Sheet E-307: Listed Clamps and Lugs for the Rod, Rebar, Tank Pad and Copper Bar

What this sheet shows

E-307 is the bolted and compression grounding connections sheet under the transformer-installation heading. It draws four details. G1 is the rod-to-continuous-copper clamp. G2 is the rebar-to-copper takeoff, and its title includes no field weld. G4 is the OEM tank ground pad. G5 is the accessible copper bar. Two further rules are printed as note lines, not as their own titled figures: G3, pile bonding, sits under the G4 notes, and G6, the wire-type GEC splice, sits under the G5 notes. The reference line cites NEC 2017 Article 250, OEM GA 08 Sep 2026, and the transformer installation specification. Design coordination is 26 SEP 2026. The line under the details marks detail geometry NTS. On G4 the illustration is enlarged 20x and the physical hole pitch is 44.5 mm. On G5 the bar is marked shown diagrammatically.

Rod clamp and rebar takeoff

G1 is a listed bronze / compatible-alloy bolted clamp. The callout says manufacturer torque and one permitted conductor. The 2/0 Cu passes through without cutting. The rod on the same detail is a 3/4 in copper-bonded rod, and the length printed with it is a 10 ft candidate. The notes require a direct-soil-burial listing, with the exact conductor and rod sizes matched. They say not to substitute plumbing clamps, and not to use two wires in a one-wire clamp. A buried connection is permitted when the fitting is listed for that environment: the sentence is a permission tied to the listing, and the sheet does not name a selected clamp. G2 is the other joint. It draws a listed concrete-encasement rebar clamp, a continuous copper lead, and an accessible transition terminal at the end of that lead. Cover, structural bar continuity and corrosion protection are to be maintained. The clamp is to be sized for the actual rebar and the actual copper conductor, and those sizes are not printed here. No exposed unprotected rebar tail in soil, and no earth-return credit is assumed. The count the sheet does give is one identifiable takeoff per pier, plus four pile-head interfaces. A careful reader keeps the two joints apart: at G1 the 2/0 passes through without cutting, and at G2 the lead ends at an accessible transition terminal, with no field weld and with no earth-return credit assumed.

Tank pad, pile bond, and the copper bar

G4 draws the OEM tank ground pad. The illustration is enlarged 20x, and the physical hole pitch is 44.5 mm, dimensioned across the two holes in that view. The threads are 1/2-13 UNC, and the same line says to verify engagement and bolt length, so that check remains an instruction on the sheet. Use a listed copper-conductor lug compatible with the OEM pad. No field drilling of the tank or unapproved pad modification. Terminal bolting and pile-head structural bolting are separate details. G3 is the next line in that block: use a maker-approved attachment for pile bonding, with no shaft drilling. That attachment is stated in the note and is not given its own figure. G5 is the accessible copper bar. Left to right, the positions are Ring A, Ring B, GEC, Site, Pier1, Pier2, Tank and Other. The bar is at least 1/4 x 2 in, the length is a proposed 24 in, and the view is shown diagrammatically. Use listed lugs. The hole pattern follows the terminal and the tool clearances. No routine energized disconnection of the GEC / bonding leads. G6 is conditional: if a wire-type GEC must be spliced, use listed irreversible compression with matching tools. A removable bolt splice is not used. The closing line keeps the jobs apart, and it is worth reading exactly: electrode clamps and wire-to-wire GEC splices are different functions.

Status

Published at Design Development — Public Edition P1 (title block: 2026-09; design coordination: 26 SEP 2026). This is a reference design for study and evaluation. The open items are written on the details themselves. The rod length is a 10 ft candidate. G1 says manufacturer torque and does not print a torque value. G2 says to size the clamp for the actual rebar and copper conductor, does not print those sizes, and assumes no earth-return credit. G4 says to verify engagement and bolt length. The copper-bar length is a proposed 24 in, the bar is shown diagrammatically, and detail geometry is NTS. The 44.5 mm figure is the physical hole pitch on the view enlarged 20x. G3 says to use a maker-approved attachment for pile bonding and does not draw that attachment. Beside the details, the sheet cites NEC 2017 250.64(C), 250.64(F)(3), 250.68 and 250.70.

Sheet guide — the devices on this drawing

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