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Old 06-23-2014, 02:58 PM   #1
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Grounding EMT used for speaker and cat5 wire


For my home audio install, I have two runs of EMT for speaker wire and one run of EMT for cat5 in the garage. The EMT is going between two walls in order to reduce the distance and complexity of the wiring between the speakers/control panels and the central amp. I'm almost positive I have to ground the EMT but I have a couple questions that I can't find answers to:

1. Do both sides of the EMT have to be grounded to the same circuit?

2. Can I run a ground THHN wire in the conduit with the speaker wire and cat5? I know you generally can't run different classes in the same raceway, or speaker wires with anything else, but haven't read anything pertaining to ground wires.

Thanks for the help!

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Old 06-23-2014, 04:56 PM   #2
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Grounding EMT used for speaker and cat5 wire


The EMT used in the fashion you're describing wouldn't be required to be grounded.

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Old 06-23-2014, 05:20 PM   #3
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Grounding EMT used for speaker and cat5 wire


There is no need. arniess, who told you that it had to be grounded? You do not need to also run a THHN ground wire. In a normal electrical situation. The EMT would become the ground, even though you would have a Ground, Hot & Neutral.

You need to read up on the NEC Article 640 & 645, if you are in the U.S.
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Old 06-23-2014, 07:56 PM   #4
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Grounding EMT used for speaker and cat5 wire


I can't find the specific post, it was a while ago and on a different forum. It sounded very similar to what I did and 640.7(A) was referenced:


General. Wireways and auxiliary gutters shall be
connected to an equipment grounding conductor( s ), to an
equipment bonding jumper, or to the grounded conductor
where permitted or required by 250.92(B)(l) or 250.142.
Where the wireway or auxiliary gutter does not contain
power-supply wires, the equipment grounding conductor
shall not be required to be larger than 14 AWG copper or
its equivalent.
Where the wireway or auxiliary gutter
contains power-supply wires, the equipment grounding
conductor shall not be smaller than specified in 250.122.
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Old 06-23-2014, 08:14 PM   #5
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Grounding EMT used for speaker and cat5 wire


That does not apply in your case. You are not running Hi-Voltage electric (anything over 120vAC). You are only doing low voltage. Audio wiring & networking at that.

The only time you would ground that EMT. Is if it is fed between buildings. Then it would need a bonding bushing on it, to protect from not only in case it comes in contact with stray voltage. But also to discharge any static electricity.

You can still bond it to ground, if you want to feel all warm and fuzzy. In what you are doing. We just use Smurf Tube for that kind of stuff.
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Old 06-24-2014, 11:33 AM   #6
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Grounding EMT used for speaker and cat5 wire


Thanks for the help. I definitely want to avoid the trouble of grounding the EMT if I can. In hindsight I should have gone with Smurf Tube. I wanted the extra protection of metal in that area of the garage when I installed it but I ended up rearranging the garage afterwards.

I was able to find the article that made me start to think it needed to be grounded.

Quote:
Ten Common NEC Violations in
Low-Voltage Systems: datcominc.com/file_library/spec/39_TenNECViolations%2008.pdf

8. Ungrounded or improperly grounded
primary or secondary protectors.
Article
800.170(A) and (B) stipulate that all primary
protectors need to be grounded and secondary
protection needs to be grounded when present in
the device. It is well known that primary protectors
need to be grounded. The code violation occurs most
of the time by running excessive lengths of ground
cable to reach a distant ground bar when other
grounding means are closer. Secondary protectors
are installed many times as a result of a specific
situation when equipment was damaged. Those
retrofit jobs often are done by unqualified personnel
who are not aware of the grounding requirements
for secondary devices.
My biggest weaknesses with the NEC manual are many of the terms and in what situations it would apply. Thanks again for the clarification.
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Old 06-24-2014, 12:42 PM   #7
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Grounding EMT used for speaker and cat5 wire


Yes it gets hard to figure out, when they are talking about the spec. of wiring theaters and auditoriums in that section.

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