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PE 4B > Unit 10 HVAC fundamentals For Facility Operators > Flashcards

Unit 10 HVAC fundamentals For Facility Operators Flashcards

1
Q

Ventilation process

A

Supplies air or removes air from a space.

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2
Q

Filtration process

A

Removes particles from the air

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3
Q

Humidification process

A

Controls the humidity of the air

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4
Q

Air conditioning

A

Collectively; Heating, cooling, filtration, ventilation, and humidification

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5
Q

Exhausting air is important because

A

Air may contain odours, excess humidity, CO, and other contaminants which may affect people’s health

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6
Q

Building changes per hour

A

Each building is required to change the air in the building. Measured in m3/hour

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7
Q

To increase building efficiencies, a percentage of building air is

A

Exhausted to the outside, and a percentage is recirculated back to the building

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8
Q

HVAC systems usually include;

6

A

Fans, filters, ducting, heating coils, cooling coils, humidity control

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9
Q

The purpose of a HVAC is to

A

Improve the comfort of the people occupying the building space.

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10
Q

Factors that influence human comfort

4

A

Temperature, humidity, air quality, air movement

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11
Q

Air quality

A

Odours, particulate, and other conditions that affect human health

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12
Q

Air movement

A

Refers to the velocity, noise, drafts, and air circulation

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13
Q

Fixed louvres

A

Used to redirect airflow, causes rain or snow to fall out of air suspension

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14
Q

Dampers

A

Used to control air flow

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15
Q

Finned heating coils

A

They use steam to heat the air. Steam circulates through the coil and heats the air that travels around the coil. Steam condenses inside the coil, and returns back to the boiler

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16
Q

Finned cooling coils

A

May use chilled water to cool the air. Water circulates through the coil, and removes heat from the air that travels around the coil. Warm water leaves the coil and returns back to chiller

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17
Q

Humidifiers

A

Add water to the air by pumping water and injecting it into the air flow using sprayer nozzles

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18
Q

Air diffusers

A

Directs the flow of air into the space without creating draft

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19
Q

Fans

A

Mechanical devices that cause air flow or movement

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20
Q

Return air

A

Percentage of exhaust air that returns from the building back to the HVAC system, recirculated to increase efficiency

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21
Q

Outside air

A

Also known as make-up air. Required to help maintain human health conditions

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22
Q

Mixed air

A

Mixture of return air and make-up air. Flows to HVAC system to be treated

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23
Q

Supply Air

A

Air treated by the HVAC system that will be supplied to the building

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24
Q

Human health is the _______ for the design of an HVAC system

A

Key criterion

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25
Q

High humidity increases the chance for

A

Mold to form inside the building

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26
Q

Effective temperature (ET)

A

Measure of comfort which involves the dry bulb temperature, relative humidity, and air movement.

In °C/°F, but not an actual temperature and cannot be measured on a thermometer

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27
Q

During summer and winter, relative humidity should be kept between

A

30% and 70%.

Above 70% the air will feel muggy, below 30% the air becomes too dry and effects nasal membrane

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28
Q

An increased airflow increases the heat loss of the body by

A

Conduction, convection, and evaporation. Helps the body remain comfortable even when room temperature is higher than normal

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29
Q

An air flow of _____ is considered to be relatively still air

Airflow of _____ would be considered a draft by most people

A
  1. 6 - 7.6m/min

19. 8m/min

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30
Q

Tests show that 2% of the people will not

A

Be satisfied no matter how the conditions are changed.

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31
Q

Ventilation

A

Provision of outside air into the building is required to replenish the oxygen supply for the occupants. Outdoor air is necessary to dilute odours

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32
Q

When the relative humidity of the outdoor air is low,

A

Moisture must be added within the building to maintain acceptable conditions for human comfort.

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33
Q

Moisture minimizes the effects of

A

Static electricity, which may be important for operation of sensitive equipment

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34
Q

________ is a method of removing excessive moisture from the building.

A

Dehumidification

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35
Q

Air movement is required in each space to assist in

A

Dissipation of body heat from occupants and prevent a buildup of odours

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36
Q

Air filters are required to remove

A

Contaminants such as dust, dirt, smoke, pollen, lint, from recirculated air and from outside air before it is introduced to the building

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37
Q

Three categories of air conditioning systems

A

Unitary systems, Central systems, combined systems

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38
Q

Unitary systems

A

Each individual room or zone is provided with a self-contained air conditioning unit

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39
Q

Central systems

A

An air conditioned air handling unit located in a central mechanical room. Conditioned air is distributed through ductwork to all zones. Mainly controlled in mechanical room, but may have supplementary thermostats

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40
Q

Combined systems

A

Air is conditioned in an air handling unit in the central mechanical room and is ducted to all areas of the building. Provides only ventilation, pre Heating and Cooling while supplementary equipment in each Zone provides Heating and additional cooling if required. More complex and costly then Central systems, but provide Superior Zone control

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41
Q

Air handling unit consists of;

A

Fan, filters, humidifier, source of heating and cooling, motorized dampers for air flow control

Possibly a humidifier or dehumidifier

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42
Q

Medium to large systems utilizing return air in mixed air may require;

A

Exhaust, or return, fan to overcome friction losses

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43
Q

Fixed outdoor air percentage system

A

Supply air is drawn through non modulating dampers. Dampers are ffixed to permit 10 to 30% outdoor air. Cheaper than variable percentages, because they do not use control systems to modulate dampers. Do not respond well to weather changes

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44
Q

Variable mixed percentage air handling system

A

Varies the ratio of makeup to recirculated air based on climate conditions. More costly, but balanced human comfort. Installed in residential, commercial, and industrial buildings

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45
Q

Completely pure and dry air does not

A

Exist in nature.

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46
Q

Moisture in the air is not in the form of droplets,

A

Rather it is water that has been evaporated into vapour, which has mixed with the air.

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47
Q

Water vapour in the air is

A

Low pressure, low temperature steam

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48
Q

Absolute or specific humidity

A

Actual mass of moisture present in a specific amount of air.

Expressed as kg per kg of dry air

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49
Q

Relative humidity (RH)

A

Ratio of the mass of moisture in a given amount of air to the maximum amount of moisture the air can contain at that temperature.

Expressed as a percentage

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50
Q

Relative humidity and temperature relation

A

Inversely

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51
Q

Dew point

A

The temperature at which air subjected to cooling becomes saturated, and below this temperature water vapour will condense from the air

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52
Q

Dry bulb temperature

A

The temperature of the air measured with an ordinary thermometer

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53
Q

Wet-bulb temperature

A

Temperature indicated by a thermometer having its bulb covered by a water wetted Wick, which is exposed to a stream of rapidly moving air

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54
Q

A wet bulb thermometer measures

A

The dry bulb temperature and subtracts the cooling effect of evaporation

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55
Q

The rate of evaporation of the moisture in the wick depends on

A

The humidity in the air

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56
Q

Wet-bulb depression

A

Difference between the dry bulb temperature and the wet-bulb temperature

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57
Q

The purpose of humidification is to increase

A

The relative humidity in the air

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58
Q

The higher the temperature of air, the _____ moisture it can absorb

The lower the temperature of air, the _____ moisture it will hold

A

More

Less

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59
Q

In order to maintain comfortable conditions inside a building during the heating season,

A

It is necessary to add humidity to the air.

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60
Q

From a health standpoint, relative humidity between ______ is desirable

A

35% and 50%

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61
Q

When slight condensation appearing on the corners of the window panes,

A

The relative humidity inside the building has reached its maximum permissible value with relation to the outside temperature.

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62
Q

Three types of humidifiers used for residential purposes

A

Pan, wetted element, and atomizing

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63
Q

Pan type humidifier with plates

A

Shallow pan or tray partially filled with water. Water is drawn to the plates by a hygroscopic action

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64
Q

Wetted element humidifier

A

Water-saturated evaporation pad through which warm air is forced. Water is fed by gravity or by spray

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65
Q

Atomizing humidifier

A

Water is broken up into small particles by a Spinning Disk or a cone, or spray nozzle. Usually used as a portable or stationary room unit

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66
Q

In a humidifier, proper evaporation is prevented when clogging occurs due to

A

Dissolved mineral salts in the water, once evaporated, stay behind in the evaporation plates and pads

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67
Q

Atomizing humidifier disadvantage

A

Water is sprayed into the air and the salts in solution in the water appear as a fine white dust, which settles in ducts and rooms

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68
Q

Three types of Industrial and Commercial humidifiers used in HVAC systems

A

Air washers, steam grid humidifiers, pan type humidifier

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69
Q

Air washers

A

One of the most versatile pieces of equipment in HVAC systems. Main purpose is humidification of air as well as;

Heat, cool, dehumidify, clean the air

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70
Q

Eliminators are installed at the outlet of the washer to

A

Prevent water droplets from being Carried Away by the air. Designed so they change direction of airflow several times causing droplets to fall

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71
Q

Are washers are not effective in the removal of

A

Greasy particles, soot or tobacco smoke

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72
Q

An air washer should be installed on the

A

Suction side of the fan where it can be maintained at pressure slightly below atmosphere to avoid leakage of water.

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73
Q

When the air washer is used, the power engineer can have considerable control over

A

Temperature and humidity

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74
Q

Steam grid humidifier

A

When steam is available, humidification is achieved by injecting steam into the supply Airstream

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75
Q

With the steam grid humidifier, to achieve satisfactory results, steam pressure should be in the range of

A

35 kPa to 70 kPa to prevent splashing of condensate and a drastic increase in temperature of supply air.

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76
Q

Steam used for humidification can cause health problems, if it contains

A

Chemicals such as amines. Steam must have high purity

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77
Q

Clean Steam humidification

A

Uses a heat exchanger that is supplied with steam as the heat source. Heat will be added to demineralized water and caused it to boil into low pressure clean Steam. Will have no chemicals and minerals, will leave no mineral dust or chemicals in the air

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78
Q

Clean steam humidification is relatively expensive because

A

Requires a heat exchanger to be used in conjunction with the steam boiler.

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79
Q

Applications for clean Steam humidification include;

4

A

Hospitals, archives, pharmaceutical industry, museums

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80
Q

Pan type humidifier

A

Offers a broad range of capacity. Installed on the inside casing of air handling apparatus, inside the supply duct, or attached to the underside of a duct.

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81
Q

Pan type humidifier can be ________ heated or _______ heated

A

Electrically

Steam

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82
Q

Static pressure

A

Not caused by air movement. Exerted by the air on duct walls. Can be read by connecting the manometer at right angles to the duct.

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83
Q

Static pressure of the air overcomes

A

The resistance of ducts and filters

84
Q

Velocity pressure

A

Caused by moving air. It is the pressure caused by the impact of the air flowing through a duct, only detected when it strikes a surface.

85
Q

Velocity pressure will be in addition to the

A

Static pressure in the system.

86
Q

Total pressure

A

Sum of static pressure and velocity pressure. Can be measured With a manometer

87
Q

Total pressure formula

A

Total pressure =

static pressure + velocity pressure

88
Q

Static pressure can be either ____ or ____

A

Positive, above atmospheric

Negative, below atmospheric

89
Q

Conversion of pressure and velocity is never 100% efficient, due to

A

The formation of Eddy currents

90
Q

Two general groups of fans

A

Centrifugal and axial flow

91
Q

Centrifugal fans

A

Air flows radially (perpendicular) through the impeller. Classified according to the shape and design of the blades

92
Q

Axial flow fans

A

Air flows axially (parallel) through the impeller. Classified on the principles are designed for

93
Q

Another common name for a centrifugal fan is

A

Squirrel cage

94
Q

Classes of centrifugal fans

A

Class 1
Class 2
Class 3
Class 4

94
Q

Classes of centrifugal fans

A

Class 1
Class 2
Class 3
Class 4

95
Q

Fans with backward inclined blades require

A

Less power to deliver a specified Air volume, making them more efficient than forward curved fans. Higher efficiencies result in quieter operation — for medium to large fans

96
Q

Backward inclined airfoil fan is mostly used for

A

High capacity, high pressure, applications where power savings outweigh the higher cost

97
Q

Radial blade fan

A

Lower initial cost, but less efficient and noisier

98
Q

Three types of axial fans

A

Propeller fan, tube axial fan, vane axial fan

99
Q

Propeller fan

A

Driven by motor, directly, or V belt. Higher moving capacity, but unable to produce High pressures. Cannot be used in ducted air distribution, but can be used in air-cooled condensers, unit heaters and exhaust fans for ventilation

100
Q

The propeller fan is the most economical type to produce

A

Large air movements at low pressures

101
Q

Tube axial fan

A

Heavy-duty suited for duct mounting. Discharges are in a spiral motion, resulting in higher friction losses in the Ducts. Noisy in operation, used in industrial air conditioning applications, where noise is less objectionable

102
Q

Vane axial fan

A

Tube axial fan with guide vanes behind the fan wheel to straighten out the Spiral Flow of air. Results in reduced turbulence and friction with improved efficiency. Relatively noisy, needs sound attenuators at strategic locations

103
Q

Fan performance curves are obtained from

A

A series of laboratory tests conducted on a fan with various restrictions at the end of the test duct.

104
Q

The purpose of fan performance curves are to

A

Allow the designers to determine the correct fan selection for the system and to help operators troubleshoot fan performance issues

105
Q

Backward inclined fan curve

A

Considered non overloading fan. Will not change significantly with changing air flow conditions

106
Q

Forward curved fan curve

A

Considered overloading. At constant speed, With changes in airflow the power of a power requirements will increase causing the fan and motor to overload

107
Q

2 fan drives

A

Direct drives or V-belt drives

108
Q

Direct drives

A

Normally used on smaller-sized air moving equipment

109
Q

V belt drives

A

Used on most Air Conditioning, Heating, and ventilation applications.

110
Q

Belt guards

A

Required for safety on all V belt drives.

111
Q

Coupling guards

A

Required for direct-drive equipment

112
Q

Considerable economy and power consumption can be obtained on large air conditioning and ventilation systems by reducing the

A

Air volume handled by the fan during periods of partial loads, such as evenings or weekends

113
Q

Four methods for volume control

A

Variable speed motor control, fluid Drive, Outlet damper control, variable Inlet vane control

114
Q

Variable speed motor control

A

Most efficient, but most expensive

115
Q

Fluid Drive

A

Used on Industrial applications, efficient but expensive. Simplified startup and de-clutching feature, relieves driven fan of shock loading during startup.

116
Q

Outlet damper control

A

Used on fans with constant speed motors. Least expensive and least efficient

117
Q

Variable Inlet vane control

A

Radial vanes installed in the fan Inlet. Reduces energy consumption by controlling amount of air spin at the fan Inlet.

118
Q

Ventilation rate

A

Air changes per hour

119
Q

Minimum number of air changes per hour for buildings is determined by

A

Number of occupants, activities, type of contaminants in area

120
Q

Ventilation must be operated in such a way that there is a balance between

A

Energy Efficiency and human comfort

121
Q

Two methods of ventilation

A

Natural and mechanical

122
Q

Natural ventilation

A

Air movement is caused by the temperature difference or wind. Not used in many buildings, except small buildings with low occupancy rates. Not very effective, difficult to maintain minimum air changes per hour.

123
Q

Mechanical ventilation divided into three groups according to the way the fan is used to move the air.

Includes;
3

A

Natural air intake, mechanical exhaust

Mechanical air intake, natural exhaust

Mechanical air intake, mechanical exhaust

124
Q

Natural air intake, mechanical exhaust

A

Stale air is drawn out by a motor-driven fan, and replaced by fresh air through windows or in intakes. Fresh air drawn into the building is neither filtered or heated. Low cost but low efficiency

125
Q

Mechanical air intake, natural exhaust

A

Fresh air forced into building by a fan or blower, moving the stale air out through the Windows or Outlets.

126
Q

Mechanical air intake, mechanical exhaust

A

In larger buildings, fans or blowers Supply fresh air into and remove stale air from the building. Designed to maximize the movement of air to increase human comfort.

127
Q

If people are having trouble opening or closing exterior doors, one possible cause is

A

Incorrect building static pressure.

128
Q

One disadvantage of the mechanical system is the

A

Greater costs for maintenance and operations

129
Q

Contaminants suspended in the air

5

A

Solid particles of visible size, solid particles of microscopic size, liquid impurities, vapour and gases, living organisms

130
Q

The greatest cost of a filter is usually not the filter itself, rather

A

The energy cost the filter causes, increase the energy requirements to operate the fan

131
Q

Mechanical filters

A

Throw away or cleanable / renewable filters.

132
Q

Dry filters

A

Efficient when the screening dust, but dust holding capacity is small. Best filters for lint removal, but ineffective for removing smoke and fine particles.

133
Q

Large air conditioning systems, dry filter is sometimes used in rotating air filter, also called

A

A a roller or curtain filter

134
Q

Dry filter replaceable bag type

A

High dust removal efficiency and low air resistance

135
Q

Try filter wedge type

A

Large filtering area, large-capacity, and a longer service life.

136
Q

To protect the more expensive filter, it is important to

A

Provide pre filtering, will result in having to change expensive filters less

137
Q

Viscous impingement filters

A

Most common filter used in ordinary air conditioning systems. Coated with viscous, sticky fluid.

138
Q

High-efficiency particle air (HEPA) filter

A

Filters much finer particles than dry or viscous. Very efficient, but very expensive. 99% efficiency, but require a pre-filter for larger particles.

139
Q

When a HEPA filter is used, ______ should be used

A

Multi-stage filtering.

140
Q

HEPA filtration systems are commonly found in

A

Hospitals, Laboratories

141
Q

Electronic air cleaners, two classes

A

Electrostatic precipitators and charged media electronic air cleaners

142
Q

Electrostatic precipitators

A

Positively charged particles, flow through a bank of metal collector plates arranged parallel to air flow. Plates are negatively charged with 6000v DC. If power supply fails, filtration ceases. Common to use throw-away type-ahead of it

143
Q

Electrostatic filter is the best filter available for

A

Removal of fine dust, smoke and fumes. Used when are Supply must be as clean as possible. Most expensive

144
Q

Charged media electronic air cleaner

A

V-shaped bank across the air duct and mounted in non-conductive frames. Has charge members held at a potential of 12,000v DC. If power supply fails, filter media will still act as an impingement filter and clean the air.

145
Q

Electronic air filters are expensive and require

A

Maintenance by a qualified person. Electrician may be required

146
Q

Air washers

A

May be used for air cleaning. Low deficiency in dust removal, practically negligible and removal of small particles, especially greasy ones.

147
Q

The most common and successful way of removing odours and Vapors in an air conditioning system is by means of an ______.

A

Odour absorber.

148
Q

In-duct air sterilizers

A

Circular channels in the direction of airflow, containing a tubular ultraviolet lamp. Airflow is subjected to ultraviolet radiation.

149
Q

Common way to classify duct systems is by _____ and _____

A

Pressure

Velocity

150
Q

Low pressure duct system

A

less than 11m/s

Less than 0.5Kpa

151
Q

Medium pressure duct system

A

11m/s to 25m/s

Up to 1.5kpa

152
Q

High pressure duct system

A

Greater than 25m/s

1.5kpa to 2.5kpa

153
Q

Low pressure system is more conventional for

A

Small and medium-sized buildings. Silent air movement, lower costs.

154
Q

Losses that are functions of velocity

A

Noise, vibration, and friction

155
Q

Materials used in sheet metal ducts are

A

Galvanized or black steel, aluminum, stainless steel and copper

156
Q

Galvanized steel

A

Corrosion resistance but with a higher cost

157
Q

Black steel heavy gauge sheets are used for

A

Kitchen exhaust ducts, ducting with waterproof Coatings, drain pans. Durable and High strength

158
Q

Aluminum, stainless steel, or copper is used where

A

The cost is justified by the need for maximum resistance to moisture.

159
Q

In order to maintain duct pressure and velocity, reducers are used to

A

Compensate for the reduction of air volume

160
Q

SMACNA

A

Sheet metal and air conditioning contractors National Association standards

161
Q

Elephant trunk style air duct

A

May lead to a high pressure drop in the system, lowering minimum air changes

162
Q

Air duct leakage is a

A

Transmission loss

163
Q

Are leakages from ducts vary from

A

5% to 30%

164
Q

Effects of air leaks in supply ducts differ from those in

A

Return air ducts

165
Q

Air leaks from supply ducts create loss of

A

Heating and Cooling

166
Q

The direction of airflow has little or no effect on

A

The transmission of noise

167
Q

To restrict spread of smoke and fire through duct systems and to minimize ignition sources, the duct lining material must satisfy

A

Local building codes and the requirements of the National Fire Protection Association standard 90A

168
Q

Manual dampers

A

Used in smaller systems to close the outdoor air intake, to prevent freezing when the system is off

169
Q

Modulating dampers

A

Produces changes in the volume of air proportional to a control signal

170
Q

Two types of modulating dampers

A

Mixing boxes, face and bypass dampers

171
Q

Face and bypass dampers

A

Used to modulate the volume of air passing through a heating or cooling coil

172
Q

2 position dampers

A

Either fully open or fully closed

173
Q

Relief dampers

A

Similar to a check valve, allow the air to flow in One Direction only.

174
Q

Single blade dampers

A

Restricted to small sizes because of the difficulty to secure proper operation with high velocity air

175
Q

Parallel blade damper

A

Best suited for 2 position damper operation, where no throttling of airflow is needed

176
Q

Opposed blade damper

A

Used for modulating air flow.

177
Q

Fire dampers

A

Installed to close in the same direction as the moving airstreams, so the air pressure will close them, but not open them.

178
Q

National Building Code requires Supply and return ducts of air conditioning systems to be equipped with _______ at the point where they pass from one firezone, to another

A

Fire dampers

179
Q

A smoke damper is a device to resist

A

The passage of smoke. Operates automatically and controlled by a smoke detector.

180
Q

Stationary air louvres are used in fresh air intake openings to

A

Minimize the amount of water and snow entering an air handling system

181
Q

Terminal devices four main functions

A

Distribute are to spaces

provide uniforms space temperatures

control effects of conduction, radiation, and convection

Provide adequate air motion

182
Q

Terminal distribution devices use

3

A

Diffusion, induction, entertainment and aspiration

183
Q

Diffuser

A

Device used to reduce the velocity of air and introducing air to an occupied space. Create turbulence for conditioned air, reduces its velocity, causes rapid mixing with room air

184
Q

One of the most effective locations for sound absorbing lining is the

A

Suction and discharge plenum of the fan

185
Q

Where available duct is insufficient to provide the required attenuation, prefabricated in duct

A

Sound absorbers or duct Splitters can be used.

Resistance to airflow will increase operating cost

186
Q

Three main media used to supply heat to a heating coil

A

Steam, hot water, glycol

187
Q

Steam or hot water systems do not require the installation of

A

An additional heating circuit, as with glycol systems

188
Q

Steam and hot water posed no

A

Environmental concerns, as does glycol.

189
Q

Using glycol eliminates concerns surrounding

A

Coil freeze up

190
Q

To reduce the risk of freeze up in Steam and hot water heating coils, important to consider;
3

A

Size of heating coil
Configuration of heating coils
The way the coil operates

191
Q

Steam coils are sized according to tube length.

Short length coils are _____
Long tube coils are _____

A

1.1m or less

Greater than 1.1m

192
Q

Methods to minimize the hazard of freeze up while controlling the output of steam heating coils

A

Use a preheat coil, use a preheat coil with a reheat coil

193
Q

Preheat coils

A

Provides Heat to the outdoor air to prevent freezing Downstream equipment. Used when there is 35% to 100% fresh air makeup. Used to increase air temperature to no more than 18°C.

194
Q

When an increase in temperature is greater than 18°C, preheat coils should be used with

A

A reheat coil to minimize chances of freeze up.

195
Q

GE control system must delay the opening of outdoor air dampers for at least

A

10 minutes at the start-up of the air handling unit and after steam is turned on

196
Q

It is good design practice to select steam coils so that at least ____ of the coil capacity is used when the air temperature entering the coil is at ____

A

40%

-1°C

197
Q

Common practice to select a control valve for a pressure drop corresponding to

A

50% of its initial steam pressure

198
Q

A vacuum develops in a coil when

A

The steam flow control valve fills the coil with steam, and then shuts off. As it gives off heat, initial volume of steam in the coil condenses to 1/1600 of its original volume

199
Q

Vacuum breaker

A

Prevents possible freeze ups caused by a vacuum in the coil. Installed after the steam flow control valve and near as possible to the inlet connection to the coil

200
Q

A steam trap will not function satisfactorily without a

A

Vacuum breaker

201
Q

It is preferable to use a _______ arrangement for hot water coils use to heat sub-freezing air

A

Parallel flow

202
Q

Glycol coils

Use of ethylene glycol solution will result in the following

A

Lower heat transfer rate, increased friction losses, larger pumps due to higher power consumption

203
Q

A glycol velocity of _____ is recommended to ensure a turbulent flow and reasonable heat transfer efficiency

A

1.2 to 1.8m/s

204
Q

Whenever possible, steam coils should be installed with

A

Tubes in a vertical position

205
Q

Support the piping ______ of the

A

Independently

206
Q

Available pressure

A

Pressure over and above the pressure in the condensate return main

PE 4B (8 decks)

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