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method.  Constant control for ventilation will be used so the system uses 3142 CFM of outdoor air
at all times. Ventilation dampers are closed during the unoccupied period and the damper leak rate is
5%.
" Cooling Coil. The system provides a constant 55 F supply air temperature to zone terminals. The
DX cooling coil is permitted to operate in all months. The bypass factor for the cooling coil is 0.050
which is representative of the type of equipment we expect to select.
" Preheat Coil. The rooftop unit contains a preheat coil to maintain minimum supply duct
temperatures during the winter. The preheat coil is located downstream of the point where return air
and outdoor ventilation air mix. The preheat setpoint is 52 F. The gas-fired heat exchanger in the
rooftop unit is used for this purpose. The coil is permitted to operate in all months.
" Supply Fan. The supply fan in the rooftop unit will be forward curved with variable frequency
drive. The total static pressure for the system is estimated to be 3 in wg. The overall fan efficiency
is 48%. The coil configuration is draw-thru.
" Return Air Plenum. The system uses a return air plenum. It is estimated that 70% of the roof load,
20% of the wall load and 30% of the lighting load is removed by plenum air.
" Zoning. A zone is a region of the building with one thermostatic control. One zone will be created
for each classroom. The music room and its adjacent office, storage room and practice room will all
be part of a single zone. Each corridor and each vestibule will also be zone. Therefore, a total of 11
zones will be created: one each for the six classrooms, one for the music room, two for the corridors
and two for the vestibules.
" Thermostats. Thermostat settings of 74 F occupied cooling, 85 F unoccupied cooling, 72 F
occupied heating and 60 F unoccupied heating will be used in all zones. The throttling range will be
3 F. The schedule for fan and thermostat operation for the design day will designate 0700 through
2100 as  occupied hours. This covers both the 0700-1700 operating hours for the school and the
1800-2100 period when custodial staff is present. All other hours will be  unoccupied . This profile
applies for the school year which runs from August through June. During the shutdown month of
July all hours will be designated as  unoccupied . Schedule data is shown in Figure 3.5.
" Supply Terminals. Nine of the eleven zones use parallel fan powered mixing box terminals with 0.5
in wg total fan static, 50% overall fan efficiency and a 110 F heating supply temperature. The two
vestibule zones use a VAV air terminal and a fan coil heater located in the space. Minimum supply
airflow for the terminals is based on ASHRAE Standard 62 requirements - 15 CFM/person for the
classrooms, 0.10 CFM/sqft for the corridors and vestibules and 803 CFM for the music room since it
contains rooms with three different space usage types and therefore three different ventilation
requirements. The heat source for the reheat coils is electric resistance.
" Sizing Criteria. Required zone airflow rates will be based on the peak sensible load in each zone.
Required space airflow rates will be based on peak space loads for the individual spaces. A safety
factor of 10% for cooling loads and 20% for heating loads will be used in calculations.
HAP Quick Reference Guide 3-5
Chapter 3 System Design Example Problem
3.4 ENTERING DATA
After weather, space and HVAC system data has been gathered, it is entered into HAP. This is the third
step in the design process. The procedure for entering data into HAP is presented below in a tutorial
format.
1. Program Setup
" (Optional) If you are running HAP, it may be helpful to switch to System Design mode before
entering data. This hides energy analysis inputs from view and simplifies the user interface. To
switch to System Design Mode, choose  Options on the View Menu, click on the Other Options
tab and then uncheck the  Enable Energy Analysis Features check box. This feature is only
available in HAP and not in HAP System Design Load.
2. Create a New Project
" (Optional) If you only wish to view this example rather than entering all the data yourself, you
can use archive data for the example problem which is provided on the HAP CD. To use this
archive file:
Copy the Example.E3A file from the \Example folder on the CD to the \E20-II\Archives
folder on your computer.
Using Windows Explorer, right-click on the Example.E3A file after it has been copied.
Select the  Properties option on the pop-up menu that appears. On the Properties dialog
that appears, uncheck the  Read-Only check box. Then press OK.
Run HAP. Use the New option on the Project Menu to create a new untitled project. Then
use the Retrieve option on the Project Menu to retrieve the data from the Example.E3A
archive. Finally use the Save option on the Project Menu to save the project. Use the project
name  Example Problem .
Skip to step 3 below.
" If you will be entering example problem data yourself, choose New on the Project menu. This
creates a new project. A project is the container which holds your data. The new project you
create will contain data for the example problem.
" Then choose Save on the Project menu. Because you are saving the project for the first time, you
will be asked to specify a name for the project. Use  Example Problem as the project name.
From here on, save the project periodically.
3. Enter Weather Data
" Click the  Weather item in the tree view in the main program window. A  Weather Properties
item appears in the list view.
" Double click on the  Weather Properties item in the list view. The Weather input form will
appear.
" From the drop-down lists on the Weather form, choose data for United States / Illinois /
Chicago IAP. Also select design cooling months of May through November, and specify
daylight savings time from April 7 through October 26. Design parameter input data for the
example problem is shown in Figure 3.2.
" When finished entering this data, press the OK button on the Weather input form to save the data [ Pobierz całość w formacie PDF ]