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Flashcards in Load Calcs Deck (22)
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1

Space Cooling Loads

Building Envelope Loads (heat gain gain thru windows, walls, roofs, etc.) and Internal Loads (people, lighting, & equipment)

2

System Loads

Fan heat gain (from fan & motor), plenum heat gain (from RA) and ventilation load (cooling load from warmer OSA)

3

Cooling Coil Load

Is the summation of space cooling loads, internal loads and system loads

4

Heating Loads

Heat loss that occurs from building envelope loads, ventilation air and infiltration of unwanted OSA. Credits for internal and solar gains are NOT accounted for. Normally assumed as worst case condition and all gains are ZERO.

5

Design Day

The "worst case" day for your air conditioning loads. The "worst case" hour of this day determines equipment capacity, fan sizes, and subsequently duct sizes.

6

Comfort zones for most commercial Bldgs.

Heating setpoint from 68 to 70°F
Cooling setpoint from 73 to 75°F

7

Wet Bulb

Moisture content in the air

8

What is a Zone?

spaces with thermostatic controls and can be a single space or a group of similar spaces.

9

Zoning General Rules

1) Perimeter spaces zoned separately (10-15 for open office perimeter)
2) Perimeter spaces with different exposures are zoned separately.
3) Corner rooms have their own zone
4) Large assembly spaces have their own zone)
5) 4-5 similar enclosed office spaces can be combined

10

U-Value

Describes the ability of a building material to conduct/transfer heat. Takes the entire assembly into account. It's the reciprocal of R-value that measures the materials resistance to heat.

11

U-Value

Describes the ability of a building material to transfer heat. Takes the entire assembly into account. It's the reciprocal of R-value that measures the materials resistance to heat.

12

SC

Shading coefficient. Given to us by glazing manufacturer. Measures the amount of solar heat gain through glass relative to a 1/8" clear pane. Values range from 0 (black/opaque) and 1 (clear)

13

SHGC

Solar heat gain coefficient is a fraction of the radiation that enters the building thru glazing. It's what we feel.

14

Usage Diversity

Plug loads/Electric Loads are generally 50% less than nameplate value due to usage diversity.

15

Where to find common misc. eq loads

ASHRAE Fundamentals Handbook.

16

Where to find common misc. EQ loads

ASHRAE Fundamentals Handbook.

17

How much cfm per person/sq.ft. is required

15 cfm

18

How much cfm per person/sq. ft. is required

15 cfm

19

Peak Load / Peak Zone Load

Used to size HVAC equipment at zone level. Think VAV boxes, FCUs, or heat pumps.

20

System Block Loads

Is based on when the peak occurs for all zones combined. Will always be less than or equal to the sum of peak loads.

21

Why is the system block load not the summation of all peak zone loads?

Peak zone loads may not all occur at the same time. An example would be zones with different solar exposures.

22

Safety factor

Provides spare capacity for central systems. Typically 0-10% for cooling and air systems and 10-30% for heating systems. Only used once in calculation. Not at zone level or in assumptions.