A jumper is a conductor, two terminations, a length and a tolerance, and the spec sheet should say all four so the shop and the inspector agree. Here is the order to write it in.

1. Conductor. DLO, 2 kV, Class I tinned copper, UL 44 RHH/RHW-2 90 °C, size from 310.16 at 1.25 × continuous current and checked against voltage drop (a 48 V bus tolerates about 0.5 V across a jumper pair). DLO sizes are odd (262.2, 313.3, 444.4, 535.3 kcmil); if the equipment lug is rated for standard kcmil, use the next standard size for the lug and confirm the DLO fits its range.
2. Lugs. Flex-rated, tinned copper, long barrel, two crimps. Tongue pattern from the equipment drawing: one-hole by stud, NEMA two-hole (1/2 in on 1-3/4 in for 250 kcmil and up; 3/8 in on 1 in below), telecom two-hole (1/4 in on 5/8 in). Angle 0°, 45° or 90° if the cable has to turn inside the compartment.
3. Length and tolerance. Measure bolt-hole center to bolt-hole center (for two-hole lugs, the hole nearest the barrel). State the tolerance: ±1/4 in to 36 in, ±1 percent above. Loose tolerances on paralleled strings cause unequal current sharing.
4. Identification. Heat-shrink color for polarity (red positive, black negative, green ground), printed heat-shrink markers or wrap labels with the cable number from the one-line, sequential numbering on multi-string sets.
5. Packing and paperwork. Poly-bagged with part number and lot label, kitted per string or per rack, certificate of conformance and lot test report when the job's QA plan asks for them. An engineering drawing with every assembly for the submittal.

Write the part number so it describes the cable (the Conversions Tech builder generates one: size, length, end A, end B, color, label and packing suffixes) and keep the drawing with the PO. Reorders then take a part number, not a conversation.

A written crimp standard turns a craft into a repeatable process. This is the standard a shop or a crew should be able to sign.

1. Match the system

Lug listed for the conductor metal, size and stranding class (UL 486A/B). Die from the lug manufacturer's chart or the industry color code; tool in calibration (12-ton hydraulic, verify ram pressure annually). Never mix a dieless indent tool with a lug that calls for a hex or U-die unless the tool is listed for that lug.

2. Prepare the conductor

Cut square with a cable cutter (no hacksaw: strand deformation). Strip length = barrel depth + 1/16 in; use the lug's strip gauge or measure. Do not nick strands; do not twist fine-strand conductor. Wire-brush aluminum and apply oxide inhibitor immediately; keep copper clean.

3. Insert and crimp

Seat the conductor to the bottom of the barrel (inspection hole shows copper). First crimp nearest the tongue, second crimp toward the barrel mouth, dies fully bottomed (the tool's bypass clicks or the die faces touch) and rotated 90° between crimps where the chart calls for it. One crimp on standard barrel 8 to 2 AWG; two on 1 AWG and up and on all long-barrel lugs.

4. Inspect

• Die index embossed and matching the lug color code.
• No cracks or flash at the die parting line; barrel flat and uniform.
• Strands visible at the inspection hole; none protruding past the barrel more than one strand diameter.
• No insulation inside the barrel; gap between insulation and barrel under 1/8 in.
• Pull test to the UL 486A table on a sample from each lot (for example 150 lb at 8 AWG, 550 lb at 2 AWG, 1000 lb at 2/0).

5. Finish and record

Heat shrink (adhesive-lined where wet) overlapping insulation and barrel; or tape to the insulation rating. Torque the stud per the equipment or 110.14(D). Tag the assembly with the lot and record date, tool serial, die, operator and pull-test result.

Power reaches a rack through a chain the integrator has to size at every step: UPS output, distribution switchgear, PDU (floor or remote power panel), busway or whip to the rack, rack PDU, and the cord to the server. Two things decide the hardware: the voltage topology and the redundancy model.

Voltage. North American data centers run 208Y/120 V for legacy and 415Y/240 V (or 480 V with transformers at the row) for density; 240 V single-phase to the server cuts current and cord size by 15 percent versus 208 V. Three-phase to the rack PDU (L21-30 or IEC 60309 inlets, 30 to 60 A) balances phases across outlets. DC (380 V) and 48 V distribution exist in hyperscale and telecom.

Redundancy. A/B feeds from separate UPS and PDUs to two rack PDUs; dual-corded servers, one cord per PDU; single-corded loads on a rack ATS. Never cross-connect A and B.

The cords. IEC 60320 defines the server side: C13/C14 (10 A, 250 V, most 1U and 2U servers), C19/C20 (16 A, blade chassis, high-density PSUs and storage), C15 (120 °C, some switches). Locking C13 and C19 cords (sleeves or latch) prevent accidental unplugging. Cord gauge: 18 AWG SJT for C13 to 10 A, 16 AWG for 13 A, 14 AWG SJT for C19 at 15 to 16 A; keep cords short (2 to 6 ft) and color-coded by feed (A red, B blue is common). Use the same brand of locking cord across a row so the latches work with the PDU.

Grounding. Each cabinet bonds to the rack grounding busbar or mesh with a 6 AWG jumper and two-hole lug (TIA-607); PDU chassis bond through the cord's EGC and the frame.

Feeder cables to the PDU and battery strings in the UPS room are DLO or THHN jumpers with NEMA two-hole long-barrel lugs; sized per the electrical course and specified per module 1.

Purchasing lives in other manufacturers' part numbers. The fastest way to source correctly is to decode them.

Burndy size codes: 8 AWG = 8, 6 = 6, 4 = 4, 2 = 2, 1 = 1, 1/0 = 25, 2/0 = 26, 3/0 = 27, 4/0 = 28, 250 = 29, 300 = 30, 350 = 31, 400 = 32, 500 = 34, 600 = 36, 750 = 39. Stud codes: 5/16 = none or 2, 3/8 = 4, 1/2 = 6, 5/8 = 7, 7/8 = 36 on flag lugs.

A cross is only right when four things match: conductor range (size and stranding class), stud or hole pattern, barrel length (standard vs long) and material and listing (CU vs AL9CU, UL 486A/B, direct burial for grounding). Dimensions should be verified on the manufacturer's data sheet when the lug has to fit a compartment. Conversions Tech publishes verified crosses in each product's cross-reference table and in the brand hubs; pattern-derived crosses are marked with an asterisk and should be confirmed for fit.

Designing a run is four calculations and a drawing.

1. Fill. Sum the conductor areas (Chapter 9 Table 5) including the EGC, divide by the allowable fill fraction (40 percent for three or more), and pick the trade size from Table 4. Example: three 500 kcmil THHN (0.7073 sq in each) plus a 1/0 EGC (0.1855) = 2.307 sq in. Table 4 gives the 40 percent column directly: 2-1/2 in EMT allows 2.343 sq in, so it fits with almost no margin; 3 in EMT (3.538 sq in) is the practical choice for the pull.

2. Pull tension and bends. Keep each pull under 360° of bends and plan pull points (conduit bodies, pull boxes sized by 314.28: 8 × trade size for straight pulls, 6 × plus other entries for angle pulls). Tension estimates follow the cable manufacturer's maximum (typically 0.008 lb per circular mil for copper with a pulling eye); long runs with many bends need a lubricant and a calculation, not a bigger truck.

3. Supports. EMT every 10 ft and within 3 ft of terminations (358.30); RMC within 3 ft and then 10 ft at 1/2 to 3/4 in, 14 ft at 1 in, 16 ft at 1-1/4 to 1-1/2 in, 20 ft at 2-1/2 in and larger (Table 344.30(B)(2)). One-hole straps, two-hole straps, conduit hangers with rod, strut clamps for racks.

4. Expansion. Steel expands about 0.00065 in per foot per 10 °F; PVC about four times that. A 200 ft outdoor steel run over a 100 °F swing moves about 1.3 in and needs an expansion fitting; PVC needs one on almost every long outdoor run (352.44).

Then the fittings list: connectors at every box, couplings every 10 ft (EMT) plus one per cut, conduit bodies at each corner that needs access, locknuts and bushings (grounding bushings at services and over 250 V), straps per the spacing, and a 10 percent overage on couplings and straps.

A bill of materials that comes back as a clean quote has five columns: line, quantity, unit, description with the governing spec, and the manufacturer part number or an approved equal. The description carries what the part number does not: conductor size and class, stud and hole pattern, voltage class, listing, environment.

Group by zone (array, combiner, inverter, storage; or rack, row, room) so the distributor can stage and kit. State pack quantities in the unit column (each, box of 25, case of 100) and let the supplier price at the pack. Flag long-lead items (large DLO, specialty lugs, branded MC4) and the required date. Put the drawing numbers for custom assemblies on the line and attach the drawings.

For trade accounts: net terms and PO acceptance, a single contact for substitutions, and a request for certificates of conformance where the QA plan requires them. A BOM with part numbers from the cross-reference hub and a builder drawing for each assembly is quotable the same day.