HVAC Component Sizes

Duct Sizing

After heating and cooling methods were determined, the ducts that would supply the treated air were sized. First, the building was broken into two zones. Zone 1 includes the dining hall, the restrooms, the office, and the break rooms. Zone 2 includes the restaurant kitchen and the entire bakery. Figure 1 below displays the two separate zones as they were divided for the eQuest analysis. It should be noted that the zones are not separated due to the exact floor plans, but they do match the total square footage of each are and are located in the correct sections of the building.

Figure 1:

To determine the total CFM required for each room, Mechanical and Electrical Equipment for Buildings (Stein, 2006) and ASHRAE 90.1 standards were used to come up with accurate CFMs required per person for our building type. These values were compared to the values that were proposed by the original HVAC Program and were determined to be accurate values to use. The maximum occupancies were slightly increased to create a more conservative design. The total CFM required was calculated by multiplying the CFM/Person and the maximum occupancy. The velocity of the air was determined to be 500 feet per minute for a comfort system category air supply.* Now that the total CFM per room and per zone were established, a duct designer developed by Loren Cook Company was used to calculate the dimensions of each major duct and branch duct. A summary of these results and conclusions can be seen below in Table 1.


Table 1:

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Equipment Sizing

In order to determine the required sizing information for the heating and cooling equipment, the building was modeled in eQuest Energy Analysis. The results yielded a peak heating load of 160,540 Btu/hr and a peak cooling load of 20.34 kW. Figure 2 displays the graphs used to determine the peak loads which occur in the months of January and July, respectively.


Figure 2:


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These values were used to determine the results in Table 2: Heating Loads and Table 3: Cooling Loads which are displayed below.

Table 2:


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Table 3:


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The sizing loads were then used to determine what capacity equipment would be necessary. These values were determined by increasing the calculated load by 30% as recommended. The air handling unit was sized by taking the total required CFMs and applying a 30% increase which results in 4381 CFM. The air handler, chillers, and furnace were each increased to an appropriate size that is sold commonly in industry. The final sizing is summarized in Table 4.

Table 4:


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Cost Analysis

eQuest was also used to determine the expected utility cost of the building. Equipped with the previously mentioned equipment and using the gas and electric rates provided by Professor James Mitchell, the building’s utility costs will follow the pattern that can be seen in figure 3.


Figure 3:

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The expected total energy cost per year is $13,311 which is equivalent to $3.15 per square foot, per year.




Mechanical and Electrical Equipment for Buildings 8th Ed., 2006. Stein; Reynolds; McGuiness



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