Grounding in the City

mpedrummer · Post by **mpedrummer** » Fri Jan 06, 2006 5:14 am

Howdy, all -

I need to clear something up that I've been told, which initially sounded silly or dangerous, and then plausible, and now I'm just not sure so I'm asking you guys.

Out in the burbs/country, you'd have a ground post, a bigass copper bar buried in the ground. How does this work in the city? I was told that city buildings are grounded to copper water pipes. This seems like a good way to electrocute a lot of people, though, right? It also seems like a massive common ground like this would be inherently noisy, with everyone's refrigerator and A/C and so on...

I'm potentially looking at buying a floor of a warehouse to build a studio, and I have been unable to figure out how I'd get an isolated ground for myself. How does this work in large buildings? Is there one grounding post, or several, or something else entirely? Can you share a grounding post and still consider it to be an isolated ground?

Thanks
MPEDrummer

Post by **Aaronw** » Fri Jan 06, 2006 5:48 am

Is this a multi-story building/high rise, or just a large (area) building?

Grounding to water pipes is a common grounding scheme, but yes, sometimes it is not the best, and you can get noise.

The studio I worked at in Seattle several years ago was downtown, but was only 2 stories high, and they had multiple grounding rods out back in the alley. But in order to do this, the concrete had to be drilled first down to the soil, then the rods driven into the ground.

You'll probably want to do the star grounding w/ isolated ground duplex outlets.

mpedrummer · Post by **mpedrummer** » Fri Jan 06, 2006 6:11 am

Just a large area. It's 3 stories tall, with the 2nd and 3rd floors being smaller than the one before. We're thinking of getting about half of the second floor (probably close to 6000 sq ft), in a section with nothing above it.

Not all of the space would be for me...not for the studio, anyway. My wife and I want to build a condo in most of it, and then a studio for her (she's an artist) and a studio for me as well. Probably with some shared storage space, too.

There's a small patch of yard at the end of the building where we want, so maybe getting posts sunk is a possibility? How much are those things, anyway?

MPEDrummer

Post by **Aaronw** » Fri Jan 06, 2006 6:38 am

Ground rods are fairly cheap. $8-12 range, maybe a little more depending on your location, but shouldn't be more than $20. They are usually in 2 different sizes (1/2" and 5/8"). Go w/ the larger one.

What is the current grounding situation for the building? Sometimes, in newer construction, they build the grounding into the concrete slab w/ a copper mesh in the middle.

mpedrummer · Post by **mpedrummer** » Fri Jan 06, 2006 7:04 am

Absolutely no idea. This is a speculation of a speculation The building is fairly old (looking, no idea of actual age yet), so I doubt any of those new fangled ideas would have been implemented.

To be honest, I haven't been inside the building yet, so nothing's set in stone. The last place I looked at, things moved along REAL fast, and I almost didn't have enough time to actually think past the initial visual and so forth. This time, I'm trying to think out as many contingencies as possible BEFORE the pace of majorly important decisions picks up.

MPEDrummer

ridgeback · Post by **ridgeback** » Fri Jan 06, 2006 12:10 pm

Let's remember what grounding is for here. Be real careful creating new ground fault paths off existing electrical services. You could be unpleasantly suprised

. People have been killed due to parallel grounding paths. If you think you're going to have an issue, hire an electrician to check it out and do the work. If the building is as old as it seems, you're going to want to bring in a new electrical service anyway. That Neutral will carry just as much noise if not more.

mpedrummer · Post by **mpedrummer** » Fri Jan 06, 2006 3:47 pm

ridgeback wrote:Let's remember what grounding is for here. Be real careful creating new ground fault paths off existing electrical services. You could be unpleasantly suprised . People have been killed due to parallel grounding paths. If you think you're going to have an issue, hire an electrician to check it out and do the work. If the building is as old as it seems, you're going to want to bring in a new electrical service anyway. That Neutral will carry just as much noise if not more.

I've been doing electrical since I was about 6, rewiring the house with my dad and grandfather...but I'm not planning on doing the electrical myself. I would want to bring in a new service, potentially two, one for the living space and one for the studio.

MPEDrummer