The short answer
As-Built Means Someone Walked the Panel
An as-built drawing is one that a person has checked against the installed equipment, wire by wire and address by address, and corrected. It does not happen by itself: startup redlines get lost, the integrator's final drawings are issued from the design files, and every change after that is made in the panel and not on paper. A small utility gets true drawings by making the walk-down a paid deliverable with a checklist, by keeping one master set in one place, and by making a drawing update part of every change.
Key points
- Issued-for-construction, redlined, and as-built are three different documents; only the last was checked against the panel.
- Redlines are the truth of startup and are lost within a month unless someone is assigned to collect them.
- A walk-down verifies wire numbers, terminals, I/O addresses, network addresses, breakers, and device tags against the drawing.
- One master set, in one place, with a revision block; every other copy is a copy.
- A change is not finished until the drawing is updated; put it in the work order.
At two in the morning the technician opened the drawing pocket on the panel door, found the schematic, and traced the high level float to terminal 214. Terminal 214 had nothing on it. The float had been moved to a new intrinsic safety barrier during a modification four years earlier, the wire number had changed, and the drawing in the pocket was the one the integrator had issued at the end of the original project, which was itself the design drawing with a stamp that said as-built. The technician found the float by pulling wires. It took an hour that the drawing would have saved, and it was the fourth time that year.
Three documents that get called by one name
- Issued for construction
- The design drawing the panel was built from. Accurate to the designer's intent on the day it was issued, before anything was wired.
- Redlines
- The construction drawing with the changes made during build and startup marked in red pen by the people who made them. The most accurate document of the project, and the one most often thrown away.
- As-built
- The drawing corrected from the redlines and then verified against the installed panel by a person with the drawing in one hand and the wire in the other. Rare, and the only one that deserves the name.
The failure is not dishonesty. Integrators issue a final drawing set from their design files at the end of the project and stamp it as-built because the contract asks for that word. The redlines lived in the startup engineer's truck and the panel shop's bench and did not all make it back. Nobody walked the panel, because nobody was paid to, and the drawing set is a faithful record of what was meant rather than what is.
What a walk-down verifies
| Item | Check against the drawing | Common finding |
|---|---|---|
| Wire numbers | Every wire label matches the schematic at both ends | Wires relabeled during startup; unlabeled additions |
| Terminal assignments | Each terminal number carries what the drawing says | Moved circuits; spare terminals in use |
| I/O addresses | Each field device lands on the module and point shown | Points swapped to work around a failed channel |
| Device tags | Nameplates and drawing tags agree | Devices added without tags; tags reused |
| Breakers and fuses | Ratings and what each feeds | Fuse sizes changed; circuits added to a breaker |
| Network addresses | IP and serial addresses match the network drawing | Defaults left in; addresses changed and not recorded |
| Settings | Drive parameters, relay settings, and transmitter ranges match the schedule | Tuned in the field; never recorded |
| Spares | Spare I/O and terminals are the ones shown | Spares consumed and not marked |
The walk-down is slow and it is not skilled work in the sense that a programmer is skilled, which is why it is skipped, and it is the only step that makes the drawing true. A duplex lift station panel takes an experienced technician a couple of hours. A treatment plant MCC room takes a few days. Both are cheaper than the hours lost to wrong drawings over the life of the panel, and neither happens unless it is on a schedule with a name beside it.
Making it a deliverable
For a new project, the specification should say that as-built drawings are produced by walking down the installed panels after startup, that the walk-down is documented with a checklist signed by the person who did it, and that final payment for the drawing deliverable follows the utility's acceptance of them. The utility should ask for the redlines as well as the finals, because the redlines are the evidence. A field verification stamp on the drawing should name the person and the date, not just the word. An integrator who has done this before will quote it as a line item; one who has not will learn something about what the word means.
Keeping them true
- 1
One master set
Decide where the master lives: a document folder on the utility's system, with the native files, a revision block, and a log of changes. Every other copy, including the one in the panel pocket, is a copy that gets replaced when the master changes.
- 2
A change is not done until the drawing is
The work order for a modification has a line for the drawing update, and the work order does not close without it. The technician who moved the float is the person who knows what changed; a redline from them the same day is worth more than an engineer's reconstruction a year later.
- 3
Redline in the pocket, revise at the desk
A red pen and a rule that the pocket copy is marked at the time of any change. Once a quarter, someone collects the pocket copies, revises the master, and replaces them with fresh prints.
- 4
Walk it on a cycle
Every panel gets a full walk-down against the master every few years, or after any large modification. The findings go into the master and into a short report that tells the utility how much drift it has.
- 5
Tie the loop sheets and the I/O list together
The schematic, the I/O list, the loop sheets, and the network drawing describe the same panel. A change in one is a change in all of them; keep them in the same folder with the same revision.
What it is worth
Wrong drawings cost hours at two in the morning, they cost mistakes when a technician acts on a drawing that lies, and they cost money every time an outside firm has to survey a panel before it can quote a change. True drawings are what allow a new technician to be useful in a month instead of a year, and they are what an integrator needs to make a change without a site visit. The technician who found the float at terminal 214 by pulling wires marked the drawing in red before leaving. That was the first as-built change that panel had seen in four years, and it was the beginning of the utility deciding that drawings were something it owned.
Frequently asked questions
- Our old panels have no drawings at all. Where do we start?
- With the panels that matter most: the ones that control the process and the ones that fail. A technician with a camera, a label maker, and a blank schematic template can document a duplex panel in a day. It is not elegant and it is far better than nothing.
- Who should do the walk-down, the integrator or the utility?
- The integrator, on a new project, because it is their deliverable and their errors to find. The utility should spot-check it, because the utility lives with the result. For existing panels, the utility's own technician, who will also learn the panel in the process.
- What software do we need for the master set?
- The one the drawings were made in, or one that opens it. For a small utility a general CAD package and a disciplined folder structure are enough; document control software is a later step. The discipline matters far more than the tool.
- How do we handle drawings for a change the vendor made?
- The vendor's change record and redline are part of the service call, and the utility updates the master from them. A vendor who leaves without documenting a change has left the utility a fault to find later.
Related topics
- Control SchematicsThe ladder-style drawing of every control circuit in a panel: how a schematic is organized by line number, the conventions for contacts, coils, and cross-references, what belongs on a schematic and what belongs on a wiring diagram, and reading one under pressure.
- Panel LayoutsThe drawing of what goes where inside a control panel: enclosure, back plate with every component to scale and keyed to the bill of material, wireways, terminals, door devices, and entries. The conventions, the required spacings, and the checks.
- I/O ListsThe document that ties the field to the controller: what every I/O list column means, how tags, terminals, and module channels are assigned, spare capacity rules, how the list drives the drawings and the program, and how to keep it true after commissioning.
- Site Acceptance TestingProving the installed system with the real field: loop checks first, then end-to-end I/O, real communications, sequences on real equipment, alarms to real recipients, and failure modes on the real network, with the record that becomes the as-built.
- Commissioning ChecklistFrom energization to handover: the sequence of commissioning activities for a control system, the prerequisites and records for each, who signs what, and the checklist that keeps a project from being declared finished while half of it has never been tested.
- How to Build Terminal SchedulesProduce the terminal schedule that lets a technician find any wire: define the strips and their numbering, list every terminal with its wire numbers, the device and the field destination, and keep it current through every change.
Direct contact
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