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 ‘+’ (Add) icon from the Air Handlers sidebar option on the Heating and Cooling screen, or the Add Air Handler button on the Air Handlers tab on the Mechanical Equipment screen  
  2. Enter a descriptive name or use the default component text and counters
  3. Select a System Type.  
  4. Select a Cooling Source and a Heating Source and Fuel Type
  5. Create a new Mechanical Equipment Schedule entry by scrolling back to the top of the screen and entering a descriptive name and number of pieces of equipment and rated capacity and efficiency values. Select the blue ‘Add Equipment’ button to add additional entries. or 
  6. Assign previously created equipment by selecting the Attach icon (paper clip)
  7. Select a Distribution Type; create Terminal Unit equipment schedules for Multiple Zone systems. 
  8. Add or edit values for fan system air flow and power.
  9. Complete remaining inputs for fan systems
  10. Select the green ‘Create’ button to add the new Zone Equipment

 

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.

 

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 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 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.

 

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  minimum flow rate to the zone while the system is operating, specified as a fraction of the maximum air flow rate. The minimum zone fraction is normally specified to meet the minimum ventilation requirement for the occupants.

   

Fan Systems

 

Total System Fan Power – Auto calculated and displayed from values entered in the mechanical equipment schedule, which represents thevalue 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).

 

DOAS Bypass Air Temperature Setpoint – Available when Dedicated Outdoor Air System is selected as the System Type.  The supply air temperature (SAT) setpoint if the DOAS includes supplemental heating or cooling or if it has an energy recovery ventilation system which includes supply air temperature control. 

 

Economizer – Check box: Should be checked 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 – Check box: Should be checked 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.  

 

Energy Recovery Ventilation – Check box: Should be checked 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 checked:

 

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 Economizer Bypass Control – Used to optimize the use of heat recovery by disabling the heat recovery any time the controller determines that the economizer is active.  Select if this control is present and in use.

 

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.

 

System Fan Power Reduction when ERV Bypassed – Enter a value in W/CFM to specify the reduction in fan power when the air bypasses the ERV core.

 

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.

 

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.