vfd

Kind: Marker
Used With: equip

Marker for a motor equip with variable frequency drive. Commonly used in combination with fan and pump.

From: VFDs

Overview

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 equipRef tag.

Points

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 run and enable to be commanded to true in order for the equipment to be on.

Speed of the VFD is commanded separately via the speed or freq point. Use of these points require that the equipment has already been commanded 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

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 point.

Fan Points

In simple cases where the fan is just a command and/or feedback sensor then it is best to model it as a point.

If annotated as an output with the cmd tag, then the point models the command status of the fan:

If annotated as an input with the sensor tag, then the point models a sensor used to verify if the fan status:

Fan Equips

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 run point.

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

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.