Which documents are needed before tracing a state?
Use the project one-line, the manufacturer connection drawing, the approved operating-state description and equipment identifiers. Record revisions before tracing. If the bypass arrangement is only suggested in a sales diagram, retain that limitation instead of treating it as the project design.
Eaton describes a maintenance bypass arrangement that routes supply around a UPS during replacement. Its network-closet examples explain a product arrangement, not a universal design for every data center. Critical Power Drafting is independent and is not affiliated with Eaton.
Sources: Eaton: UPS maintenance bypass installation best practices
What should the state-to-load worksheet show?
Use one row per approved state and affected load group. Copy actual device labels from the controlled drawing. The labels below describe review questions, not switch positions or an operating sequence.
| State to review | Trace on controlled drawings | Question to resolve |
|---|---|---|
| Normal supply | Named source through approved UPS path to load | Are the source and load boundaries explicit? |
| Project-defined internal bypass | Relevant manufacturer drawing and downstream path | What protection remains in this particular state? |
| Project-defined maintenance bypass | External path around the UPS and its load connection | Which supply supports the load while the UPS is isolated? |
| UPS unavailable | Approved design state and affected loads | Is any alternate path actually documented? |
| Return to normal | Approved state reference and drawing revision | Are interlocks and restrictions referenced consistently? |
How do you find a drawing contradiction?
Illustrative example. A fictional one-line labels a load as supplied through UPS-01. A separate bypass detail shows an alternate connection to the same load, but uses a different source identifier. Enter both document references in a discrepancy row and ask the designer to confirm the intended source. Do not resolve the difference by relabeling the detail without approval.
Review whether internal and external bypass names are being used consistently. A shared label can conceal different arrangements. Follow the actual connection and manufacturer reference rather than relying on the word bypass alone.
Where an alarm, status indication or interlock is referenced, check that its identifier can be followed into the relevant approved drawing. An absent reference is an open drafting issue, not evidence that the function does not exist.
What should remain outside this drawing check?
Do not infer redundancy, fault protection, battery autonomy or safe isolation from the worksheet. Those depend on the approved design and equipment. Record unresolved engineering questions for the responsible engineer.
This is a document review, not a switching procedure. Only authorized site personnel may carry out approved operations. Engineering sign-off is performed only by the registered engineer on the job. Close each drafting discrepancy against an approved revision and retain the before-and-after reference.
Common questions
What else should the bid team know?
Can a bypass line prove an uninterrupted supply?
No. The operating state, source condition and actual equipment arrangement need technical verification.
Should a reviewer invent missing switch states?
No. Request the approved state description and keep the review incomplete until it is available.
Who approves changes to the design?
The responsible design authority; engineering sign-off belongs to the registered engineer on the job.