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#89226 09/08/04 12:59 PM
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What part of the code covers burglar alarm wiring and fire alarm wiring installations? what size ground wire should be used to ground a alarm panel? Is it OK to run the ground wire to the nearest cold water pipe or is it required to be run back to within 5ft of where the water pipe enters the building?

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#89227 09/08/04 01:51 PM
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725.9 Class 1, Class 2, and Class 3 Circuit Grounding.
Class 1, Class 2, and Class 3 circuits and equipment shall be grounded in accordance with Article 250.

250 does not allow you to arbitrarily grab a water pipe. You should probably be going back to the service disconnect enclosure ground bus if you are looking for a "loop free" ground. That is the point where "star" grounding should originate.


Greg Fretwell
#89228 09/08/04 03:36 PM
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Article 760 covers fire alarm systems and again steers you back to 250 RE grounding (760.9 2002 NEC).
Typically the grounding will originate in the panel serving the control panel and be routed with the branch circuit conductors feeding the panel. No different than a duplex receptacle.

#89229 09/08/04 03:57 PM
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Would anyone critique me if I said that the wire gage should be at least #14 AWG and that is should be either green or bare for it's entire length? See 250.120(A) and 250.119.


George Little
#89230 09/08/04 04:34 PM
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I think the #14 would be fine if fed with a 15A or smaller circuit. If it's a commercial application it would more than likely be fed with 20A and be required to be #12.

Here is another thought. I did some wiring today in a Notifier fire alarm system power supply and noticed that at the branch circuit terminal bar the connection point for the "ground" did not say ground it said earth. both on the term strip and on the directory inside the panel cover. I wonder if something like this has raised the question.

#89231 09/08/04 05:15 PM
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The alarm panel in question is typically used in residential dwellings and is not feed with line voltage.The panel is powered by a transformer that is pluged into a 120 volt plug remote from the panel itself. The panel is of steel construction and inside there is a terminal for a ground connection. What is the proper way to ground the alarm panel?

#89232 09/08/04 05:45 PM
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OOOhhhhhhh!
Your system is not required by the NEC to be grounded so the proper way to ground it is to ground it by what ever way the manufacturer recommends to ground it. I would imagine they are using the ground in this case to look for ground faults on the field wiring or to clear static off the case/board. The ones I have seen do in fact ask for a wire to cold water pipe....and as I remember the wire size is determined by conductor length. Your not dealing with life threatening voltage here, 12V maybe 16V off the transformer.

#89233 09/08/04 05:49 PM
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just reading the manufacters instructions for a burg/fire alarm panel I used to install. It says" Connect the control panel earth ground screw through a #16 AWG or larger wire to a cold metal water pipe or a buried ground rod. DO NOT use a gas pipe, plastic pipe, or AC Ground connections. This panel is fed with a 16.5 VAC transformer.It also says that this equipment should be installed in accordance with NFPA -72 national fire alarm code. Is there a difference in grounding requirements because it is considered under different jurisdiction?

#89234 09/08/04 06:09 PM
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trekkie
We must have posted at the same time.
NFPA 72 does not tell you how to ground the panel that part of the install will fall under 70. The reason they say to install per NFPA 72 ( IF the panel is used as part of a required Fire Alarm Control Panel.) is about where you put smoke detectors, heat detectors duct detectors, pull stations, strobes and horn/strobes. How the system is monitored an by whom. How much standby and alarm time is required with no A.C. power and how it is tested and maintained. ( This list just scratches the surface of NFPA 72 requirements.)

#89235 09/08/04 06:20 PM
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thanx for the reply's guy's...kentvw, soooo the cold water pipe is used for grounding in this situation.The telephone and catv systems do not have life threating voltage either but are required to be grounded (bonded) so they will have the same potential between systems in case there is lightning or accidential contact with power lines.

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