ERV Efficiency Rule

Type: erv_efficiency — Built-in check; no custom expression.

Note: This rule is custom — not part of ASHRAE Guideline 36. It was created for open-fdd.

What the rules engine does

The erv_efficiency rule flags when Energy Recovery Ventilator (ERV) effectiveness falls outside the expected range. The engine computes effectiveness from OAT entering, OAT leaving the ERV, and return air temp. In heating mode (OAT < oat_low_threshold), effectiveness should be between erv_efficiency_min_heating and erv_efficiency_max_heating. In cooling mode (OAT > oat_high_threshold), it should be between the cooling min/max. When effectiveness is too low or too high (or OAT–RAT delta is too small to trust the calc), a fault is flagged. AHU with ERV only.

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erv_effectiveness_fault (erv_efficiency)

ERV effectiveness outside expected range based on OAT.

name: erv_effectiveness_fault
description: ERV effectiveness outside expected range based on OAT
type: erv_efficiency
flag: fc16_flag
equipment_type: [AHU_ERV]

inputs:
  ERV_Outside_Air_Temperature_Sensor:
    brick: Outside_Air_Temperature_Sensor
    column: erv_oat_enter
  ERV_Discharge_Air_Temperature_Sensor:
    brick: Discharge_Air_Temperature_Sensor
    column: erv_oat_leaving
  ERV_Return_Air_Temperature_Sensor:
    brick: Return_Air_Temperature_Sensor
    column: erv_eat_enter

params:
  erv_efficiency_min_heating: 0.5
  erv_efficiency_max_heating: 0.9
  erv_efficiency_min_cooling: 0.5
  erv_efficiency_max_cooling: 0.9
  oat_low_threshold: 55.0
  oat_high_threshold: 65.0
  oat_rat_delta_min: 5.0

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