DBS Grounding Question

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curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
Occupation
Electrical Contractor
We are just finishing up the rough wiring for a new single family dwelling and today the GC informed us that the low voltage contractor wants us to provide the ground for his DBS satellite dish. The house is about 6000 sqft with 3 levels and the dish is located at the opposite end of the house from the electrical service. It would take approximately 150? of wire to connect the dish directly to the grounding electrode system. 820.40(A)(4) says the grounding conductor shall not exceed 20? or a separate ground shall be used. Even if I did install a ground rod closer to the dish I?m still looking at 40?-50? of ground wire to reach the dish and then another 100?+ of wire between the ground rod and the existing grounding electrode system. 820.40(B)(1)(1) permits the interior metal water piping to be used if the connection is with 5? of its entrance to the building. This point would be at the same location as the service so doesn?t help much. This house is being built under the 99 NEC and I don?t see the 5? limit in 820-40(b)(b). All of the interior piping is copper and there is piping pretty close to the dish. Suggestions anyone?

Curt
 

jii

Member
Re: DBS Grounding Question

Curt
If you drive your supplemental ground rod, bond it with #6 to the grounding electrode system,then continue to an accessible location with in 20 ft. of your dish. 820.40(B)(1)(6)allows you to use the grounding electrode conductor,this would no different then using a common grounding electrode conductor for separately derived systems.
John
 

curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
Occupation
Electrical Contractor
Re: DBS Grounding Question

John, thanks for the reply. My problem is that the dish is located on the roof of the top level of the house. It will take at least 40? of wire to reach a supplemental electrode on the ground level. I could bond it to the interior metal water piping reasonably close to the dish but the 2002 NEC does not permit this. It looks it might be acceptable in the 99 NEC. At this point I think I am going to tell the GC either to have the LV contractor move the dish which I doubt will happen or he can deal with the ground. In reality less than 10% of dishes in my area get grounded but we seldom have lightning.

Curt
 

jimwalker

Senior Member
Location
TAMPA FLORIDA
Re: DBS Grounding Question

I would handle this in one of 2 ways
1.install to his specs and design with waiver of any resposibility ,signed by dish company and owner.
2.tell him to do it himself.
I see you walking right into a trap.
In the event it gets hit they will be looking at you.What could you possibly charge to be worth the hassle.Note they did not ask you to run any cable or install outlets.Your being brought into the biggest risk of the entire install and getting very little,while the dish company makes all the big $$$$$
If they can run all the other cables then why not the ground :roll:

[ September 29, 2004, 07:28 PM: Message edited by: jimwalker ]
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Re: DBS Grounding Question

This is a common problem with dish installations and is one reason few get grounded properly. The other reason is people don't understand what is required and the seriousness of it. Sometimes with existing construction this can be a big problem but since this is new you have no excuse!

It will make you (un)happy to know that the ground wire should be run on the outside of the house. In the event the dish does get hit I wouldn't want the lightning run into the house on purpose and this is why grounding to the copper water lines is out of the question.

Drive a supplemental ground rod below and as close to the dish location as possible. Bond it to the dish with a #6 wire. This wire should be run as straight as possible down to the ground rod, no sharp bends. This should be done like a lightning protection system.

Next you need to bond your supplemental ground rod to the GEC. That should be run outside too. Best way is buried around the house- run it around the footings or if it's been backfilled rent a trencher. This will provide an even lower resistance to ground as a bargain.

Yeah, it's going to cost a few dollars but this should be a small cost to someone who is building a 6000 sq ft house. Figure it out and charge accordingly instead of trying to get around it!

-Hal
 

curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
Occupation
Electrical Contractor
Re: DBS Grounding Question

Hal

I?m not trying to get around anything!

I don?t feel that your method is code compliant since the ground wire is still going to be longer than 20?. I was just asking for opinions here. If I can not do this in a code compliant manner I?m not going to do it. I?ll let the GC and LV contractors work it out. We are done with our work and are now being asked to come back and finish another contractor?s job. We don't normally get involved in installing antennas so don?t deal with their grounding. The few times I have been on jobs at the same time as one of the DTV or DN installers they have specified that they will only mount the antenna close to the electrical service panel so they can properly ground the dish.

Curt
 

dereckbc

Moderator
Staff member
Location
Plano, TX
Re: DBS Grounding Question

Curt, you are getting hung on 20 feet as gospel. Read the exception. Your best alternative is to add a rod as close as possible to the dish, and use 6 AWG to bond dish to rod, and 6 AWG from rod to GES. Your two other alternatives are a plate, or local metal underground system.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Re: DBS Grounding Question

...If I can not do this in a code compliant manner I?m not going to do it. I?ll let the GC and LV contractors work it out.

Usually in cases like this, since the GC and LV contractors aren't licensed to do electrical work and can't pull a permit it's up to you as the EC to get this right. If the inspector red tags it, you are the one who gets the violation.

We are done with our work and are now being asked to come back and finish another contractor?s job.

I don't see what the problem is, sounds like an $extra$ to me.

-Hal
 

curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
Occupation
Electrical Contractor
Re: DBS Grounding Question

Actually in California general contractors are allowed to do electrical work as long as they are doing 2 other unrelated trades on the project. The low voltage contractors usually install alarm systems including smoke detectors so are require to hold an electrical contractors license. For residential projects most jurisdictions prefer to issue one permit for all trades to either the general contractor or property owner instead of issuing separate permits for each trade.

I?m going to give the GC a price to do the work as suggested by Hal & Dereck and can pretty much guarantee he is going to tell me I?m crazy. I would rather do this additional correctly or not at all.

Thanks for the input!

Curt
 

gndrod

Senior Member
Location
Ca and Wa
Re: DBS Grounding Question

Curt, If the antenna is properly connected, there should be three RG6/U shielded coax cables (equipment with two receivers)connected back to the Structured Media Distribution panel that automatically grounds the cables and antenna to the distribution hub. The according to Media specs the hub must ground directly to the Sevice GEC at that location #6 AWG Cu. If the antenna is the promenant height above the roof ridgeline and lightning liability is an issue then the owner should be aware of a safety option for installng lighning rods. (relocating the antenna below the ridge line would also be a prudent design.) Above all do not ground to any metal plumbing pipes to exposed conductor lines on the roof.
Some the background in my previous life was in electronic systems so take this data for what its worth knowing just enough to be dangerous. Another idea is to contact subcontractor Jim Donohue(LightningMan.com)for another take on this matter.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Re: DBS Grounding Question

Well, depending on the installation there are two RG/6's (or possibly only one) coming from the dish LNB. None of us mentioned the requirement for the shields of these cables to be grounded where they enter the house. Don't know about any "structured media distribution" thingy, :roll: the cables are normally grounded via a ground block and if it's close to your #6 from the dish it can certainly be bonded to that. I've been known to install a PVC riser through the roof with a weather head close to the the dish location for the lead-in cables.

If for some reason the RG/6's have to enter the house somewhere else, the ground block has to be bonded to the service ground also and again, if its more than 20 feet you have to drive a supplemental ground rod and bond it to the service ground just like the ground for the dish.

-Hal
 
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