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Dish far from house ground


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#51 OFFLINE   westom

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Posted 21 October 2012 - 08:33 PM

My knowledge of NEC requirements are limited, at best. I'm interested in hiring someone more knowledgeable.

You are still confusing ground as defined by the NEC (only for human safety) with ground that makes surges irrelevant (for electronics safety). Ground for human safety is often insufficient (due to too much impedance).

For example, a long wire transmitter antenna might have 100 volts on one point. And the same wire might have zero volts on another point. That would not happen with electricity that concerns code. But that is relevant to another electricity that concerns surges. Wire can be electrically different at both ends. Therefore a connection from satellite dish to earth must also be short (ie 'less than 10 feet'). That wire must not have sharp bends. And other factors never found in the NEC. Because those same requirements (low impedance) are irrelevant to human safety.

The term is called impedance. Impedance is irrelevant to how 60 cycle works. And is significant to how surge protection works.

Various requirements both for human safety and for protection means a dish (typically) must have its own earth ground (as wire as short as possible to be both low resistance and low impedance). Those same requirements also say why a coax cable must be earthed (as short as possible) to single point ground before entering the building.

An engineering application note demonstrates these concepts that also apply to your dish (and would be irrelevent to a pool and to NEC):
http://www.erico.com...tes/tncr002.pdf

Another example of different electrical characteristics when earthing for human and electronics safety. An 18 AWG wire (ie lamp cord) is typically considered a 10 amp wire (for human safety). The same wire may conduct a surge current up to 60,000 amps. Due to electrical differences in those two currents.

A 12 AWG wire (often used for earthing communication cables) and the 6 AWG wire (often used for earthing AC electric wires) are both more than sufficient (thick enough) to perform both human and electronics safety. And also should remain sufficiently 'thick' many decades later for both purposes. Those wires are thick enough to provide low resistance. But impedance is mostly defined by wire length. Low impedance means that same wire is typically shorter than required by code.

Edited by westom, 21 October 2012 - 08:48 PM.


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#52 OFFLINE   P Smith

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Posted 21 October 2012 - 09:55 PM

The term is called impedance. Impedance is irrelevant to how 60 cycle works


I think NEC definitions must be same as for electromagnetic definitions. Those you are incorrect.
Impedance would be a complex parameter what defined at freq not eq 0 (constant current) and includes resistance, capacitance and inductance.

So, the impedenace is totally relevant to freq 60 Hz (and any AC) , and irrelevant for DC.

#53 OFFLINE   westom

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Posted 21 October 2012 - 10:31 PM

So, the impedenace is totally relevant to freq 60 Hz (and any AC) , and irrelevant for DC.


Put numbers to your summary. When done, impedance for a wire at 60 Hz is almost identical to wire resistance at DC. Parameters for both 60 hz and DC do not explain currents that occur in wires during lightning. Does not even explain why the 10 amp (18 AWG) wire can also conduct a lightning current approaching 60,000 amps.

60 Hz electricity is from a voltage source. Surges are from a current source. Just another of so many electrical differences. Those so many differences explain why NEC requirements do not define lightning protection.

#54 OFFLINE   veryoldschool

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Posted 21 October 2012 - 10:40 PM

Does not even explain why the 10 amp (18 AWG) wire can also conduct a lightning current approaching 60,000 amps.

Maybe it would for a few nano seconds before it vaporized.
A.K.A VOS

#55 OFFLINE   P Smith

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Posted 21 October 2012 - 11:58 PM

Put numbers to your summary. When done, impedance for a wire at 60 Hz is almost identical to wire resistance at DC. Parameters for both 60 hz and DC do not explain currents that occur in wires during lightning. Does not even explain why the 10 amp (18 AWG) wire can also conduct a lightning current approaching 60,000 amps.

60 Hz electricity is from a voltage source. Surges are from a current source. Just another of so many electrical differences. Those so many differences explain why NEC requirements do not define lightning protection.

I'm lost here ... :confused:

#56 OFFLINE   westom

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Posted 22 October 2012 - 07:34 AM

I'm lost here ... :confused:

Posted were first year electrical engineering concepts that you must understand before you can dispute or reason any of this. You have assumed impedance at 60 Hz is significant because you have not calculated what that wire impedance is.

Why must the wire connection to earth ground be so short for transistor protection. And can be so much longer for human protection? Even the concepts called voltage source and current source are relevant. Just another reason why NEC requirements do not define earthing also for protection from lightning. And why protection from lightning means both meeting and exceeding NEC requirements.

#57 OFFLINE   Neurorad

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Posted 23 October 2012 - 09:36 PM

I'll ground the dish and mast using 17 AWG copper clad steel, but I probably won't ground the dish properly, if I can avoid it. Direct strike isn't a concern, and not at all concerned with surges from the dish.

I'll ground the pet fence and irrigation system, though, and add the whole house SPD (using a short, straight connection of course). Those are now on my short list, with DirecTV installation, and new WAPs.
Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense. -Buddha

#58 OFFLINE   woodybeetle

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Posted 26 October 2012 - 09:49 AM

SO I have watched this thread unfold and havea couple of comments that are warranted in my opinion.

a. the 1 gauge wire from the dish to ground is not a ground source, it is intended to bleed off static discharge built up in the antenna (LNB).

b. the usage of a 10 gauge wire to bond to the earth ground is designed to minimize near lightning surges, and is normally sufficient.

c. a customer will always read the NEC and decide that he knows what is best, thus installing outside of code.

d. a well trained installer will avoid the install due to the liability it will induce in the future.

Food for thought:

Installed a 22 story MDU, 186 apts in building,

# 6 copper from LNBs to bonded ground, 8 Feet away
# 4 copper from coax to bonded ground plate in first closet, 31 feet from dish
# 8 copper from coax to bonded ground plate every 2nd floor

All ground points installed by electrician and passed city inspections at a cost of approx 3800 dollars for work performd

Lightning impacted(direct strike) adjacent building (140 ft away)

Spent 3 days reinstalling our system, all electronics dead, most of coax scorched on center conductor, roughly 60 DTV set top boxes would not power up.

Point of ingress of the lightning to the satellite system, a ethernet port from the internet provider to our monitoring system, his system was grounded as well.

Satellite Company Insurance claim of 37000
Property insurance claim of 250000+


Moral of the tale, No matter the intention of the installer, mother nature will find a weak point and exploit it.
Daniel D. Corum
DDCESI/Idiot Proof Television

#59 OFFLINE   P Smith

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Posted 26 October 2012 - 10:32 AM

After your morale, would you post practical advise regarding grounding, at least for that mentioned MDU setup.

#60 OFFLINE   Neurorad

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Posted 26 October 2012 - 10:53 AM

Daniel, I agree with you, on every point. I wonder how well the incoming ethernet connection was grounded. Any SPD on that setup?

I hope I get an installer who isn't well-trained. Signed up for DirecTV yesterday, install scheduled.

Does the installer show up with the equipment, or is it shipped to my address? If the installer refuses to install improperly (i.e. does his job well, no criticism here), am I supposed to hand him the equipment, if it was shipped?
Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense. -Buddha

#61 OFFLINE   P Smith

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Posted 26 October 2012 - 11:41 AM

New install ? Everything will be installed by a tech. If you will think he did grounding wrong, do not sign his work order.

#62 OFFLINE   westom

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Posted 26 October 2012 - 09:34 PM

a. the 1 gauge wire from the dish to ground is not a ground source, it is intended to bleed off static discharge built up in the antenna (LNB). ...

Point of ingress of the lightning to the satellite system, a ethernet port from the internet provider to our monitoring system, his system was grounded as well.

If a ground is for static discharge, then a 36 gauge (hair thin) wire would be sufficient. Why is that a 1 gauge wire? Nobody installs a more than quarter inch thick (maybe 80 amp) wire to discharge static. Protection already inside each LNB makes static discharges irrelevant. That 1 gauge wire is for even earthing a direct lightning strike.

If an ethernet port was damaged, then that is most likely an outgoing path; not the incoming path. Damage on that outgoing path means some other incoming path must exist. If a coax between two buldings was not properly earthed at both buildings, then a lightning strike to one building was a direct strike, incoming on the coax, and outgoing (destructively) to earth via ethernet. Damage is on the outgoing path; not incoming path.

If an interconnection is not earthed at both buildings, then a lightning strike to one building can be a direct strike incoming to electronics inside the other building. Which electronics are damaged? Which electronics have an outgoing path to earth?

Earthing appliances does not provide transistor protection. Protection is about earthing a surge current. Not about earthing appliances. Earthing the appliance may simply make that appliance a better and destructive connection to earth.

Many electricians understand ground as only defined by code. Grounding for surges involves requirements not defined by code. Code addresses human safety. Code does not define transistor safety. Transistor safety requires earthing that exceeds what is required by code. To earth before a surge current gets anywhere near to appliances.

Apparently coax was not earthed; violated those earthing requirements. Worse, lightning currents were apparently permitted inside that other building. Therefore earthing was also defective over there.

#63 OFFLINE   Neurorad

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Posted 06 November 2012 - 02:36 PM

Just some followup, and closure...

Installer had no issue using the 8 awg bare copper that I installed from the ODU location to the cold water bond, in the MBa below.

Dish is mounted on the back of the house, not visible from the street; success.

Install took about 3 hours total, no real problems. In preparation, I ran RG6 from the attic/ODU location to the wiring closet, and added the 8 AWG bare copper.
Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense. -Buddha

#64 OFFLINE   AntAltMike

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Posted 06 November 2012 - 08:27 PM

Lightning impacted(direct strike) adjacent building (140 ft away)

Spent 3 days reinstalling our system, all electronics dead, most of coax scorched on center conductor, roughly 60 DTV set top boxes would not power up.

Point of ingress of the lightning to the satellite system, a ethernet port from the internet provider to our monitoring system, his system was grounded as well.

Satellite Company Insurance claim of 37000
Property insurance claim of 250000+


Moral of the tale, No matter the intention of the installer, mother nature will find a weak point and exploit it.


I was part of the crew that installed five 4.5 meter Patriot Dishes and 9 Blonder Tongue cut to channel antennas on National Captioning Institutes roof in 1994. We grounded the hell out of everything, but some other contractor installed a small, Ku dish and its lnb polarity switching cable was the path for the lightning damage, and as far as I know, the NEC no longer requires rotor lines to be grounded. Grounding the rotor cables used to be required, back when they were flat and it required BOTH outer conductors to be grounded.

#65 OFFLINE   AntAltMike

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Posted 06 November 2012 - 08:34 PM

If a ground is for static discharge, then a 36 gauge (hair thin) wire would be sufficient.


I've long assumed that the reason that mast grounding mandated 8 gauge aluminum, 10 gauge copper or 17 gauge copper clad steel was based on physical ruggedness to best assure that the wire would withstand physical stress over the years.

Why is that a 1 gauge wire?


most likely, Dan succumbed to finger fatigue.

#66 OFFLINE   n3ntj

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Posted 07 November 2012 - 08:45 AM

I've spent a lot of time reading about 'proper' satellite dish grounding. The NEC seems to be pretty specific, but not specific enough.

I'm planning a new install, replacing Comcast cable. I've spent a lot of time running cables in my house, for LAN and distributed audio, and I've done my best to stay 'within code'.

I could do this install myself, but I don't have the time. I really want to get it done.

It seems most subcontracted DirecTV installers try to ground 'properly,' but aren't aware of the NEC rules - it's not part of the training, and it's not clear in the installation guides.

Where I want the dish placed is far from the service entrance, and whole-house ground, at the house back corner. The installer will want to place the dish at the front of the house, near the service entrance, because that is the easiest place - and near the service entrance.

I've researched grounding fairly extensively. This graphic gem from Mike Holt helps (link fixed):

www.mikeholt.com/mojonewsarchive/GB-HTML/HTML/GroundingSatelliteDishandLead-InCables~20020303.htm

Bottom line - what wire/cable can I run from the dish to the service entrance for grounding?

Looks like a 17 AWG copper clad steel messenger wire would suffice, for both mast and coax, according to the NEC guidelines and Mike Holt. Can people confirm? I've read of the need for a 10 AWG copper wire, for coax grounding.

(Water main is buried outside and behind drywall inside, not an option.)

Thanks so much.


If the dish is on the opposite side of the home from your electrical service grounding system, then a separate ground rod in the proximity of the dish (within 6 meters) would be required by the NEC. Then, both ground rods (dish and electrical service) are required to be bonded to each other using at least #6 copper to prevent a possible voltage difference between the two.

The grounding terminal clamp can not be used for another conductor.. each conductor gets its own grounding terminal clamp, although new construction also requires a shared grounding system with phone, cable, satellite, etc. The terminal strip where the coax from the dish is connected (somewhere near the dish) must also be bonded to the dish's ground rod as well. In my travels I find that most satellite dishes are NOT properly grounded or bonded per NEC requirements and most D* installers I talk to have no idea what grounding, bonding, or NEC even mean.

HD Snob - "Friends Don't Let Friends Watch Cable".
Electrical/RF Engineer & Inspector
DirecTV Equipment: HR24-200 (2), 5LNB Slimline, AM21, SWiM 8 installed (MRV), Cinema Kit (Wifi connection)
Configuration: Native OFF. Units OFF when not in use.
TVs: 2 Panasonic Plasma TV's each using HDMI (one 1080p/one 720p)
DirecTV customer since 1998. Plus HD DVR package w/ NHL Center Ice & MLB Extra Innings.
OTA Antenna: Homebrew UHF & VHF antennas w/ 30dB amplifier fed w/ RG-6 Quad-shield coax.


#67 OFFLINE   Neurorad

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Posted 08 November 2012 - 07:59 AM

If the dish is on the opposite side of the home from your electrical service grounding system, then a separate ground rod in the proximity of the dish (within 6 meters) would be required by the NEC. Then, both ground rods (dish and electrical service) are required to be bonded to each other using at least #6 copper to prevent a possible voltage difference between the two.

Agreed. This is true for ALL cables entering a house (phone, cable, mains, pet fence, landscape lighting), to diminish damage from nearby surges. As the small, wall mount dish does not convey surges from nearby strikes, I'm not too concerned about 'proper' grounding of it. The dish and mast SHOULD be grounded in some form, to reduce static discharge buildup - though it's usually an issue for larger dishes.

The grounding terminal clamp can not be used for another conductor.. each conductor gets its own grounding terminal clamp, although new construction also requires a shared grounding system with phone, cable, satellite, etc. The terminal strip where the coax from the dish is connected (somewhere near the dish) must also be bonded to the dish's ground rod as well. In my travels I find that most satellite dishes are NOT properly grounded or bonded per NEC requirements and most D* installers I talk to have no idea what grounding, bonding, or NEC even mean.

Agreed. 2008 NEC guidelines for new construction mandate the use of an Intersystem Bonding Termination (IBT), a 'common' ground block, for communications systems, grounding conductors, and bonding conductors.

"The IBT provides a single, easily identifiable, physical termination device to which bonding (grounding) conductors of all other systems are to be connected. No struggle to locate an acceptable bonding location. No need for additional listed hardware to facilitate the connection. The installer simply connects the protection device's bonding (grounding) conductor to the IBT terminal and … DONE!"

http://www.ashirepor...er-Systems/1953

It will make satellite dish installations easier.

If I wanted my dish installation to meet code, in my preferred location, at the rear of the house, it would have required a series of grounding rods, I believe 20 feet apart, strung together with 6 AWG copper, connecting the ODU/ADU to the service entrance ground. I think it would have to be buried 24 inches below grade, but not certain.
Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense. -Buddha

#68 OFFLINE   n3ntj

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Posted 08 November 2012 - 02:26 PM

Yes to the above, except that a satellite dish MUST also to shed static charge that can accumulate simply from wind blowing across it. That is why the dish itself also needs to be properly grounded (as noted in NEC chapters 810 and 820).

HD Snob - "Friends Don't Let Friends Watch Cable".
Electrical/RF Engineer & Inspector
DirecTV Equipment: HR24-200 (2), 5LNB Slimline, AM21, SWiM 8 installed (MRV), Cinema Kit (Wifi connection)
Configuration: Native OFF. Units OFF when not in use.
TVs: 2 Panasonic Plasma TV's each using HDMI (one 1080p/one 720p)
DirecTV customer since 1998. Plus HD DVR package w/ NHL Center Ice & MLB Extra Innings.
OTA Antenna: Homebrew UHF & VHF antennas w/ 30dB amplifier fed w/ RG-6 Quad-shield coax.


#69 OFFLINE   Neurorad

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Posted 09 November 2012 - 09:38 AM

The dish and mast SHOULD be grounded in some form, to reduce static discharge buildup - though it's usually an issue for larger dishes.


Yes to the above, except that a satellite dish MUST also to shed static charge that can accumulate simply from wind blowing across it. That is why the dish itself also needs to be properly grounded (as noted in NEC chapters 810 and 820).


Yes, I did mention that. ;)
Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense. -Buddha




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