External Controllers

An External controller is a type of Standard controller that places its sensor externally, rather than placing the sensor on a duct or zone.

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Figure 12 - A controller with the type set to Outdoor is referred to as an external controller.

This means that the user can now control their components based on the external weather conditions, from either the weather data in the TBD file or the conditions entered manually within Systems.

External controllers can be used in both the plant room and air-side systems.

Creating

To create an External controller, the user would need to create a controller but not connect any sensors to it.

Then, the user needs to open up the controller’s Properties dialog and change the controller’s type to Outdoor.

Please note that if the user places a sensor onto this controller, it will no longer be an External controller and will revert back to being a normal Standard controller.

Properties

As an External controller is a type of Standard controller, we have already discussed most of the available properties in the section “Standard Controllers - Properties”.

In fact, apart from the lack of being able to see the sensor’s placement, the only difference in the properties between an External controller and a Non-Thermostat Standard controller of normal type is the available options in the Variable field.

There are six different options available to choose from for an External controller, with all options available in both the plant room and air-side systems. The options are:

  • Outdoor Drybulb

  • Outdoor Hum Rat

  • Outdoor RH

  • Outdoor Enthalpy

  • Outdoor Wetbulb

  • Outdoor Pollutant

Outdoor Drybulb

With this variable selected, the sensor will take the external drybulb temperature for the hour as the reading passed onto the controller.

This drybulb temperature will be taken from the weather data entered in the TBD file or the external conditions entered manually into Systems; depending on the External Conditions option chosen in the Simulate dialog.

Outdoor Hum Rat

With this variable selected, the sensor will take the external humidity ratio for the hour as the reading passed onto the controller.

This humidity ratio will be calculated from the weather data entered in the TBD file or the external conditions entered manually into Systems; depending on the External Conditions option chosen in the Simulate dialog.

Outdoor RH

With this variable selected, the sensor will take the external relative humidity for the hour as the reading passed onto the controller.

This relative humidity will be taken from the weather data entered in the TBD file or the external conditions entered manually into Systems; depending on the External Conditions option chosen in the Simulate dialog.

Outdoor Enthalpy

With this variable selected, the sensor will take the external enthalpy for the hour as the reading passed onto the controller.

This enthalpy will be calculated from the weather data entered in the TBD file or the external conditions entered manually into Systems; depending on the External Conditions option chosen in the Simulate dialog.

Outdoor Wetbulb

With this variable selected, the sensor will take the external wetbulb temperature for the hour as the reading passed onto the controller.

This wetbulb temperature will be calculated from the weather data entered in the TBD file or the external conditions entered manually into Systems; depending on the External Conditions option chosen in the Simulate dialog.

Outdoor Pollutant

With this variable selected, the sensor will take the external pollutant level for the hour as the reading passed onto the controller.

Please note that this external pollutant level is set, before a simulation, in the Simulate dialog. As only one value is set, this pollutant level is also constant for the year.