[L7]_Cooling Loads - Part I

Question 1

IND405

What is the difference between space and system loads?

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Answer 1

Space load calculated include the necessary values to satify the envelope load, but does not account for other heat gains/losses that occur from equipment outside of the envelope.

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Question 2

IND405

(Yes or No) It is possible to have a scenario where HVAC equipment heat gain loads can be larger than the combined space loads of a project?

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Answer 2

Yes.

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Question 3

IND405

List the four (4) common System Loads outside of Space Loads.

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Answer 3

1. Infiltration/Ventilation Load
2. AHU Fan Load
3. Ductwork Load
4. Plenum Load

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Question 4

IND405

What is the most common type of ventilation for existing building projects?
* Natural Ventilation
* Mechanical Ventilation

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Answer 4

Natural Ventilation

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Question 5

IND405

What is the difference between Block & Peak building loads?

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Answer 5

Peak loads mean that the size of the system is based on the total peak CFMs in each room, while block loads mean that the size of the system is based on when the building as a whole is busy.

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Question 6

IND405

To obtain the maximum amount of comfort in a space which is better? Single-Zone T-Stat or Multi-Zone T-Stat

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Answer 6

Multi-Zone T-Stat

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Question 7

IND405

What is the largest heat gain or loss in terms of system loads?
a) Miscellaneous heat gain
b) Ductwork heat gain
c) Outdoor air introduced in mechanical ventilation

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Answer 7

Outdoor air introduced in mechanical ventilation

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Question 8

IND405

What is the purpose of a psychrometric chart?

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Answer 8

To determine the properties of air, such as temperature, humidity, and enthalpy in order to calculate HVAC system loads at specific outdoor and indoor design temperatures.

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Question 9

IND405

What is an economizer cycle?

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Answer 9

A cycle that uses outdoor air to cool a space instead of mechanical refrigeration.

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Question 10

IND405

What is an Air-Barrier?

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Answer 10

A material or system that prevents the movement of air through the building envelope.

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Question 11

IND405

What is an Insulation Barrier?

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Answer 11

A material or system that reduces heat transfer through the building envelope.

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Question 12

IND405

What is thermal bridging?

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Answer 12

The transfer of heat through materials that are poor insulators, such as metal studs or concrete slabs.

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Question 13

IND405

In a window, do you usually want or not a thermal break?

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Answer 13

Yes, you want to include a thermal break to stop heat transfer through the window frame.

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Question 14

IND405

Latent heat gain in a building is caused by which of the following?
A. Solar radiation
B. Ventilation and occupants
C. High thermal mass walls
D. Dark roofs

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Answer 14

B. Ventilation and Occupants

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Question 15

IND405

Match the equation component with its description:
1. U
2. A
3. CLTDCorrected

A. Cooling Load Temperature Difference (adjusted for conditions)
B. Area of the surface being analyzed
C. Overall heat transfer coefficient

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Answer 15

1 = C
2 = B
3 = A

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Question 16

IND405

True/False: The sun is directly overhead at 23.5°S latitude on June 21st.

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Answer 16

False

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Question 17

IND405

What is the typical summer indoor design condition for most comfort systems?
A. 65°F and 60% RH
B. 75°F and 50% RH
C. 70°F and 40% RH
D. 80°F and 55% RH

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Answer 17

B. 75°F and 50% RH

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Question 18

IND405

Calculate the Cooling Degree Days (CDD65) for a day with an average outdoor temperature of 90°F.

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Answer 18

CDD65 = 90°F - 65°F = 25°F

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Question 19

IND405

The equation 𝑄𝑆 = 𝑈⋅𝐴⋅𝐶𝐿𝑇𝐷 𝐶𝑜𝑟𝑟𝑒𝑐𝑡𝑒𝑑 is used to calculate ________.

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Answer 19

Sensible Heat Gain

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Question 20

IND405

True/False: A roof with a U-value of 0.055, an area of 5,478 ft², and a corrected CLTD of 61.5 has a peak hour BTU load of 18,529.33 BTU/hr.

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Answer 20

True

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Question 21

IND405

Which factor influences solar heat gain through windows the most?
A. Thermal mass of the window frame
B. Solar Heat Gain Coefficient (SHGC)
C. Type of window shading
D. CLTD of the exterior wall

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Answer 21

B. Solar Heat Gain Coefficient (SHGC)

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Question 22

IND405

True/False: Solar transmission through glass includes both conductive and radiative components.

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Answer 22

True

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Question 23

IND405

The cooling load for glass radiation transmission is calculated using the equation 𝑄𝐺𝑙𝑎𝑠𝑠𝑆𝑜𝑙𝑎𝑟 = 𝐴⋅𝑆𝐻𝐺𝐹⋅𝐶𝐿𝐹

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Answer 23

True

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Question 24

IND405

Match the ventilation scenario to the space type:
1. Public Restrooms
2. Clean Rooms
3. Operating Rooms

A. Scenario 1 (100% outdoor air)
B. Scenario 2 (exhaust-only)
C. Scenario 3 (high ACH)

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Answer 24

1 = B
2 = A
3 = A

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Question 26

IND405

Calculate the total heat gain 𝑞𝑇 using 𝑄=2,000 CFM, and Δℎ = 25 Btu/lbm.

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Answer 26

qT = 4.5⋅Q⋅Δh
𝑞𝑇 = 4.5⋅2,000⋅25 = 225,000-Btu/hr

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