Ground block inside, ok??

Bradtothebone · Feb 21, 2008

ksat1 said:
I appreciate everyone's input, from both sides, pros & cons to either option I guess. Reading through this has actually given me a new idea, which may not do anymore than to ease my mind regarding the possible fire hazard, but even if that's really all it does, it will be worth the effort.

I like having the GB inside, protected from the elements, to minimize corrosion issues. My closest, and most logical, ground point is also inside, as I noted in my initial thread. So, if the GB were outside, the path to ground would still pass through the wall to get to the interior water line.

Given that, my thought is to keep it all inside, but maybe isolate it somewhat. I have excess cable, so think I'll mount an electrical junction box of some sort part way down on the concrete basement wall. The GB can then be removed from the floor joist above and mounted inside of that box, behind a cover, completely enclosed. I would then only have about a 3' vertical run of ground wire down to the water line.

Any thoughts on that idea?

Also just want to say this forum is the most useful site I've ever stumbled across on the web, THANKS!:up

A couple of thoughts: First, the junction box really doesn't do anyting for you inside the house. I'd go ahead and just mount the ground block on a floor joist.

Second, although it doesn't strictly meet code, you're probably OK grounding to the nearest water line, although you need to make sure that you have a continuous copper line all the way back to the grounding point of the electrical service. In other words - no plastic pipe spliced in, or a dielectric union somewhere. You probably won't have a dielectric union unless you're on a hot water line (they're used at HW heaters, mostly). So, ground to a COLD water line. If the actual ground wire from the ground block to the grounding point is subject to damage (exposed within reach of occupants), it should be in conduit to protect it.

Brad

charlesrshell · Feb 21, 2008

Bradtothebone said:
A couple of thoughts: First, the junction box really doesn't do anyting for you inside the house. I'd go ahead and just mount the ground block on a floor joist.

Second, although it doesn't strictly meet code, you're probably OK grounding to the nearest water line, although you need to make sure that you have a continuous copper line all the way back to the grounding point of the electrical service. In other words - no plastic pipe spliced in, or a dielectric union somewhere. You probably won't have a dielectric union unless you're on a hot water line (they're used at HW heaters, mostly). So, ground to a COLD water line. If the actual ground wire from the ground block to the grounding point is subject to damage (exposed within reach of occupants), it should be in conduit to protect it.

Brad

I agree with you Bradtothebone. My grounds are to cold pipes and way far away from the 5' pipe entry into the basement. But, I tested the pipes to make sure they were grounded to the home ground. I used a multi-meter and tested the pipes from the ground block on the pipe to an A/C outlet ground wire and the ohm reading is 0. I am no electrician but to me that means a good ground.

dishcomm · Feb 25, 2008

Mike500 said:
Codes require outside mounting.

That's what they make weatherproof boxes for.

no they do not....The only stipulations are the ground must be NEC approved and the ground wire no longer than the shortest run form the ground block ot the first receiver.
Protecting the ground block and connectors from the weather is an ideal option. Based on your logic the gound block I placed just inside the crawlspace door on a job I did yesterday(Sat) is a code violation? I have been doing this satellite stuff for ten years, voice/data over 20 years.

dishcomm · Feb 25, 2008

vegassatellite said:
Let's just put it this way: If a catastrophic amount of current made its way on to your cables, would you want that current entering your home before it crosses to the ground connection?

Imagine a home with overhead power lines and a tree limb fell on the power line to the home, causing the power lines to hit the dish on the way down. For a brief moment, all the power the power company makes available to its customers through their transformer suddenly energizes your coax.

The coax is probably going to get vaporized as well as the #10 ground wire. The ground block may well get flash melted, throwing hot metal slag everywhere. The lower resistance of a ground path means the bulk of the current will flow that way. Personally, I would rather that path be outside the home.

wow!! I see your point. But in the event of such an unsual and catostrphic series of events, would it not be a disaster anyway?...BTW I NEVER Install a dish near powerlines. EVER...For the same reasons tyou exlained in your scenario above..That and if lightining strikes the pole carrying the elect. service to the home could "jump" from the elect. service line to a nearby dish.. SO that's a no no. If that means putting the dish in a less conveient area of the roof, so be it..

dishcomm · Feb 25, 2008

Andrewwski said:
They put it inside quite often here. Not just the satellite companies though - the cable and telephone companies do too.

I have no problem having it inside as long as it's near the point of entrance.

Prior to the mid 80's all telco ground blocks were typically inside the basement of homes built on basements. The house I grew up in was built in the 60's..Our telco ground block was in the basement..It was in the late 80's when the telcos started putting interface boxes on the exterior of the home but still ran the ground wire to a cold water copper pipe if the home was so plumbed.

vegassatellite · Feb 25, 2008

dishcomm said:
wow!! I see your point. But in the event of such an unsual and catostrphic series of events, would it not be a disaster anyway?...BTW I NEVER Install a dish near powerlines. EVER...For the same reasons tyou exlained in your scenario above..That and if lightining strikes the pole carrying the elect. service to the home could "jump" from the elect. service line to a nearby dish.. SO that's a no no. If that means putting the dish in a less conveient area of the roof, so be it..

The power company has a lot of available power coming from that transformer. The weak point in such a contact would obviously be the coax cable. I've been informed by electrical engineers that in the few milliseconds it takes for the aluminum shield to rise to its melting point, up to 400 amps of power could run a distance of 50 feet down the coax in the time before the connection is severed by the aluminum shield being vaporized. Most of that current is going to be dissipated along the ground path, i.e., from the coax to the ground block to the ground wire and ground electrode. So, for the most part, the part of the system that will get destroyed is the ground block and everything on the dish side. Personally, I would want to keep that event outside.

Lesser currents such as those restricted by a breaker that don't vaporize the coax can make it so hot as to make combustion of nearby flammable objects a great possibility. I've been in a few basements where the ground block and/or the coax leading to it from the dish passed by shear fabric curtains, towels on shelfs above dryers, etc.

Jim5506 · Feb 26, 2008

If you get a direct strike, the ground is not big enough to protect the house or equipment.

Ground is to bleed off potential which helps reduce the probability of a strike.

The ground is NOT protection, it is prevention.

Once thet current passes the shield it is everywhere in your house it doesn't stop at 50 feet. Even if interrupted it still has momentum and pressure within it.

Van · Feb 26, 2008

I'd put it outside if at all possible, I've seen high power electrical from 220 to lightning damage after its went through the coax and the ground block and ground wire or what was left of them and it would be much better to have it outside instead of in a house.

vegassatellite · Feb 26, 2008

Jim5506 said:
If you get a direct strike, the ground is not big enough to protect the house or equipment.

Ground is to bleed off potential which helps reduce the probability of a strike.

The ground is NOT protection, it is prevention.

Once thet current passes the shield it is everywhere in your house it doesn't stop at 50 feet. Even if interrupted it still has momentum and pressure within it.

I'm just repeating what some electrical engineers have determined. It takes much less than a second for a power company transformer load imposed on the shield of coax to melt the aluminum and thus open the circuit. Most of the current that gets through can be handled via the ground circuit for the short duration that it takes to vaporize the coax upstream of the ground block. The damage downstream of it will be less significant.

Ground block inside, ok??

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