F-1: Hydraulic System Loads Flashcards
What does TECA stand for?
Thermal Environmental Comfort Associations (of BC)
What is TECA?
- Not-for-profit trade associations of contractors, manufactures wholesalers / agents of heating + cooling equipment
What does RHWHA stand for?
Residential Hot Water Heating Association (of BC)
What is the main purpose of a building’s heating system?
Provide comfort
What is the definition of comfort?
A person feels neither too hot or too cold
How does one achieve comfort?
Body can dump heat at the same rate as heat gained from environment
What are the heating professionals job?
Provide a constant, uniform temp within the building
What are the 5 ways the human body loses heat?
1) Radiation
2) Convection
3) Evaporation
4) Conduction
5) Respiration
How much body heat is lost via thermal radiation?
48%
What is Radiation?
Is the transfer of heat via infra-red waves
Warm –> cold object
What is Cold 70?
When there are 2 temperatures felt in the same room even though the air temp is the same.
What is Convection?
heat lost through air currents
30% body heat loss
What is Conduction?
Heat loss through touch
Sticking a metal rod in a fire and touching the cool end
- losses are min
How is heat lost through Evaporation?
Sweating
22% body heat is lost
How is heat lost through respiration?
Breathing
- very min (not even considered)
What is the highest of all methods of heat loss?
Radiation
What is the Ideal Heat curve?
Heat is warmer at the floor and cooler as it raises…
Floor temps= 80F (skin temp) -> 68F at 5 feet
How do forced air systems operate?
as one big zone
Where is a thermostat usually located?
Hallway or central part of the house
Which side of the house is usually colder? The south or north side?
North side
How is Heat described / measured?
By intensity and quantity
What is happening when the end of a metal rod is stuck in a fire?
Fire end = quantity of heat
Going to cold end = intensity of heat (temperature)
Heat transfer via conduction
How is the quantity of heat measured?
BTUs
BTUH (BTU per hour)
Define BTU
the quantity of heat required to raise the temp of 1 lb of water by 1F
What is the temperature differential that Boilers operate on?
20F
What does a storage type water heaters operate on?
90 - 100F
What must the return temp of water be of a non-condensing boilers?
140F
Why does it have to be 140F?
To keep condensation from forming on the external surface of a heat exchanger
What kind of problems would condensation cause?
corrosion
sooting
cooling of flame
plugged heat exchangers premature failure
Why are heat loads always considered BTUH?
Heat quantities are expressed within a 1 hour time frame
True or False: Water can hold more heat than air
True
What is 1 cubic foot of air in BTUs?
0.018 BTU
What is Zoning?
applying heat to only certain areas of a building
What is the downside of Hydraulics when compared to air?
Hydraulics has more controls / valves
How does a building lose heat (via the 5 types of heat loss)
Radiation
Conduction
Convection
Thermal conductors (aka conductors) allow heat to what?
Move through them easily
Glass, metal and concrete are known as what?
Conductors
Does heat move easily through Insulators?
No
What are some good types of insulators? (3 points)
Fiberglass batts
Polystyrene board
Spray foam
Is Air considered a good insulator?
Yup
What is dead air space?
the space between sealed glass panes
What is dead air space filled with?
Argon gas (inert gases)
increases insulation values
What do the “R”, “K”, and “U” values of materials represent?
Thermal resistance or conductivity
What happens to the rate of heat transfer when the temp differential is doubled?
The rate of heat transfer will also double
What happens to the rate of heat transfer when the temp differential is halved?
The rate of heat transfer will also be halved
What does IDT stand for?
Indoor Design Temp
What does ODT stand for?
Outdoor design temp
What does IDT and ODT represent?
Both represent the temp differential used in heat loss calculations for buildings
What is the min IDT for indoor living spaces?
22C - 72F
What is the min IDT for unfinished basements?
18C - 64F
What is the min IDT for heated crawl spaces?
15C - 59F
What is the temp most designers use for all heated areas of residential buildings?
72F
What does the ODT use as a value?
The January 2.5% value
What is the January 2.5% value?
It is the LOWEST expected temp, all but 2.5%, of what is considered the coldest month of the year
Why do we find the temp difference between the IDT and ODT?
The value is used when estimating the building heat loss
True or False: Buildings gain heat the same way they lose it.
True
What is “dry bulb”?
ambient air temp
What is transmission loss?
Heat loss via conduction
What does “R” value signify?
thermal resistance
What does R values indicate?
the number of hours it would take 1 BTU to pass through 1ft2 of material when the temp diff between two sides of the material is 1F
R = 12hrs/btu/ft2/1F
Why do we have to turn the R value into a K value?
In order to do calculations we need to have BTU per hour NOT hour per BTU
True or False: We always round BTUs to whole number
True
K values are used as what only?
Single material
True or False: Every material used in construction has an R value attached to it.
True
How do we find “U” value?
1) Add up all the “R” values
2) Divide the sum into the U value (aka 1)
What is the K and U an expression of?
materials ability to conduct heat through it.
What are K and U values expressed in?
BTUH
What is R value an expression of?
materials resistance to the flow of heat through it.
What is R value expressed in?
Hours / BTU
Why are we interested in coming up with a U value?
So it can be used in a formula to give us BTUH heat loss
The lower the U value =
The better the insulator
When calculating transmission loss, only surfaces that separate a heated space from the outdoors have to have heat losses calculated for them.
Yes
What is an Unconditioned space?
when a floor, ceiling or wall has a heated room behind it.
What are Exposed walls?
Walls that separate heated (conditioned) spaces from the outdoors
When will Ceiling losses be counted (in transmission loss)?
for rooms on a top floor
Ceilings are listed into 2 categories, what are they?
1) roof w/ attic space - resi construction w/ trusses
2) built up roof, no attic space - flat or vaulted roofs
When will floor spaces be counted?
If they are located over unheated space (carport)
What is Thermal Bridging?
It’s when an area / object has a higher thermal conductivity than the surrounding materials.
What does thermal bridging create?
a path of least resistance for heat transfer
What is thermal bridging also called?
Cold bridging
Thermal bypass
Any area where there isn’t a continuous, unbroken layer of insulative material is considered what?
Thermal break
What % can thermal breaks account for?
30%
What is Slab edge loss?
A calculation used for slab on grade construction
How do we reduce thermal bridging in slab on grade construction?
By using a strip of polystyrene
sandwich it bn the two concrete masses
What is rigid polystyrene XPS) used for?
it’s commonly attached to the outside of the foundation wall (with a sheet of galvanized sheet metal) to reduce heat loss via concrete to soil/ outside air
What happens if a basement concrete floor is more than 2 feet below grade?
a downward loss should be calculated.
What is Infiltration losses?
when heated interior air escapes outdoors or cold outside air forced into living space.
- Is a heat loss dt convection
What is heat loss infiltration?
Inward flow
What is heat loss exfiltration?
Outward flow
What is infiltration / exfiltration?
uncontrolled air leakage through joints in construction / cracks around windows
What causes Infiltration?
wind and stack - stack driven pressure differentials.
What does infiltration rates depend on?
Climate / tightness of construction
What does ASHRAE stand for?
American Society of Heating, Refrigeration and Air Conditioning Engineers
What rate determines a tight or airtight construction?
<0.5 air changes / hour
What is “piping tax”?
heat loss through the piping
What is “warm-up allowance” or “pickup allowance”?
The additional capacity needed for start-up of a cold system
