Motors

Overview

The motor tag is paired with the equip tag to model equipment that operates with an electric motor. Haystack defines the following standardized motor subtypes:

• fan-motor: fans used to move air
• pump-motor: pumps used to move fluid

Often these motors are driven by a variable frequency drive, or VFD, that exposes many points. If a motor uses a VFD, then it should also be tagged with the vfd marker. Typically, motors such as fans and pumps are sub-components of a larger piece of equip that we nest via the equipRef tag.

Points

The standardized points for motor control are:

• run cmd: primary on/off command
• enable cmd: secondary on/off command
• run sensor: run status sensor
• enable sensor: enable status sensor
• alarm sensor: bolean alarm condition

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 that requires both run and enable to be commanded to true in order for the equipment to be on. In all cases, true models the on state, and false models the off state.

If the motor is driven by a variable frequency drive, then it should be tagged with the vfd marker. Points related to the drive speed control:

• vfd speed cmd: speed command as percentage where 0% is off, 100% if full speed
• vfd freq cmd: speed command as a frequency in Hz
• vfd speed sensor: speed status as percentage where 0% is off, 100% if full speed
• vfd freq sensor: speed status as frequency in Hz

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 driven by 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 more easily modeled as just 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:

• false (off) or true (on)
• variable speed 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 the fan status:

• false indicates 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"

Fan Equips

When the fan motor is a VFD, it should be modeled as an equip entity using the standard VFD points described above. If you wish to standardize modeling all fans as equip, then simple single speed fans 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 motor equip
id:@ahu-fan-run    equipRef:@ahu-fan discharge fan run cmd point
id:@ahu-fan-status equipRef:@ahu-fan discharge fan run status point
id:@ahu-fan-speed  equipRef:@ahu-fan discharge fan drive 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, however we must flatten the discharge and fan tags into the points.

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 as 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.