There is a note on the drawings that says: “exterior metal water pipe per NEC 250-104” with a “full size grounding conductor per NEC 250-66” going from the pipe to the equipment ground bar in the CT can, or maybe its the main breaker panel.
What does NEC say in 250-104 about grounding to a water pipe?
There is also a note about bonding to the rebar in the slab and the structural steel. Is a copper ground rod also required?
“Put your creed in your deed.” Emerson
“When asked if you can do something, tell’em “Why certainly I can”, then get busy and find a way to do it.” T. Roosevelt
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What they are saying is that you need to have a 'ufer' (20 ft. of #4 copper wire) in the slab, as well as running a bond wire (#6 or larger) to the water pipe where it enters the building, if that pipe is metal.
No, you do not need a ground rod.
I thought ufer was an alternate ground method for rocky ground. And the incoming water line is pvc."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
The Ufer is one of several accepted grounding methods; the ground rod is another. The Ufer has proven itself to be vastly superior to every other method.
If you have a plastic main, then you need not bond the incoming water line.
But if the internal piping is metallic then it still needs to be bonded..
William the Geezer, the sequel to Billy the Kid - Shoe
No, it does not - at least, not the same sort of grounding.
Internal piping is more than adequately grounded, against faults, at the appliance that might energize it.
This is not to be confused with the use of the incoming water line as a 'grounding electrode,' which is what we are discussing here.
No! Unless the section numbers have change 250-104 is specifically about BONDING of the internal water piping.The confusion is that the arch mixed them up. From the orginal message "There is a note on the drawings that says: "exterior metal water pipe per NEC 250-104" "From the 2005 NEC"250.104 Bonding of Piping Systems and Exposed Structural Steel
(A) Metal Water Piping The metal water piping system shall be bonded as required in (A)(1), (A)(2), or (A)(3) of this section. The bonding jumper(s) shall be installed in accordance with 250.64(A), (B), and (E). The points of attachment of the bonding jumper(s) shall be accessible. ""(1) General Metal water piping system(s) INSTALLED IN or attached to a building or structure shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or to the one or more grounding electrodes used. The bonding jumper(s) shall be sized in accordance with Table 250.66 except as permitted in 250.104(A)(2) and (A)(3). "While not code the Handbook has this addition comment."Bonding the metal water piping system of a building or structure is not the same as
using the metal water piping system as a grounding electrode. Bonding to the
grounding electrode system places the bonded components at the same voltage level.
...
In those cases where it cannot be reasonably concluded that the hot and cold water
pipes are reliably bonded through mechanical connections, an electrical bonding
jumper is required to ensure that this connection is made. Some judgment must be
exercised for each installation. The special installation requirements provided in
250.64(A), 250.64(B), and 250.64(E) also apply to the water piping bonding jumper. "250.52 covers using the external water pipe as a ground electrode."250.52 Grounding Electrodes
(A) Electrodes Permitted for Grounding
(1) Metal Underground Water Pipe A ...".
William the Geezer, the sequel to Billy the Kid - Shoe
Here is the actual detail off the drawings.
"Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Yes, the arch confused things.He shows exterior pipe, which when metallic and underground, must be used as one of the ground electrodes under 250.52 (IIRC the number correctly).250-104 has to do with bonding interior metal water piping. Now if the exterior underground piping is used as a ground electrode, per 250.52, then the interior portion is covered. But if you don't have underground metallic piping, but do have internal metallic piping then 250.104 covers it.BTW, 250.66 covers the size of the wire.I see that he also calls out a triple ground rods AND TESTED TO 5 OHMS. This is much more than what the NEC requires. The NEC does not require a ground rod(s). It is only one type of ground electrode and if you have the ufer, that alone is enough. And you only need one ground rod if it test below (20 or 25 ohms, can't remember) or else need two and no testing.Now I see that he also calls out connecting to the concrete encased electrode (ufer). That is a required ground electrode under 250.52, if it is available.Here is the wording on that."(3) Concrete-Encased Electrode An electrode encased by at least 50 mm (2 in.) of
concrete, located within and near the bottom of a concrete foundation or footing that is in
direct contact with the earth, consisting of at least 6.0 m (20 ft) of one or more bare or
zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of
not less than 13 mm ( 1/ 2 in.) in diameter, or consisting of at least 6.0 m (20 ft) of bare
copper conductor not smaller than 4 AWG. Reinforcing bars shall be permitted to be
bonded together by the usual steel tie wires or other effective means. "Note - you can either make the connection with the conductor withing the concrete using an approved connector or someplaces bend an end of the rebar and leave it poking up above the finished concrete.He also calls out connecting to structural steel. That is called out under both 250.52 as a ground electrode and under 250.104 being bonded. Similar to the dual way that the water pipe is treated.I have not studied those sections to figure the differences between the 2. But since you already have the required ground electrodes it does not matter. .
William the Geezer, the sequel to Billy the Kid - Shoe
The short answer is if you are are using building steel as an electrode it is tied to the foundation and the conductor is sized by 250.66. (at least a #8) If the steel framing is not tied to the foundation, electrically it gets bonded per 250.104 with a conductor sized to the largest circuit likely to energize it with 250.122. (could be as small as #14)
Bill, I've never seen galvanized rebar, or other electrically conductive coated steel reinforcing bars. Definitely never saw it in Utah.
Where do you get it and what kind of coating is it? Ask at supply house I guess so they can wonder what I'm talking about.
I thought from other reading that just plain rebar was accepted, and tie wired together sure isn't much of a connection but that's all they are asking for. Seems like a difficult trick to have 20' encased and still have enough to bend it up for a connection, particularly since the bar is supposed to be within 2" of the bottom of the concrete.
And in the plan 3 5/8" by 20' ground rods 30' apart + the Ufer? Seems kinda much.
Joe H
Don't ask me I did not write that.But it does say that bare is acceptable. As is any other rebar that has a conductive coating.What is not acceptable is something like epoxy coated rebar.Not sure, but I think that both are used where the water is corrosive and/or exposed to salt.http://www.galvanizedrebar.com/faqs.htmhttp://www.zbarusa.com/"Seems like a difficult trick to have 20' encased and still have enough to bend it up for a connection,"You have all of the interconnected rebar."tie wired together sure isn't much of a connection "Isn't there a "large" overlap of the rebar sections required by the building code?And don't forget, that the rebar is surrounded by a large area of "moist" conductive concrete. The resistance per sq inch might be high, but you have a large surface area.
.
William the Geezer, the sequel to Billy the Kid - Shoe
Don't ask me I did not write that.
Didn't figure you did, mostly I can figure out what you're talking about, NEC not so much.
Guess living in the boonies I'm not going to run into any galvy rebar, bet it's pricy too.
And the conductive coating, only thing I can think of would be like the coating on ground rod.
Think I'll put some weld on the bar on my next one, make the whole thing a one piece loop.
And yes, 40 diameters overlap is required.
Joe H
Edited 11/13/2009 9:45 pm by JoeH
The ufer is better than copper ground rods?"Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Absolutely. Test data has shown the Ufer to be an entire order of magnitude better ... even in conditions that make grounding difficult.
Ufer is now required to be used "if available" so, if you have rebar in your footer, you must use it.
When we do ATm buildings I always do a Ufer. I think code requires 9 linear feet of half inch ground rod. Galvanized ground rod clamp and #4 wire to it. I turn the end of the rebar up so it comes up under the panel then clamp a galvanized ground clamp to it.
Ya know, now I see the need to go back and find the ground wire that goes to the rebar. Not sure I saw it last time ..."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Hum, have to admit I had never heard cege referred to as Ufer before, had to google Ufer to see where it came from.
In own house, even welded all the rebar together for a good ground, about 500 ft of cege and acheived a 0.52 ohm ground. Can run a light bulb without a return wire, (not that I've ever wired a shed with just one feed wire or anything like that or anything <G>)
You used the word "cege" twice so I have to think it was intentional, rather than a typo for "cage". I don't recognize that word."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
cege = Concrete Encased Grounding Electrode
>cege = Concrete Encased Grounding Electrode <
that makes a lot more sense than Ufer
I will agree ... after all, I don't think Ufer is in the dictionary. That said:
I once met Ufer; he visited my house as I was growing up.
That's right, it's a man's last name. The methof is named after the man wih invented it.
Herb Ufer was an engineer at UL, leaned to the Army during WW2. Needing a way to ground 'temporary' ammunition depots in desert or rocky areas, he came up with the idea.
It worked far beyond expectations.
Yet, the NEC panel was not willing to accept it until the 60's. That's when a Reno electrician. Max McComb, documented the Ufer's performance in Sierra Nevada ski resorts, where the lift towers were frequent lightning targets. With is documentation, the method was accepted.
Follow-up studies were made in the 90's, looking back at the original systems installed back in WW2. Amazing everyone - again - these grounds were as good as the day they were made. That's when the Ufer became the preferred method.
Calling this method a "Ufer" makes as much sense as calling a screwdriver a 'Phillips," a wrench an "Allen,' or a grease fitting a "Zerk."
And, personally, I have no problem calling a submarine esvape/rescue device a "Steinke Hood."
Edited 11/14/2009 8:35 am ET by renosteinke
Edited 11/14/2009 8:35 am ET by renosteinke
Hijack!
Back to the original question ... If the water line is pvc, and the concrete slab sits on 2" foam thermal insualtion and a 6 mil visqueen vapor barrier, where is the grounding path?"Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
The footing part of the monoslab is supposed to be sitting in the dirt.