Go Back  DoItYourself.com Community Forums > Electrical, AC & DC. Electronic Equipment and Computers > Electrical - AC & DC
Reload this Page >

Media Center Location, Grounding Media Center, Whole House Surge Protection

Media Center Location, Grounding Media Center, Whole House Surge Protection


  #1  
Old 05-13-09, 09:47 AM
M
Member
Thread Starter
Join Date: May 2009
Location: Florida
Posts: 6
Received 0 Votes on 0 Posts
Media Center Location, Grounding Media Center, Whole House Surge Protection

Hi, first post here. I'm getting started on some long overdue wiring and electrical work on my house and I have a few questions. Last week, I removed the a/c ducts from the attic to install new ones. Now that there's room to move around up there, it's my chance to get some work done. I should mention that this is an old block ranch style house built in 1960, 1250 sf, Central Florida near coast, very cramped attic. Previous owners had a new service head and ground installed - moved 10 ft from the original location, with a new 200-amp service panel, probably 10 or 15 years old.

The first thing I'm doing is adding a Leviton Structured Media Center as a distribution hub: Leviton SMC-280, plus installing Leviton media outlets in the walls. Then add a few dedicated circuits in the living room for av equipment. And finally, add whole-house surge protection.

The first question I have is about the media center location. I'd like to install it inside the house in a hallway - vs installing it in the garage right next to the service panel. Installed in the hallway, wire runs would be real short and clean. Access would be real easy. The only problem I see is that Leviton's instructions call for grounding the enclosure with 10-gauge wire. I could run the ground wire all the way down to the service panel - about 40 feet. But I've read in a couple places that the grounding point should be no more than 5 feet away. So I'm wondering how important it is for the ground to be within 5 feet - and if it's even necessary to ground the enclosure at all?

The second question I have is about surge protection. In the summer, the lightning is really bad here. So I would like to add a whole-house unit (looking for recommendations). I would like it to protect my phone line, Brighthouse cable tv line used only for cable internet, and 4 coax cables coming in from DirecTV satellite dish. That's 5 total coax cables. I don't think any of the whole-house units have protection for 5 coax lines, or do they? Or is it even necessary to protect the DirecTV lines? I bought this APC battery backup (BH500NET): APC Back-UPS HS. It has surge protection for one coax line and one phone/data line. I plan to mount this under the media center, so when the power blinks out, I don't lose my internet connection. (Cable modem and router will be mounted in the media center and plug into the UPS.) I could plug my phone and cable tv line into this. Not sure if that would be adequate protection. Plus that would still leave vulnerable the 4 DirecTV coax lines. What if lightning were to hit my satellite dish (or phone line or cable tv line for that matter), then travel down the cables? Would it follow the cables to my distribution center, then wreak havoc on everything connected to the media center? Is that the logic for Leviton's instructions to ground the media center? Either way, it seems that my goal should be to keep lightning from ever getting as far as the media center in the first place. Is that reasonable thinking?

I'll stop here. This post is too long already. Any suggestions you can offer would be very much appreciated! As I said earlier, with the a/c ducts down, now is the time to act. I'm a clean slate for ideas! I can post pics, house layout, anything needed.

Thanks!
-Kyle
 
  #2  
Old 05-13-09, 12:04 PM
I
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,941
Received 45 Votes on 43 Posts
Originally Posted by melbeach View Post
I could run the ground wire all the way down to the service panel - about 40 feet.
That's the correct procedure.

But I've read in a couple places that the grounding point should be no more than 5 feet away.
That's a different type of grounding. The box is equipment grounding -- antennas and grounding blocks go to your grounding electrode (earth ground). Equipment grounding is achieved through the ground bus in the main panel whereas the grounding electrode is the first 5' of a metal pipe, ground rod, or a few other possibilities.

I would like to add a whole-house unit (looking for recommendations)....I don't think any of the whole-house units have protection for 5 coax lines, or do they?
The whole-house units mount in or near the electrical panel and protect only the incoming power lines. All of the major panel manufacturers make surge protectors which are compatible with their panels. These only provide "basic" surge protection -- you should still use a UPS or surge protector strip with computers and electronics.

The coax cable and phone cable should be protected with a stand-alone surge protector (not the whole house unit).

Or is it even necessary to protect the DirecTV lines?...Plus that would still leave vulnerable the 4 DirecTV coax lines. What if lightning were to hit my satellite dish
Probably not that important. If lightning strikes the dish, your house will probably be on fire so the survival of the satellite receiver is the least of your worries. No surge protector can withstand a direct or nearly direct hit.

Adequate protection is provided by ensuring your dish is grounded through a grounded coax block before entering the house or by a separate lug on the dish. The dish installers are usually pretty good about taking care of this correctly.

(or phone line or cable tv line for that matter)
The cable TV and phone also go through (or should) grounded blocks before entering the house. Again the installers usually do this just fine. You can additionally add surge protectors for these specific services.
 
  #3  
Old 05-13-09, 12:16 PM
P
Member
Join Date: Feb 2002
Location: port chester n y
Posts: 2,117
Received 0 Votes on 0 Posts
The resistance of 1000 feet of #10 copper conductor is 1 Ohm. Let's see----

400 ft would be 40% of 1 Ohm = .4 Ohms

40 ft woud be 4% of 1 Ohm = .04 Ohms.

Difficult to understand why such a low resistance could be a problem , and where could you find a Ground- point within 5 ft of the equiptment that would have a lesser or equal resistance? I'm presumng the resistance of the Ground-path is the important design-factor.

This may no apply here, but a seperate Ground-rod , for a CATV system for example , not "Bonded" to the Service Ground , could cause a serious condition.
 
  #4  
Old 05-13-09, 03:53 PM
M
Member
Thread Starter
Join Date: May 2009
Location: Florida
Posts: 6
Received 0 Votes on 0 Posts
Thanks for the info Ben! That helps alot. Of course naturally, this leads to some new questions.

Originally Posted by ibpooks View Post
Equipment grounding is achieved through the ground bus in the main panel whereas the grounding electrode is the first 5' of a metal pipe, ground rod, or a few other possibilities.
I can't find any evidence of grounding to a metal pipe. There really isn't any plumbing in the vicinity of the service panel. Plus I'm on a slab. Now outside near the new grounding rod, my gas meter has an old wire attached to it that runs into the ground. This wire has since been cut. If I follow the metal gas line back into the garage, there's no other wires attached to it - but there may have been once upon a time. The previous owners did some pretty shoddy stuff around here. Sounds like I need to have an electrician come in and inspect my grounds.

Originally Posted by ibpooks View Post
The coax cable and phone cable should be protected with a stand-alone surge protector (not the whole house unit).
Are you talking about a standard strip-type surge protector? Or are there stand-alone units that are in kind of the same genre as the whole-house surge protector - that can be mounted near the service panel - or at least away from equipment?

Originally Posted by ibpooks View Post
If lightning strikes the dish, your house will probably be on fire...


Originally Posted by ibpooks View Post
Adequate protection is provided by ensuring your dish is grounded through a grounded coax block before entering the house or by a separate lug on the dish. The dish installers are usually pretty good about taking care of this correctly.
That's funny you mention this. I mentioned before that the service head and ground were moved and upgraded a few years ago. When I moved in, my utitlies (phone and cable) were grounded at the old grounding rod. When Brighthouse came out to turn on my cable, he noticed this, moved my cable line over to the new location, and grounded to the new grounding rod. He said that it's critical (in case of lightning strike) that I move my phone line over and ground to the new grounding rod. When DirecTV came out, I pointed this out. But he said it's no big deal and grounded to the old grounding rod. He may have just done this to save time and cable. It would save me some time if I could leave his work as it stands. But if it is important to have all utilities grounding at the same location, that would be no problem either. Yet another reason to have an electrician out to inspect this. Really, I wouldn't mind destroying all signs of the old service head, service panel, and ground - if it's safe. It's all still sitting there on the back wall in it's ancient glory. I'm not that sentimental.

Originally Posted by ibpooks View Post
The cable TV and phone also go through (or should) grounded blocks before entering the house. Again the installers usually do this just fine. You can additionally add surge protectors for these specific services.
FWIW, every lightning incident I've had here in Florida involved the phone lines - in old apartments I once lived in. It was always the phone or answering machine that got zapped. I guess that's why I'm paranoid about stopping these surges at the source. In cases where your phone gets zapped, what's usually the cause? Shouldn't the current travel down the grounding rod instead of entering the house?

Thanks again! Sorry for being so long-winded. This is an accumulation of stuff that's been building up in my head for a long time. It's finally time to take action, so now it comes to the forefront...
 
  #5  
Old 05-13-09, 04:36 PM
M
Member
Thread Starter
Join Date: May 2009
Location: Florida
Posts: 6
Received 0 Votes on 0 Posts
Originally Posted by PATTBAA View Post
Difficult to understand why such a low resistance could be a problem , and where could you find a Ground- point within 5 ft of the equiptment that would have a lesser or equal resistance? I'm presumng the resistance of the Ground-path is the important design-factor.
This may no apply here, but a seperate Ground-rod , for a CATV system for example , not "Bonded" to the Service Ground , could cause a serious condition.
Yeah, I read this info awhile back here: http://icc.com/residential/RM_Standards.aspx and here: Cabling Installation & Maintenance - The top 10 issues for residential cabling systems - and didn't quite understand everything I was reading. From the first link:

Distribution Device (DD)
The DD is the central point to which all horizontal cables are terminated and cross connected to the various services used by the owner. The DD houses all of the cables and hardware required to affect proper termination and cross connection. Space for surge suppression should be located next to, or within the DD for each conductive cable entering or leaving the building. Access to the building electrical ground shall be provided within 1.5 m (5 ft) of the DD, and in accordance with applicable local and/or national codes. The DD may consist of a passive cross-connect facility, or an active cross-connect facility, or both.
As Ben pointed out, I don't think this applies to what I'm asking. I think the 5 ft spec is referring to the grounding electrode - where I'm interested in equipment grounding for my media center box. Looking at the above quote, you can see where I got confused though. I guess my defintion of a "Distribution Device" is different. I thought my media center was a distribution device. I also think these links might be reffering to multi-family dwellings? Oh well, I stand corrected.

Thanks!
-Kyle
 
  #6  
Old 05-15-09, 12:26 PM
M
Member
Thread Starter
Join Date: May 2009
Location: Florida
Posts: 6
Received 0 Votes on 0 Posts
Hey, I found answers to all my earlier questions in this post, but there's one still bugging me.

Over the years, it seems that the only problems I ever had with lightning involved bad storms with alot of near strikes - then I check the phone and it's dead. Everything else is fine.

I'm wondering how that happens. (This always happened in various old apartments in Florida, so that could be a clue.) If the lightning strikes the actual phone line at the main pole and travels toward your building, shouldn't the current then get diverted down the building's grounding rod and into the ground? If lightning strikes nearby on the ground, shouldn't it just dissipate into the earth? I don't understand what event would cause the current to make it far enough to reach phone equipment inside - especially as consistently as it happens around here.

If anyone can give me a clue about how this happens - or what makes phone lines more susceptible than cable tv lines, I would appreciate it.

Thanks!
-Kyle
 
  #7  
Old 05-15-09, 08:07 PM
I
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,941
Received 45 Votes on 43 Posts
The lightning strike causes the potential (voltage) of the ground to increase substantially as the strike dissipates into the earth. Essentially, the current "spreads out" in a radial pattern around the strike and can increase ground potential for quite a long distance. This problem is compounded by the fact that the variations in the minerals, moisture, etc in the soil creates "hot spots" which are more conductive than the surrounding materials.

For example a nearby strike may cause the ground voltage to be 1000V at the pole and 500V at your house. This difference in potential will cause current to flow on the copper wire which spans the distance potentially damaging anything in its path.

This is somewhat counter-intuitive because we always think of the earth as being a constant zero reference voltage no matter where you are, but the incredible amount of energy discharged by lightning actually violates that principle.
 
  #8  
Old 05-16-09, 06:51 AM
T
Member
Join Date: Oct 2005
Location: USA
Posts: 1,784
Received 68 Votes on 64 Posts
Originally Posted by melbeach View Post
If anyone can give me a clue about how this happens - or what makes phone lines more susceptible than cable tv lines, I would appreciate it.

Thanks!
-Kyle

One factor is that phone lines have to be able to pass D.C, and low frequencies, like the ringing voltage. Cable TV starts much higher in frequency, so it is somewhat easier to block a portion of the lightning energy. It is true that lightning contains significant high frequency energy as well, but part of the battle is won.
 
  #9  
Old 05-16-09, 11:18 AM
M
Member
Thread Starter
Join Date: May 2009
Location: Florida
Posts: 6
Received 0 Votes on 0 Posts
Thanks, that makes more sense now. I just have to accept the fact that phone lines need special attention.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: