Fans, pumps, and compressors which use a variable frequency drive or VFD are typically sophisticated devices that expose many points. VFDs should be modeled as their own
equip entity using the
vfd tag. If the VFD is a sub-component of a larger piece of equip then it can nested via the
The standardized points for VFDs are:
The primary on/off point of equipment is always modeled with the
run tag. Paired with
cmd it models the on/off command point; paired with
sensor it models the run status point. Many VFDs also include a secondary
enable point which requires both
enable to be commanded to true in order for the equipment to be on.
Many VFDs will also provide many of the same points as an electric meter. Measurements such as electric demand, consumption, voltage, and current should follow the same conventions as elec meters.
Fans may optionally be defined as either an
equip or a
point. If the fan motor is a VFD then it is recommended to make the fan a sub-equip. However in many cases a simple fan in a terminal unit such as a
vav is better modeled as a
In simple cases where the fan is just a command and/or feedback sensor then it is best to model it as a
If annotated as an output with the
cmd tag, then the point models the command status of the fan:
- false (off) or true (on)
- variable speed then it is 0% (off) to 100% (full speed)
If annotated as an input with the
sensor tag, then the point models a sensor used to verify if the fan status:
- false indicated no air flow (off) or true indicates successful airflow (fan is on)
- if numeric the point is differential pressure across the fan measured in "inH₂O" or "kPa"
When the fan motor is a VFD it should modeled as an
equip entity using the standard VFD points described above. If you wish to standardize modeling all fans as equip, then simple non-VFDs fan should define their state via a
Example of a VFD fan on an AHU:
id:@ahu ahu equip id:@ahu-fan equipRef:@ahu discharge fan vfd equip id:@ahu-fan-run equipRef:@ahu-fan run cmd point id:@ahu-fan-status equipRef:@ahu-fan run status point id:@ahu-fan-speed equipRef:@ahu-fan speed cmd unit:"%" point
Note that the fan is modeled as an sub-equip of the AHU via the
equipRef tag. The VFD points are defined under the fan itself.
Pumps may optionally be defined as either an
equip or a
point. If the pump is a VFD then it is recommended to make it an equip level entity. However if the pump is modeled a simple on/off point as a component within a large piece of equipment such as a
boiler then it is modeled as just a
point. Pumps should follow the same point and equip level modeling conventions as fans.