2024 ppq Flashcards
(29 cards)
The sizing of pipework in a hydronic heating system consists of selecting the correct diameter of pipe to allow the necessary flow of hot water to the emitters. Detail the important criteria and process to be carried out to ensure a successful design.
Criteria - Required flow rate based on heat load
the water velocity
pressure drop keep below acceptable limits
system layout
pipe material
Process includes, calculating the heat load, then determining the required flow rate, this leads to choosing the pipe size then calculating the total pressure losses
ensure compatibility with the pump
adjust pipe sizes if needed
what is a hypocaust
a from of underfloor heating used by the romans that involves using hot air and smoke from a furnace to heat rooms
what is foul drainage
foul drainage refers to pipes that carry human waste and other organic waste, through soil pipes, waste pipes and combined discharge pipes.
what ways can a home maximize solar gain
south facing living areas
minimize north facing windows
thermal mass placement - materials such as concrete and brick
living room dining room and kitchen facing south
bedrooms and bathroom facing north east
what is an air handling unit
a large metal box containing various components used to:
Draw in outside or return air,
Filter and condition it (heating/cooling),
Supply the treated air to the interior spaces via ductwork,
Remove stale air (optional).
what are the main components of an air handling unit
air intake louver - allows fresh air in
Filter - cleans the air separating any dust or pollen
Mixing box - mixes fresh air with inside air
heating and cooling coils - heats and cools air
humidifier - adds moisture to the air
Fan section - drives air through the ductwork
Silencers
Dampers -regulate air flow volume
Control panel
When sizing domestic hot and cold water pipework, what are the issues that could be created due to incorrect sizing?
undersized pipe - insufficient water flow
high velocity and noise
increased pressure drop
reduced lifespan of components
oversize pipe - stagnant water which can lead to bacteria growth
long wait for hot water
higher installation costs
poor temperature control
what is voltage drop
voltage drop refers to when current flows through a cable and resistance and impedance causes the voltage to drop due to a loss of electrical energy
how is voltage drop determined
basic voltage drop can be determined by using the equation 2xLxIxR or it can also be determined using manufacturer data or regulation tables.
what 6 factors affect voltage drop
current
cable length
conductor size
material type
installation conditions
power factor
what are the main characteristics of a consumer unit
they have circuit protection so in the event of a short circuit or and overload of electricity they trip causing all electric to go off.
cable sizing is essential to handle the expected load and prevent overheating.
earthing - a proper earthing system is essential for safe operation of the installation.
what are the 4 main forms of cable containment
Trunking systems - enclosed rectangular or square cross section channels made from PVC
conduit systems - cylindrical tubes used to route cables
cable tray systems - Open perforated trays or solid-bottom channels that carry large numbers of cables, typically above ceilings or in plant rooms
cable ladder systems - ladder like structures with rungs usually used to support heavy cables
what are the advantages and disadvantages of trunking systems
adv - easy to install and modify
good protection from mechanical damage
can accommodate multiple circuit types
dis- limited ventilation
overcrowding risk
what are the advantages and disadvantages of conduit systems
adv - high durability
can be concealed in walls
protect against moisture and tampering
dis - labor intensive installation
cost
what are the advantages of cable tray systems
quick installation
easy access for installation or upgrades
supports heavy cable loads
what are the advantages of cable ladder systems
supports heavy cable loads
good ventilation
suitable for long runs and high capacity circuits
what is the order of the circuit and what cable system is used at each
main circuit board - cable ladder
distribution boards - cable trays or trunking
sub circuits- conduits or trunking
final circuits - conduit or trunking
what are the two main types of natural ventilation used in buildings
wind driven ventilation - air enters from wind ward side and leaves at other side of building
stack ventilation - warm air rises at escapes at high level openings causing cold air to come in at lower openings
what external factors effect natural ventilation in buildings
wind speed and direction
outdoor temperature
humidity and air quality
surrounding buildings
building orientation
topography
When examining below ground drainage systems, what are the 3 main types of piping arrangement
combined drainage system- carries foul water and surface water
separate drainage system - two separate pipe systems - one for foul water one for surface water
partially separate- some surface run off stays with the foul water
what are the advantages and disadvantages of a combined drainage system
adv - only one set of pipes
lower cost
simple layout
dis - can become overloaded during heavy rainfall
all water gets treated causing heavy load on treatment sites
what are the advantages and disadvantages of separate drainage systems
adv - reduced risk of overloading
surface water can be directly discharged to river
environmentally sustainable
dis - requires two sets of pipework
increased costs
more space required
what are the advantages and disadvantages of partially separated drainage systems
adv - offers a compromise between cost and environmental efficiency
allows reuse of existing infrastructure
dis - still partially overloads system
not as good as fully separated system
can be difficult to retrofit correctly
what are the 4 modes in which water is transported in
low temperature hot water
medium temperature hot water
high temperature hot water
chilled water
