Satellite System Grounding
Part 2 - NEC Overview
Presented by Todd Humphrey

All references to sections of the NEC, are from the 2005 NEC. The NEC has two articles applicable to satellite systems. Articles 810 and 820 apply to satellite mast, and the coax that connects equipment. Article 810 specifically covers antenna mast, and coax, whereas Article 820 is intended for Cable Television. Article 810.4 -Other Articles, states "Coaxial cables that connect antennas to equipment shall comply with Article 820."

Since nowhere does Article 810 exclude coaxial cable from having to meet the requirements of 810, it is my recommendation that coaxial cable meet the requirements of 810 and 820. Since 810 and 820 have virtually the same grounding requirements, meeting both 810 and 820 is simple. In any situation where 810 and 820 seem to conflict, I recommend the more safe option.

 

The Mast Ground

Article 810 says the mast must be grounded using one of the following conductors. (810.21(H))

  • 10 Gauge Copper Wire -Solid or Stranded, Insulated or Bare
  • 8 Gauge Aluminum
  • 17 Gauge Copper clad Steel or Bronze wire

Article 810 says nothing about the use of solid or stranded, therefore there is no restriction from using solid or stranded wire. There is no length limitation on the ground wire.

The ground wire must be grounded to an NEC approved grounding point. See below for approved grounding points.

 

The Coax Ground

The coax must be grounded in the same manner as the mast. It must also meet Article 820, per 810.3. Article 820 adds the following conditions to those found in 810.

  • The Ground wire must be copper or other corrosion resistant conductive material. (no aluminum).
  • The Ground wire must be insulated.
  • The Ground wire must not be smaller than 14 Gauge, and shall have a current-carry capacity approximately equal to that of the outer conductor (shield), but no larger than 6 gauge.
  • The ground wire shall not be longer than 20 feet.

The ground wire must also be grounded to an NEC approved grounding point.

 

Summary

  • A satellite dish mast must be grounded with at least a 17 Awg copper coated steel wire.
  • The coax must be grounded as close to Point-Of-Entry as possible and the ground wire must be no smaller than 10 Awg Solid Copper. Article 810 says 10 Awg, but Article 820 says 14 Awg. To meet both requirements, you should use 10 Awg.

 

Note: Both DIRECTV and DISH Network require a 10 Awg Solid Copper ground wire for the coax. There is a good chance, future versions of the NEC will reflect this as well. I recommend a 10 Awg ground wire, regardless of the current NEC.

NEC Approved Grounding Points

 

There are 5 general locations where you can ground a satellite system.

 

Ground Rod and Ground Wire

1. Electrical service electrode (ground rod), or the conductor that connects the ground rod to the electrical service panel.

The ground rod must be the main electrical ground rod, or if a separate ground rod is installed, bonded to the primary ground with 6 gauge ground wire. It is a common practice among some installers to install a 5 foot ground rod and not back bond. This can lead to several problems. See part 7 for more information about installing isolated ground rods.

 

Service Panel Pan Clamp

2. The metal electrical service panel. A Service Panel includes the meter housing, circuit breaker , or sub panel, if the sub panel is connected to the breaker panel by a rigid metal conduit. A rigid metal conduit is typically schedule 40 steel.

 

Service Power Conduit

3. A metal electrical raceway or rigid conduit. The metal conduit or raceway that feeds power to your service meter, or runs between service panels. To ground to a conduit, a copper or galvanized steel strap is wrapped around the pipe and secured with a screw that, when tighten, pulls the clamp tight.

 

 

 

 

 

 

Water Service Ground

4. Water pipe. BUT ONLY with in five feet of the water pipes entrance to the structure and only if the water pipe is metal and in direct earth contact for at least 10 feet before entering the property. Attaching a ground wire to a water valve is NOT ACCEPTABLE and should not be accepted.

Water Spicket Ground

See part 7 for more information about grounding to a water pipe. Attaching a ground wire to any water pipe beyond 5 feet from where the pipe emerges from the ground is not allowed. The image to the right shows a ground wire attached to the main water service as the line exits the ground and enters the structure. The point were the water supply pipe emerges from the earth is the pipes point of entry.

5. The grounded metal structure of a building. If the buildings metal structure is grounded by one of the above means, a ground wire can be bonded to the metal structure. This is usually used with mobile homes and commercial buildings.

 

NEC Summery

The only aspect of Article 820 that conflicts with 810 is the mention of the 14 gauge ground wire. To meet both 810 and 820 for coax grounding, you must use a 10 gauge ground wire. The 8 gauge aluminum and 17 gauge copper coated steel allowed under 810 for mast ground do not meet the requirements of 820 for coax ground.

The mast can be grounded with 17 Gauge Copper Coated Steel, but the coax must be grounded with 10 gauge copper. The NEC requires both ground wires to be grounded to an approved ground point. The NEC also requires that the coax ground wire be capable of carrying at least as much current as the outer shields of the coax being grounded.

 

NEC Shortcut

The NEC addresses the mast and the coax as separate systems ,and that each system needs to be grounded. If you follow the NEC to the letter, each ground wire must be grounded as stated above. A common grounding practice is to connect a 17 Gauge copper coated steel ground wire from the dish mast to a coax grounding block. Then ground the ground block with 10 gauge copper to an NEC approved grounding point. By grounding the mast to the ground block and sharing a single 10 gauge ground wire for both mast and coax, the NEC grounding requirement of the mast is not meet. This sharing, or piggy-backing of grounds is a common practice within the satellite dish industry and is fully supported by both Dish Network and DIRECTV.

Is piggy-backing grounds good or bad? It most likely is just fine. The practice is wide spread and to date there has never been a problem with this practice.

 

Return to Part 1 - The NEC, Service Providers & Local Authorities                    Go To Part 3 - Why Ground?
 

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