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#9212 - 04/21/02 12:12 PM Isolated Ground Circuits  
Currently  Offline
Member
Joined: Apr 2002
Posts: 53
TN
With the cost and complexity of computer equipment and home entertainment or theater systems in today's homes, is installing Isolated Ground circuits overkill? I researched the NEC 2002 and it is rather vague when it comes to residential applications.

What do you "Sparkies" recommend when faced with a customer who has an elaborate system in one corner of the living room or den with one outlet and the proverbial 2 powerstrips hanging off the duplex? Dedicated 20A circuit with a gangbox?

I ask because not a month goes by when I see a mention of a fire that starts in the area of an entertainment center in the local papers.


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#9213 - 04/21/02 02:36 PM Re: Isolated Ground Circuits  
caselec  Offline
Member
Joined: Apr 2002
Posts: 558
San Jose, CA
I can not see an isolated ground being necessary for any home installation. There are not many electrical devices in homes that generate enough noise on the equipment grounding conductor to cause problems. Besides most home entertainment equipment doesn't even have an equipment grounding conductor. Unfortunately many people think an isolated ground means connecting the ground from the desired receptacle to a ground rod without connection to the buildings grounding system. An isolated grounding conductor still must be connected to the buildings grounding system but the connection is made at the service panel. In reality if you have a dedicated circuit going to one receptacle and it is being fed from the service panel it does have an isolated ground unless you have steel studs and use a metal box. To avoid fires it is important to make sure that the circuit feeding this equipment is installed properly and is sized correctly. Make sure if you use power strips that they are UL listed and not overloaded. Make sure you plug all of you equipment directly into the receptacle or power strip and do no use the extra outlets provided on the back of some equipment.


Curt Swartz

#9214 - 04/21/02 02:57 PM Re: Isolated Ground Circuits  
sparky66wv  Offline
Member
Joined: Nov 2000
Posts: 2,236
West Virginia
If you run a dedicated circuit with NM cable and plastic boxes, would you not in essence have an iso-ground circuit?

Only other way to make it better would be to have an isolated ground Xformer... right?


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

#9215 - 04/21/02 02:59 PM Re: Isolated Ground Circuits  
sparky66wv  Offline
Member
Joined: Nov 2000
Posts: 2,236
West Virginia
Oops! Sorry CASELEC...

Is there an echo in here?

(I should stop "skimming posts" and read the dern things...)


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

#9216 - 04/21/02 04:39 PM Re: Isolated Ground Circuits  
Currently  Offline
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Joined: Apr 2002
Posts: 53
TN
Thanks,
That is what I needed to know. The dedicated circuit is electrically an Isolated Ground with the circumstances you described. (Use IG's all the time at work)
I also understand the principle behind IG's and that they should be terminated at the bonding point.

My second question about the power strips is still a little unclear. Would it be preferable to have a double duplex in the wall or the strips (with resettable 15A breakers in them) are considered safe practice? Some of these are real cheesey and the comment on UL listing is noted.

I have been visiting this site for a week now and there is a lot of "meat" here. This forum is the "cleanest and nicest" that I have seen for a long time in internet land.

[This message has been edited by Currently (edited 04-21-2002).]


#9217 - 04/21/02 05:31 PM Re: Isolated Ground Circuits  
George Corron  Offline
Member
Joined: May 2001
Posts: 717
Lorton, Va USA
There is really no advantage over outlets in the wall to the plug strip device, unless you have transient protection on them. The cheaper ones are MOV's and are "one shot" or their clamping range is nearly worthless, so be very careful, cheap can damage your equipment.

IG outlets are also nearly worthless since most problems, even in commercial locations, occur over your neutral conductor, not your ground. I would not consider them for a house.

Sparky, just copy and paste this one, it's easier [Linked Image]


#9218 - 04/21/02 05:37 PM Re: Isolated Ground Circuits  
amp-man  Offline
Member
Joined: Jun 2001
Posts: 141
Sacto, California US of A
Current-ly,

I recommend two or more duplex receptacle outlets at the home entertainment center location. If the homeowner is a real enthusiasist, or it's a larger custom home (say 4,000SF +), I put in two dedicated 20A branch circuits, each serving two duplex ROs in a 4S box.

The power strip approach has its advantages, if the strip is top quality--
--you can get a strip with a surge-supressor in it
--if you want to shut off the power to the equipment (vacation?), you can do it easily with a power strip.
--it's easier to unplug/plg in the equipment with a strip, as the wall outlets are usually behind the cabinet.

One suggestion--mount the strip on the wall or vertically in the cabinet. I've seen way too many strips that are covered with a layer of dust, with the slots of the unused receptacles choked with dust and lint. If anything causes a short and arcs, you're likely to get a fire. Of course the other option is good housekeeping...

Cliff



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