Zone List

To create or modify a zone, go to

DM HVAC->Building Definition->Zones->Zone List

Zones Dialog Box

Building Definition--Zones.Zone List dialog box

See the Common Schedule Dialog Box Features section for more information about how this dialog box works. This section describes the Rename, Find, Previous, Next, New, Copy, Save and Delete buttons.

Zone Above: The zone that is above this zone in the zone hierarchy.

<None>: No zone is above this zone. All of the other sections in the dialog box will be forced to be on.
Other Zone: There is a zone above this zone. By default, most of the settings for the zone are based upon the zone above it. Only settings that are specifically overriden are specified in this zone.

System Type: The type of system that is modeled by the zone.

Variable Air Volume: The system is a variable air volume system. The peak zone values will be coincident peaks.
Constant Volume: The system is a constant volume system. The peak zone values will be a sum of the room peak values.

Room Supply CFM Basis: How the room supply airflow is calculated.

Use calculated room loads: The room supply airflow is based upon the calculated room load.
Prorate using fixed supply CFM: The room supply airflow is prorated based upon the Fixed Supply CFM. The supply airflow based upon the calculated room load is compared with the fixed supply airflow. Each room is then adjusted up or down based upon this ratio. The total supply air for all of the rooms will equal the fixed supply airflow.

Fixed Supply CFM: The total airflow to be supplied to the zone when Room Supply CFM Basis is set to Prorate using fixed supply CFM. This field is disabled if Room Supply CFM Basis is set to Use calculated room loads.

Indoor Air Defaults

The Indoor Air Defaults section sets the default temperature and humidity values for rooms in the zone. It is possible for specific room types or individual rooms to override these values.

These values are required for zones that have Zone Above set to <None>.

For other zones, there are two checkboxes that are enabled. If the boxes are not checked, then these values for the zone are based upon the values in the zone above. If the first box is checked, the temperatures are set specifically for this zone. If the second box is checked, the relative humidity is set specifically for this zone.

Heating Temperature: The goal temperature used when heating the rooms in the zone.

Cooling Temperature: The goal temperature used when cooling the rooms in the zone.

Relative Humidity (%): The goal relative humidity used when cooling the rooms in the zone.

ASHRAE 62

The ASHRAE 62 section sets values that are used when performing the ASHRAE 62.1 zone ventilation calculation.

These values are required for zones that have Zone Above set to <None>.

For other zones, there is a checkbox that is enabled. If the box is not checked, then these values for the zone are based upon the values in the zone above If the box is checked, then these values are set specifically for this zone.

See ASHRAE 62.1, Appendix A Definitions for more information on all of the values. The explanations for these values are taken from that document.

Show Definition: Press this button next to each value to display a definition while using the program.

Ep: Primary air fraction to the zone. Set Ep to 1.0 for single-duct and single-zone systems.

Er: In systems with secondary recirculation of return air, fraction of secondary recirculated air to the zone that is representative of average system return air rather than air directly recirculated from the zone.

For plenum return systems with local secondary recirculation (e.g., fan-powered VAV with plenum return), set Er less than or equal to 1.0.

For ducted return systems with local secondary recirculation (e.g., fan-powered VAV with ducted return), typically Er is equal 0.0

Ez: A measure of how effectively the zone air distribution uses its supply air to maintain acceptable air quality in the breathing zone.

Ceiling supply of cool air, Ez = 1.0.
Ceiling supply of warm air and floor return, Ez = 1.0.
Ceiling supply of warm air 15F or more above space temperature and ceiling return, Ez = 0.8.
Ceiling supply of warm air less than 15F above space temperature and ceiling return provided that the 150 fpm supply air jet reaches to within 4.5 ft of floor level, Ez = 1.0. For lower velocity supply air, Ez = 0.8.
Floor supply of cool air and ceiling return provided that the 150 fpm supply jet reaches 4.5 ft or more above the floor. Note: most underfloor air distribution systems comply with this provision. Ez = 1.0.
Floor supply of cool air and ceiling return, provided low-velocity displacement ventilation achieves unidirectional flow and thermal stratification, Ez = 1.2.
Floor supply of warm air and floor return, Ez = 1.0.
Floor supply of warm air and ceiling return, Ez = 0.7.
Makeup supply drawn in on the opposite side of the room from the exhaust and return, Ez = 0.8.
Makeup supply drawn in near to the exhaust and return location, Ez = 0.5.

Minimum Zd: The minimum discharge outdoor air fraction for the zone.

The formal definnition is Zd = Voz/Vdz. Voz is the zone outdoor airflow. Vdz is the zone discharge airflow.

For non-VAV systems, this minimum value should be set to 0.

For VAV systems, Vdz is the minimum expected discharge airflow for design purposes. As the designer, you must decide what the minimum discharge outdoor air fraction for the system will be. The minimum Zd that you specify implicitly defines the minimum Vdz for the zone.

People Diversity

The People Diversity section sets whether or not the number of people in the zone is diversified compared to the number of people in the rooms in the zone.

If the checkbox is not checked, the number of people in the zone is the sum of the number of people in the rooms in the zone.

If the checkbox is checked, the number of people in the zone is based upon the SF / Person or People setting. The people load in the zone will be adjusted based upon the number of people in the zone compared to the sum of the number of people in the rooms in the zone.

SF / Person: Select this to set the number of people in the zone based upon the zone area.

People: Select this to directly input the total number of people in the zone.

Plenum

The Plenum section controls whether or not the zone has a plenum return. When a zone has a plenum return, some of the room loads are moved to the system load instead. These include the roof load, the portion of the wall load that is above the plenum, and a percentage of the lighting load.

Plenum Return: Whether or not the zone has a plenum return.

Percentage of Lighting Load to Plenum: For zones with a plenum return, the percentage of the lighting load that is transferred to the plenum. The lighting load in the plenum is included in the system load but not the room load.

Tempered Air

The Tempered Air section controls whether or not the zone has tempered air and the settings of the tempered air if it does.

OSA is Tempered: Whether or not the outside air is tempered before it reaches the air handler.

Tempered Low Temperature: If OSA is Tempered is checked, this temperature is used instead of the OSA Low Temperature Dry Bulb temperature forwhen calculating heating loads.

Tempered High Dry Bulb Temperature: If OSA is Tempered is checked, this temperature is used instead of the OSA High Dry temperature when calculating cooling loads.

Tempered High Wet Bulb Temperature: Whether or not the web bulb temperature is tempered in addition to the dry bulb temperature. If this is checked, this temperatured is used instead of the OSA High Wet temperature when calculating cooling loads..

AHU and Coil Settings

The AHU and Coil Settings section controls values that are used in the supply air requirements calculations and the psychrometric calculations.

Heating Temperature Difference: The temperature difference between the heating temperature in the room or zone and the air at the supply diffusers. This temperature difference is used as an input in the heating supply air requirement calculations.

Cooling Temperature: The temperature of the air at the supply diffusers. This temperature is used as the desired end condition for the psychrometric calculations and as an input in the cooling supply air requirements calculations.

Coil Bypass Factor (%): The percentage of air that is not conditioned by the coil.

Fan Position: Where the fan is positioned.

Blow Through: The fan is positioned before the coil. This location requires a higher coil dew point temperature.
Draw Through: The fan is positioned after the coil. This location requires a lower coil dew point temperature.

Fan Brake Horsepower: This is the horsepower of the fan brake.

Motor Position: Where the motor is positioned.

In Airstream: The motor is positioned in the ductwork. The temperature gain from the motor is included in the psychrometric calculations.
Out of Airstream: The motor is positioned outside the ductwork. The temperature gain from the motor is not included in the psychrometric calculations.

Motor Efficiency (%): The efficiency of the motor. A higher value results in a lower temperature gain from the motor.

Duct Settings

The Duct Settings section controls values in the ductwork that are used in the psychrometric calculations.

Supply Duct Temperature Gain: The change in temperature in the air in the supply ductwork between the air handler and the diffusers. The temperature gain is often caused by ductwork that is in an unconditioned space, typically outside.

An increase in this value results a decrease in the coil dew point.

Supply Duct Air Leakage (%): The percentage of supply air that is leaked out of the ductwork between the air handler and the diffusers. This air is leaked outside the building. Do not include air that is leaked out of the ductwork but remains inside the building.

An increase in this value results in an increase in the mixed air volume. If the amount of air leaked exceeds the outside air volume, it will increase the volume of outside air required.

Return Duct Temperature Gain: The change in temperature in the air in the return ductwork between the diffusers and the air handler. The temperature gain is often caused by ductwork that is in an unconditioned space, typically outside

An increase in this value results in a higher mixed air temperature and a higher coil dew point temperature..

Return Duct Air Leakage (%): The percentage of return air that is leaked out of the ductwork between the diffusers and the air handler. This air is leaked outside the building. Do not include air that is leaked out of the ductwork but remains inside the building.

An increase in this value results in an increase in the outside air volume.


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