Earthing my LNB.....Help

[angusc]

Ok,

I have done a search and read much about the "have you earthed your LNB" type comments of advise given by many here. I live in China in a 10th floor apartment block where they use the 'dirty Neutral' and from what I can make out they connect the Neutral and the earth wires together at some point in the electrical system.....?

I'm not an electrician so know no more than this from a terchnical perspective.

I'm using a UPS in line between my AV kit and the wall socket.

However I do know that all my AV equipment is running with a voltage on their cases and the LNB cable also gives a low shock when it touches a soft part of the skin such as forearm etc.

I do not have a handy GPO socket to connect a cable to the LNB outer sheath to ground it, nor do i have any water pipes running anywhere nearby my TV and lounge, so what can i do to earth out this stray voltage?

I do have a cable TV socket next to the power socket but I do not know if it has a good earth or should even be considered as an earthing point?

I did notice that the aluminium window frame allowed the LNB cable to pass its current through me via the window frame, so could I use that as an earthing point for the LNB? Also would this then earth out the rest of my AV system or not?

I have been plauged with "LAN not working" issues on my DM500 Clone for many months and today i discovered that I could get it to work everytime if i unplugged the AV Phono cables form the DM500 and then rebooted the box. Sometimes did not even have to reboot the box, just unplugging the Phono cables did the trick as restarted the LAN lights.

Sorry for the long post and thanx for any advise that you can give to help me out with my issue.

[fandtm666]

you must have a GPO to power the ups so

1: turn the power of to you power point from the fuse box outside.
2: unscrew the gpo face plate
3: connect a new 6mm earth wire to where the houshold earth is
4: nick a small notch on edge of gpo so when screwed back allows earth wire to sit flush
5: crimp a terminating connector to the end of new wire
6: now make up a new length to reach from lnb connection to earth wire you just installed.
7: add appropriate crimps and connect
8: insulate exposed crimps.
9: switch power back on

[ol' boy]

You can do 2 things.

Weld your LNB to the Sydney Harbour Bridge
or
Use the incomming Neutral as an earth.

[Godzilla]

How about you run your earth off your steel water pipes. I am assuming that they are steel of course, should do the trick.

[gw1]

I live in China in a 10th floor apartment block where they use the 'dirty Neutral' and from what I can make out they connect the Neutral and the earth wires together at some point in the electrical system.....?

I'm not an electrician so know no more than this from a terchnical perspective.

I'm not an electrician either but for a while I lived in China and I saw plenty of bad wiring! That's ok though, we have lots of dodgy wiring in Australia too

However I do know that all my AV equipment is running with a voltage on their cases

This is normal - it doesn't necessarily imply your apartment wiring is faulty or dangerous. It is normal practice for modern AV equipment to be unearthed to avoid earth loop hum that could otherwise occur when several products are connected together (to sound processor and video projector etc). So you have a bunch of products, some with metal cases, all connected together but unearthed. All it takes is one of them to have a switchmode power supply and immediately you'll feel a tingle when touching any of those products if another part of your body has a path to earth (eg bare feet on concrete). It's only life threatening if one of the products is faulty and conducts significant current from primary to secondary (chassis). However the tiny tingle currents can be enough to upset or even damage equipment sensitive to line level voltages (100-250V AC) when hooking things up.

Ethernet uses magnetic transformers precisely to avoid this kind of problem. Other interfaces such as USB and RS232 aren't isolated though so if you're having noise problems then unplug those cables when not needed. When attaching/removing RS232 you should ideally power down everything beforehand because, unlike USB, most RS232 interfaces have very little protection against high voltages arising from switchmodes. Humax receivers tend to have current limiting resistors on their serial ports but most other products don't.

Some dreamboxes have trouble with unstable ethernet due to inappropriate or poor quality capacitors around their ASIX AX88796 ethernet controller IC. The capacitors are important for noise rejection and your noisy environment might be causing the fault to manifest. Clones are more likely to use cheap capacitors than the genuine dreams, which won't help. The issue was widely discussed a couple of years ago; for example , and . If other ethernet equipment (eg laptop) is OK plugged in at the same point as your DM500 then that would be further evidence for it being a fault in your receiver. You can do the modification yourself if you're confident at soldering, otherwise print out the instructions and take your receiver to a TV repair shop and they'll be able to do it for you.

By the way, some people found the problem went away after cooling their receivers in a refrigerator. That's because capacitors are heat sensitive (especially cheap ceramics).

[angusc]

You can do 2 things.
Use the incomming Neutral as an earth.

So it is OK to use the Earth of the system even though it is somehow connected to the Neutral circuit? This will not further damage my DM or be harmful to my wife touching the Dreambox

you must have a GPO to power the ups so

1: turn the power of to you power point from the fuse box outside.
2: unscrew the gpo face plate
3: connect a new 6mm earth wire to where the houshold earth is
4: nick a small notch on edge of gpo so when screwed back allows earth wire to sit flush
5: crimp a terminating connector to the end of new wire
6: now make up a new length to reach from lnb connection to earth wire you just installed.
7: add appropriate crimps and connect
8: insulate exposed crimps.
9: switch power back on

OK so the GPO is the Power and not the Telephone socket

So which should I use the earth connection or the Neutral....I guess the answer is the earth connection.....

I was just worried about the neutral involvement.....if its OK then i will do it tomorrow as you suggest.

Please just clarify which connection to use.

Thanx for the detailed replies!!

[machine]

If your so concerned,
just buy an earthing kit, it's been explained a milli0in times before.

Even an Idiot like me picked it up

[jonc]

I would not go anywhere near neutral as in some cases it is far from it, if the wiring is as bad as here in Thailand .. and some upcountry chap was paid to wire your condo when it was built.

We redid our complete wiring after a major short one day doing just what was suggested to you complete with fire (and no pole fuse to pop) with a proper P/N/E cabling including earth cable/rod the whole 10 yards..

Now no more 100v earth leaks, zaps etc .. everything just works as it should touch wood.

[angusc]

If your so concerned,
just buy an earthing kit, it's been explained a milli0in times before.

Even an Idiot like me picked it up

Thanx Machine you are some machine.

Its funny how using the search with say the words "earth" gives different results that using the words "earthing kit"......I'm serious.

Anyways after searching Machines suggestion and taking in to account the other comments, can i ask if the following is on the right tracks for my 10th floor apartment earthing plan?

Nickbo said in an eralier post: "a little tiger bolt into the brick wall acts as my earthing point."

So that said, I have 3 of these holding my dish to the outside wall and also have a plastic bracket between my LNB and the dish = no route to earth for the LNB. So can i run a 6mm earth cable from the wall bracket "tiger bolts" to the LNB F-connector or even just a jumper link from LNB F-Connector to the Dish LNB arm? Is my H-H mount conductive through the gearing?

Then behind my AV cabinet can i drill a hole and install another "Tiger bolt" and then earth all my AV kit including the STB's to this Raw bolt in the wall? does that work to give me a good earthing?

Simple yes, or a no with slight explanation please. don't want to keep this thread going for too long........ just want to get my LAN connection to work.

[jgm]

Nickbo said in an eralier post: "a little tiger bolt into the brick wall acts as my earthing point."

So that said, I have 3 of these holding my dish to the outside wall and also have a plastic bracket between my LNB and the dish = no route to earth for the LNB. So can i run a 6mm earth cable from the wall bracket "tiger bolts" to the LNB F-connector or even just a jumper link from LNB F-Connector to the Dish LNB arm? Is my H-H mount conductive through the gearing?

Then behind my AV cabinet can i drill a hole and install another "Tiger bolt" and then earth all my AV kit including the STB's to this Raw bolt in the wall? does that work to give me a good earthing?

Simple yes, or a no with slight explanation please. don't want to keep this thread going for too long........ just want to get my LAN connection to work.

Brick is an insulator unless wet & even then it isn't much of a conductor. If your water pipe is metallic all the way to the underground mains, you can fasten a clamp onto it anywhere handy & use that as your earth. Neutral SHOULD be at the same potential as earth (they should be tied together at the meter box), but should never be used as an earth. Earth is provided as a protection against incorrectly wired equipment (eg active & neutral reversed), or in case there is a problem with the neutral circuit.

Also, double insulated equipment (eg devices with figure 8 appliance leads) should NEVER be earthed.

[angusc]

I have done a little more investigation in to my set up at home and if i put a volt meter set to VAC scale, between the casing of any of the AV equipment including the satellite boxes or the LNB earth connector and to the earth connection in the wall socket, I get a reading of 68.0 VAC. Is this a "normal" reading / occurance?

Is it OK to still earth my satellite box to the Earth directly at the wall socket? The reason i ask is that if i "flash" a wire directly from the earth connection to the box chassis then there is a small spark where the voltage is arcing across. I do not want to cause any perminent harm if i make a perminent connection and cause an un natural path to earth......

With some suggestions in this thread that you should not earth any devices that are designed to be double insulated devices and the average AV system has a mixture of both earthed and non earthed items, all of which are linked together by Phono leads from component to component. This seems virtually impossible to follow unless using all optial connections between components.

I do not have anything like water pipes near to my AV kit to earth to, other than using the earth connection in the wall power socket. Even the heating pipes are plastic in this apartment. if I measure the voltage from the LNB earth connection to my window frame then i get a reading of around 63 VAC which suggests around 5 VAC potential difference to the power sockets earth connection.

[Godzilla]

Forget about a bolt in brickwork as an earth point, as mentioned, if the brickwork is not wet, it wont work.

Maybe if you cannot earth your LNB, you should consider turning off the power at the wall before doing any connections to minimize risks to your equipment.

[gw1]

if i put a volt meter set to VAC scale, between the casing of any of the AV equipment including the satellite boxes or the LNB earth connector and to the earth connection in the wall socket, I get a reading of 68.0 VAC. Is this a "normal" reading / occurance?

Yes, as I said above, that's normal whenever you're using unearthed equipment with switchmode power supplies.

I am not an electrician, therefore I would recommend against any modification or interference with your house wiring. In particular I would NOT advise connecting your neutral wire to anything. It may be safe but if there's a wiring fault it could turn out to be lethal. If you think your home wiring is questionable you get a local electrician to do a safety test for you.

Try taking your dreambox to friends' places to see how it behaves in their environments. IMO the fault is more likely to be in your dreambox than in your home wiring.

[cozbert]

The Neutral should definately not be used as it could become live, the earth and neutral bars would most probably be connected together at the MAIN board in the building this is called a MEN link and is how most suburban houses in australia are connected this is a very safe method of earthing.

Most appliances are double insulated eg no earth pin, this is so that the manufacturers can cut costs in manufacturing out all the interference that comes on in the earthing conductor from washing machines, airconditioners and just about any other device you can think of.

i would recommend buying a normal plug top and attaching an earth cable to the EARTH pin inside the plug and then earthing your LNB. earthing all of you tv system may introduce noise issues in picture and sound.

Cheers
Cozbert

[tristen]

Good advice from GW1 and Cozbert.

I'm not an electrician either, but I've worked with a few over the years.
Their advice was to NEVER assume that the neutral conductor is at earth potential - sometimes it isn't, as my own experience has confirmed on more than a few occasions.

In the course of my electronics servicing and installation activities over many years, I have also encountered so-called earth cables/connections, which had been incorrectly installed, disconnected or otherwise interfered with.

I have also found mains outlet sockets, which had been incorrectly connected, with neutral, active and/or earth connected to the wrong terminals.

Assume nothing - check it with a meter first.

When working with the mains or cables connected to the mains, take extreme care. Mains voltages are lethal.

[angusc]

If I connect the LNB outer connection to the Wall socket Earth connection then this is in effect earthing out the entire AV system as everything is interlinked with AV cables.

Currently 68VAC between LNB and earth connection.

Is it correct / safe to make the connection and will it prevent earth leakage issues?

[tristen]

If I connect the LNB outer connection to the Wall socket Earth connection then this is in effect earthing out the entire AV system as everything is interlinked with AV cables.

Currently 68VAC between LNB and earth connection.

Is it correct / safe to make the connection and will it prevent earth leakage issues?

GW1 has already correctly answered this question in posts #5 and #13.
Yes, you will be able to measure an AC voltage.
It is very low leakage current only and present in units equipped with a switch-mode power supply. As such it will not harm you or your wife. It is merely unexpected and for most, a little unpleasant.

The quick-and-simple solution :-
Get a three pin mains plug.
Connect a piece of insulated wire to the earth pin only. (You must already have a reasonably good earth connection or else you would not be able to measure the 68 VAC to which you refer).
Fit an alligator / crocodile clip to the free end of the cable.
Push the plug into a spare mains socket.
(If you don't have a spare mains socket use a double-adaptor or similar device).
Disconnect your Dreambox from the mains.
Connect alligator / crocodile clip to the "F" connector of the LNB cable, which is connected to the satellite receiver.
Re-connect the Dreambox to the mains - and "Bob's your uncle".

As an aside, I have never had any problems with Dreamboxes being un-earthed". Perhaps I have been lucky.

[updatelee]

How about you run your earth off your steel water pipes. I am assuming that they are steel of course, should do the trick.

you dont see steel very often used for residential plumbing here in Canada, I doubt else where either. copper is quite common in older houses but even newer ones have all been switched over to pex along time ago. even the septic and water lines are plastic now days.

[z80]

Just use an inlet water pipe .

Even if its plastic it will have water in it...

[Godzilla]

Hmmm a stainless steel bolt with a sealing washer placed from inside the plastic pipe to outside with 2 locking nuts to lock it should do the trick.

Just add your wire to the left over part of the bolt and add a third nut to hold it on.

You could even adapt a T piece into your plumbing and build it all inside a cap on the end of the T.

Now there's no excuses that you don't have an earth no matter what your piping is made of.