Part B Exam - Unit 11

Modern radiators are made of ______________, which allows designers to save space.

Light steel pressings

Radiator valves are special ________ valves used to control the flow of steam to radiators.

Globe

Why are vacuum pumps used in large buildings (in steam systems)?

To overcome resistance in long runs of the return piping

A condensate pump returns water to the system through:

A Hartford loop connection

What are the main sources of trouble in the radiator, convector, and univents?

The valves and traps

When is it common to arrange the overhaul of each item in the radiator, convector, and univent?

During the summer

In hot water heating systems, large pipe sizes are necessary in order to:

Keep flow resistance to a minimum

In hot water heating systems, the maximum water temperature is limited to:

77degC

In forced circulation hot water systems, the closed expansion tank provides ______________, which allows the system to operate in pressures that are ____________.

A cushion of air above the water level

Well above atmospheric pressure

What is a disadvantage of using series loop forced circulation systems?

They have low heat capacity

The varying pressures in forced circulation systems are ___________, while temperatures are ___________.

85 to 140 kPa

70 to 94degC

What is a disadvantage of using one pipe forced circulation systems?

It's necessary to increase the size of convectors towards the end of the system

In the two-pipe direct return system, the circuit lengths are:

Different

In the two-pipe reverse return system, the circuit lengths are:

The same

What is the purpose of the flow control valve in multi-zone forced circulation systems?

They prevent natural circulation

What are some advantages of hot water heating as opposed to steam heating? (4)

Smaller and more compact since no boiler steam space is required

Piping slope is not as critical

Less corrosion

Less costly

What are some disadvantages of hot water heating as opposed to steam heating (5)

Boiler must withstand high pressure due to high head

Considerable power is required

Greater danger of damage due to potential of freezing

More damage will result if a leak occurs

Air pockets may develop in the piping system

What is usually used to heat up radiant panels?

Continuous serpentine coils

When using radiant panel heating, ceilings should not exceed ____degC, walls should not exceed ____degC, floors should not exceed ____degC.

46

38

30

What are some advantages to radiant panel heating? (3)

More even heat distribution

More comfort for buildings

Heating elements are completely out of sight

What are some disadvantages to radiant panel heating? (3)

Panels are slow to heat up and cool down

Any leakage is costly to repair

Changes in heating system are difficult to make

The snow-melting system may use one of these 3 things:

A heat transfer solution

Electric resistance heating cables

Infrared radiant lamps

Coils are embedded at least ____ cm below the surface of the concrete when using snow-melting systems.

5

Why is a small valve installed below the air vent?

So it can be isolated and serviced when the heating system is in operation

What can be used to extract only hot water from the boiler?

A dip tube

What kind of valves are balancing valves?

Plug valves or globe valves

What kind of valves are riser stop valves?

Gate valves or ball valves

The typical pressure setting for hot water systems is:

103 to 124 kPa

Circulating pumps are of the _________ design.

Centrifugal

The in-line circulating pump is favoured in:

Smaller installations

An open expansion tank is limited to systems with a maximum temperature of:

80degC

What happens when a bladder is used with an expansion tank?

The air trapped in the system can't be vented

Where is the point of no pressure change located?

At or near the boiler

The pressure at the highest point of the hot water system should be at least:

12 kPa

What are some chemicals used for cleaning new hot water systems? (3)

Trisodium phosphate

Soda ash

Caustic soda

What is an important rule to remember concerning antifreeze?

Antifreeze should not be circulated through the boiler

Which heating systems usually supply all the heat required?

Forced warm air heating systems

What are some heating sources of the forced warm air heating system? (4)

Fixed heater

Electric resistance coil

Fin-coil heat exchanger

Forced air furnaces

The fixed heater receives heat produced by:

The combustion of oil or gas

What do the fin-coils do in the fin-coil heat exchanger?

It heats the air in the secondary warm air heating system

What is often not required in a highboy upflow furnace?

A return duct

Lowboy furnaces are a little over _____ m high.

1.2

Lowboy furnaces are used where:

Headroom is limited

What are some examples of fired space heaters? (3)

Unit heater

High efficiency furnaces and heaters

Solar air piping

What is the most widely used application of solar thermal air heating?

Cladding on south facing walls that absorb solar energy

What are some advantages of fired space heaters? (5)

Positive air circulation

Smaller ducts

Furnaces can be located anywhere

Air can be cleaned and humidified

Controlled quantities of external ventilation air may be drawn into the system

What are some disadvantages of fired space heaters? (2)

Can be quite noisy

Ducts are more difficult to enclose

The blower in the furnace is of the __________ type.

Double inlet

The rotor in the blower has ___________ vanes.

Forward curved

The operating principle of the blower and motor is similar to that of a:

Centrifugal pump

Where are humidifiers usually installed?

In the warm air plenum of the furnace

Fine dust that collects on the blades of the fan should be wiped off:

Annually

Which bearings require no lubrication?

Sealed ball bearings

How often do sleeve bearings need a few drops of oil?

Twice a year

The ratio of V-belt distance vs. V-belt vertical movement is:

16 to 1

How often should cleaners be cleaned?

Four times a year

In the surface combustion chamber, gas and combustion air are mixed in the upper chamber at a pressure that is:

Slightly above atmospheric

The surface of the surface combustion heater mat is:

760 to 900degC

In the directly fired refractory heater, the surface temperature ranges from:

980 to 1260degC

In the internally fired or vented heater, emitting surface reaches a temperature of ____degC or over.

400

In the low-temperature catalytic heater, the catalyst is where:

Oxidation takes place

Emission temperatures for the low-temperature catalytic heater may vary from:

315 to 455degC

What are the advantages of electric heating? (5)

Produce no toxic gases

Requires less space

Individual room temperature control is easily obtained

Lower installation and maintenance costs

Clean and silent operation

What are the disadvantages of electric heating? (2)

Operating costs are higher

An electrician is required to repair the system

Which air conditioning system is usually installed with little ductwork, and is factory-assembled?

Unitary system

What is the unitary system controlled by?

A space thermostat with a sensing bulb

Which unitary system requires no piping connections?

Window air conditioner

In the condenser compartment of the window air conditioner, condensate evaporates when:

A slinger ring on the fan throws the condensate against the condensing coil

Window air conditioners typically range from ______________ tonnes of refrigeration.

0.3 to 1.8

Packaged air conditioners usually deliver conditioned air directly to the space through:

A discharge plenum

The packaged air conditioner is normally available in a _______________ tonne range.

2.7 to 13.6

The packaged air conditioner is designed to handle the substantial heat released from:

Computer equipment

The rooftop unit is in the __________ tonne range.

2.7 to 68

What is the most common central air conditioning system?

Forced air system

Where is the forced air system normally located?

In the basement

The forced air system is well-suited for buildings of what construction?

Wood frame

In the high velocity terminal reheat system, the ____________ is reduced.

Size of supply ductwork

In the multi-zone system, dampers are linked together, but are ____° out of phase.

90

The cold deck of the multi-zone system normally supplies air at:

12.5degC

What is a standard feature in mixing boxes?

Acoustic installation

In the dual duct system, mixing of the hot and cold air is accomplished with:

Dampers

In the dual duct system, each main supply duct is of ______________ design.

Medium or high velocity

Why is perimeter heating installed below windows?

To offset heat loss and prevent cold drafts

The heating cycle operates in smaller capacities up to:

23 tonnes

The ratio of secondary to primary airflow in the induction system is:

4 to 1

In the VAV with perimeter heating, air is supplied at approximately:

12.5degC

Any building areas that are facing ______ will have a higher degree of temperature fluctuation.

South

It is important to consider the construction details and materials used because of the difference in ___________ in each component.

U-factor

What are the two methods of measuring infiltration?

Crack method (formulaic) and air change method (approximation)

Maximum solar heat gain should not always be assumed to be:

The time of the overall maximum load

The space in between glass panes for heat loss reduction are filled with:

Argon gas

Minimum air ventilation in residential buildings should be ____ L/s per person or ____ L/s per square metre of floor space

3.5

0.15

What is included for spaces that are occupied sporadically?

A CO2 sensor

In the runaround system, the charging station is higher than both coils, which makes it possible for:

Gravity to charge the system slowly

Where should the expansion tank be located in the runaround system?

At the point of no pressure change

What are the advantages of the runaround system? (7)

Streams can be remote

Can be grouped in the same system

No contamination

Readily adaptable

Less space is needed

Maintenance is simple

Energy is added to the glycol and recovered when preheating ventilation air

What are the disadvantages of the runaround system? (3)

Recovery range is quite low (45% to 55%)

During cold season, full recovery rate cannot be used due to frost

Temperature difference must be high enough

The thermal wheel is adapted for which applications?

Commercial and industrial

Which air conditioning heat recovery unit uses a single exchange unit?

Thermal wheel

What serves as the heat carrier in the thermal wheel?

The mass of the material