Cable Schedule.
A cable schedule is the master register of every electrical and instrumentation cable installed at a facility. It records cable number, type, size and core count, from-end device, to-end device, route, length, and termination details. The cable schedule is the document the cable-pulling crew works against, and the document the panel-builder references when wiring marshalling cabinets.
Three drawings included on a new account.
What Cable Schedule means.
A cable schedule is the master register of every electrical and instrumentation cable at a facility, and it is the document the cable-pulling crew and the panel builder actually work from. Each record carries the cable number, the type and construction, core or pair count, conductor size, screening, armour, the voltage and insulation class, the from-end device and its termination, the to-end panel and terminal numbers, the route, the length, and the as-installed and test data filled in during construction. It is built by combining several sources. The I/O list and equipment list say what has to be connected, and the layout and routing drawings say how far and along which tray or duct each cable runs. That second input is the important caveat for anyone expecting it to come off a P&ID, because the data that makes a cable schedule a cable schedule, route, length, tray reference, termination point is physical-layout information the P&ID does not carry. A reading of the drawing set produces the upstream half, the structured tag and signal inventory that says which connections exist, and that inventory is the precondition for the schedule. The routing and length come from the layout drawings. The honest way to turn an existing cable schedule into structured data is to digitize the cable-schedule document you already have, not to imply the P&ID yields it.
What columns belong on a cable schedule
Cable number, per the project numbering convention. Cable type and size, e.g. 2C 1.5 mm2 IS Pr or 3C 4 mm2 SWA plus 1C earth. Cores or pairs. Insulation rating. Voltage class. From-end. Device tag, terminal box, gland plate position. To-end. Panel, terminal block, terminal numbers. Route reference, cable tray, conduit, direct buried. Length, allowing for routing margin. Termination kit details. Test certificate reference. Pulled-and-terminated date for as-built tracking.
How the schedule gets built
The I/O list, the equipment list, and the layout drawings combine to size and number the cables. Each tag in the I/O list maps to one or more cores in a multicore signal cable. Instrument-air solenoids and motor starters drive separate power and control cabling. The cable schedule grows iteratively from a layout-driven draft to a construction-issue document. Late changes, an added instrument, a re-routed equipment package trigger cable-schedule revisions that the field crew has to reconcile against the as-installed condition.
Instrumentation and electrical cable types on a schedule
The cable type column is what the pulling crew and the panel builder read. The construction decides the segregation and earthing rules that follow it.
| Cable type | Typical construction | What it carries | Practical constraint |
|---|---|---|---|
| Single pair, individually screened | One twisted pair, foil screen with a drain wire, armour and outer sheath | One analogue loop or one digitally addressed transmitter | The screen is bonded at one end only, normally the panel |
| Multipair, individually and overall screened | Several pairs, each foil screened, plus an overall screen, armour and sheath | The home run between a field junction box and the marshalling cabinet | Pairs are allocated by the junction box schedule, not chosen in the field |
| Triad | Three conductors twisted together, screened | A three wire RTD element | All three conductors must come from the same triad or the lead resistance does not cancel |
| Thermocouple extension | Conductors of the same alloy pair as the sensor, colour coded by type | A thermocouple signal back to the transmitter or card | Alloy and polarity must match the sensor type; copper anywhere in the run introduces an error |
| Fieldbus trunk, type A | One screened pair, 18 AWG, armoured, to the IEC 61158-2 type A specification | A digital fieldbus segment shared by several devices | Terminators at both ends of the trunk, and a budget for spur length and device count |
| Coaxial | Single conductor, dielectric, braided screen | Radar level, some analysers, and some high frequency signals | The impedance must match what the device expects |
| Ethernet, industrial | Four pairs, screened, with an industrial outer sheath and connector | Control network, remote I/O, and camera or analyser traffic | Segment length limits, and a separation distance from power cable |
| Fibre optic | Single mode or multimode fibres in a loose tube, armoured | Control network between buildings or across a large site | Immune to induced noise; needs splice, patch and loss records of its own |
| Low voltage power | Two, three or four cores, unscreened, armoured | Motor feeds, heaters, panel supplies, and heat tracing | Physical separation from instrument cable, with defined crossing rules |
Where each cable schedule column comes from
The schedule is a joining document. Almost every column is owned by another document, which is why it goes stale first.
| Column | What it records | Document that owns the value |
|---|---|---|
| Cable number | The unique tag of this cable | The cable numbering convention for the project |
| From and to | The device, junction box, cabinet or panel at each end | P&ID, instrument index and the panel layout |
| Cable type and core count | Construction, size and how many cores or pairs | The cable specification |
| Voltage and signal class | What the cable is allowed to carry | The segregation philosophy |
| Route and length | The tray or duct route, and the cut length with slack | Cable routing layouts |
| Gland type and size | The gland at each end, and its hazardous area certification | The hazardous area schedule and the equipment certificate |
| Termination detail | Terminal numbers at each end | The loop diagram and the junction box schedule |
| Screen and armour earthing | Where the screen and the armour are bonded | The earthing philosophy |
| Test record | Continuity, insulation resistance and the date tested | Commissioning records |
Common questions
Is the cable schedule the same as the cable list.
Does Tagsight produce the cable schedule directly.
How is a cable schedule used during construction and commissioning.
Get the cable schedule template.
Twelve columns covering cable number, tag, signal class, from and to, construction, cores, length and JB termination. Plain .xlsx.