the network equipment, he could have done this too!  Oh well, I guess I'll have to call them back out.

It makes me feel better having an electrician do all of this anyway.  This way, I know it will be connected correctly, and my precious equipment will be safe.

Thanks for the help!
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by:Rob Williams
ID: 17163962
Well worth doing it right. Once you have the proper grounding in the room you can use it for replacement or new equipment as well.
The phone company here has a requirement of 3 or 4 things including a grounding point, before they will even start work. Have to admit a lot of people don't even bother grounding at all, but there can be some risks.
Cheers.
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