|
0 members (),
516
guests, and
17
robots. |
|
Key:
Admin,
Global Mod,
Mod
|
|
|
|
Joined: Apr 2002
Posts: 2,527
Moderator
|
Hello E-C.Net Webmaster— Thanks indeed for the pics.
In the photo of an opened-up drytype, is the upper horizontal bar on glastic knobs {a/k/a johnny balls} the neutral bus? It’s not unheard of busbars are specifies to be of silver-plated copper stock. It looks like the bottom six bus stubs on the fiberglass rail may be the lowside six phase leads. Is that correct?
No reflection on you personally, but in that drytype image, the white-textured jumpers remind me of old ones that were commonly asbestos covered.
Looks like a very interesting jobsite, but I imagine the Divison-16 paper on this project must be at least a foot thick...
[This message has been edited by Bjarney (edited 06-19-2002).]
|
|
|
|
|
Joined: Oct 2000
Posts: 3,682 Likes: 3
OP
Administrator Member
|
We augured the holes and set the XIT ground rods today. In the pictures you will see the the 12" strap attached to the ground rod (bolted with stainless steel hardware and silver soldered of course). We made this connection before dropping them in the hole. The 4/0 copper that comes standard on these rods will not be used except for on the one by the electric room. It will be used to bond the system to the building ground system. The next step is to bolt and silver solder the tails you see coming off the rods to the buried strap in the previous pictures.
Bjarney,
Yes the bussbar in which you are referring is the neutral buss. The three behined it are the primary termination pads. The six on the bottom are the duel outputs I referred to. X1,X2,X3 and Y1,Y2,Y3. The white over the jumpers is a vinyl covering installed at the factory.
Actually this is a design build job. We (I) are engineering the job. The specs come from the client whom we did a job like this for before. Despite the last part of our name, "Electrical Contractors and Engineers" we do not have a PE on staff at this time. We hired an engineering firm to help out and provide stamped drawings for the AHJ and as a CYA.
- Nick ![[Linked Image]](https://www.electrical-contractor.net/Forum/Images/GrStrap5.jpg) ![[Linked Image]](https://www.electrical-contractor.net/Forum/Images/GrStrap6.jpg)
|
|
|
|
|
Joined: Apr 2002
Posts: 2,527
Moderator
|
Nick— Sounds like the work could make for some interesting and profitable repeat business. A minor aside—on ANSI terminal markings for three-winding transformers… H1-H2-H3 primary; X1-X2-X3(-X0) secondary; Y1-Y2-Y3(-Y0) tertiary. Anther oddity for this type of transformer is that on the secondary and tertiary terminals, there will be typically six 120-volt ø-n measurements, but also you’ll be able to sort out six 120-volt ø-ø readings. The two 208Y/120V “groups” are interleaved, for lack of a better term.
|
|
|
|
|
Joined: Oct 2000
Posts: 3,682 Likes: 3
OP
Administrator Member
|
For anyone interested here is a couple of pictures of the completed ground
straps. ![[Linked Image]](https://www.electrical-contractor.net/Forum/Images/GrStrap7.jpg) XIT ground rod connection to the 12" strap ![[Linked Image]](https://www.electrical-contractor.net/Forum/Images/GrStrap8.jpg) 2" strap connection from the rack buss to the 12" strap.
- Nick
|
|
|
|
|
Joined: Aug 2002
Posts: 1,691
Member
|
Isn't silver solder prone to chemical attack? I read in a radio engineering magazine where a process called "cadwelding" is used for joining grounds.
Has anyone heard of that process? Apparently you join the two ends inside a crucible filled with some high-temp burning powder that melts the two metal ends together permanently.
|
|
|
|
|
Joined: Sep 2001
Posts: 806
Member
|
AKA Thermite welding. Uses a graphite form which is placed around the conductors, and filled with a mixture of powdered filler metal (copper for electrical work), an oxidizer, and a top layer of some kind of ignitor powder (magnesium powder?). Used for creating "radial" ground systems at AM broadcast tower bases, and other places where the highest connection reliability is desired. Also used for welding rebar, railroad tracks, etc. http://www.cadweld.com/erico_public/product/Cadweld.asp
|
|
|
|
|
Joined: Aug 2002
Posts: 1,081
Member
|
Nick, thanks for the great pics!
How far down do those XIT rods go? Do the straps simply get covered over in concrete?
|
|
|
|
|
Joined: Apr 2002
Posts: 2,527
Moderator
|
SvenNYC—as far as I can tell, the usual “45%” silver-brazing materials are not at all corrosive after installation. [Athough the flux paste can sting a little if wet and gets in cuts on the hand.] A fluoride-based flux is used for installation, but the residue seems to be quite inert.
An alternative is “15%” sil/phos brazing rod—needing no additional flux for copper-to-copper joints, but requires somewhat more heat in joint makeup. It has a higher melting point compared to the 45% material, but a very wide glass temperature for void filling. The after-sweat flux remains are very small, and although I have not used it to salt my fries, I’ve never found it to be the least concern, much less significantly visible after joint sweating.
[This message has been edited by Bjarney (edited 08-22-2002).]
|
|
|
|
|
Joined: Apr 2002
Posts: 2,527
Moderator
|
ThinkGood—as far as I can tell, chemical rods are not intended to be concrete encased, but backfilled with a diatomaceous-earth slurry to a few inches below the top, with the accessible but subsurface upper end is placed in a valve box for venting and testing/inspection.
Sandwiched between the copper tube and “the earth,” conductive, chemically charged “veins” form in the hardened slurry and adjacent soil through the several inches of intermediate conductive slurry, and is a key part of a desirably low-resistance system.
|
|
|
|
Posts: 75
Joined: June 2012
|
|
|
|
