Switched Wiring

[Aaroninnh]

That's a fine choice, but is not required in existing buildings, to my knowledge. So if the telephone and cable are properly grounded now, leaving it alone is a good option. If they aren't properly grounded now, using an intersystem device would be a good way to go.

Thats up to the AHJ, of course. If I was that AHJ, I would require it as fundamental changes to the grounding electrodes/GEC are being made, I would require that entire piece be brought up to code...which requires the ISBT.

Even if not required its just smart to do it now anyways as the hack jobs I have seen done by the cable guys, satellite guys are terrible. Clamps to the side of a painted service panel. Useless.

As to moving the telco's ground? Nope, I agree I wouldn't touch that right now if its fine, however I would want the terminal there and ready for the next install, whatever that is.

Just one guys opinion.



As to the rods, I'll disagree with you there. I work in Telecom and in the areas I work in (mostly Pennsylvania North/East), we have to put in large ground rings. The first rod usually gets us around to between 10-15 ohms, more than adequate for residential use. For the second rod to have much impact, it has to be pretty far from the first. The NEC requirements for the second rod (6 or 8 feet, I cant remember) usually only slices off another 2-3 ohms.

Again, YMMV depending on your soil types.

 

[wwhitney]

Thats up to the AHJ, of course.

I believe that 250.94(A) Exception says otherwise.

As to the rods, I'll disagree with you there. I work in Telecom and in the areas I work in (mostly Pennsylvania North/East), we have to put in large ground rings. The first rod usually gets us around to between 10-15 ohms.

That's with a 5/8" 8' long ground rod? If so, I'm amazed, and if working in your area I would agree it may make sense to document the resistance rather than drive a second rod. I don't have any geographically distributed experience myself, but I understand from casual conversation on other forums that that would very rare.

Cheers, Wayne

 

[Sponsor]

 

[Aaroninnh]

I believe that 250.94(A) Exception says otherwise.

Yes, it basically says that in an existing building a telco doesn't have to bond to the ISBT if one doesnt exist. I am not arguing that point and am agreeing with you 100%.

What I am saying is that if I was the inspector, I would require an ISBT be installed if the electrician is replacing the GEC. That is new work being done, and therefore that portion of the new work should be brought up to modern code.

Just like if I was inspecting a kitchen renovation I would require GFCI's be used for countertop receptacles even if GFCIs were not required when the original kitchen was built. Make sense?

That's with a 5/8" 8' long ground rod? If so, I'm amazed, and if working in your area I would agree it may make sense to document the resistance rather than drive a second rod. I don't have any geographically distributed experience myself, but I understand from casual conversation on other forums that that would very rare.

No, we use 5/8 10' rods, a minimum of 18" under the surface with test wells every few rods. Everything cad welded, all copper tinned. The first 10-15 ohms is easy, but it takes a LOT of rods far apart for us to get down into the 1-3 ohms we shoot for.

I think you'll find in a lot of the country one rod gets you well under the 25 ohms. This second rod provision was really more for some edge cases, with really dry soil and its and in an area where the first rod doesn't get you to 25, then a second one 8 feet apart isn't going to bend the needle much, so its really a waste all around. Like I said, for us the second rod only buys an extra 2-3 ohms.

All electricians I know just drive 2 rods. Time is money and its cheaper to drive 2 than it is to do testing.

 

[Jadnashua]

Grounding can be really problematic depending on where you live and can change considerably season to season. Wet ground tends to conduct better than dry ground.

Long time ago, one of college instructors happened to be in charge of communications at Ft Bliss in El Paso, TX. When he needed to go out on a field exercise, he'd have his cooks order extra salt for a month or so in advance. To get a suitable ground, they'd mix the salt with the water and saturate the ground around where their grounding went and keep it wet during the exercise. That was the only way they found to get a reliable ground to provide decent communications and protect antennae if they happened to get a lightning storm. El Paso gets most of its annual rainfall in July. It can come down hard enough that it literally washes boulders, basketball sized and smaller in general, onto many of the roadways down the mountain that sits near the city. I'm sure if you tried to establish a ground then, you'd not need any extraordinary efforts.

Places where you have ledge just underneath the ground can be very problematic, too. NH is called the granite state for a reason!

 

[Aaroninnh]

Places where you have ledge just underneath the ground can be very problematic, too. NH is called the granite state for a reason!

Absolutely! Sometimes we have to lay them in trenches too!

 

[Thomas K]

Well, electrician came back and installed another ground rod. He said it wasn't really required where I live, and isn't enforced by the city's code. However, I feel better having two ground rods as we get a lot of lightning storms. And I will install a new ISBT on the new ground wire near meter. I will have to disconnect the telephone ground in house, as it's on a copper pipe I am removing. It's only what looks to be a 14 ga wire clamped to pipe. It had a South Central Bell tag on it, and they were dissolved in 1992. I'll make sure it is going to telephone box, reroute it to new ISBT, and hope I don't get in trouble for doing so.

I'm also going to run new 6 ga wire over to remaining copper water piping, no more than 5' away from where it enters house. I wanted to splice a new wire onto the shorter existing original Ground Conductor that was attached to pipe I removed, but I think it has to be unspliced.

Now if I can just educate myself on retrofitting ground wires to all of that NM wiring that doesn't have a ground wire. Retrofitting with green insulated ground wire would be easier, if you ask me, because a lot of the wiring in attic is covered with blown-in insulation and I could just run new ground to boxes. Seems like if fishing to switchbox through wall, though, it would be better to just run new 14-2 w/ground NM.

I'm not sure how retrofit works. I've heard that the main retrofit ground wire has to be a larger gauge than ground wires going to outlets and light fixtures, but I could be wrong about that.

 

[wwhitney]

I'm also going to run new 6 ga wire over to remaining copper water piping, no more than 5' away from where it enters house. I wanted to splice a new wire onto the shorter existing original Ground Conductor that was attached to pipe I removed, but I think it has to be unspliced.

You need to have one unspliced conductor from the service neutral bar to one grounding electrode. That's your official "Grounding Electrode Conductor". All the other grounding electrodes can be connected with jumpers, which may be spliced.

Now if I can just educate myself on retrofitting ground wires to all of that NM wiring that doesn't have a ground wire. Retrofitting with green insulated ground wire would be easier, if you ask me, because a lot of the wiring in attic is covered with blown-in insulation and I could just run new ground to boxes.

Generally if you can run an individual green conductor to the box, you could run a new 12/2 or 14/2 NM cable. That would be preferrable.

I've heard that the main retrofit ground wire has to be a larger gauge than ground wires going to outlets and light fixtures, but I could be wrong about that.

No, that's not required. If your panel were full of 15A and 20A circuits without EGC, then you could run a separate #12 EGC to everything for grounding. But again, new NM cable is a better choice.

Cheers, Wayne

 

[Jadnashua]

Running new wire with ground is better. FOr any that are really difficult to access, you can put in either a GFCI breaker for that branch, or a GFCI receptacle. It needs a label (normally they come in the box with the GFCI) that says essentially, GFCI protected, no equipment ground. Any receptacles downstream from the GFCI one can now become 'grounded' ones as long as you put the labels on the cover. Safer than no ground.

 

[Thomas K]

That answered my questions.

 

[Aaroninnh]

Code allows you to run a new ground from the panel where the ungrounded circuit originates. Green THHN is fine if thats what you want to do. You can also steal a ground from another circuit that is close by to the receptacles you want to add a ground to. They left it somewhat vague intentionally as they want to make it as easy as possible to convert ungrounded to grounded, as any ground is better than no ground!

I agree with wwhitney though, if you can pull a green THHN why not just run a new 14/2 or 12/2 and make it nice and clean.