Detached garage grounding

[Del91574]

Lou Apo
 
another question -
 
If lightning strikes the ground why would it travel into the building on it's earth lead to a piece of equipment and conduct current to the neutral in that device if that neutral is isolated from earth? I'm  a little confused here. I can see the lightning traveling in on a data line and finding an earth ground but not traveling in on a ground wire and finding a neutral.
 
Mike.

Megohm meter. Commonly used to find these sorts of things. There's things you can't take into consideration, but ground paths and insulation integrity are tested and certified often in mission critical applications.
 
Doesn't get done in a residential situation EVER. Closest I've seen to a megohm meter being used on a residence was post-Sandy and people attempting to salvage panels and cable because of hte insurers.

 

[mikefamig]

This is all very interesting but in the end I think that what I've learned is that there is no way to protect my current installation from lightning and that the practical thing to  do is to keep my fingers crossed.
 
The garage has:
one buried cat6 cable connected to two ethernet switches, two ip cameras and a television set top box
a second buried cat6 cable connected to two elk expanders and a keypad
one awg 16/4 used to power the elk adapters and carry audio to a speaker.
 
I am not planning to pull this out and replace it but theoretically I could replace the cat6 cables with fiber and the speaker is only connected to speakers and could be left as-is but I don't know how the power cable could be made safe from lightning other than to install another power supply in the garage to eliminate the wires altogether.
 
I wish that we had this conversation before I did the job but maybe it will help rsw686 or someone else down the road.
 
Mike.

 

[mikefamig]

The simplest of these would be the speaker.

Lou
 
How would you deal with the speaker? How would you protecyt the Elk panel from the buried speaker wire?
 
Mike.

 

[apostolakisl]

Lou
 
How would you deal with the speaker? How would you protecyt the Elk panel from the buried speaker wire?
 
Mike.

 
 
Buried wire vs 2 panels with 2 grounds are different issues.  Buried wire poses 2 issues.
 
1) Broken insulation and thus a connection to ground
2) Inductance: long stretches of wire are subject to EM induced potential/current in the wire from lightening strikes that may not strike the ground at all.  This is an issue even with wire contained inside the same structure if it is a long run.
 
Both of these issues are "solved" by using burial grade twisted pair shielded wire and grounding the wire at the Elk panel end of the line.  I put "solved" in quotes because even a slight error in the twist can result in an induced potential on the wire.  The length of the wire and the strength of the EM wave will at some point result in a failure.  But odds are, if done in the normal correct way, you'll protect yourself from all but the most extreme of cases.  
 
Wire like this is the safest bet short of not using a conducting wire at all.
 
http://cables4sure.com/300ft-cat6-direct-burial-shielded-gell-type-bulk-cable-black.html?gclid=CjwKEAjw1_KwBRDEz_WvncL4jGwSJAAEym0dNH7Rceh9hsxGKslNDuNdsHfK5aCe_vs86sDLeYWGZBoCYLDw_wcB

 

[mikefamig]

Buried wire vs 2 panels with 2 grounds are different issues.  Buried wire poses 2 issues.
 
1) Broken insulation and thus a connection to ground
2) Inductance: long stretches of wire are subject to EM induced potential/current in the wire from lightening strikes that may not strike the ground at all.  This is an issue even with wire contained inside the same structure if it is a long run.
 
Both of these issues are "solved" by using burial grade twisted pair shielded wire and grounding the wire at the Elk panel end of the line.  I put "solved" in quotes because even a slight error in the twist can result in an induced potential on the wire.  The length of the wire and the strength of the EM wave will at some point result in a failure.  But odds are, if done in the normal correct way, you'll protect yourself from all but the most extreme of cases.  
 
Wire like this is the safest bet short of not using a conducting wire at all.
 
http://cables4sure.com/300ft-cat6-direct-burial-shielded-gell-type-bulk-cable-black.html?gclid=CjwKEAjw1_KwBRDEz_WvncL4jGwSJAAEym0dNH7Rceh9hsxGKslNDuNdsHfK5aCe_vs86sDLeYWGZBoCYLDw_wcB

So you are saying that a braided shield on the cable as is common with microphone cable is what you would go with?
 

 

[apostolakisl]

So you are saying that a braided shield on the cable as is common with microphone cable is what you would go with?
 

Ideally twisted pair and burial grade as well.  You'll need to check if 23g wire times the current times the distance is going to work with your speaker.  I am running my elk speaker on cat5e and it works fine.  It might be 100 foot run?

 

[mikefamig]

Ideally twisted pair and burial grade as well.  You'll need to check if 23g wire times the current times the distance is going to work with your speaker.  I am running my elk speaker on cat5e and it works fine.  It might be 100 foot run?

I think that you misunderstand my question ....my wire has been buried and working for a year or so and of teh proper impedance for the amplifier. My concern is not whether i am satisfying the amplifiers needs in the way of speaker or wiring. I want to know why you say that the speaker is the easiest wire to protect from lightning strike. It is analog as opposed to digital and I don't think that fiber is the answer. Why did you claim that the speaker is the easiest wire to protect.For me it is the one wire that I do not know how to protect. How should I treat the speaker wire to protect the elk panel from lightning?
 
Mike.
 
Mike.

 

[kurtmccaslin]

I have the same issue and am planning to protect my speaker wire with a ditek surge protector.   (when I get around to installing the speakers in the garage)
 
I have not researched to figure out what voltage surge protector I should use yet.

 

[apostolakisl]

I think that you misunderstand my question ....my wire has been buried and working for a year or so and of teh proper impedance for the amplifier. My concern is not whether i am satisfying the amplifiers needs in the way of speaker or wiring. I want to know why you say that the speaker is the easiest wire to protect from lightning strike. It is analog as opposed to digital and I don't think that fiber is the answer. Why did you claim that the speaker is the easiest wire to protect.For me it is the one wire that I do not know how to protect. How should I treat the speaker wire to protect the elk panel from lightning?
 
Mike.
 
Mike.

 
 
I say it is easy because you can do it and stay completely clear of your electrical panel.  It is just a straight shot wire to the speaker which presumably can be mounted independent of anything grounded or connected to power.  It is also not sensitive to interference.
 
But I also have to ask why you need a siren in your out building anyway.  Can't you mount it on your main building and be able to hear it in the out-building?  It can't be that far away?

 

[a41]

There's a reason grounding is one of the most misunderstood topics in the NEC...
 
I'd have to say your electrician was right, the best way to do it would be to run a ground wire to the detached garage.  It's not about protection from lighting or surges, it's about protecting electrocution.  
 
There have been quite a few code revisions since this was written, but this series of 12 articles on EC&M does a pretty good job explaining the subject:
http://ecmweb.com/bonding-amp-grounding/grounding-vs-bonding-part-1-12

 

[drvnbysound]

I say it is easy because you can do it and stay completely clear of your electrical panel.  It is just a straight shot wire to the speaker which presumably can be mounted independent of anything grounded or connected to power.  It is also not sensitive to interference.
 
But I also have to ask why you need a siren in your out building anyway.  Can't you mount it on your main building and be able to hear it in the out-building?  It can't be that far away?

 
I need to go back and read through this thread, but I can say that I want a speaker in my detached workshop - not solely for alarm conditions, but also for voice announcements (via Elk chime). For example, if my family is not home and I go out to the shop to do some work, I could get a notification when the front door or garage door is opened, alerting me that someone is home.
 
In my case, my detached building is primarily a wood shop. I've been using my router table or table saw before and had my wife enter the door behind me... and it scare the crap out of me when I look up and see her there. Depending on volume levels (my table saw is fairly quite), I may be able to hear the chime from the local shop door as well (a strobe could be useful for this too if speaker volume is an issue). I'm planning to be using the TWA for this speaker which gives me some added volume control with the built in pots.

 

[mikefamig]

I say it is easy because you can do it and stay completely clear of your electrical panel.  It is just a straight shot wire to the speaker which presumably can be mounted independent of anything grounded or connected to power.  It is also not sensitive to interference.
 
But I also have to ask why you need a siren in your out building anyway.  Can't you mount it on your main building and be able to hear it in the out-building?  It can't be that far away?

 
I took the approach of making ear piercing noise inside and not disrupting the entire neighborhood with outdoor sirens. The nearby neighbors can hear it but there are no sirens or speakers outdoors. My garage is 100 feet away from the house.

 

[mikefamig]

But I also have to ask why you need a siren in your out building anyway.  Can't you mount it on your main building and be able to hear it in the out-building?  It can't be that far away?

 
Like drvnbysound I also like to hear voice announcements in the garage when zones change in the house. If I am in the garage it will tell me if my wife comes home when the overhead door goes up or if someone takes the liberty of walking into the front door.

 

[mikefamig]

There's a reason grounding is one of the most misunderstood topics in the NEC...

Agreed and forums like this are good or hashing out ideas and trying to understand it from different angles.
 

I'd have to say your electrician was right, the best way to do it would be to run a ground wire to the detached garage.  It's not about protection from lighting or surges, it's about protecting electrocution.  

The topic of conversation here has been primarily concerning protecting equipment from lightning but of course the grounding system is there to protect from bodily harm.
 
I feel that I have a fairly good understanding of how having a grid of ground wires and cabinets protects us from electrocution by conducting stray current to ground via that grid but lightning strike - not so much.
 
Mike.
 

There have been quite a few code revisions since this was written, but this series of 12 articles on EC&M does a pretty good job explaining the subject:
http://ecmweb.com/bonding-amp-grounding/grounding-vs-bonding-part-1-12

Thanks for the link.

 

[mikefamig]

There's a reason grounding is one of the most misunderstood topics in the NEC...
 
I'd have to say your electrician was right, the best way to do it would be to run a ground wire to the detached garage.  It's not about protection from lighting or surges, it's about protecting electrocution.  
 
There have been quite a few code revisions since this was written, but this series of 12 articles on EC&M does a pretty good job explaining the subject:
http://ecmweb.com/bonding-amp-grounding/grounding-vs-bonding-part-1-12

 
a41
 
I read the article in your link and I think that it helped me to better understand the basics of grounding, bonding and the difference between the two. I have always incorrectly used those two terms interchangeably in the past.
 
Thanks, Mike.