Why do I get an electric shock from my equipment?
TV sets, satellite TV and Terrestrial TV receivers.
Most receiver chassis are not connected to anything. They are "floating" and rely on a ground connection through your other equipment. If that, too, is floating then you must connect a ground somewhere as charge tends to build up through whatever leakage paths are available. The voltage on the metal casing of equipment with a switch mode power supply is usually about 110 volts AC.
The current available from this 110v "float" is minimal and, presumably, within safe limits (it shouldn't kill you) but I wouldn't like it on mine because it can surprise you - especially if you are up a metal ladder holding the LNB!
In Europe (not UK), the dish itself and the incoming LNB cable shield must be grounded so this problem does not arise. Grounding the dish can eliminate problems caused by airborne static charge, too. A one metre copper rod buried* in damp soil is ideal but a cold water pipe (NOT gas pipe) is usually OK - but note that newer properties may have a plastic incoming water pipe, so the copper pipes in the house may not be grounded (although they are supposed to be "earth bonded").
In dry weather, airborne dust carries a charge of static electricity. This charge can accumulate on a dish and, when the voltage reaches a critical level, a spark can discharge to the nearest "earthed" point, which is often the outer screen of the coaxial cable.
| For this reason, it's a good idea to connect the cable through an "earth bond plate", which will remove static charge. |  |
The same comments apply to TV sets and other mains-powered equipment. You can earth the outer shield of the TV aerial cable to remove charge. This is not a "mains safety earth". It is merely bleeding off unwanted charge, so the wire doesn't need to be thick.
Warning
You should not connect or disconnect anything from equipment which is still powered - even if it is switched to standby. Always put it into standby then switch off at the wall socket and unplug it. Interconnected equipment should ALL be powered off before you touch any connections. (This is not because it might be dangerous to you but because you might feed the 110 volts into a socket that isn't designed to tolerate it without circuit damage.)
Warning
If two dwellings share a common dish, the LNB cables should always be connected through an earth bond plate, and earth bonded by a qualified electrician, because there is a risk that the dwellings may be supplied with different mains electricity phases. The result of this is the possibility of a 450 volt shock if a fault occurs in either dwelling without the presence of earth bonding!
Warning
*If you install an earth rod, do not hammer it straight into the ground. Instead, you should carefully dig a deep hole, taking care to look for underground service pipes and cables. Place the rod in the hole then back fill the hole and tamp the soil down. This will not provide "earth bonding" for safety purposes but it will "bleed off" unwanted electrical charge.
More about earth rods ... click HERE
Read about the dangers of Static Electricity ... click HERE
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