BAS-408 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
A successful connection is not a successful integration; meaning, authority, timing, quality, failure response, and ownership must survive the boundary.
Case overlay
A VRF vendor offers 500 exposed points but cannot identify which may be commanded or how stale data is reported.
Calculation/evidence callout: Reconcile requested, available, mapped, writable, tested, rejected, deferred, and owner-approved points/services.
Normal-rule anchor
Sharing a wire or IP network does not imply shared data semantics or service support; protocols and product profiles define different capabilities.
Case overlay
Two devices both say BACnet-compatible, but one supports only read properties and the other expects priority writes and COV.
Calculation/evidence callout: Build a layer/service matrix and calculate required-versus-supported coverage.
Normal-rule anchor
BACnet object discovery does not prove correct physical identity, units, commandability, priority effect, or process response.
Case overlay
Two devices share an instance number and a writable AO appears to accept a command that is overridden at a higher priority.
Calculation/evidence callout: Construct object identifiers, reconcile instances, priorities, COV updates, and required BIBB/service support.
Normal-rule anchor
BBMD or foreign-device configuration is a network design decision with operational impact; adding entries until discovery works can create loops, duplicates, or exposure.
Case overlay
A supervisor on a new VLAN cannot discover devices, and two BBMDs contain inconsistent peer tables.
Calculation/evidence callout: Calculate subnet membership, broadcast paths, FDR expiry, duplicate networks/devices, latency, and permitted communication matrix.
Normal-rule anchor
Software settings cannot compensate for reversed polarity, improper topology, missing reference, duplicate MAC, wrong baud, or uncontrolled stubs.
Case overlay
A trunk has intermittent devices, long free-air runs, star branches, duplicate MAC addresses, and mixed baud settings.
Calculation/evidence callout: Calculate cable/segment budget from project/manufacturer criteria, node/address counts, token rotation estimate, error rate, and poll/update expectation.
Normal-rule anchor
A plausible Modbus number can still be wrong because of address base, function, type, sign, byte/word order, scale, or stale response.
Case overlay
An energy meter value changes from 12.4 kW to 2.7 x 10^23 after a gateway firmware replacement.
Calculation/evidence callout: Decode supplied registers under alternate endian/type assumptions, apply scaling and units, and compare polling load and exception rates.
Normal-rule anchor
A gateway is an active system component that can alter meaning, timing, authority, and failure behavior; it requires its own monitoring, backup, and recovery plan.
Case overlay
A gateway maps a three-state mode into Boolean, substitutes zero on timeout, and drops source timestamps.
Calculation/evidence callout: Calculate mapping coverage, transform error, age/latency, timeout/retry window, cache behavior, and loss/recovery duration.
Normal-rule anchor
Integration does not transfer design authority or qualification; listed life-safety and proprietary equipment remain under approved interfaces and responsible vendors.
Case overlay
A BAS contractor is asked to write smoke-control commands through a gateway and reset a chiller safety remotely.
Calculation/evidence callout: Classify points by read/write, consequence, owner, verification method, latency, and failure/fallback requirement.
Normal-rule anchor
An integration that works by opening broad ports, sharing credentials, or leaving permanent vendor access creates an operational defect even when point data is correct.
Case overlay
A gateway requires outbound cloud access and a vendor requests inbound remote administration using a shared account.
Calculation/evidence callout: Reconcile required data flows against allowed rules, privileges, certificates, sessions, logs, and revoked access.
Normal-rule anchor
The integration is complete only when failure is visible, fallback is safe and approved, recovery is proven, every writable point is controlled, and ownership is explicit.
Case overlay
The gateway restarts with stale cached commands, reconnects after five minutes, and clears quality before source data is fresh.
Calculation/evidence callout: Measure latency, freshness, loss detection, fallback, recovery, point/test coverage, unresolved issues, and zero unowned temporary states.