Is grounding of dish necessary?

[johntoto11]

Hello folks, I'm doing A self install of A Directv HDVR2 (Directivo). I have mounted A dish mast with A 20 inch piece of plastic PVC pipe on the end of the mast, (to help the dish clear the roof line), on the side of my house. The install kits I have, came with rg6 cable that has A grounding wire attached to the cable. I intend to attach one end of the grounding wire on the cable, to the bottom of the mast and the other end to the grounding block. The grounding block will be connected to the central building ground with copper grounding wire. Will the fact that I have the PVC pipe extension make A difference as to weather the dish is grounded correctly? Do I even need to ground the dish? We get some fierce thunder storms in the summer , here in Florida, and want to do this correctly. Thanks, Dennis in Fla.

[Tomsoundman]

Do need to ground for static electricity purposes.

There are some interesting reads on the subject and from what I understand, it is not for the purpose of a lightning rod, but to dissipate static electricity.

Anyone else please respond or correct me.

[apc1]

To dissapate static electricity and stray RF signals. Though grounding of the mast is a controversial issue in terms of it's usefullness.
John, what i'm trying to understand is why you chose PVC over metal? Have you seen these?
http://www.starkelectronic.com/wing2.htm
Scroll down to the DS-3000 mount. This may be what you need. Just make sure to mount the mast as sturdy as possible.
Hope this helps.

[waydwolf]

(ponders wandering into where angels fear to tread...)

    There are several reasons to ground a dish, not the least of reasons is that the NEC(National Electric Code) *REQUIRES* it and the NEC is the basis for your local electrical codes which will almost certainly be even more stringent.

    First, it IS to work as a lightning rod. Lightning rods are not there to attract lightning. A copper rod the width of a tree and fifty feet long wouldn't last long under repeated assaults from lightning never mind those simple metal spikes and copper braids that are used for lightning rod systems. They are there to dissipate charge from an area to prevent formation of leaders that result in discharges and BANG.

    Ungrounded, your dish would act like a round metal ball on a flag pole, collecting charge and potential until a leader formed and BANG.

    Second, static dissipation is incredibly important as well as electricity always seeks the lowest potential it can find like water trying to flow downhill. Natural airflow, especially wind, physically knocks electrons loose, creating ionization. The equipment is also electrically charged as part of its operation. If the static builds sufficiently, the insulators between it and the lowest potential will act like a dielectric that's reached its breakdown and current will flow to where it shouldn't. Like through the LNB downconverter circuitry, the receiver box, you if you're touching it, your TV, VCR, etc.

    Ground should NEVER EVER be a four foot ground rod. It isn't remotely NEC compliant and the Perfect-10 catalog even says so clearly yet installers keep using them. Ground is supposed to be the same as for your receivers: the household electrical ground.

    If the installer cannot reliably connect to the electrical box outside, then the next acceptable outside place would be the eight foot ground rod nearby but ONLY if it has a #6 or better ground strap to the cold water inlet AND the ground of the household system. Sometimes you'll see the ground strap inside one of those BX armor jackets and other times, you'll see one huge looking copper braided cable like something you'd jump start a car with.

    Going straight to a clamp at cold water is also acceptable but ONLY at the inlet penetration and NOWHERE else(NEVER EVER a hot water pipe or garden spigot or the like) and ONLY if it is actually also connected to the household electric ground. Finding the household ground clamp and strap there will clue you in immediately.

    Why is this unified ground so important? Because if you have two separate ground potentials, you may not have current flowing to where it should in case of a fault and should it not flow directly to the safest place in accord with proper safe electrical design, it might be flowing through electronics that may burst into flame, or... you.

    Also, multiple ground references in a system can and usually do lead to ground loops which have been known to foul receivers, digital cable boxes, and especially prevent cable modem operation. The neutral line of your household electrical system is bonded to ground at the service entrance and fouling that up with improper grounding is not a good idea.

    Ground the dish and then call a qualified electrician to install a good lightning rod system on top of it to keep from being one of those lighning-caused house fire statistics. My former firefighter father went to too many of those.

 

[johntoto11]

Thanks, I think I can remount my dish on the southern side of my house, without the PVC extension. I'll just have to run some xtra rg6. I'll check on A electrician to come out and tell me if things have been connected properly. Between my home theater equipment, and my computer alone I have over $4500.00 tied up in electronics. Whats A qualified electrician normally get for A house call such as this?

[waydwolf]

Originally posted by johntoto11
Thanks, I think I can remount my dish on the southern side of my house, without the PVC extension. I'll just have to run some xtra rg6. I'll check on A electrician to come out and tell me if things have been connected properly. Between my home theater equipment, and my computer alone I have over $4500.00 tied up in electronics. Whats A qualified electrician normally get for A house call such as this?

    It varies greatly, depends on their quality and size of operation, and some other things. I generally check out their rep with various recent electrician customers and get references for a few and then call and ask them for further references before choosing one.

    It may sound unscientific, but if I see an electrical company with multiple trucks and crews at a local or state construction project that on questioning says they do residential as well, I usually have less to fear as the state of CT is very strict on what work quality they expect and accept of their contractors so they usually know their stuff.

    Good luck shopping. You should get a head for average prices in your area after three or four inquiries.

    Remember, better alive than crispy.

 

[Jacob S]

You may also want to get a surge supressor and you can also get a supressor for the phone line and cabling before it goes into the receivers.

[DarrellP]

So how do you tie in your ground system to the house common ground when the dish is on the opposite side of the house from your electric service and all the water pipes are PVC?

[drjake]

Next best thing is to connect to a piece of metal conduit, since that is connected to your household grounding system.

[Todd Humphrey]

Lightning rods are designed to protect structures from lightning by providing a safer path for the strike to travel.
If you have a building that is at a high risk of being hit by lightning, you install a lightning rod and condutor to provide a path of low resistance in the event that you are hit by lighting.

Tall buildings, water towers, silos, wind mills, barns and other structures that are higher then others an in the open, as in the farm building, are at a higher risk and stand a good chance of being hit. The rods will minimize the effects of the strike

If you are concerd about lightning, purchase a lightning rod and install to manufacterurs spec.

The grounding requirement of the NEC for antenna mast is outdated. I have spoken to several engineers about lighning. One is a SBCA instructor with a 50 year back ground in lightning research, another a professer, smart smart people. They both agree that installing a ground conductor for a dish mast is most likely not a benefit and may do more harm.

BUT, you still ground because the NEC says so. The only reason I even told you this is because the logic behind grounding the mast does not hold up when dealing with DBS antennas. The grounding requirements for a DBS antenna are the same as if it where on 100' tower next to your house. Dont try to figure out WHY you ground the mast, just do it.

The ONLY reason most professional installers ground the antenna mast is because the NEC says so and in the event of a disaster we do not want to hit the blame because we did not follow code.

Grounding the coax is very improtant. It disipates static, neutralizs the 60 volts between the cable shield and the house ground (if your reciever uses a switch mode power supply and does not have a three-prong plug) and provides a safe pathway for any current that my show up on your coax.

Acceptibe grounds are:
home grounding electrode
grounding conductor between service panel and electrode.
metal water service pipe within 5 feet from POE
metal raceway
service panel enclosure

Wolf

If the coax is grounded thereby discharging any static from the receiver, then how can the dish have any higher risk for lightning strike then metal gutters, metal chimny pipes, metal vents, metal flashing, metal roofs, metal siding ......?

When none of those are ever grounded.

[AntAltMike]

Originally posted by Todd Humphrey

Grounding the coax is very important. It... neutralizes the 60 volts between the cable shield and the house ground (if your receiver uses a switch mode power supply and does not have a three-prong plug)...
Run that by me again. I know what a switching power supply is, but how does it develop a 60 volt potential difference between the cable shield and the house ground?

Acceptable grounds are:
home grounding electrode
grounding conductor between service panel and electrode.
metal water service pipe within 5 feet from POE
metal raceway
service panel enclosure)
How does the NEC define the term "service panel enclosure"? I was once told that referred to the box that the electrical meter was in. I have these little copper corner clips that I sometime use to connect a ground wire there. More recently, I see the term being used in internet threads on grounding to refer to the main circuit breaker panel, which several electricians have told me is NOT an acceptable connection point for an antenna system ground.

What do you mean by "metal raceway"? Is this the structural steel of the building, if bonded, or something else?

If the coax is grounded thereby discharging any static from the receiver, then how can the dish have any higher risk for lightning strike then metal gutters, metal chimney pipes, metal vents, metal flashing, metal roofs, metal siding... (W)hen none of those are ever grounded.

I take it you meant that the coax ground discharges any static from the antenna, rather than the receiver. Off-air antenna downlead coax connections for off-air antennas often do not provide an adequate static discharge path for the antenna or mast as the better grade 300 ohm to 75 ohm matching baluns are actually dual-wind transformers, whereas the smaller, cheaper ones are single-wind autoformers that do not isolate the input from the output. Further, grounding of a dual-boom log periodic antenna does not ground the mast it is mounted on, as the boom is electrically isolated from the mast

Metal satellite dishes are ordinarily attached directly to the masts and therefore connected electrically, but some of the larger dishes (Channelmaster, Prodelin) are fiberglass and electrically isolate the LNB from the mount. While I know of no satellite connection technique that electrically isolated the coax shield from the LNB (other than Glass Plus), it is commonly isolated on 30" and larger dishes, since their LNBs are usually mounted in plastic clamps, rather than fitted into feedhorn support tubes. In that situation, a coax shield ground does not effectively drain away the static electricity.

It is also possible that the coax is not considered mechanically reliable enough to serve as the mast ground as hurricane force winds are much more likely to break the coax than a conforming, 8 gauge aluminum, 10 gauge copper or 17 gauge copper clad steel ground wire.

A non-grounded antenna may be slightly more vulnerable to lightning strikes than ungrounded siding and gutters, if only because it is often the highest point on the building (though this is less likely with DBS than with most other antennas), but it is more important to ground an antenna mast than siding or gutters since all antennas have downleads that are highly conductive and provide a most efficient path into the house. Grounding the mast provides a second, more efficient path the try to drain away as much of the electrical energy of the lightning as possible.


All that having been said, I don't believe that the safety benefit of grounding amounts to a hill of beans. I ground so that I will not be blamed for something that goes wrong.

[JayeDVXIII]

hey there wolf guy

i've been pissed off in the past b/c when i did the dish movers program, the jerk-off installer they sent refused to install my dish because he could not ground it.

I lived in an apartment on the second floor and there was no electrical service equipment nearby..plus I was not allowed to have any wires or anything else going out of my balcony to areas outside my exclusive use.

So basically he left the dish with me and I put it up myself and no, I did not ground it. However, I did stick the "ground wire" into the wood of the balcony floor. Who knows if this did any good. (LOL)

It seems sucky that the FCC law that keeps landlords from preventing me from installing a dish does subsequently keep me from being able to ground the service if i live on an upper floor

[Todd Humphrey]

I still need to dig into the NEC to determine that exact term "service panel".

My point on grounding a DBS antenna mast is basically that the it has never been shown to be a benefit to anyone. When the rules were written, the common practice of grounded an antenna mast was routing a ground conductor in a very straight path to a ground rod, which was often NOT coupled to the house ground (even thought it should be) because as you pointed out the antenna is isolated from the mast. However with a DBS dish the mast is either electrically coupled to the coax via the LNB or isolated from the coax and earth ground due to fiberglass. The need to route two ground conductors is, in my opinion, not needed to provide a safe installation.

Can anyone provide stats that show DBS dishes are more likely to be hit by lightning if the mast is not grounded? I simply do not think the same rules you would apply to a 100 foot tower should apply to a 18" dish mounted to the side of your house.

If there are stats to show I am wrong, then fine I am wrong, but mean while techs all over the place not not grounding, they are grounding improperly, and that can be more dangoures then not grounding at all.

Another point, A common practice today is to use a 17 awg copper coated steel messanger style cable to provide the ground conductor to the mast and then that conductor is routed though the ground block where a single conductor carries the potential load for both the mast and the cable.

As far as apartment goes. By the book, an installer cannot install on a apartment unless they can get to building ground. This is another place where the NEC is out of date on this issue. What I require all customers who fall in to this situation to do is, purchase a surge strip with satellite rated coax loop though ports. I install the surge strip immediatly were the cable enters the building. Having the surge strip and its built in ground block just inside the building meets code. The tricking part is I can not find a reference that allowes for bonding to a receptical. But this is what I do.

The 60 volts on the coax ground comes from the potential between the receiver chassis, and therefore coax ground, and the electrical ground or neutral. When it is wet outside and you are grounded with wet feet (or in case I kneel down) and you touch a ungrounded coax, you can get a good jolt. there is no current present but what you are feeling is the switch mode power supply hitting you because the manufacturer did not use a three prong plug.

Take a hughes or a 301, plug it in and test the potential between the chassi and the receptical ground. The 301 is 60 volts and hughes about 51 by our test. When you get zapped the potential drops to zero, if you are a great conductor, then it charges back up again very fast.

Not a danger, no current and only 60 volts which drops to 0 immediatly.

[Todd Humphrey]

Sorry for all the typos.

www.dbsinstall.com