I am in the process of constructing a shop building and have to install a Ufer ground in the footing as the primary ground. I am not very familliar with this application and am wondering if it would beneficial to also install a conventional ground rod outside of the building? Thanks in advance for any advice you might have!
Karl
Replies
Dawg,
Eleven_Practical_Grounding Tips
The Ufer Ground
When tieing the rebar in an Ufer ground system, every 4th vertical rebar of the outside mat should be saddle tied with a doubled wire to every horizontal bar and the Ells that run to the outside longitudinal footing bar. Each corner Ell should be double tied.
The connecting rod, which may be a piece of rebar for a saddle clamp connection to the grounding wire from the panel or a piece of all thread for a double nut and eye connection, should also be double wire tied to each horizontal bar. It can skip the top bar in the stem wall to give room to "S" bend it so as to exit the top of the stem wall where desired.
Only the outside mat of a double vertical reinforcing system is used. Likewise only the outside longitudinal bar of the footing is used. Other than these considerations the rebar system is placed and tied as usual.
In some jurisdictions, an insulated grounding conductor may be run thru the concrete and saddle clamped to the bottom outside logitudinal footing rebar. If doing it this way, I like to Copper Coat the connection, then tape it in a manner so as to waterproof the copper.
Some juridictions require an additional exterior ground rod, some don't. A good Ufer system will outperform and outlast a good conventional ground rod.
SamT
Sam,
As I read the thread I was thinking, 'what the heck are these guys talking about?'
I read the Ufer link, very interesting........I've been around a few water storage tanks and transmission towers and now those foggy questions are crystal clear.
Thanks for some good info!
Eric
I lined the trench and forms for my footing with 6 mil black poly. Any idea how bad that would eff up Ufer grounding? My guess is that I created a giant capacitor, and that Ufer grounding would be effective for radio frequency, but probably not for power.
Years ago a friend of mine used to do ground rods for TV transmitters and recording studios. His method was to put together 3/4" type K water pipe, some up to 60 ft. long, with a 3/4 female fitting on the top, and the bottom crimped and perforated. Stand the thing up, and run water thru it from a hose. It just washes its way down into the ground. He got prehistoric seashell fossils washing up out of some holes on Mt. Wilson.
-- J.S.
I lined the trench and forms for my footing with 6 mil black poly. Any idea how bad that would eff up Ufer grounding? My guess is that I created a giant capacitor, and that Ufer grounding would be effective for radio frequency, but probably not for power.
ROTFLMFAO
Yep, Giant Capacitor.
LOL
SamT
Hi Guys,I have not been on the forum for a long long time.
Some of you may remember me as "Bee".I am going to build a home in another county and the use of a Ufer ground is required. And now I know a lil about it, thanks a lot.Best regards,
Brian aka beeLOL I see my old sig pic is still listed, I had forgotten about itView Image
we were wondering what the hell happened to you...
I am a DIYr and put in a new 200 AMP subpanel from my 200 AMP main panel (at the garage in the back alley) to the house. At the garage (new) I put in a Ufer and a clamp to the copper water line. Then I ran a ground to the subpanel and also connected the panel to the existing ground rod and the copper water line. The building inspector (who happened to be trained as an electrician) said I had to disconnect the grounding rod or the equipment ground from the main panel. Any idea why? Can one have too much grounding?
Brian
"I am a DIYr and put in a new 200 AMP subpanel from my 200 AMP main panel (at the garage in the back alley) to the house."I just want to verify that the house and garage are SEPARATE STRUCTURES.Also I am not clear if the you have service and the main panel in the garage with the sub-panel in the house or vs versa. But that doesn't really make any difference in what I am going to say.EACH STRUCTURE requires a ground electrode system. That is ufer ground, underground metallic water pipe connections, ground rod or other approved electrodes and the ground electrode conductor to the panel.If there are no metallic paths between two structures then you can run 3 wires (2 hots and neutral) from the main to the sub-panel. In that case you treat the sub-panel as a main and bond the neutral to the ground. Note- some areas don't allow this method.With a metallic path between them (and you apparently have one with the water line) then you need to run 4 wires (2 hots, neutral, and EGC). In that case the neutral is not bonded and on some panels you need to get a ground bus bar kit. BUT THE EGC AND GROUND ELECTRODE SYSTEM IS CONNECTED TOGETHR AT THE GROUND BUS.He may be talking about unbonding the neutral and either did not explain it correctly or he doesn't know what he is tlaking about.
Great thanks for the info. I appreciate it. That's what I thought too. The power comes into a main panel at the garage and the house and garage are separate structures. And I ran two hots and a neutral (2/0) and a #4 ground between the two buildings. And as you said I bought a separate bus for the the ground and connected all of the grounding systems together and did not bond the neutral. So I guess maybe he doesn't know what he is talking about. The water system between the house and the garage is copper and is connected. So the grounding system at the house consists of the water system and the grounding wire that goes to the main panel (since the original grounding rod that was connected to the old main panel that was originally on the house is not connected as requested by the inspector). Does that sound correct? Should I reconnect the ground rod or does it not matter?
Thanks, Brian
Water pipes are very good electrods. However, they are not allowed to be used alone. Mainly becuase they might be replaced at some point in the future with plastic.Thus a 2nd electrode is needed. Typically that is a ground rod (or for newer construction the ufer).I don't think that technically the EGC from the main panel can be treated as a ground electrode, but it might.So put it this way. Connecting the ground rod also is the most correctedness, but I am not sure that it really matters in a case like this.But since it is there, I would.
Great thanks for the advice!