Electrical Safety – Earth bonding

Discussion in 'Multi-receiver/TV systems - Domestic only' started by satelliteman, Jun 2, 2008.

  1. satelliteman

    satelliteman Administrator Staff Member

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    Electrical Safety – Earth bonding requirements - Single Dwelling and Multiple Dwelling Units


    A brief outline.


    Communal TV/Satellite Earth Bonding

    Safety is provided by ensuring that an aerial/satellite system is connected to the main earth terminal of a building, the same earth that all other services are connected to and relies on this connection of the aerial/satellite system to the building’s protective earth to minimise any dangerous voltages that could be present. All communal systems must be connected to the building’s main earth (MET) via a minimum of a 4mm2 copper cable and only to be carried out by a qualified electrician.



    Domestic System Supplementary Earth Bond - Recommendation

    Where a TV/Satellite system includes Class II equipment, a voltage will be present on the screen of the coaxial cable which can be minimised by the use of a supplementary bond. The small values of touch current associated with one piece of class II equipment are considered safe and will not create a problem, but several pieces of class II interconnected equipment in one household has to be considered. The cumulative touch current from a number of interconnected Class II items shouldn't exceed 3.5mA. Where touch current in excess of 3.5mA is likely, a supplementary bond is recommended to conduct the touch current to earth. Typically seven units would be the maximum recommended number of interconnected Class II units in order to keep below the 3.5mA maximum allowable touch current. All such work is a recommendation and should be completed by a suitable qualified electrician.

    BS EN 7671:2008, BS EN 60065:2002, BS EN 60728-11:2005, BS EN 60950-1:2006 , BS EN 60990:2000, BS EN 62305-4:2006, IEC 62368-1 Ed 1.0, Electricity at Work Regulations 1989, Directive 2006/95/EC, Health and Safety Directive.


    The above is for general information purposes only and as such electrical earth bonding should not be brought up for discussion on the forum. Please consult a qualified electrician if in doubt.
  2. 101michael

    101michael Member

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    My Satellite Setup:
    1m dish, Antiference 7x20 multiswitch, quattro LNB.
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    London
    When i purchased my antiference multiswitch i also purchased its earth bonding kit...

    This included 'quick fit' f type modules which slide onto the ins and outs of the multiswitch connected together with earth wire, im a bit worried that it may slightly degrade signal quality that now i have the coax going through another connecter, would it be best to just have the wire screwed around the ins and outs rather than through the included push on connectors?
  3. satelliteman

    satelliteman Administrator Staff Member

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    There will be no loss if correct connectors are fitted.

    You can connect the 4mm earth cable to the multi-switch earth tag itself if you wish.
    :)
  4. 101michael

    101michael Member

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    hm, well im a bit confused now...

    There is an earth bar at the side of the multiswitch, once all the ins and outs are connected via the earth bonding kit does this need to go through the earth bar before the main earthing, or can i bypass the earth bar and go directly to the earth cable which is coming out of the consumer unit?

    thanks
  5. satelliteman

    satelliteman Administrator Staff Member

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    Connect a 4mm earth to the multi-switch either as per the bonding bars kit OR just connect the earth directly to the multi-switch via it's earth tag (this will be a hole with a screw somewhere on the switch)

    Both will serve the same purpose.

    ***Note***
    If your not qualified to do the above work, consult an electrician.

    Satman :)
  6. 101michael

    101michael Member

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    OK...i sort of think i understand..

    but take a look at this _http://www.antiference.tv/isys7-installation-schematic

    Right, i have the earth bonding and connecting all ins and outs together...but why do that if i can just connect my earth straight to the earth post?

    Or am i meant to connect all ins and outs to the earth post too?

    Sorry if i seem to be repeating the same question. I will get my electrician to take a look, but i just like to know whats meant to be done prior.... thanks again
  7. satelliteman

    satelliteman Administrator Staff Member

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    OK,

    On larger systems ie. flats and apartments where say 100+ sub feeds are connected. If you require to service the switch Or replace it, then when you take the switch out, each subscriber cable will still be earthed.

    If you connect to the earth tag only. When the switch is taken out to be replaced, the sub cable are not in the protection zone.

    As it's only 16 cables or so and it's domestic, you can just connect to earth tag Or continue to install the kit.

    Hope you understand my explanation

    Paul
    Satman :)
  8. rolfw

    rolfw Believe it when I see it Admin. Staff Member

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    If you install the earthing kit, then also earthing the earth tag on the switch is probably overkill, but it only takes one further piece of cable to do the lot.

    It is the UK only which insists on this double earthing, not the same on the continent I believe.
  9. 101michael

    101michael Member

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    sateliteman...

    ok i understand BUT:

    why not connect the say, 20, multiswicthes in a star architecture from their earth post to the main earthing point? so if you remove one switch then the others are not affected?

    Is this possible? im not an electrician so i have no idea, does this mean all ins and outs are pre looped within the switch to the earth post, if not why not?

    Sorry about all the questions, ill still get my electrician to have a look, but i just like to understand as much as possible...rather than nod accordingly.
  10. satelliteman

    satelliteman Administrator Staff Member

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    Not all larger systems can be wired in a star configuration.

    If your going to earth a multi-switch back to the board, even if it's a domestic set up, you need to also make sure you are using benchmarked cabling (copper to copper)

    Other cables may not carry the current and trip the RCD in the event of a fault.

    ** INFO: The maximum resistance between the buildings earth point (PE) and the furthest point on a system is 3.5 Ohms. Now 2 Ohms of that is between the PE (primary Earth) and your earth bar at the multi-switch location. This shouldn't be a problem as your cable runs won't be too long.

    ** INFO: This method of safety provision ensures that any hazardous fault currents that maybe present on the distribution system are taken to earth.

    ** INFO: Either a faulty TV/ SAT RECEIVER or some other mains operated equipment being connected to the system would generate these hazardous voltages and pass them around the system unless some electrical protection is provided.

    This info is mainly for IRS systems on commercial properties, ie. apartments, flats etc...

    This can also apply to LARGE domestic set ups around the home whereby IRS systems are being used.

    Note** If your not qualified to work with electrics around the home, consult a qualified electrician.


    :)
  11. vjeko

    vjeko Member

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    My Satellite Setup:
    planning new satellite/network cabling for entire house
    My Location:
    Croatia
    My questions are associated with earthing/protection from thunder,
    so I'll sneak them in here:

    I'm a bit confused by what I see on the web as far as earthing/protection
    is concerned. When I go to a U.S. web site, the usual practice as I understand
    it is to connect
    (a)the dish and what it is mounted on, directly to earthing/lightning
    protection which is connected to the main earth/grounding.
    (b)coax cables are grounded via ground blocks at closest spot
    near entry to the building or immediately after entry into the building
    - again connected directly to the main ground/lightning protection.
    So, I don't see any grounding of the multiswitch output terminals.

    On the other hand, on a web site here in Croatia I saw the attached
    picture as an example of good grounding (something similar to
    what is being talked about here i.e. multiswitch inputs and outputs
    earthed (except for a bad point that on the picture it seems the rule of one point
    ground is not followed as I don't see all connections to the central point
    (to the right of the two power outlets).

    So, I'm confused - you can't earth the coax near the dish AND
    near the multiswitch as this would lead to voltage drops/probable
    interference and who knows what - which way to go and for what reason
    (protection from induced static charge from atmosphere/lightning
    near the dish or only inside near the multiswitch - but then
    protection has been moved near the multiswitch)

    Second question - (specific to me/problems created by my electrician)
    The corner of the house on which I will be mounting the dish
    has no lightning protection from roof to earth (closest is on the roof,
    going to earth at the other three corners of the house).
    Dish will be on 2nd floor balcony, roof is above third floor and
    wiring will go down into 1st floor. Does it make sense to connect
    an earth cable down to 2nd floor from the roof and earth the
    dish (I know electrons don't know about direction except for
    lowest path of resistance but I'm not sure what would happen
    if thunder struck near the antenna - would it go back up
    to the roof via earth lead or jump to the metal drain pipe
    or skip through the coax through the house to earth
    (or most likely a combination of all three which only God
    knows about)

    Any pointers on the dish and coax/multiswitch grounding
    would be appreciated as my lack of knowledge is at
    the moment making me hesitant to proceed with the installation.

    Attached Files:

  12. cgw59

    cgw59 Member

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    Northern Ireland & Biot France
    Hi All,
    It is vital that all non insulated equipment is properly earthed no matter what it is connected to. This is to prevent a person being in a position where they may be able to touch an "Earthed" item and a "Non Earthed" item, for example if a cable which is not connected directly to earth were to be removed and a fault occur in the connected equipment then when a person would try to reconnect the cable to an "Earthed" switch etc then they would form part of the earthing circuit and could suffer fatal injuries.
    Be safe and ensure that all equipment is earthed and if possible switch off any source of electrical supply prior to attempting work on any item capable of carrying electrical current.
    Electricity is like a wild animal in zoo, fine when it's in the cage (insulator)but it WILL kill if you let it out !!

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