How many grounding blocks?

[diyguy]

I live in an older house with cable wires running on the outside of the house. At the demarc box the cable is grounded before it enters a splitter. From the splitter cable is run 4 directions around the outside walls with some runs as long as 75 feet. Would I need to add grounding blocks to each of the 4 cables where they actually enter the house or is the one grounding block at the demarc block sufficient?

 

[korsjs]

cable is suppose to be grounded before it enters the house. local codes vary from city to city. i don't want to tell you that you will be ok since there is always that slight chance. some here at this site are hardcore about grounding.

welcome to the site.

 

[cableman265]

here in the st louis area, it is grounded only once before it is split off.

 

[riffjim4069]

I live in an older house with cable wires running on the outside of the house. At the demarc box the cable is grounded before it enters a splitter. From the splitter cable is run 4 directions around the outside walls with some runs as long as 75 feet. Would I need to add grounding blocks to each of the 4 cables where they actually enter the house or is the one grounding block at the demarc block sufficient?

That should be minimally sufficient, but as an added measure of protection you may wish to use an A/V Surge Protector like one of these at each outlet: http://www.primewirecable.com/surge7.aspx?CatSubID=86

Personally, I have two OTA antennas and each antenna has both the mast and coax cable grounded outdoors. Also, each coax and preamp runs through a surge protector in the wiring closet...and each coax (and HDTV) is plugged into another surge protector prior to being plugged into the set.

Both satellite dishes are properly grounded (mast and coax) and all three coax cables coming from the LNBs run through a 3750 joule surge protector prior being connected to a DP-34 switch; coax are then ran directly to the satellite receivers.

My Cable coax is properly grounded (like yours) just prior to being split (3-way) into the house. I then use a 3750 joule surge protector like I do with satellite. The odd of your being affected by a lightning strike are pretty slim, but it's better to be safe than sorry.

 

[vurbano]

actually RS sells some very small inline cable surge suppressors that do a fine job. I have them placed on the back of all cable modems/sat recievers I use.

 

[diyguy]

Well, I think putting ground blocks right before entry into the house in addition to the ground block at the demarcation would be totally optional since I can't find it in the NEC. It probably wouldn't hurt though and if nothing else could help cutout any potential RF/EMI interference.