44 replies to this topic

[westom]

James T Kirk, on Sep 6 2011, 11:14 PM, said:

I find need to register some surprise at a few of your statements, particularly the two above.
(1) You could not know how much I wished I found lightning protection to be as simple as you describe. I nor anyone I know or have known in the radio and television broadcasting industry have ever been able find this task simple.
(2) For me lightning is utterly capricious.

  You do everything that every informed homeowner must do. And then more.  The simple stuff as described must be implemented by all.  Homeowners need only worry about a destructive surge maybe once every seven years.    Your tower means, for example, protection on the coax is more than just earthing its shield.  Due to electrical characteristics not found in residential venues, your coax cable must implement a GDT that earths both shield and center conductor.  Your single point ground must be more than ground rods. You probably also implement a bulkhead that also increases impedance to wires entering the building.  To have earthing that is just a little bit better, you must expand that earthing system immensely and expensively.

  But all surge protection systems implement the simple concepts as posted.  Any homeowner that does not have that minimum has virtually no protection.  

  Lightning is not capricious.  Any damage means a human has made a mistake.  The number of possible mistakes can be so numerous that lightning appears to be capricious.    But every failure means a human should locate and fix a mistake.  To learn from damage.

  A case study for a Nebraska radio station demonstrated the concepts.  And yes, earthing at the utility transformer is important for station protection.  In one west coast station, inadequate (maybe missing) earthing of the utility transformer therefore connected 33,000 volts directly into the station via the lower voltage service.  If the utility transformer is not properly earthed, then plasma inside that transformer can short the 33,000 volts to 240 volt service.  Into radio stations.  And into residential homes.  Just another example of what all home owners should inspect.  And what should be carefully inspected (maybe upgraded) in all facilities.

  From another industry professional:
> Well I assert, from personal and broadcast experience spanning 30 years, that you can
> design a system that will handle *direct lightning strikes* on a routine basis. It takes
> some planning and careful layout, but it's not hard, nor is it overly expensive. At
> WXIA-TV, my other job, we take direct lightning strikes nearly every time there's a
> thunderstorm. Our downtime from such strikes is almost non-existant.  The last time
> we went down from a strike, it was due to a strike on the power company's lines
> knocking *them* out, ...
> Since my disasterous strike, I've been campaigning vigorously to educate amateurs that
> you *can* avoid damage from direct strikes.  The belief that there's no protection from
> direct strike damage is *myth*. ...
> The keys to effective lightning protection are surprisingly simple, and surprisingly less
> than obvious. Of course you *must* have a single point ground system that eliminates
> all ground loops. And you must present a low *impedance* path for the energy to go.
> That's most generally a low *inductance* path rather than just a low ohm DC path.

  The protector is simple science.  If it does not have earthing, then it cannot make hundreds of thousands of joules irrelevant.  Earthing is an art.  An art that, if not understood, can make lightning appear capricious.  Lightning always is electrically predictable.  Because it is an art, sometimes prediction occurs after damage.  But in every facility, earthing that energy before it can enter a building is always essential for effective protection.

  So that lightning does not find earth destructively through a structure, earth lightning rods.  So that lightning does not find earth destructively through appliances, earth a 'whole house' protector.  Then do even more at facilities at greater risk such as radio stations.

  The principles for all protection systems are same.  Protection is always about where energy dissipates. A protector does not absorb surges.  An effective protector shunts / bonds / connects / switches / conducts / diverts energy to earth.  A protector is only as effective as its earth ground.  What every homeowner must understand to have effective protection.

[James T Kirk]

Hi Westom

My conclusion is that we shall need to agree to disagree on the capriciousness of lightning and the control of its impact being simple.

Our broadcast sites are regularly struck multiple times in the one storm event and survive very well. It is well understood that an extensive earthing system, checked regularly for its efficacy and low impedance equipotential bonding to the facility's technical earth point is the first stage in making this survival possible. However the variability of where the strike first meets the facility is a determining factor in the success or otherwise of the protection systems.

I'm unsure of your background so please forgive me if I describe a situation you may be savvy with. Take a typical high power FM radio and television broadcast facilty. The tower is up to 200m tall, superbly bonded to an extensive earthing system which is made available to a single technical earth point for equipment within the building. Coaxial feeders are bonded to the tower near the antenna, where the feeder leaves the tower and at the building entry at the technical earth. On top of this are a variety of essential gas, MOV, Transorbs, low pass filters and of course fusing on the cables entering and leaving the building.
This facility is struck hundreds of times every summer and survives. It almost sounds like I'm underlining your argument for you, until the capriciouness of lightning rears itself.

You see most of our lightning strikes hit the top of the tower, but not all. Our earthing systems are so good we have confidence that if the top is struck the four legs will essentially share the currents to ground. The interesting thing is what happens to this superb installation when the strike hits one leg of the tower adjacent to the building 20metres from the ground? You can't say for sure, there's certainly good odds that the currents on that leg exceed the other three. There's a very good chance the electromagnetic field generated about that leg are higher than in a strike higher up. When we actually took a strike of the one just described, the induced currents into cabling within the building were sufficient to damage equipment installed to best earthing practises.

This is by no means human failure, it is an opportunity to revise, respond and improve. Lightning is undoubtedly capricious and the prevention of damage is anything but simple.

James

[bellotv]

Now I have to wonder if a strike like the one above that James has described hits a domestic antenna connected by a typical 5mm diameter earth lead to a 6 foot earth stake  or even a cold water pipe how it would all fare ? Probably not very well I would imagine.

[westom]

James T Kirk, on Sep 7 2011, 10:08 PM, said:

The tower is up to 200m tall, superbly bonded to an extensive earthing system which is made available to a single technical earth point for equipment within the building. Coaxial feeders are bonded to the tower near the antenna, where the feeder leaves the tower and at the building entry at the technical earth. On top of this are a variety of essential gas, MOV, Transorbs, low pass filters and of course fusing on the cables entering and leaving the building.

  The many things you must also do to addresss the 'art' of earthing are numerous.  For example, the coax shield down the tower must be bonded to the tower at multiple points.  The GDT you must have on that coax wire is well beyond what homeowners also need do.

  Many basic solutions routinely done in every broadcast station, underground mine, munitions dump, rocket launch facility, telco CO, etc must also be found in every home. For a homeowner, it costs typically $1 per protected appliance.

  This protection was not necessary in 1970 homes.  Transistor existed mostly in industrial and commercial facilities. Since 1970, all homes have required single point earthing.  Every incoming wire connected low impedance (ie 'less than 3 meters') to that single point earth ground.  Even in the 2000, we were still building homes without that required solution.

  Effective protection is not absolute.  We expect protection better than 99% of the time.  More than sufficient for homes that suffer maybe one surge every seven years.  If single point earthing of every incoming conductor does not exist, then such protection does not exist.  That resulting damage is a human failure.  No excuse for not implemented these simple and well proven protection methods.  

  Demonstrated in the case study of a Nebraska radio station.  Some broadcast engineers do not even understand it.  For example, they disconnected ground on wild speculation that grounding was increasing surges.  As you noted, even the coax must be bonded to a tower at multiple points.  Most everyone here (even many broadcast engineers) would not know that.  Layman need not know that. But every layman should know what must be installed in every residence.  Single point earth ground.  And every wire connected low impedance (ie 'less than 3 meters') to earthing either directly or via a 'whole house' protector.  If that basic protection does not exist, then a home has virtually no protection (except that already inside every appliance).

  Homeowners need not know about a bulkhead you probably have to create higher impedance between electronics and the earth ground.  But homeowners must know what they need and what you also use.  Single point earth ground.  All incoming wires connected short (‘low impedance’) to that single point earth ground. A protector is only as effective as its earth ground.  Separation between appliance and protector increases protection.  In every case, protection is always about where energy dissipates.

  Every homeowner should understand that.  Need not know about other solutions that are implemented in broadcast stations.

Edited by westom, 07 September 2011 - 11:46 PM.

[Tazzy2Heads]

bellotv, on Sep 7 2011, 10:02 PM, said:

Now I have to wonder if a strike like the one above that James has described hits a domestic antenna connected by a typical 5mm diameter earth lead to a 6 foot earth stake  or even a cold water pipe how it would all fare ? Probably not very well I would imagine.

Hi 'bellotv'

I've always thought that at best an earthed tv antenna earthed to the household M.E.N. earth stake might bleed off a bit of static build up and that's about it,and the whole lot would get blowen to bits in a lightning hit.
The humble earth stake and Main Earth wire are the most important connections in the electrical installation and are the most neglected, most average
punters would not even know where it was unless it got caught in the whipper snipper. Others are sticking up through the concrete footpath totally cemented
in and never going to get wet to help maintain conductivity. I've seen them well up under verandahs and even up under the middle of the house when the house has been added onto.
The earth wire to  water pipe bond tends to fare a bit better unless the DIY's have had a go at the plumbing.
  I've never liked the idea of connecting to the house earth system because the Main Earth is connected to the Main Neutral Link at the switchboard to carry
  fault current and as a back up Neutral if the Main Neutral goes missing on the in coming supply neutral. If the main earth stake and or  bond connection  is dodgy you could have a live metal roof or water pipes etc. I've seen main earth stakes you can pull out with your hand when they have been hammered into fill instead of proper ground as such.
I think if people were to get serious about antenna earthing in the house type situation an earth connection and an earth strap external conductor should be fitted when the house is built and the public educated that it and their Main Earth System has to be maintained,like a commercial earth system.
Also pigs might fly !!
  Cheers all Tazzy , this has been a very interesting topic guy's good job as they say.

[James T Kirk]

westom, on Sep 7 2011, 11:45 PM, said:

The many things you must also do to addresss the 'art' of earthing are numerous.  For example, the coax shield down the tower must be bonded to the tower at multiple points.  The GDT you must have on that coax wire is well beyond what homeowners also need do.

Hi Westom

Unfortunately you appear to have simply repeated what you have previously said again and again.
I was going to leave it alone, agree to disagree as I said last time however you gave a clear impression to the reader and said "The many things you must also do to addresss the 'art' of earthing are numerous." Needless to say I soon became disappointed with what followed.
In my comment below I'll assume in your circles a GDT is a gas discharge tube, this may assist the reader also.

It appears that your commenting on what occurs at a broadcast site is not appropriate and is well beyond your knowledge and skill.
You will not find GDT's on high power transmitter feeders (coax), the potentials that occur all the time are regulaly high and there's other reasons I'll leave alone for now.
You will not find feeders on towers terminated more often than that I noted in my previous post.

It may be wise to refrain from commenting beyond what you know for sure.

James

[James T Kirk]

bellotv, on Sep 7 2011, 10:02 PM, said:

Now I have to wonder if a strike like the one above that James has described hits a domestic antenna connected by a typical 5mm diameter earth lead to a 6 foot earth stake  or even a cold water pipe how it would all fare ? Probably not very well I would imagine.

Tazzy2Heads, on Sep 8 2011, 12:03 AM, said:

Hi 'bellotv'

I've always thought that at best an earthed tv antenna earthed to the household M.E.N. earth stake might bleed off a bit of static build up and that's about it,and the whole lot would get blowen to bits in a lightning hit.
The humble earth stake and Main Earth wire are the most important connections in the electrical installation and are the most neglected, most average
punters would not even know where it was unless it got caught in the whipper snipper. Others are sticking up through the concrete footpath totally cemented
in and never going to get wet to help maintain conductivity. I've seen them well up under verandahs and even up under the middle of the house when the house has been added onto.
The earth wire to  water pipe bond tends to fare a bit better unless the DIY's have had a go at the plumbing.
  I've never liked the idea of connecting to the house earth system because the Main Earth is connected to the Main Neutral Link at the switchboard to carry
  fault current and as a back up Neutral if the Main Neutral goes missing on the in coming supply neutral. If the main earth stake and or  bond connection  is dodgy you could have a live metal roof or water pipes etc. I've seen main earth stakes you can pull out with your hand when they have been hammered into fill instead of proper ground as such.
I think if people were to get serious about antenna earthing in the house type situation an earth connection and an earth strap external conductor should be fitted when the house is built and the public educated that it and their Main Earth System has to be maintained,like a commercial earth system.
Also pigs might fly !!
  Cheers all Tazzy , this has been a very interesting topic guy's good job as they say.

Bellotv & Tazzy

All I can do is agree with you, I pretty much did so in advance when I wrote:
"Realistically for antenna installers there are many points where surges can impact a building that you simply have no control over. As you know, the roof and gutter are isolated from the antenna cable by the balun in some cases, some times not depending on impedance matching technique used. If you were to always assume not and install coax surge diversion between the antenna and the socket or splitter and properly bond the surge diversion to the best available earth, your best effort genuinely has been achieved. You cannot be expected to sort the vulnerabilities created by other services"

You guys are dealing with isolated mounts and antennas that regularly sit at 120vac relative to ground that comes from the capacitively established reference chassis potential in TV's and STB's. As Tazzy said the electrical authorities not only operate with a MEN system but also they now bond the neutral to the mount on the house's fascia board and so if the fascia is Colorbond and the gutters and their mounts are colorbond too there's the possibility even the roof sheets might be bonded to neutral. I have little doubt you'll be responding noting you've been aware of this for some time and the consequential tickles you've felt. This is an area that needs installers to be so very careful, this tickle you get when everything is normal is not much different to a 240vac live coax when standing on an isolated roof, if the roof is anything other than isolated as you know it's potentially fatal.
Some plumbers still replace the incoming rusted galv pipe with plastic and completely remove the home's suspect earth bond without contacting an electrician first, fortunately most plumbers are aware of this nowadays.

Bellotv, re your first post, how good was it when you put all this together and the TV worked? Now I know you thought about the likelihood of that Samsungs front end being cinders, were you able to conceal your surprise to the customer when you produced a received picture?

You guys are set traps by customers and inadvertently by the trades they employ every day, I hope when you are having your discussions on this forum on which is the best DVB_T meter to use, you occasionally bring up the subject of having the venerable and modest moving coil or digital multimeter with you on the roof too.

Lightning protection? I'm sure it's your best efforts based on what the customer understands and decides they need after receiving your advice, there is little more you can do. Because you must tell them even if you put surge diversion and an overkill of earthing and bonding, there are no guarantees, most are likely not to bother, especially if fusion is on their insurance policy. You'd all know the story better than myself.

When the big one hits, for me its a success if the house doesn't burn down.

James

[beeblebrox]

When lightning hits water pipes in a building it gets kind of wild... a job we did a while ago a 30ft mast was hit,  this mast actually had an earthing strap (pretty rare here in Melbourne) but most of the earth wire vapourised, it also took out a set of guy wires went down through the eye bolts, into the building plumbing on one side, burst all the pipes in the wall of the laundry, and started a fire in that wall, went down another guywire found the phone cabling for the block of flats and fried  the mdf and the trunk out to the street and another underground cable to another building distributor plus every coax cable in the roof and took out most tv.s

simple solutions do not work in these type of cases...

James T Kirk, on Sep 8 2011, 05:06 PM, said:

You guys are set traps by customers and inadvertently by the trades they employ every day, I hope when you are having your discussions on this forum on which is the best DVB_T meter to use, you occasionally bring up the subject of having the venerable and modest moving coil or digital multimeter with you on the roof too.

James

Yes a good multimeter is still invaluable, wouldn't be without my trusty 20yo fluke

[westom]

Tazzy2Heads, on Sep 8 2011, 01:03 AM, said:

I've always thought that at best an earthed tv antenna earthed to the household M.E.N. earth stake might bleed off a bit of static build up and that's about it,and the whole lot would get blowen to bits in a lightning hit.

  Lightning is not the destructive force you have assumed.  For example, research from the US Forestry Service generations ago noted that well over 95% of all trees struck by lightning have no apparent damage.  But so many only see the rare exception.  Then assume all lightning is that destructive.

  TV antennas are required to have their own earthing where lightning is more frequent.  Direct strikes to properly earthed TV antennas without damage is routine.  Static would bleed off in the other required earthing connection; where the antenna lead enters at a service entrance.  And inside protection circuits found inside a receiver.

  A TV antenna earth ground has two purposes.  First is human safety.  Second is to harmlessly earth direct lightning strikes.

  Water pipes are now considered insufficient earthing in an increasing numbers of venues.  In part, due to reasons cited by James T Kirk.  Even pipe solder joints subvert earthing; increase impedance.  Pipes must always be connected to / integrated in the earthing system for both human safety and transistor safety.  But a cold water pipe is no longer considered sufficient earthing in an increasing number of jurisdictions.

[bellotv]

James T Kirk, on Sep 8 2011, 05:06 PM, said:

Bellotv, re your first post, how good was it when you put all this together and the TV worked? Now I know you thought about the likelihood of that Samsungs front end being cinders, were you able to conceal your surprise to the customer when you produced a received picture?
James

I had pretty well convinced them that the front end was most likely fried.
I was not very good at concealing my surprise.   

Magnum72, on Sep 9 2011, 07:49 AM, said:

I have replaced many foxtel boxes in that suburb, most have earthed wallplates installed but the dishes are mounted on the tin roofs-the ones with tile roofs/timber frame's seem to have less trouble.

Hi Magnum72

What are these earthed wall plates ? Are these a foxtel product ?How do they connect to earth ?

Bellotv

[westom]

bellotv, on Sep 11 2011, 09:54 PM, said:

What are these earthed wall plates ? Are these a foxtel product ?How do they connect to earth ?

Those wall plates are safety ground; not earth ground.  A wall plate must connect to the breaker box; not to an earth ground rod.

  The expression for earthing for surge protection contained many critically important numbers.  For example, "less than 3 meters".   A wire connected to an earth ground rod that is significantly longer, that has sharp wire bends, that is inside metallic conduit, etc is not earthed - as far a surge current is concerned.

  That home with repeated surge damage would probably be a perfect example of a building without proper earthing.  For example, if all utilities do not enter at a common point (ie the service entrance), then the building has encouraged surges to find earth destructively via appliances.

  Most of previous posts were probably quite new to many.  That means reading it the first time would not provide the critically important points in that post.  The expression "less than 3 meters" says why safety grounded wall plates are not earth ground.  Many also confirm earthing an appliance with earthing a surge.  An earthed appliance may be more easily damaged by a surge.  A surge earthed without entering a building and distant from appliances means superior protection inside all appliances is not overwhelmed.

[M'bozo]

bellotv, on Sep 11 2011, 09:54 PM, said:

How do they connect to earth ?

This document might be relevant, from page 35 onwards.

(It's not something I've ever seen on an Austar installation)

[westom]

M'bozo, on Sep 12 2011, 05:58 AM, said:

This document might be relevant, from page 35 onwards.

See page 14:

Quote

NOTE: SMART WIRED INSTALLATIONS ARE ALWAYS TO BE EARTHED USING A GROUNDING BLOCK!

[jsmith]

Personally if I was in a high strike area I wouldn't be relying on earthing procedures alone (although I agree if done correctly it should protect), rather a lightning arrestor such as this and these.

JSmith  

[bellotv]

bellotv, on Sep 11 2011, 09:54 PM, said:

what  are these earthed wall plates ? Are these a foxtel product ?How do they connect to earth ?
Bellotv

Thanks Magnum73 and M'Bozo

Must be  a Fox thing .Never seen them on Austar around here either

jsmith, on Sep 12 2011, 01:03 PM, said:

Personally if I was in a high strike area I wouldn't be relying on earthing procedures alone (although I agree if done correctly it should protect), rather a lightning arrestor such as this and these.

JSmith  

Wonder if they make a 75 ohm version suitable for DTV installs or just the 50 ohm Comms versions shown .

westom .

Are you in Australia or overseas,????

You keep referring to service entry as if it was a standard .???

Almost every house I visit can have the Phone cable ,Electricity cable and Water entering the property and the house either overhead or under ground or a mix of both and at any position the utility fancies.
There is never any common entry point that could serve as a easy earth/ground  bonding point.

TV antennas are mounted where the will get the best reception .This could be anywhere and statistically almost certainly would not be within 3 meters of a designated service entry point.

Your advice is good and logical but not very practical to apply in a typical Australian domestic home .

Edited by bellotv, 12 September 2011 - 05:47 PM.

[westom]

bellotv, on Sep 12 2011, 05:45 PM, said:

You keep referring to service entry as if it was a standard .???

Almost every house I visit can have the Phone cable ,Electricity cable and Water entering the property and the house either overhead or under ground or a mix of both and at any position the utility fancies.
There is never any common entry point that could serve as a easy earth/ground  bonding point.

Does not matter if some utility wires are overhead and others underground.  All must connect short to the same earth ground before entering.  And yes, you are correct.  Most all buildings do not have proper utility connections because - as should be obvious - most do not understand why a common service entrance is so critical. Or what it does.

  One reason why those posts are so difficult to grasp: a well proven concept understood even 100 years ago is still unknown to most.  Since transistors have only existed in homes since 1970, then most homeowners and builders would not yet learn why well proven technology (and construction methods) is critical to appliance protection.  Especially when destructive surges occur typically once every seven years.

  Only recently (maybe in the pat decade) were cable TV companies training their installers to properly earth.  Most are only taught what to do; not why it is so important.

  One utility demonstrates bad and preferred earthing.  This applies to most homes; how to kludge a solution for defectively constructed (wired) buildings:
  http://tinyurl.com/yefm8n9

  A TV antenna is not earthed 'less than 3 meters'.  A TV antenna must have a connection to earth that is short as possible, no sharp wire bends, etc.  That antenna's lead must also be earthed as short as possible at the service entrance ground - typically a different ground.  This paragraph describes two different earthing connections.

  Obviously, effective protection is simple, inexpensive, and easy when protection is implemented before footings are poured.  Earthing is more expensive (and sometimes difficult) when installed too late. Since many homes were built long before transistors, then that utility's kludge solution is necessary.

  Effective protection means a homeowner has no other alternative.  Protection is always about where energy dissipates.  Any recommendations that does not address where energy dissipates is protecting only from transients that typically are not destructive.

  A common service entrance is standard anywhere that construction practices use well proven techniques.  As so often learned from experience, home contractors are particularly slow to learn and adapt to new techniques.  Especially when those techniques are not required by codes.

  Either a solution keeps hundreds of thousands of joules harmlessly absorbed outside the building.  Or no effective protection exists.  Detailed were some simple concepts (ie single point earth ground) that accomplish effective protection.  Any solution worthy of consideration must always state how  that energy dissipates harmlessly.

[beeblebrox]

bellotv, on Sep 12 2011, 05:45 PM, said:

Wonder if they make a 75 ohm version suitable for DTV installs or just the 50 ohm Comms versions shown .

Yes there are versions around, I carry one in the truck but don't often use it here in melbourne usually only on commercial jobs.

[Tazzy2Heads]

Magnum72, on Sep 12 2011, 09:40 PM, said:

Westom, are you sure? They are described by Foxtel(discuss with them if you like) as an earthing wallplate, they plug into mains and only have 1 wire connected to the earth as opposed to  the neutral or active, I thought the electrical wiring in a house all ran back to the breaker then like at my house a earth ran from there to the ground rod.

Never seen a pal earthing wallplate but I am sure they exist.

  Hi 'Magnum 72',
We don't have real 'FOXTEL' yet in Tasmania , only 'almost Foxtel '(AUSTAR)so I havn't  seen a FOXTEL Sat receiver. Do they have a three pin 240v power
  lead plug or are they only two pin and classed as double insulated?.
  What is it that makes the difference between not earthing a one receiver installation and earthing a multiple receiver job ?
  If they have a Three pin plug and a three core lead and a metal chassis where the 'F' connector antenna input is I don't see much difference between the
  power lead safety earth and the wall plate safety earth other than if the box is taken away the coax is still connected to earth at the wall plate .
  When people discontinue their Foxtel service and the receivers go back does the earth wire stay to supposedly protect the dish and coax or are the
  customers on their own ?, and how many people would leave them plugged in anyway.
  I don't see the earth wall plate as anything else than a safety earth because it is relying on how good the earth contacts are in the power point , any point
  that has been in use for a few years with people plugging and unplugging would have spread the contacts a bit, also I have seen an older house with bare earth wiring that took some lightning and all the soldered joints along the main earth where branch earth wires connected were blowen apart.
  The way Foxtel earths the coax wallplate with a three pin plug to the nearest power point I would think is a cunning way of their installers legally connecting to the 240v house wiring without having an Electrical Contractors Licence as plugging in a plug is not deemed as electrical work under the
  regulations and a proper permanent connection is and they would be in 'zee poo poo'.Does Foxtel check the power points for earth and polarity before
  plugging IN ?

How do you guys earth your antennas ? Do you all put in your own separate earth stakes with conduited earthing cables down the side of the new
McMansions or connect to the main earth stake yourselves or get the licenced 'sparkie' to connect for you ?
If you are connecting to the house 240v system main earth wire in the roof space or any other earthwire it can only be a safety earth for all the reasons in 'Westom's
posts, and those that worry about such things may say you are doing illegal electrical work unless you are licenced to do so.

Cheers Tazzy

[westom]

Magnum72, on Sep 12 2011, 09:40 PM, said:

They are described by Foxtel(discuss with them if you like) as an earthing wallplate, they plug into mains and only have 1 wire connected to the earth as opposed to  the neutral or active,

Calling that wire an earth ground is a misnomer from too long ago that leads to confusion. The building contains only safety ground wires.  The building's electrical system must connect to earth ground at come common point - the AC main power panel.

  Impedance is why the earth ground must be so short, no sharp bends, no splices, separate from non-ground wires, etc.  Tazzy2Heads describes an example if earthing a surge via a wire that violates so many earthing requirements (and safety codes).

  Surges must be earthed before that energy can enter the building.  Separation between that earthing and electronics increases protection.  

  Just because a bread loaf is entitled 'enriched wheat bread' does not mean it is whole wheat bread.  It could be white bread with molasses.  Just because the title includes the word 'wheat' does not means it is 'whole wheat' or was even made from wheat.  They could call it JackStand.  That is just a title.  Does not say what it is or what it does.  Just because it is called an earthing wallplate does not mean it provides an earth ground.

  Word association is how spin creates myths or confusion.  A wallplate ground is only a safety ground.  Will not effectively earth a surge.  Titles say nothing. Facts, numbers, and basic electrical concepts are always required to even understand what a JackStand is.

Edited by westom, 13 September 2011 - 01:55 AM.

[Missiontech]

As this is my first post I should say that I was an Optus, Telstra and Foxtel installer up until 2004. This means that my product information is somewhat dated but as a registered cabler I try to keep abreast of things by keeping reasonably up to date with the online Foxtel installer manuals etc; of course not having field experience with the newer technologies can certainly be a limitation.

For those who are in a multi-level home built on either a slab or pod-slab then this topic is at best theoretical as it would be highly unlikely that they would be able to adequately retrofit a satisfactory surge protection system. Considering that many homes have various cable lead-ins, as with Optus/Telstra HFC, Telstra POTS, Foxtel satellite etc & mains power and solar power systems then not much can be done when the building has been plastered.

Question:
For the satellite installers amongst us, I gather from one or two posts that lightning may be a contributing factor when it comes to failed STB’s; is there any feedback from Foxtel on this?