By Mike Holt, for EC&M Magazine
Q1. I need to know the current NEC rules regarding the use of RG-6 W/messenger ground wire for an 18 in. satellite dish. What I understand is that I must attach the messenger wire to dish, then attach both the coaxial and messenger wire to a grounding block. Then I must ground the grounding block to a proper grounding source.
A1. Both the dish and the lead-in cable must be grounded in accordance with 810.21 and the messenger ground wire (that is part of the cable to the dish) can be used for this purpose as you described. But, be sure you ground the grounding block with a 10 AWG ground wire in accordance with 810.21.
Author’s Comment: See my explanation on how to properly ground the dish and cable.
Q2. I represent a large multi-family management company. Many of our residents want to install small satellite dishes in their apartments. Our policy is the dish must be installed per the manufacture installation procedures, which references the NEC. Additionally our policy states that all wiring must stay within the tenants "rented" space. To clarify, all wiring and the dish must stay on the patio or balcony. Given these parameters, how can a small satellite dish be grounded properly per NEC and still be installed by our tenants?
A2. There is no way to meet your management policy and comply with the NEC’s requirements.
Author’s Comment: See my explanation on how to properly ground the dish and cable.
Q3. I want to install a 2-way satellite system on the patio of my apartment that is enclosed on three sides. The installer want to ground the dish to a metal rod that is driven into the ground (which is not feasible from the third floor). There is no cold water piping outside the apartment. So, can I ground this dish properly, or am I stuck with a phone line dial up?
A3. The installer was wrong. You cannot use a metal rod driven into the earth for grounding of the dish and lead-in cable, unless the metal rod is bonded with a 6 AWG conductor to the building grounding electrode system in accordance with 810.21(J). In addition, the NEC does not allow you to use the local water pipe [810.21(F)(1)(b)]! Looks like your going to have to stick with a phone line for dial up connection! Sorry.
Author’s Comment: The 2002 NEC changed 810.21(F)(1)(b) to require that where the connection is made to metal water pipe, I had to be within 5 ft from the point of entrance of the water pipe into the building.
Q4. I am installing a Satellite TV system (18" DSS) near the electrical service. Is it okay to ground the dish mast and the coax grounding blocks to the same rod that was installed as the ground for the electrical service or do I have to install a new 8 ft grounding rod for the dish mast as the instructions say?
A4. DO NOT add an independent ground rod in accordance with the installation instructions, they are wrong. The dish and cable is required to be grounded to the service grounding electrode system, and yes you can use the same ground rod as the service ground rod as you suggested, see 810.21(F)(1)(a).
How to Ground a Satellite Dish and the Lead-In Cables
Grounding (the intentional connection to earth through a ground connection or connections of sufficiently low impedance) is intended to prevent the destruction of electrical components, as well as electric shock that can occur from superimposed voltage from lightning, voltage transients, and contact with higher voltage systems. In addition, earth grounding helps in reducing static charges on equipment to ensure the proper performance of sensitive electronic equipment.
According to insurance industry data, failure to properly earth ground communications systems has led to $500 million dollars of property or equipment damage annually due to lightning, surges. Proper grounding of the antenna mast and lead-in cables in accordance with the NEC is somewhat effective in protecting receiving equipment from voltage surges, as well as voltage transients from lightning.
The National Electrical Code requires the mast (Dish) to be grounded [810.15]. Figure 1
In addition, the lead-in cable from an "outdoor antenna" must be provided with a listed antenna discharge unit (grounding block) located as near as practicable to the entrance of the conductors to the building [810.20]. The discharge unit must be grounded to an acceptable location in accordance with 810.21(F)(1)(a) through (f), with a 10 AWG copper conductor (bare or insulated) that is run in as straight a line as practicable [810.21(E)] to the electrode. Figure 2
810.21(F) (1) Grounding Locations Figure 3
a. The building or structure grounding electrode system as covered in 250.50,
b. The grounded interior metal water piping system within 5 ft from the point of entrance into the building as covered in 250.52, Figure 4
c. The power service accessible means external to enclosures as covered in 250.94,
d. The metallic power service raceway,
e. The service equipment enclosure, or
f. The grounding electrode conductor or the grounding electrode conductor metal enclosures
If the grounding conductor is run in a metal raceway, then both ends of the metal raceway must be bonded to the grounding conductor [810.21(D)]. When an electrode such as a ground rod is installed to ground the mast or lead-in cable, it must be bonded with a 6 AWG copper conductor to the grounding electrode system at the building or structure served [810.21(J)].
Caution: If the lead-in from an outdoor antenna is not properly earth grounded, the receiver can be destroyed by voltage surges caused by nearby lightning strikes. If the mast is not properly grounded, the Low Noise Block (LNB), as well as the dc rotor motors that control the positioning larger satellite dishes could be destroyed by voltage surges caused by nearby lightning strikes.
Mikes Comment: If you have any comments or feedback, please let me know, (-REDACTED-)
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