Commercial HVAC Equipment

Question 1

What does DDCV stand for?

Answer 1

Dual Duct Constant Velocity

Question 2

What does DDVAV stand for?

Answer 2

Dual Duct Variable-Air-Volume

Question 3

Which system supplies heating and cooling at the same time through separate ducts to the zone?

Answer 3

Dual Duct Constant Velocity (DDCV) system

Question 4

The duct (DDCV system) that holds and uses the heating coil is known as?

Answer 4

The Hot Deck

Question 5

The duct (DDCV system) that holds and uses the cooling coil is known as?

Answer 5

The Cold Deck

Question 6

Which part of the DDCV system varies the hot and cold air streams to a given space?

Answer 6

The dual duct box

Question 7

What is the biggest difference between a “constant volume dual duct system” to a “variable air volume dual duct system”?

Answer 7

The air is not drawn into the building by a constant volume fan and DDVAV is split into two airstreams that flow through two variable volume fans, where as DDCV has one airstream.

Question 8

What can the mixing boxes do for the DDVAV system?

Answer 8

They can vary both the proportions of hot and cold air as well as the total flow rate of air to the zone.

Question 9

What does MUA stand for?

Answer 9

Makeup Air Unit

Question 10

What happens to the building if the exhaust fan is in operation and there is no air being replaced?

Answer 10

The building experiences a negative pressure

Question 11

What would be an indicator of negative pressure in a building?

Answer 11

Back drafting of combustion appliances such as gas hot water heater or furnace. … A musty smell or stagnant, stale air. A rush of air or draft when opening an exterior door. Exhaust fans not working properly.

Question 12

Are there filters used in a make-up air unit?

Answer 12

Yes

Question 13

What are the two types of MUA systems?

Answer 13

Direct gas fired and indirect gas-fired

Question 14

Is there a heat exchanger installed in a Direct Fired make up air unit?

Answer 14

No

Question 15

Where are the products of combustion discharged into from a DFMUA?

Answer 15

Discharged into the makeup airstream and supplied to the building or process.

Question 16

When referring to a recirculating direct fired MUA, where is the return air damper located compared to the burner?

Answer 16

Right behind the burner

Question 17

What is the isolation damper used for in a DFMUA?

Answer 17

Prevent cold air from dropping through a unit into a warm building.

Question 18

What helps prevent the burners from operating if the dampers are not fully open?

Answer 18

The damper actuator motor end switch

Question 19

The air that is flowing past the burner comes from where in a DFMUA?

Answer 19

Outside

Question 20

What is the average range of air that needs to pass the burner for proper burner combustion?

Answer 20

2500 to 3200 fpm

Question 21

What is the average discharge supply air temperature for a direct fired MUA?

Answer 21

Between 50 degrees F (10 degrees C) and 100 degrees F (38 degrees C)

Question 22

List the common safety components that could be included in a MUA.

Answer 22

Flame proving sensors, high velocity air switches, low velocity air switches, and high temperature limit

Question 23

When would a high velocity Air Switch open for a DFMUA?

Answer 23

When the air flowing through the unit becomes too high

Question 24

When would a low velocity Air Switch open for a DFMUA?

Answer 24

When the air is lower than the set value

Question 25

Main gas shut off, pilot gas manual valve, pilot solenoid valve, main gas pressure regulator, are a part of what in the DFMUA?

Answer 25

The housing

Question 26

What does an indirect fired make up air have that a direct fired make up air does not?

Answer 26

A heat exchanger

Question 27

What is the substance that a heat pump uses to transfer heat from one place to another?

Answer 27

Refrigerant

Question 28

Will the evaporator coil in a heat pump absorb heat or release heat from its surroundings?

Answer 28

Absorbs heat

Question 29

What is the main difference between a standard cooling system and heat pump?

Answer 29

The heat pump cycle is fully reversible and can provide heat in the winter and cooling and dehumidifying in the summer.

Question 30

List the components of a heat pump.

Answer 30

Refrigerant, reversing valve, coil, evaporator, compressor, expansion device, plenum, and suction line accumulator

Question 31

Which component of a heat pump reverses the refrigerant flow to change from heating to cooling mode?

Answer 31

The reversing valve

Question 32

Which device lowers the pressure of the refrigerant in a heat pump system?

Answer 32

The expansion device

Question 33

What happens to the efficiency of the heat pump when there is frost build up?

Answer 33

Decreases reducing its ability to transfer heat to the refrigerant.

Question 34

The indoor coil should be installed where when using a forced air gas furnace?

Answer 34

The warm downstream side of the furnace

Question 35

What does EES stand for?

Answer 35

Earth Energy Systems

Question 36

List the possible residential heat pump loop systems

Answer 36

Open loop systems, closed loop systems, domestic hot water heating systems, supplementary heating systems, heat distribution systems

Question 37

Where is the heat absorbed from in an open loop system?

Answer 37

Ground water from a conventional well

Question 38

What are the two types of energy recovery systems?

Answer 38

Open system and closed system

Question 39

What does an HRV do for a building?

Answer 39

It captures the heat from a buildings exhaust air and transfers it to the fresh air entering the building.

Question 40

When looking at an HRV, do the two air streams, the exhaust air and fresh air, come into contact with each other?

Answer 40

No

Question 41

Can an HRV be used in the summer months?

Answer 41

Yes but its more important to use in colder climates

Question 42

What happens if there is frost buildup inside the HRV’s heat exchanger?

Answer 42

Its defrost mechanism comes on

Question 43

An HRV is designed to remove excess what?

Answer 43

Heat

Question 44

At what temperatures do the efficiencies of an HRV become negligible?

Answer 44

20 degrees F (-7 degrees C)

Question 45

Are there filters used in the HRV units?

Answer 45

Yes

Question 46

What are the two different types of duct systems an HRV can be installed?

Answer 46

A stand alone system and a forced air duct system

Question 47

What are the three different methods that an HRV duct system can be installed?

Answer 47

Fully ducted systems, simplified systems, and exhaust-ducted systems—fully ducted systems are best

Question 48

What type of HRV duct system would be used for radiant heating?

Answer 48

Stand alone system

Question 49

What kinds of problems could there be if there is a negative pressure in the house?

Answer 49

Can cause spillage of carbon monoxide and other combustion by products.

Question 50

What kinds of problems could there be if there is a positive pressure in the house?

Answer 50

Causes moist air to be pushed into the walls and roof.

Question 51

Could the low speed operation of an HRV system meet the ventilation requirements?

Answer 51

Yes

Question 52

Can an HRV be used for an air cleaner?

Answer 52

Yes

Question 53

What is the approximate temperature that the HRV will activate the Defrost cycle?

Answer 53

23 degrees F (-5 Degrees C)

Question 54

What is another way of preventing frost build up in the HRV?

Answer 54

By using dampers

Question 55

What does ERV stand for?

Answer 55

Energy recovery ventilation

Question 56

What is the biggest difference between an HRV to an ERV?

Answer 56

The rotating enthalpy wheel on the ERV

Question 57

What is the material used for the ERV’s heat wheel to transfer water molecules to the other air stream?

Answer 57

Type A silica gel