Bonding TV ariels & amps

[jibjob]

Hi all,

I've been asked by a TV ariel installation company to quote for bonding a soon to be installed TV ariel and amplifier. The service will be shared by a number of flats in the same buliding. Can't find anything in the BRB regarding the regs on this.
Can anyone help/enlighten?

 

[Deleted member 9648]

Never heard of this before,the only thing I can think is that the leads from a common ariel might introduce an earth potential into each flat,so in theory the braid of each lead might require main bonding where it enters the flat!!......Impractical and I've never heard of such a thing being done before.....perhaps you should contact the company and enquire what their reasons are for asking for bonding??

 

[Martin Dawes]

Perhaps it is to dissipate a static charge? I don't think it's a requirement in the regs but it's certainly not a bad idea.

Remember, if it's a PME system then it will need a seperate earth rod.

 

[jibjob]

Just spoke to installer. He says it's a requirement in communal dwellings where the ariel and amp are used by multiple occupants. This protects each one should a fault occur with anothers equipment. It needs to be a clean earth so would need to go back to the MET or other direct route. He suggested I take a look at Confederation of Aerial Industries - find aerial and satellite installers (Confederation of Aerial Industries Limited) for further info.
Seperate earth rod if PME? Not sure if I understand why, would the receiving equipment be considered outside the equipotential zone?

 

[Martin Dawes]

I was just assuming that the aerial will be mounted outside the equipotential zone.

I've not been asked to do anything like that before with regard to earthing aerials but I can definitely see the issue.

 

[MNR]

I was running in supplies for blocks of flats communal aerials and they did specify a 4mm2 clean earth to be run as well.

 

[Hawk81]

Perhaps it is to dissipate a static charge? I don't think it's a requirement in the regs but it's certainly not a bad idea.

Remember, if it's a PME system then it will need a seperate earth rod.

why? the separate earth rod for everything PME is not true!

 

[Martin Dawes]

why? the separate earth rod for everything PME is not true!

Where else could you bond it to? You can't take it to the PME?

 

[Hawk81]

Where else could you bond it to? You can't take it to the PME?

why can it not be taken to the PME?

 

[Martin Dawes]

why can it not be taken to the PME?

Because you would be taking the PME outside of the equipotential zone. You would need electricity board permission and in my experience they are reluctant to give you an answer.

 

[Hawk81]

Because you would be taking the PME outside of the equipotential zone. You would need electricity board permission and in my experience they are reluctant to give you an answer.

the airel is not going to introduce another earth potential to the installation. plus you do not need board permission to export a PME earth. they prefer it if you dont but it is simply up to yourself.

 

[Martin Dawes]

the airel is not going to introduce another earth potential to the installation. plus you do not need board permission to export a PME earth. they prefer it if you dont but it is simply up to yourself.

I was told something completely different by my NICEIC inspector. He pulled me on a garage/studio conversion that I installed a few years ago and said that I should have installed a seperate earth rod. He wasn't impressed either....

 

[Hawk81]

I was told something completely different by my NICEIC inspector. He pulled me on a garage/studio conversion that I installed a few years ago and said that I should have installed a seperate earth rod. He wasn't impressed either....

the NICIEC are not always right

 

[Martin Dawes]

This is true. And I could well be wrong. It seems to me that installing an earth rod would go a long way to covering yourself if a problem ever occurred though.

 

[Spudnik]

I think basically it is to stop any voltage appearing on the cables, or more to the point, the exposed parts of any equipment they are connected to.

Quote:



"In essence an aerial system cannot be left so that any hazardous voltage can be present on the outer conductor of any cable or accessible metalwork of any equipment. This means that we need to equipotentially bond all communal systems within blocks of flats, apartments, offices etc to the MET of the building. In order to do this a verified, continuous and robust connection needs to be provided from the distribution equipment to the building’s MET. Our regulations state that the minimum CSA of this connection should be 4mm2 copper.

In addition class II electronic equipment (televisions, DVD recorders, set top boxes, audio equipment – including AV amps, etc) is designed in such a way that a touch current of up to 0.5mA could be present on any exposed metalwork. Whilst as a single item this is not a problem the guaranteed safe let-go current for the population is 3.5mA. Hence joining 7 pieces of this type of equipment together (either via aerial or SCART leads etc), even in different rooms, could put a touch current of this amount on the coaxial cable. On new builds and when doing rewires it would therefore be useful to leave a verified earth cable next to the distribution point to take care of this possible hazard. This even applies in a single household."

Borrowed from here:

Downloads - Electricians - Aerial systems for a digital age

 

[nick611]

the tv amp will be in roofspace of building or hallway cupboard.this is not outside of building.take a 4mm or 6mm from landlords supply and this is fine.this reg only apply,s to communial ariel.s

 

[Deleted member 9648]

Perhaps it is to dissipate a static charge? I don't think it's a requirement in the regs but it's certainly not a bad idea.

Remember, if it's a PME system then it will need a seperate earth rod.

The bonding should be taken back to the pme...the purpose of main bonding is to ensure there can be no potential difference between conductive parts and extraneous conductive parts....introducing another earth potential via a rod would totally defeat the object of the excercise.

 

[Deleted member 9648]

I was told something completely different by my NICEIC inspector. He pulled me on a garage/studio conversion that I installed a few years ago and said that I should have installed a seperate earth rod. He wasn't impressed either....

I'm afraid your NIC inspector was talking out of his posterior........Next time you see him ask him to point out the regulation to back up his nonsense.

 

[Hawk81]

The bonding should be taken back to the pme...the purpose of main bonding is to ensure there can be no potential difference between conductive parts and extraneous conductive parts....introducing another earth potential via a rod would totally defeat the object of the excercise.

that is the point i was trying to make. people blindly go around banging in spikes because they see PME.

 

[Deleted member 9648]

that is the point i was trying to make. people blindly go around banging in spikes because they see PME.

Agree totally....they will happily install outside lights and sockets directly off the MET PME but as soon as a shed/garage/ariel is mentioned they come over all unnecessary.

 

[Martin Dawes]

The bonding should be taken back to the pme...the purpose of main bonding is to ensure there can be no potential difference between conductive parts and extraneous conductive parts....introducing another earth potential via a rod would totally defeat the object of the excercise.

Even for equipment outside of the equipotential zone?

 

[cbw]

The last HMO I did needed a 10mm bond back to MET, this was done at the amp, simply by looping the seperate outgoing cables together, I am looking for a picture that I know I have...................

 

[Deleted member 9648]

Even for equipment outside of the equipotential zone?

Why would you want to bond something outside the equipotential zone?

 

[nick611]

i would only fit stake to garage if it had seperate water main/metal structure unless i ran a10mm swa and could satisfy 10mm mainbond.otherwise there is no need

 

[jibjob]

Thanks for all your comments guys, very helpful, time to put it all into practice I guess

 

[Martin Dawes]

Why would you want to bond something outside the equipotential zone?

I thought that was what the original question was all about? Talking about bonding an aerial. As an aerial would expected to be mounted outside of an equipotential zone, it throws up questions.

 

[jibjob]

Well, it seems to be established that bonding an ariel being used by more than one dwelling is a sensible idea but how it's done is dependant on the earthing system present. The ariel may well be mounted on a chimney or in the loft. Either way it will connected to equipment within the building some of which may be earthed some that won't. It's the method that's in question, back to the MET or a new spike? A previous post pointed out that you wouldn't put in a spike if you where installing outside lights, you'd run an earth from the dwelling.
As bonding is there to protect against dangerous voltages, I would of thought bonding the ariel to the MET is the right way to go, PME or otherwise. By bonding to a spike you run the risk of introducing a different potential. Please put me right if you think I'm wrong but be gentle

 

[mhar]

Before flatscreens there were very high voltages present in crt tv's. The aerial input was double insulated from these voltages but this could break down. I have experienced this twice and know of a plumber wetting himself climbing into a loft and touching a metal splitter whilst touching pipework - class II tv, faulty insulation with no path to earth except up aerial cable. Obviously this is less of an issue now but surely it makes sense to bond when making a direct electrical connection between properties. I do this as a matter of course and won't take a feed of a dish or an aerial for a neighbour unable to receive from their property unless I can bond. Bonding the dish is pointless as the lnb (unit on the feedarm) is insulated from the dish by it's plastic holder
Having said this I placed an order with my aerial suppliers for a bonding (bus) bar two weeks ago to be told they were not stocking them anymore

 

[netblindpaul]

IF you bond an aerial system then you bond the aerial construction to the MET, thus you now put a giant lightning magnet on the roof of the building.
Next comments please?...

 

[needasparks]

Yes got to agree with netblindpaul. don't think the general idea is to earth the aerial but it would give it a potential. interesting point.
Let me pull up me chair to listen.

 

[mhar]

Good point!
I did a CAI (confederation of aerial industries) smatv/matv ((satellite) master antenna television) course some 20 years ago and bonding was compulsory. Have just tried to look this course up but it appears it is no longer current but, not being a CAI member anymore, I may not be able to find it because of restricted access. However they are running similar courses for part P compliancy.
Did find this though Earth Bonding - Aerial Concepts

 

[needasparks]

bouncing this back up the list to see more of an answer on it as never come across it before and the link above mentions its law.

What are the views from the clever peeps.

 

[La Poste]

I like this topic also.

The fact that the aerial will now act as a huge lightning conductor opened my eyes.

I mean if you have a metal dvd recorder and the coaxial input socket is made of metal then this will give electrical continuity from the aerial to the metal chasis of the dvd recorder.

I presume the metal chasis of the dvd recorder is earthed although I don't really know for sure and this earthed chasis would provide a return path for currents back to the MET via the circuit CPC.

If the case of the dvd player is earthed and the aerial is sticking out the side of the building have I already got a massive lightning conductor already?

The lightning would go down my aerial to my dvd recorder, along the circuit CPC to the MET and then back to the earthed spike at the transformer.

Does this make sense or am I barking up the wrong tree?

 

[mhar]

The discussion is more about multiple dwellings.
Most dvd's dvr's etc are class 2. I looked into the issue of what is required in a single dwelling after a lightning strike on an aerial which travelled down the cable, burst through the insulation and arced onto a central heating pipe blowing a hole in it. Unfortunately the customers ch system was a continuous fill system from a header tank, it took him ages to turn off his main stopcock and the water damage was staggering. I was informed that there were no earthing obligations on an installer. Second incident I detailed in an earlier post where a plumber got a severe belt off a splitter. Again as this was contained within a single dwelling there was no earthing obligation on the installer. In this latter incident I was informed that the customer was at fault for not providing a safe environment for the plumber to work in!
The issue is with multiple dwellings and introducing different potentials in these

 

[Marvo]

I like this topic also.

The fact that the aerial will now act as a huge lightning conductor opened my eyes.

This thread interests me as well because our local (South African) electrical regs have recently been amended in this regard. It's now a requirement that all antenna and satellite dish systems be earthed...not just communal ones. It's now also required that an earth block is installed in the roof space as part of the electrical installation for other contractors such as audio-visual to access and utilize. The earth block is connected to the main consumer unit earth bar via a suitably sized conductor.