BAS-205 Visual Aid Library
Figure-use rule
Each figure is an orientation and reasoning aid, not a project drawing. Learners must pair it with the current sequence, point list, wiring/piping documents, manufacturer instructions, and as-found evidence.
Normal-rule anchor
BACnet is not a cable or connector; network success requires every layer and demarcation to work.
Case overlay
A controller has an Ethernet jack and an RS-485 port, but the project team calls both BACnet wiring without defining topology or owner.
Calculation/evidence callout: Count nodes/segments/interfaces and reconcile route, ownership, media, and unresolved requirements.
Normal-rule anchor
RS-485 electrical behavior and product instructions govern the segment; a protocol screen cannot repair the wire.
Case overlay
An MS/TP trunk has a star branch, long stubs, mixed cable, and intermittent devices near a separate building.
Calculation/evidence callout: Calculate segment lengths/load from supplied data and compare topology, reference, and cable criteria.
Normal-rule anchor
Termination belongs at physical segment ends as required; cabinet order, device address, and visual convenience do not define an end.
Case overlay
Three termination resistors are active and the shield is bonded to signal common at an intermediate controller.
Calculation/evidence callout: Calculate expected equivalent termination resistance from supplied design and reconcile every landing and end.
Normal-rule anchor
MAC, device instance, network number, IP address, and label are different identities; changing one may affect several systems.
Case overlay
A replacement controller ships at a duplicate MAC and reuses an existing device instance on another routed network.
Calculation/evidence callout: Validate uniqueness and ranges from supplied constraints; calculate node counts and token/address utilization.
Normal-rule anchor
Discovery proves a response, not topology quality, timing margin, unique identity, correct objects, or process function.
Case overlay
All devices slow after one controller is added, while one node disappears only during high traffic.
Calculation/evidence callout: Estimate token cycle/response from supplied data and compare before/after latency and errors.
Normal-rule anchor
BACnet/IP does not define cable category, connector workmanship, switch design, or acceptance test; project/IT/manufacturer sources do.
Case overlay
A field-made plug passes link but pair split and bend damage cause intermittent errors.
Calculation/evidence callout: Reconcile length/channel limits from supplied criteria and interpret wiremap/link/test evidence without overclaiming certification.
Normal-rule anchor
Installers implement assigned network values; they do not invent addresses, VLANs, routes, firewall rules, or internet exposure.
Case overlay
Two controllers share an IP, one has the wrong mask, and the BAS team requests an any-any firewall rule.
Calculation/evidence callout: Convert masks/prefixes using supplied aids, identify network/host ranges, compare gateway reachability, and reconcile assigned values.
Normal-rule anchor
IP reachability, BACnet routing/broadcast, device identity, application service, and physical process are separate layers.
Case overlay
Devices discover on one subnet but not another, and a technician proposes public internet exposure to test remotely.
Calculation/evidence callout: Map required flows/routes and calculate supplied TTL/session/latency values; define named, logged, time-bounded remote access.
Normal-rule anchor
Start at the highest-discrimination safe boundary; changing baud, addresses, termination, switch settings, and program together destroys evidence.
Case overlay
A controller is down after replacement while the rest of the trunk works and the supervisor shows a stale old device.
Calculation/evidence callout: Compare expected/actual readings, latency/error counts, identity maps, and test coverage before and after correction.
Normal-rule anchor
A working network without controlled identity, ownership, baseline, and recovery evidence is not complete.
Case overlay
The trunk communicates, but three addresses, a temporary laptop route, and the remote session remain undocumented.
Calculation/evidence callout: Reconcile nodes/ports/addresses/tests/issues and calculate as-built and restoration completeness.