Zones & IAQ faults
Comfort, ventilation and humidity where people are.
Ten rules for fan-coils and occupied zones: over- and under-ventilation by CO₂, humidity out of band, condensation risk on chilled surfaces, biased sensors, and occupied setpoints or night setbacks that drifted away from policy. Several are diagnostic — they protect comfort and the building rather than claim savings.
How to read it. One occupied day in a classroom. Blue is CO₂, which rises as people arrive. The dashed green line is the ventilation limit. The teal line is the outdoor-air damper, which should open as CO₂ climbs but stays flat, so CO₂ spends the afternoon above the limit (red).
The rules
- FCU-01
Fan-coil valve leaking by
The coil valve is closed but the discharge air is still well away from the zone temperature.
Capacity-basedBAS trends - FCU-02
Fan-coil fan out of step with its call
The fan runs unoccupied with the valve closed, or the valve opens while the fan is off.
Capacity-basedBAS trends - FCU-03
Four-pipe fan-coil heating and cooling together
Both the heating and cooling valves of a fan-coil are open at once.
Capacity-basedBAS trends - ZONE-01
Over-ventilating a lightly occupied zone
CO₂ is far below the demand-control setpoint while the outdoor-air damper is wide open.
Capacity-basedBAS trends - ZONE-02
Under-ventilated zone (CO₂ high)
CO₂ stays above the comfort / code limit while the space is occupied.
Diagnostic · comfortBAS trends - ZONE-03
Zone humidity out of band
Occupied relative humidity sits outside the comfort band for a sustained period.
Diagnostic · comfortBAS trends - ZONE-04
Condensation risk on a chilled surface
A chilled beam / radiant / supply surface is colder than the zone dewpoint.
Diagnostic · reliabilityBAS trends - ZONE-05
Zone temperature sensor biased vs neighbours
One zone sensor reads persistently offset from the median of its neighbours.
Diagnostic · data qualityBAS trends - ZONE-06
Occupied setpoints outside policy
During occupied hours the zone is asked for cooling colder, heating warmer, or a deadband narrower than the building's setpoint policy.
Capacity-basedBAS trends - ZONE-07
Night setback too shallow
The unoccupied cooling and heating setpoints are within a few degrees of the occupied ones — the zone is kept at comfort conditions overnight and at weekends.
Capacity-basedBAS trends
See these rules run on your building.
Send twelve months of interval data and a BAS trend export. Energy Agent returns a ranked list of what is wasting money, what each item is worth per year at your tariff, and what to do about it.