HVAC 2

Question 0

What is external combustion air?

Answer 0

Air that is brought in from outside to aid in the boilers combustion… So that it doesn’t waste the warm and humidified building air

Question 1

What is the plant?

Answer 1

This is the place where the warm or cool water or air is created, usually in the mechanical equipment room

Question 2

What is a downdraft furnace?

Answer 2

When the flow of forced air travels down words, reversing the flow natural for gravity

Question 3

What is a lowboy?

Answer 3

When the furnace is reduced to 5 feet in height so that it can fit in a big closet or attic

Question 4

Which way does heat flow in a condenser and which way does heat flow in an evaporator?

Answer 4

Evaporation takes the heat… Eva takes the heat

Condensation releases heat

Question 5

What does an evaporator of chiller do? And what is it often called?

Answer 5

It releases the latent heat of evaporation and dissipates it into the surrounding outside air… It is often called a cooling tower

Question 6

What is a blowdown and why does it exist?

Answer 6

It is a small valve in the base of the cooling tower which drains off dirt and minerals. Dirt and minerals are there because the loss of water in evaporation requires that water must be added, and that water usually include stirred and minerals, which when evaporated get left behind.

Question 7

What is an economizer cycle?

Answer 7

This refers to seasonal adjustments in the source of cool air.

… Could be a pond water in the early winter in late spring… Could be cool enough air from outside

Question 8

Why is it called the COP or coefficient of performance… And not simply efficiency?

Answer 8

This is because he pumps do not create energy, they just move it from one place to another.

COP = energy delivered/energy used
Efficiency also = energy delivered/energy used

Question 9

There are only three basic categories of HVAC distribution systems. What are they?

Answer 9

Electrical, hydronic, and forced air

Question 10

Describe the cost variation of an electrical HVAC system. What is the archetypal system?

Answer 10

Lowest first cost but highest lifecycle cost. Think of a radiant system… It’s advantage is that it can be turned on in selective rooms

Question 11

Talk about a one pipe system, a two pipe system, the three pipe system, and a four pipe system!

Answer 11

The one pipe system has one line, and this means each register it’s excessively colder on the way back to the boiler.

A two pipe system can deliver to registers directly and then return from those registers, combining the return to the same boiler.

A four-pipe system allows you to heat and cool… It’s basically two separate two pipes.

A three - pipe is like a four-pipe, but it combines the returned water…. Cheaper initial piping but more expensive as the boiler and chiller deal with combined temps

Question 12

What is a cold air register?

Answer 12

A return air register

Question 13

What can an HVAC system due to eliminate infiltration in the building?

Answer 13

Positively pressurize the building, by running the supply fan at a greater rate than the sum of the return air fan rate and the leakage rate of the building

Question 14

What is the deck temperature?

Answer 14

That is the temperature of the air right as it is leaving the equipment room.

Question 15

In a supply duct, exterior insulation is used for _____ _____, while interior insulation is used for ______ _____. Usually.

Answer 15

Temperature control. Noise control.

Question 16

Put all your ducts in a row.

Answer 16

1. Single duct
2. Dual duct
3. Multizone
4. Fan coil unit
5. Variable air volume

Question 17

What the term unitary system mean?

Answer 17

If anyone of a number of systems which act on their own to condition separated spaces… Are zones very spread out? Do you need separate heating bills? Etc

Question 18

A heat pump system is just a… And a heat sink is just…

Answer 18

Just a group of heat pumps serving a building. And the heat sink is water circulated throughout the building.

Question 19

What does the term induction refer to?

Answer 19

Any system where a small amount of supply air at a very high velocity is delivered to a box unit and mixed with air brought in from the room, which induces a greater airflow than just that little bit of supply air delivered.

Question 20

What is another term for a squirrel cage blower?

Answer 20

A centrifugal fan

Question 21

There’s basically three kind of filters you can use in an HVAC system. What are they?

Answer 21

Fibrous filters. They remove a lot of dust and lint but they must be replaced regularly.

Electrostatic filters. More expensive, producing less resistance to air movement, they can be cleaned and washed.

Activated charcoal filters. Remove odors and chemicals, only used when this is necessary. They block the flow of air. They must be replaced regularly.

Question 22

What percentage of the total building does the mechanical room take up?

Answer 22

5% to 10% of the total floor area of the building

Question 23

How many BTU would it take to melt a ton of ice over 24 hour period?

Answer 23

12,000 BTU hours

Question 24

What is the formula for sizing a duct?

Answer 24

A = 144*Q_cfm/v

Where:

A is the cross sectional area
Q_cfm is the flow rate in cubic ft/min
v is the velocity measured in feet per minute

Question 25

How do you determine Q_cfm?

Answer 25

Q_cfm = q_tot / 1.08 (T_eq - T_i)

Where:

q_tot is the total thermal load in BTU hour
T_eq is the temperature of the air supplied in the duct (55° for cooling or 140° for heating)
T_i is the desired interior temperature for the room

Question 26

What is the equivalent circular diameter?

Answer 26

That’s the diameter that a duct would be if it were circular… And if it were it would be the most efficient shape

Question 27

The definition of benchmarking

Answer 27

Numbers that represent the total energy consumption in BTUs per square foot for various kinds of buildings in the US… Obviously over a certain time period.

Question 28

What is commissioning? And who requires that?

Answer 28

And organize process to ensure old building systems perform interactively according to the architectural engineering and client intent.

LEED requires it.

Question 29

What does groundwater aquifer cooling and heating utilize?

Answer 29

The differential thermal energy in water from an underground well, cooling a building in summer, heating a building in winter.

Question 30

What does geothermal energy use?

Answer 30

Heat contained within the earth surface, like underground geothermal springs are lava formations.

Question 31

In theory what does a fuel cell do?

Answer 31

Combines hydrogen and oxygen to produce electricity, heat, and water… But it’s not cost-effective

Question 32

What is biogas?

Answer 32

Gas from biomass