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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 airpump-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 commandenable
cmd
: secondary on/off commandrun
sensor
: run status sensorenable
sensor
: enable status sensoralarm
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 speedvfd freq
cmd
: speed command as a frequency in Hzvfd speed
sensor
: speed status as percentage where 0% is off, 100% if full speedvfd 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.