Hydronic Heat-Exchanger Fault Rules
Hydronic heat-exchanger rules (HX-*) cover one indirect liquid-to-liquid
four-port heat exchanger. The primary side normally belongs to the external or
source network; the secondary side normally belongs to the served/load loop.
Both identities stay fixed while signed heat transfer may reverse.
Point dictionary: points/hx.points.json.
Brick 1.4.4 provides exact generic Heat_Exchanger; ASHRAE 223 PPR2.1 provides
exact HydronicHeatExchanger with paired primary/secondary inlet and outlet
connection points.
Excluded from the initial family: air/refrigerant heat exchangers and coils, direct-contact devices, phase-changing steam service, potable-water service, and an HX bank whose temperatures/flows do not preserve one coherent identity.
Index
| ID | Name | Sev | Method | Status |
|---|---|---|---|---|
| HX-0001 | Hydronic heat-exchanger effectiveness degradation | 3 | statistical | verified |
| HX-0002 | Heat exchanger active with one-side flow missing | 2 | rule | verified |
| HX-0003 | Heat transfer persists with control valve commanded closed | 3 | rule | verified |
Topology and telemetry
| Tier | Required contract | Supported rule |
|---|---|---|
| Flow proof | final both-flow exchange command plus individual primary/secondary branch flows | HX-0002 |
| Performance | four connection-point temperatures, both branch flows, configured fluid properties, validated actual and frozen expected effectiveness | HX-0001 |
| Isolation | final isolating-valve command plus validated signed heat-transfer derivation | HX-0003 |
primary and secondary are side identities, never synonyms for hot/cold or
supply/return. Positive heat_transfer_rate means primary loses heat and
secondary gains it; cooling normally has the opposite sign. HX-0001 and
HX-0003 are magnitude-based and work in either direction.
Common-header/fleet flow, duplicated side sensors, unaligned timestamps, a baseline fitted on the scored interval, or missing glycol properties make the thermal rules NO_EVAL. The CXF graphs do not calculate effectiveness: the host must validate every denominator and side energy balance before publishing the derived point.
Source and validation posture
EnergyPlus 25.1.0’s official HeatExchanger:FluidToFluid model and
PlantLoopChainHeating.idf/PlantLoopChainCooling.idf testfiles provide the
healthy Layer 3 path. The library has not yet claimed a completed simulation
campaign for these rules. Guelpa and Verda (Applied Energy 258, 2020,
doi:10.1016/j.apenergy.2019.114059) provide field precedent for fouling
detection from primary flow and both-side temperatures across 325 district
heating substations, but no source provides portable alarm thresholds.
Relationships
- HX-0002 is proof/evaluability context for HX-0001, but no global suppression is encoded because fault IDs are not instance-scoped.
- HX-0003 can explain degradation or wasted transfer while HX-0001 remains a separate performance verdict.
- PMP-0001/PMP-0003 may locate a failed pump behind HX-0002; they are related workflows, not duplicate HX signatures.