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Commercial HVAC Equipment 4th year ILM 110405a > Commercial HVAC Equipment 4th year ILM 110405a > Flashcards

Commercial HVAC Equipment 4th year ILM 110405a Flashcards

1
Q

What does DDCV stand for?

A

Dual duct constant velocity system

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2
Q

What does DDVAV stand for?
________________________

A

Dual duct variable-air-volume system

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3
Q

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

A

DDCV or dual duct constant velocity

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4
Q

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

A

The hot deck

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5
Q

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

A

The cold deck

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6
Q

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

A

Constant volume supply Fan

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7
Q

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

A

the difference is that the air is not drawn into building by a constant volume fan as it is in the usual dual-duct system, but it is split into two air streams that flow through two variable volume fans.

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8
Q

What can the mixing boxes do for the DDVAV system?
________________

A

it serves each thermal zone, these mixing boxes can vary both the proportions of hot and cold air as well as the total flow rate of air to the zone.

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9
Q

What does MUA stand for?
___________________

A

make- up air unit.

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10
Q

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

A

poor air flow, undesirable continuous air-pressure difference between the inside and the outside of the home.

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11
Q

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

A

cold air infiltration, increase of energy.

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12
Q

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

A

yes

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13
Q

What are the two types of MUA systems?
___________

A

Direct gas fired and indirect gas fired

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14
Q

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

A

no

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15
Q

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

A

gas burners are installed directly int he outside make-up air stream, supplied to the building or process.

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16
Q

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

A
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17
Q

What is the isolation damper used for in a DFMUA?

A

to prevent cold air from dropping through a unit into a warm building and warm air from escaping through a unit during colder months when it is not in operation.

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18
Q

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

A

the damper actuator motor.

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19
Q

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

A
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20
Q

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

A

velocity range 2500 to 3200 fpm.

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21
Q

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

A

between 10 celsius and 38 celsius

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22
Q

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

A
  1. flame proving sensors
    2.high velocity air switches
  2. low velocity air switches
    4.high temperature limit
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23
Q

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

A

when the velocity of air flowing through the unit becomes too high.

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24
Q

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

A

when the velocity of the air is lower than than the set value.

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25
Q

What is the specific velocity range for proper combustion?
___________________________________________

A

2500-3200 fpm

26
Q

What is the discharge air temperature range for a DFMUA?
___________________________

A

10 and 38 celsius.

27
Q

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

A

valve train

28
Q

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

A

has a sealed combustion chamber.

29
Q

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

A
30
Q

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

A
31
Q

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

A
32
Q

List the components of a heat pump.
________________________________________________________________________
________________________________________________________________________
_______________________________________________________________________

A
33
Q

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

A
34
Q

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

A
35
Q

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

A
36
Q

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

A
37
Q

What does EES stand for?
_________________________________________________

A
38
Q

List the possible residential heat pump loop systems.
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
__________________________________________________________________

A
39
Q

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

A
40
Q

What are the two types of energy recovery systems?
________________________________________________________________________
________________________

A
41
Q

What does an HRV do for a building?
________________________________________________________________________
________________________

A
42
Q

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

A
43
Q

Can an HRV be used in the summer months?

A
44
Q

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

A
45
Q

An HRV is designed to remove excess what?*
___________

A
46
Q

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

A
47
Q

An HRV is designed to remove excess what?*
________________________

A

moisture

48
Q

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

A
49
Q

Are there filters used in the HRV units?
_________________________________

A
50
Q

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

A

stand alone system
forced air duct system

51
Q

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

A
52
Q

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

A
53
Q

When the installation of an HRV system is completed, what should be done to the
system at start up?

A
54
Q

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

A
55
Q

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

A

can cause moist air to be pushed into the walls and roof of the house where it can condense and lead to deterioration of building materials.

56
Q

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

A

yes, for most circumstances

57
Q

Can an HRV be used for an air cleaner?

A

no

58
Q

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

A

-5 celcius

59
Q

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

A
60
Q

What does ERV stand for?
________________________________________________________________________

A

energy recovery ventilator

61
Q

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

A

the way the heat exchanger works, with ERV the heat exchanger transfers a certain amount of water vapor along with heat energy, while a HRV only transfers heat.

62
Q

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

A

type A silica gel

Commercial HVAC Equipment 4th year ILM 110405a (1 decks)

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