Grounding question

[Darken]

Hi Folks,

I had asked a question about grounding my antenna last year but unfortunately had to put that project on hold. I have started looking back into now. I am considering simply putting a grounding block under my current service provider's box (bell canada) that is next to my electical box. I noticed the bell box (that I will still be using for my home phone line and internet) has a ground wire to the electrical box already. So my question is, if i run coax with ground messenger from my antenna which will be behind the house, to the front of the house where my elecrical box is and connect it to a grounding block...can i

1) simply tighten another ground wire to the same spot that bell is using on the electical box. Basically have two ground wires one on top of the other?

2) Since there is one end of a messenger ground connected to the mast and the other end to the grounding block, i assume this would safely ground both the mast and coax to the electrical box?

3) Once the coax connects to the grounding block from the antenna and the grounding wire to the electrical box, the coax then needs to continue into the house. In my case the cable isn't going to enter the house near the electrical box. It will enter the house approximately another 30 feet away. Is this ideal for grounding? (i understand it may not be ideal for the signal but my concern right now is grounding). Once the cable connects to the grounding block from the antenna does it need to enter the house right away or is it safe to extend the cable along the ground for another 30 feet or so before it enters the house?

Thanks so much to those who answer

Darken

[Tower Guy]

In the U.S.:

1 yes
2 yes
3 no

I don't know the rules in Canada.

[rickbb]

Generally speaking;

Put the coax grounding block nearest to where it will enter your house. You can then run a bare copper or aluminum ground wire from the block over to your service ground.

This keeps the coax short for good signal and completes the grounding path.

BUT, you really should check with your local building/electrical codes. They can be very different from place to place.

[Darken]

Thanks for the replies.

So if I understand correctly, i would be better off putting the grounding block closer to where i want the coax to enter the house and then extend a grounding wire approx 30 feet to the electrical box (main ground) as opposed to having the grounding block next to the electrical box and extending the coax 30 feet to where it enters the house? The real issue unfortunately is that the antenna is on the east end of the house, the electrical box is right in the middle and the coax will need to enter on the west end because that is where the living room is. So either the coax or the ground wire will need to be extended after the ground block, just trying to figure out which one is best.

[ADTech]

The National Electrical Code (if in the US), which is our only reference, explicitly states that the coax grounding should take placed as near as practicable to the point of entry. It does not provide alternatives.

You're on your own if you wish to deviate from that.

[rickbb]

Again just speaking generally here, you really need to have a look at the codes for where you live to get the correct information for your location.

The reason for putting the coax grounding at the point of entry to the house is to keep any spike from a nearby lighting strike from going into the house on the coax. Cable on the outside is more susceptible to picking up that spike than on the inside.

If you have 30 more feet of coax on the outside of the house AFTER you ground it you are kind of defeating the grounding. And most likely violating your local codes. That's why the recommendation to run a grounding wire the 30 feet to the service ground and not the coax. But again, check your local codes.

On the other hand if you want to enter the house AT the service panel, then putting the grounding block there is what you would want to do.

Of course nothing is 100% and if the strike is close enough it's going to get in.


As to where to enter the house the only thing to consider is you want your coax run to be as short as you can to keep any loss from long runs at a minimum. Other than that, it's really up to you where the entry point is. It may not matter though, depends on your signals, and total length of run.

[Darken]

Ok great. Thanks for the responses. I'll keep things simple by drilling a new house entry hole below grounding point which is on the electrical box. My coax and ground wire will be dropping down from the roof at is approaches the electrical box so is it better to put the grounding block level with the electrical box and then simply run the grounding wire horizontally to ground it to the box and then run about 3 more feet of coax down to where i'll drill a new hole into the house or should i put the grounding block near the ground where the entry point is to have only a foot (or less) of coax before it enters the house and then run the grounding wire back up about 3 feet to the electrical box? Seems odd to run the grounding wire right past the electrical box to the grounding block and then have to run it right back up from the block to the electrical box...

Also i havent bought the tripod yet to mount the antenna but can i simply screw the ground wire into any screw on the tripod as im setting it up or do all tripods and mounts have a dedicated area where i can screw in the ground?

Thanks again for all your advice

[rickbb]

2 separate things. Up until now we have been addressing just the coax grounding.

To ground your mast you need to run a separate ground wire and clamp it to the mast. Any screw or bolt that makes good contact near the bottom of the mast will do.

[Darken]

Ok I guess I wasnt visualizing it correctly. So a "separate ground wire' would mean 2 ground wires? If i have a coax/messenger ground wouldn't that ground both the tripod and the coax to the grounding block? So my coax/messenger ground needs to be secured to the tripod and run to the grounding block to be grounded through the electrical box BUT i also need a separate ground just for the tripod? Is this where i could fasten another ground from the tripod to a nearby grounding rod? Or i suppose i could also just run the 2nd ground the same route as the original one to the grounding block? Is this correct?

Thanks again for helping me make sense of this

[rickbb]

No, lets start over.

Coax has it's own built in ground wire, it's called shielding. A coax ground block looks like this;

http://ecx.images-amazon.com/images/I/41w5%2B5iDdjL.jpg

You attach the coax from the antenna to the block, the coax into the house to the other side of the block and a ground wire from the screw on the block to the service ground. You mount this block on the house where it enters the house.

The mast needs a ground wire from the mast to the service ground, no other ground block needed on it. Just run it from the mast to the service ground point. Good connections are all that's required for it.

In addition look here;

http://www.hdtvprimer.com/ANTENNAS/basics.html

scroll down to the section "Grounding Outdoor Antennas"

AND I really can't stress enough that you check out your local code requirements on this.

[Darken]

firstly, thanks for your patience. these concepts are new to me so im trying my best follow.

So in this case i would have 3 ground wires all under the same screw on the service ground (which is my electrical box). I still have some bell canada services and their system is already grounded to the service ground, i will have a ground wire from my grounding block to ground my coax and i will have a separate ground wire from the mast directly to the service ground as well. Does that sound about right?

Thanks again

[rabbit73]

That sounds like too many wires under the same screw. You might need an Intersystem Bonding Terminal Block/Bar (IBTB):
https://www.google.com/?gws_rd=ssl#q...nding+terminal

https://www.erico.com/catalog/literature/E803S-NAEN.pdf
http://www.erico.com/category.asp?category=R2431
https://www.erico.com/catalog/literature/E828B-NAEN.pdf

When you are adding other wires to the house electrical system ground, it is important not to disconnect the house electrical system from its own ground connection, even for a moment, for safety reasons. You should use a split bolt to add another wire to an existing wire that is grounded. It is also why the IBTB has a "lay in" feature for the house ground wire, so that it isn't necessary to disconnect it from its ground.

The coax shield should be grounded with a grounding block that is connected to the house electrical system ground with 10 gauge copper wire for electrical safety and to reject interference. For further compliance with the electrical code (NEC), the mast should also be grounded in a similar manner to drain any buildup of static charge, but the system will not survive a direct strike.



From my personal experience, using a grounding block to ground the coax shield is the most important thing to do. It will protect you from leakage current shocks from AC operated equipment.

CECB Leakage Current
Getting A/C voltage on converter box's antenna input !
http://www.digitalhome.ca/forum/81-o...ml#post1457594

Equipment Leakage Current
http://www.digitalhome.ca/forum/81-o...ml#post1457668

Do you know that there is a grounding thread on the Canadian forum?

[Darken]

Interesting. Im learning a lot. So in this scenario to avoid having 3 ground wires all under the same screw on the service ground (my electrical panel) could i not simply run my coax and ground wire from the antenna and mount to the grounding block and screw the ground wire from the mount to the same screw as the ground wire leading to the service panel. In this case, on the grounding block there would be the mount ground wire and the ground wire leading to the service ground under one screw and on the actual service ground there would be the the existing Bell Canada ground wire and i would add the grounding block ground wire under that same screw. This way i wouldnt have 3 ground wires on the service panel and i wouldnt need to add an IBTB.

Your post makes reference to not removing the house system from its own ground for even a moment but is loosening the screw that Bell Canada is using on the service ground to add a second ground wire considered removing the house from its ground?

Thanks for your contribution

[rabbit73]

is loosening the screw that Bell Canada is using on the service ground to add a second ground wire considered removing the house from its ground?

I can't see it from here, but if loosening the screw that Bell Canada is using also loosens the ground connection for the house electrical system ground, don't do it. Use a split bolt to connect your new ground wire to the Bell Canada wire or the house electrical system ground wire.

could i not simply run my coax and ground wire from the antenna and mount to the grounding block and screw the ground wire from the mount to the same screw as the ground wire leading to the service panel. In this case, on the grounding block there would be the mount ground wire and the ground wire leading to the service ground under one screw and on the actual service ground there would be the the existing Bell Canada ground wire and i would add the grounding block ground wire under that same screw.

That is called a piggy-back arrangement and is not according to the US code, but it is often done. Our code says to run separate 10 gauge wires from the mast and the grounding block to the house electrical system ground.

http://www.dbsinstall.com/diy/Grounding-2.asp

A common grounding practice is to connect a 17 Gauge copper coated steel ground wire (messenger on your coax) from the dish mast to a coax grounding block. Then ground the ground block with 10 gauge copper to an NEC approved grounding point. By grounding the mast to the ground block and sharing a single 10 gauge ground wire for both mast and coax, the NEC grounding requirement of the mast is not meet. This sharing, or piggy-backing of grounds is a common practice within the satellite dish industry and is fully supported by both Dish Network and DIRECTV.

Grounding thread on Canadian forum:
Grounding Info & Standards For OTA
http://www.digitalhome.ca/forum/81-o...dards-ota.html

[Darken]

Thanks for the answers. So there was a point made referring to the ground connection for the house:

"but if loosening the screw that Bell Canada is using also loosens the ground connection for the house electrical system ground, don't do it"

Ive attached a picture of the bell box, you see where the black ground connects to the electrical box. Would this be an example where it is unsafe to loosen it?

Thanks

[rabbit73]

Thanks for the photo.



It looks like the black wire grounds the Bell box to a bolt on a plate at the top of the meter box. The plate is connected to the conduit and connected to the box with a clamping screw. With all that paint I wonder how good the connections are.



It looks like loosening the nut over the black wire will not disturb the electrical system ground, but it will disconnect the Bell ground. I don't know if that would cause a problem. What does the orange tag on the black wire say?

If you want to stack two wires on the same bolt you might put a washer between the two.

As an alternative, you can leave the Bell wire in place, scrape some black insulation off the Bell wire, and attach your new ground wire to the bare section of Bell wire with a split bolt.



they come in different sizes
http://www.homedepot.ca/product/8str...ge-of-2/910183

I'm not an electrician and don't know your local regulations, so take my advice for what it is worth without a guarantee.

[Darken]

Thanks for the suggestions. The orange tag simply says that if the wire becomes loose or if i need to move the wire to contact them.

So when you say i can scrape some of the black insulation off the wire, do you mean about where the orange tag is?

Or if i wanted to add a washer between the two i could just add the washer on top of the current setup and with the new ground underneath it? Im pretty sure another washer would fit on top of the current bolt

Don't worry, not holding you to any of this. Just looking at my options

Thanks

[rabbit73]

So when you say i can scrape some of the black insulation off the wire, do you mean about where the orange tag is?

Yes, but don't nick the wire by keeping the blade at a low angle.

Or if i wanted to add a washer between the two i could just add the washer on top of the current setup and with the new ground underneath it? Im pretty sure another washer would fit on top of the current bolt

Well, if you did it that way it would at least be another nut. I would remove the nut, make sure the connection area was clean, and stack it this way from bottom up:
Bell wire
washer
your new ground wire from grounding block
replace nut.

[rabbit73]

Keep in mind that an incoming call will send about 100 volts AC for the ringer. The DC voltage to operate the phone is about 50 volts DC on-hook. When you pick up the phone the off-hook voltage is much less because the phone is drawing current. It probably will not appear on the ground wire when you are making the connection, but in case it does, I want you to be aware of that possibility.