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grounding question

Discussion in 'DIRECTV Installation/MDU Discussion' started by islander66, Oct 17, 2007.

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  1. islander66

    islander66 AllStar

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    Oct 16, 2007
    I grounded my slim line dish 5nlb to the multi switch, then ran the copper wire to the ground Comcast had installed. I don't think most of my house is grounded, (except the meter) because it's 45 years old and has mostly two prong plugs. I think the kitchen and plug for the HR20 may be grounded to the water pipe. (something is grounded there)

    Anyway, I do have a multi meter with resistance function. Can I check to see if the dish is grounded?
     
  2. gulfwarvet

    gulfwarvet Tips & Resources Collaboration

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    first a question about the ground Comcast installed for you before hand. how did they install it? if they installed a 6ft copper grounding rod or if they installed a grounding block running the regualtion ground wire to your water pipe. you should be fine by connecting a ground to what Comcast installed.

    far as your multi meter resistance function, yes you can double check the dish being grounded. by placing a wire lead from the ground rod, then running another one from your dish and connect to the meter. if you have zero resistance it's grounded, if you hve high resistance that mean's it's not grounded.

    but from what you said, it seems like your fine if you used 10 gauge copper wire for the grounding of the multiswitch.
     
  3. Milominderbinder2

    Milominderbinder2 Cutting Edge: ECHELON '08

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  4. islander66

    islander66 AllStar

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    Oct 16, 2007

    Thanks for the response.

    The Comcast ground is a copper wire about 10 gage, that goes down below a concrete slab that was poured after the ground was installed before I moved here. The Comcast cable has a grounding block but I connected the ground wire from the dish and multi switch to the copper ground wire screw.

    I don't have a grounding block, but wouldn't the multi switch be the same thing? It appears to have a place to attach a ground wire on the top and bottom.

    I could connect the ground wire to the copper pipes. I think the other ground I saw was connected to copper drain line, that connects to a cast iron stack.

    I'm also in the hot south, so that the water lines are only a foot below the surface anyway. So, I was thinking the Comcast ground below the slab where it is nice and damp would be ok.

    About the resistance check. Can I touch one of the connectors to the ground wire from the dish and the other to the ground rod? They are about 100' apart. Or do I need to run another line from the dish to the post other than the ground I have now?

    I also don't think the ground wire is 6 gage. It was the one with the cable wire.

    I'm thinking it's ok, (better than nothing) but thanks for any more info.
     
  5. islander66

    islander66 AllStar

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    Oct 16, 2007
    Thanks for the link Craig! I found that but it didn't say anything about using the multi switch as a ground block. It seems like the multi switch would be a better option to use as a ground block.
     
  6. armophob

    armophob Difficulty Concen........

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    Nov 13, 2006
    Fort Pierce, FL
    Pictures could better explain your situation. The concrete slab has been poured over the ground rod?
     
  7. gulfwarvet

    gulfwarvet Tips & Resources Collaboration

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    please forgive me on the typo i had about 6 gage it was to be 10 gage. OOP'S

    your Multiswitch can serve as the same as what a grounding would be. you should be fine by using it. but are you sure the ground rod under the concrete slab is still functional?

    far as the resistance check, hum you could do it the way you were thinking. but for extra reassurance's (if need be). you could do it the other way if you wish. but i really think your fine with the way you have it setup. (btw.. thats the same way i have mine., and never had a problem) if the grounding rod is still functional?
     
  8. islander66

    islander66 AllStar

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    Oct 16, 2007

    I can't be sure the ground rod is functional, yet it is nice thick wire that looks good, and goes down into a damp earth. I'll do the resistance check, and try and run an extention cord to use as another wire.

    Then when I redo a back room and update the electrical, I'll update the ground as well.

    thanks again
     
  9. gulfwarvet

    gulfwarvet Tips & Resources Collaboration

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    if it was me, i would purchase a new 6ft grounding rod and hammer that sucker in the ground just to be sure. If i had any doubts over the existing grounding rod.

    but i wish you Good luck, and please keep us updated on what you do :)
     
  10. islander66

    islander66 AllStar

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    Oct 16, 2007

    yeah, ill do that. i have a big sledge hammer. ill also patch up some other trouble spots (splices) with some junction boxes, etc, otherwise there might not be a house for the satellite dish to sit on top of.
     
  11. joe diamond

    joe diamond Hall Of Fame

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    IF you redo the ground rod.......the phone NID & electric distribution box should be bonded to the new rod using the 10 ga wire & new clamps. As you pound in the new ground rod move away from the building about a foot to make sure you don't drive the rod into the wall footer.
    The concrete pour over the old ground rod is probably a code violation because it is now not possible to inspect it. If it is black iron pipe it is also probably a violation.

    Don't worry about all this too much. Most power surges come in through the phone wire anyhow ( I think).

    Joe
     
  12. islander66

    islander66 AllStar

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    Oct 16, 2007
    Thanks Joe, and everyone. I'll be moving in that direction soon.
     
  13. Milominderbinder2

    Milominderbinder2 Cutting Edge: ECHELON '08

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    The ground wire has to be outside of your house, National electric Code. Never through a switch.

    Craig
    EE U of I, NEC nerd
     
  14. donshan

    donshan Godfather

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    Jun 18, 2007
    It can help to do some tests to see how bad it it is. Your electric meter and panel are grounded to the power company ground and you want your sat grounds to be electrically connected to that same ground potential. The best way is to run a 6 ga. copper ground wire to the power company ground. Then they have to be the same.

    To do a test tou can get a coil of stranded 18 ga wire ( green is the code convention for ground_), connect it to the meter ground with a split bolt or clamp and then run the test wire close enough to the Comcast ground to use your meter to make a resistance measurement between the two. There should be less than one ohm resistance between the two. If your soil is high conductivity this may be the case, but I would guess that in the majority of cases of separate ground rods there will be a soil resistance of several hundred ohms or more. When this is the case the Comcast ground is not really a "ground". When you plug your D* receiver into 120v the receiver will think "ground" is the white neutral wire from the wall plug ( which runs to the power company grounded panel). This "ground" may be different from the dish connected to the Comcast ground and ground loop currents could be created. Test the resistance from that water pipe ground to the power company ground- it should be less than one ohm too. Usually the power electrical panel is grounded to the building water pipes, however the water pipe system is not really a reliable ground due to pipe dope in water pipe fittings and corrosion common in older houses.

    The test will reveal how bad it is, but running a 6 ga copper ground between the the power company ground rod and the Comcast ground would make sure the resistance reading is zero between the two grounds. DO NOT use your test 18ga wire as a final ground- that is not heavy enough wire size.
     
  15. K4SMX

    K4SMX Hall Of Fame

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    This is all really good info. The only thing I might add is that I think before you measure the resistance between the alleged grounds, you might want to put your multimeter in the AC voltage scales to make sure there's no voltage potential between those two points of any amount whatsoever. This protects your meter fuse from blowing, protects you from any unexpected voltages on what is supposed to be a grounded line, and insures that you get accurate resistance measurements from donshan's test.

    I can't even begin to count the number of times I've found AC voltage on things that were supposed to be neutral or ground wires, especially in older buildings. The worst was when I was troubleshooting a problem with a blower fan motor in a vent hood. I had hooked a clip lead to the ground wire in the Romex. The other end of the clip then dropped onto the nice, satin chrome finish of the bezel around the gas indoor grill below. A giant flash and a nice "weld" mark where the alligator clip touched the bezel ensued. Turned out the ground wire was at 110 VAC. I treat every wire as a potential enemy after that experience.
     
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