To add an air handling unit to your building, identify the appropriate Heating and Cooling equipment types present and complete the inputs below for air handlers, including Distribution and Fan Systems.  If an air handler is served by plant loops (such as chilled water or hot water loops), then those should be created first.

 

HVAC systems with air handlers must have at least one equipment schedule entry (see the Mechanical Equipment page for details).  If multiple air handlers serve the same block, the equipment schedules will auto calculate weighted averages for heating and cooling efficiencies and fan power.   Air Handlers may be added and edited from either the Mechanical Equipment screen, or the Heating and Cooling screen.

 

Follow the steps below to add air handlers.  Refer to the TSPR data entry options for details.  After creating an air handler entry, select and assign to blocks by ‘dragging and dropping’.  See the Heating and Cooling page for additional details.

 

Adding Air Handlers for TSPR 


  1. Select the green ‘+’ (Add) icon from the Air Handlers sidebar option on the Heating and Cooling screen, or the green ‘Add Air Handler’ button below the Air Handlers System Assignment summary table on the Air Handlers tab of the Mechanical Equipment screen.
  2. Select a previously created and unassigned mechanical equipment schedule entry with the ‘Use’ button or proceed to step 6.
  3. Review previously entered inputs and the default component name and edit as needed or desired.
  4. Add or assign additional equipment schedule entries as needed.
  5. Select the green ‘Create Air Handler’ button to add the component.
  6. If you choose not to begin an air handler entry by selecting a previously created equipment schedule entry, select the blue ‘Start from scratch’ button.
  7. Enter a descriptive name for the air handler (or use the default component text and counters)
  8. Select a System Type.  
  9. Select a Cooling Source and a Heating Source and Fuel Type.
  10. Create a new Mechanical Equipment Schedule entry by scrolling back to the top of the screen and selecting the blue ‘Add Schedule Entry’ button or 
  11. Assign previously created equipment by selecting the Attach icon (paper clip).
  12. Review and edit component values including inputs for distribution, fan systems and system controls as needed.
  13. Add Terminal Unit equipment schedules for Multiple Zone systems by selecting the blue ‘Add Schedule Entry’ button or Assign previously created equipment by selecting the Attach icon (paper clip). 
  14. Select the green ‘Create Air Handler’ button to add the new Air Handler.


TSPR Data Entry Options for Air Handlers

 

Name – Default component text and counters are automatically added. This entry may be edited to include other descriptive or identifying text.

 

System Type – Nine common types of HVAC systems are available to select when adding Air Handler Unit distribution equipment to a building. After making a selection, select the appropriate Heating and Cooling sources and distribution type of the system. Refer to the HVAC System Types section for a table of suggested configurations, and guidance regarding System Type selections, including Dedicated Outdoor Air Systems (DOAS).

 

Cooling Equipment

 

Cooling Source – Pull-down menu selections of cooling equipment types:

 

No Cooling – If no mechanical cooling equipment is installed

 

Central DX – Packaged or Built-up systems using DX coils.  Available selection for Packaged Rooftop Air Conditioner, Packaged Rooftop Heat Pump, Packaged Rooftop VAV with Hot-Water Reheat, Packaged Rooftop VAV with Electric Reheat, DOAS, or Other Systems.

 

Plant – Available selection for VAV with Hot-Water Reheat, VAV with Electric Reheat, DOAS or Other Systems. Select if a Plant Cooling Loop was previously entered. The Plant Loop name and type (Chiller) will be available to select under the Plant Loop field.

 

DOAS Maximum SAT Setpoint – The maximum setpoint to which the DOAS cooling coil is controlled. This input is only displayed if a cooling coil is specified for a DOAS system.  Values should be greater than or equal to 72 oF and less than 100 oF.

 

Number of Stages for Cooling – Available option when the Cooling Source is Central DX (Packaged or Built-up systems using DX coils).  Selections include ‘Single Stage’ or Multi-Stage’.


Plant Loop (Cooling) – Menu item available if Plant is selected as the Cooling source. Pull-down menu selections: Previously defined Cooling Plant Loops.

 

Calculated Efficiency (Cooling) – COP is auto calculated to remove the supply fan energy and is displayed from Rated Efficiency values entered in the mechanical equipment schedule.   Efficiency of the cooling system in coefficient of performance (COP) is the ratio of the rate of heat removed to the rate of energy input, in consistent units, for a complete refrigerating system or some specific portion of that system under designated operating conditions.  A maximum value of 8 COP may be entered; typical COP values for air conditioning and heat pump systems are in the range of 2-5. 

 

 

Heating Equipment

 

Heating Source – Pull-down menu selections of heating equipment types:

 

No Heating – If no mechanical heating equipment is installed

 

Central Furnace – System where a furnace heats the air, and heated air is distributed through the building using ducts.  A furnace can be specified to be gas-fired or electric resistance by selecting the appropriate fuel type.  Available selection for Packaged Rooftop Air Conditioner, VAV with Electric Reheat, Warm Air Furnace, DOAS, or Other Systems. Select "Single Zone" or "Multiple-Zone" for the Distribution Type.

 

Heat Pump – Select this for heat pump systems. The tool requires a ‘heat pump’ heating to be coupled with a ‘Central DX’ cooling system. These units provide both heating and cooling functions.  Available selection for Packaged Rooftop Heat Pump, DOAS, or Other Systems.

 

Plant – Available selection for VAV with Hot-Water or Electric Reheat, DOAS, or Other Systems. Select if a Plant was previously entered. The Plant Loop name and type (Boiler) will be available to select under the Plant Loop field.

 

DOAS Minimum SAT Setpoint -- The minimum setpoint to which the DOAS heating coil is controlled. This input is only displayed if a heating coil is specified for a DOAS system.  Values should be less than or equal to 65 oF, and lower than or equal to the ERV Bypass Supply Air Temperature Setpoint.

 

Fuel Type – Menu item available if central furnace or heat pump selected as the heating type. Pull-down menu selections: Natural Gas (default for central furnaces; not available for heat pumps), Fuel Oil, Propane or Electricity (only option for heat pumps).

 

Condenser Type – Menu item available if heat pump is selected as the heating type. Pull-down menu selections: Air (default).  Water source heat pumps and ground source heat pumps are available as options for zone equipment.

 

Calculated Efficiency (Heating) – Auto calculated to remove the supply fan energy and displayed from values entered in the mechanical equipment schedule,  and displayed from values entered in the mechanical equipment schedule. For heat pumps, the efficiency of the heating system in coefficient of performance (COP), which is the ratio of the rate of heat removed to the rate of energy input, in consistent units, for a complete refrigerating system or some specific portion of that system under designated operating conditions.  A maximum value of 8 may be entered; typical COP values for heat pump systems are in the range of 2-5. If central furnace, is selected as the heating source.  For furnaces, enter the percentage of the rate of heat delivered to the rate of energy input.  A minimum of 60% may be entered; typical values are between 74%-92%.  

 

Distribution

 

Distribution Type – Pull-down menu selections:

 

Single Zone – Select if the cooling source and heating source serves a single zone (controlled through a single thermostat). This is the default value for Central DX with Heat Pump.

 

Multiple Zone – Select if the cooling source and heating source serve multiple zones.

 

Terminal Unit – Menu item available if "multiple zone" is selected as a Distribution Type (except DOAS). Pull-down menu selections:

 

Reheat – Select if reheat coils are provided for each individually controlled zone, regulating the temperature of the air being furnished.

 

Parallel Powered Induction Units – Select if parallel powered induction units are installed and in use. These are air system terminal units that mixes varying amounts of secondary (recirculated) air and primary (conditioned supply) air to produce a variable total flow of air to a zone. The unit contains a small fan that acts to induce the secondary air and a heating coil for heating the mixed secondary and primary air. The secondary and primary air streams enter the unit in parallel. The fan sits in the secondary air stream and runs only when the primary air flow fraction is below 0.3 and the fan’s availability schedule is on or it is activated by an availability manager.

 

Series Powered Induction Units – Select if series powered induction units are installed and in use. These are air system terminal units that mixes varying amounts of secondary (recirculated) air and primary (conditioned supply) air to produce a fixed flow of air to a zone. The unit contains a small fan that acts to induce the secondary air and a heating coil for heating the mixed secondary and primary air. The fan runs at a constant volume flow rate whenever the unit is on (and the fan’s availability schedule is on or it is activated by an availability manager). The fan is downstream of the primary and secondary air inlets.

 

Note: for additional information regarding VAV zone terminal unit types, including Powered Induction Units (PIU), see https://designbuilder.com//helpv2/Content/VAV_Terminal_Units.htm.

 

Reheat Source – Menu item available if 'multiple zone' is selected as a Distribution Type (except DOAS). Pull-down menu selections include Gas Fired, Electric Resistance, and Hot Water Plant. See details:

 

Hot Water Plant Loop – Pull-down menu available if Hot Water Plant was selected as the Reheat Source.  Select from previously defined Heating Plant Loops.

 

Calculated Minimum Air Flow Fraction – Displayed from values entered in the mechanical equipment schedule if "multiple zone" is selected as a Distribution Type (except DOAS) and Reheat is selected as the Terminal Unit.  Value is auto calculated and displayed as the ratio of the Minimum Supply Airflow to the Design Supply Airflow.  The minimum zone fraction is normally specified to meet the minimum ventilation requirement for the occupants.


Terminal Unit Equipment Schedule Inputs:

 

Reheat – Yes/No drop down menu option to identify if a terminal unit provides reheat.

 

Damper Control – Drop down menu option available when Reheat is set to ‘Yes’.  Options include ‘Single Maximum’ and ‘Dual Maximum’.  When Reheat Source is ‘Electric Resistance’ or ‘Gas Fired’ this option will be auto set to Single Maximum.  When Reheat Source is ‘Hot Water Plant’, both options are displayed.

 

Design Supply Airflow   

 

Minimum Supply Airflow   

 

Maximum Supply Airflow During Reheat – Available input when Damper Control is set to ‘Dual Maximum’.   Input value should be greater than the Minimum Supply Airflow.

 

Maximum Airflow During Reheat Fraction – Auto calculated field which will display the ratio of the Maximum Supply Airflow During Reheat to the Design Supply Airflow.

   

Fan Systems

 

Enter or select the following required fan system component values when adding an Air Handler Mechanical Equipment Schedule entry:

Total System Fan Power – Auto calculated and displayed from values entered in the mechanical equipment schedule, which represents the value of electric power for all fans (supply, return, relief, exhaust) required to operate at fan system design conditions, divided by the design supply airflow rate (W/CFM).

 

Economizer – Yes/No drop down menu option:  Select 'Y' if an economizer is installed and in use. Available input for all system types except Dedicated Outdoor Air Systems.  An economizer helps to provide free cooling to a building by increasing the intake of outside air when conditions are amenable. The economizer control is modeled as ‘differential dry bulb’ for TSPR buildings. In differential dry bulb control, the economizer will increase the outdoor air flow rate above the minimum outdoor air flow when there is a cooling load and the outdoor air temperature is below the zone exhaust air temperature.

 

Systems with and without economizers can be combined within an air handler serving one or more blocks. Eventually a feature will be added to TSPR tool to calculate a weighted average value for economizer effectiveness based on the rated cooling capacity of the combined systems.

 

Demand Control Ventilation – Yes/No drop down menu option:  Select 'Y' if a demand control ventilation control (DCV) system is installed and in use.  Selecting DCV indicates whether the air loop is capable of varying the amount of outdoor air provided through a system, based on actual number of occupants in spaces.  Note:  if this box is checked, the 'Percent Area DCV Control' must be specified by clicking on the block the Air Handler has been assigned to and entering a value. 

 

Energy Recovery Ventilation – Yes/No drop down menu option available from the Equipment Schedule table, or a Check box on the Air Handler form: Select 'Y' or check the box if an energy recovery ventilation (ERV) system is installed and in use.  Selecting ERV enables a heat exchanger for exhaust air heat recovery. Heat exchanger performance may be specified in the effectiveness fields to exchange sensible energy, latent energy or both between the supply and exhaust air streams. 

 

Systems with and without ERVs can be combined into a single air handling unit serving one or more blocks. The ERV sensible and latent effectiveness should be weighted based on the outdoor air intake of the individual systems. An effectiveness of zero should be assumed for systems with no ERV, when they’re combined with systems with ERV.

 

Input fields available when Energy Recovery Ventilation is selected:

 

ERV Sensible Effectiveness – The sensible heat exchange effectiveness at the heating/cooling conditions.  

 

ERV Latent Effectiveness – The latent heat exchange effectiveness at the heating/cooling conditions. This value can be specified as 0.0 if the heat exchanger does not transfer latent energy.

 

ERV Supply Temperature Control – Used to control the discharge temperature of the ERV to avoid overheating by reducing the wheel speed or opening a bypass damper to maintain a constant ERV supply air temperature.  Select if this control is present and in use.


Heat Exchanger Type Pull-down menu selections include Plate or Wheel.


ERV Bypass Supply Air Temperature Setpoint – Available option if the air loop has ERV and ERV Supply Temperature Control is selected.  Enter a value in °F that is greater than 45 and less than or equal to 65.  


System Fan Power Reduction when ERV Bypassed – Available input if ERV and ERV Supply Temperature Control is selected. Enter a value in W/CFM to specify the reduction in fan power when the air bypasses the ERV core.  This value should be less than the total system fan power. 

 

Fan Control – Pull-down menu selections:

 

Constant Air Volume – Select if the fan systems are supplying the same volume of air at all times, based on the HVAC system operation schedule. 

 

Variable Air Volume – Select if the fan systems vary the air flow rate based on zone heating or cooling demand. This will be the only selection available if the Distribution Type selected is 'Multiple Zone'.

 

Supply Air Temperature (SAT) Reset – Pull-down menu item available if the Distribution Type selected is 'Multiple Zone'. Available input for all system types except Dedicated Outdoor Air Systems.  SAT reset works by automatically changing the supply air temperature setpoint to better meet the zone heating and cooling loads. The setpoint is reset based on either outside air temperature or the cooling demand of the warmest zone.  Select OAT (Outside Air Temperature) or Warmest Zone if SAT controls are present or select none if no SAT reset is applied.


Reset Minimum Setpoint Temperature – Available input if ‘Warmest Zone’ is selected for the SAT Reset.  Value should be between 40-65 oF. 


Reset Maximum Setpoint Temperature -- Available input if ‘Warmest Zone’ is selected for the SAT Reset.  Value should be between 45-70 oF, and higher than the minimum setpoint temperature.


Fan Static Pressure Reset – Check box:  Menu item available if the Distribution Type selected is 'Multiple Zone'.  Static pressure reset works by changing the static pressure set point whenever possible based on the zone cooling demand; thereby reducing the air flow resistance that the AHU supply fans must overcome and hence reducing the fan energy consumption. Select if systems with static pressure reset controls are installed and in use. 

 

Note:  HVAC system control entries other than Economizer and ERV (e.g. Supply Air Temperature Reset, Fan Control and Fan Static Pressure Reset should be the same for all systems that are combined into a single weighted air handling unit.