WorksheetsUnit 216 – Central Heating: full quiz
Total questions: 69
Worksheet time: 35mins
What is meant by gravity circulation in older heating systems?
Circulation created naturally through convection without a pump
Water moved by a high-speed pump through all radiators
Heat transfer only by radiation from the boiler
Airflow used to distribute heat around the building
Why are gravity systems no longer commonly installed?
They are slow, inefficient, and do not meet modern energy efficiency standards
They are too noisy in residential properties
They require copper piping only, which is expensive
They cannot operate with thermostatic radiator valves
Why do radiators progressively get cooler in a one-pipe semi-gravity system?
Each radiator returns cooler water back into the main ring, reducing temperature for the next
The boiler output temperature is set too low
Air vents remove too much heat from the circuit
Heat is lost entirely through the feed and expansion cistern
List one advantage of a one-pipe semi-gravity system.
It is cheap and simple to install
It allows complete independent zone control
It guarantees equal heat at every radiator
It eliminates the need for any venting
List one disadvantage of a one-pipe semi-gravity system.
Radiators get progressively cooler; poor control; not Part L compliant
Requires complex wiring for valves and sensors
Cannot be used with modern boilers
Needs oversized expansion vessels
What is the main purpose of the open vent pipe?
To act as a safety outlet for overheating and allow trapped air to escape
To increase boiler efficiency by recirculating flue gases
To provide a bypass around zone valves
To reduce scale formation in the hot water circuit
What is the minimum height the open vent should rise above the F&E water level?
450 mm above the water level
150 mm above the water level
1 m above the water level
300 mm above the water level
Alexander is installing a heating system in his house. He notices that the open vent pipe does not have any valves fitted. Why is it important that the open vent does not have any valves?
Closing it could cause dangerous pressure build-up or explosion
Valves would draw air into the system
Valves reduce heat transfer across radiators
It prevents proper chemical inhibition
What distance should separate the cold feed and open vent to ensure a neutral point?
They should be within 150 mm of each other
They should be at least 1 m apart
They should be installed on opposite sides of the boiler
They should be no closer than 450 mm
What is the function of the feed and expansion cistern?
To maintain system water level and accommodate expansion
To store domestic hot water for taps
To provide make-up gas for the boiler
To filter magnetite from the heating water
Why must the F&E cistern be located at least 1 m above the circulator?
To maintain sufficient static head pressure
To keep the pump cool during operation
To reduce noise from the boiler
To allow gravity return of hot water
In a two-pipe semi-gravity system, which part is pumped and which is gravity fed?
Heating is pumped; hot water primary circuit is gravity fed
Heating and hot water are both pumped
Heating is gravity fed; hot water is pumped
Both heating and hot water are gravity fed
List one advantage of the two-pipe semi-gravity system.
All radiators heat to the same temperature
It requires no circulator pump at all
It uses smaller radiators than other systems
It eliminates the need for an expansion vessel
List one disadvantage of the two-pipe semi-gravity system.
Uncontrolled hot water temperature; low efficiency
Requires complex electronic controls
Cannot operate with thermostats
Needs continuous manual venting
Why are older systems often not compliant with Part L?
They lack full control, are inefficient and cannot meet energy-saving requirements
They use copper pipework instead of plastic
They are incompatible with condensing boilers
They require oversized radiators
What pipe sizes are typical in a C-Plan semi-gravity system?
15 mm cold feed, 22 mm/28 mm primaries depending on design
10 mm cold feed, 35 mm primaries
22 mm cold feed, 15 mm primaries
28 mm cold feed, 22 mm primaries
Why is a heat sink required in a solid fuel system?
To dissipate excess heat when circulation stops
To store domestic hot water
To reduce boiler flue emissions
To balance pressure across zone valves
What does the heat sink normally consist of?
A radiator fitted with two lock-shield valves
An expansion vessel with a Schrader valve
A mid-position valve on the hot water circuit
A magnetic cleaner installed on the return
What benefit does a fully pumped system give compared to gravity?
Faster heat-up and improved control
Lower electrical consumption under all conditions
No need for an expansion cistern
Eliminates air from the system without vents
Why does a Y-Plan system use an automatic bypass valve?
To prevent pump over-pressurising when valves close
To divert flow to the domestic hot water cylinder permanently
To increase radiator surface temperature
To isolate the boiler from the heating circuit
What does the mid-position valve control?
Flow to hot water, heating, or both
Boiler firing rate only
Air removal from the system
Expansion vessel pressure
What is the purpose of a zone valve in an S-Plan?
To isolate and control each heating/hot water zone
To measure system pressure
To blend hot and cold water in the cylinder
To vent air automatically from the radiators
When must a property have additional heating zones fitted?
When the property exceeds 150 m²
When the property has more than two bathrooms
When the boiler output is over 24 kW
When underfloor heating is installed
What is meant by boiler lock-out?
The boiler shuts down when water exceeds safe temperature (around 85°C)
The boiler ignites repeatedly without heating
The boiler cannot start due to low gas pressure
The boiler is manually isolated for maintenance
Why does aeration cause magnetite and noise?
Air reacts with iron to form rust and sludge, restricting flow
Air increases water temperature above design
Air dissolves inhibitor chemicals completely
Air expands the vessel beyond capacity
What is the purpose of an air separator?
To remove air from circulating water and reduce corrosion/noise
To control boiler firing rate
To separate hot and cold water circuits
To filter scale from domestic hot water
Why must a circulator always draw on the cold feed?
To maintain positive pressure and prevent air being drawn into the system
To increase heat at the first radiator
To reduce flow through the boiler
To protect the mid-position valve from damage
What is the function of an H-frame configuration?
To correctly position vent and feed to maintain a neutral point
To support radiators mechanically on a wall
To mount the boiler safely
To provide electrical isolation for pumps
What is the purpose of a magnetic system cleaner?
To collect magnetite and debris using a strong magnet
To measure water hardness
To dose inhibitor automatically
To balance radiator flows
What does inhibitor protect the system against?
Corrosion and scale build-up
Excessive noise from the pump
Electrical faults in controls
Freezing of external pipework
Why must one radiator be left without a TRV?
It must remain open to allow bypass and prevent pump strain
TRVs overheat the room if all are fitted
The radiator without a TRV provides domestic hot water
It prevents the boiler from short-cycling by design
Thomas is replacing a radiator in his home and wants to ensure the TRV does not activate while the radiator is removed. What should he use?
Decorator’s cap
Seal the radiator permanently
Increase radiator heat output
Adjust lock-shield settings
What does an automatic bypass valve protect?
It protects the pump and boiler from over-pressure
It prevents corrosion in radiators
It stops air from entering the system
It blocks sludge from reaching the boiler
Why must a filling loop be temporary and disconnected after use?
To prevent contamination of the mains water supply
To avoid overfilling the expansion vessel
To reduce noise in pipework
To stop heat loss through the loop
What is the role of a pressure relief valve (PRV)?
To release excess pressure safely
To dose corrosion inhibitor
To mix hot and cold water
To start the circulator automatically
Why do sealed systems require an expansion vessel?
To accept the 4% expansion of heated water
To store domestic hot water during peak times
To remove sludge from the circuit
To improve boiler efficiency by recirculating water
What is the purpose of the Schrader valve on an expansion vessel?
To check and top up the air charge
To vent water from the vessel
To control boiler temperature
To isolate the vessel from the circuit
What does an automatic air vent do?
Automatically releases trapped air from the system
Prevents water expansion in the vessel
Measures system pressure
Opens to allow domestic hot water flow
Samuel is installing a heating system in a building. He needs to decide where to place the drain-off valves. Why should Samuel install drain-off valves at low points?
To allow complete system drainage
To increase flow to radiators
To prevent air entering the system
To improve boiler combustion
What does a pressure gauge indicate?
The system pressure for safe operation
The boiler flue gas temperature
The water hardness level
The electrical load of the pump
What British Standard must radiators comply with?
BS EN 442
BS 7671
BS EN 806
BS EN 60335
Which type of radiator relies mainly on convection?
Panel radiators with convector fins
Cast iron column radiators
Towel warmers only
Skirting convectors without fins
Why is TBOE the most efficient radiator connection method?
It maximises heat distribution across the radiator
It reduces pipe length regardless of layout
It eliminates the need for balancing
It allows the use of smaller valves
Why are BBOE connections the most common?
They allow neat pipework with acceptable performance
They produce the highest output of all methods
They require no balancing of radiators
They are mandatory under Part L
Alexander is considering installing skirting convectors in his home. What is one disadvantage he should be aware of?
Dust buildup can block fins and stop convection
They require high water temperatures to operate
They cannot be installed on internal walls
They overheat rooms rapidly
Why are LST radiators used in public buildings?
To prevent burns by keeping surface temperature below 43°C
To increase acoustic insulation
To reduce water usage
To meet electrical safety standards
What is the main benefit of underfloor heating?
Even heat distribution at lower operating temperatures
Rapid warm-up compared to radiators
Lowest installation cost among heating systems
No need for thermostatic control
List two disadvantages of underfloor heating.
High installation cost and slow heat-up time
Requires only electric power supply
Limited to small rooms only
Produces uneven heat distribution
What copper grades are used in domestic heating?
R220 (microbore coil) and R250 (straight lengths)
R300 and R500
R100 and R150
R250 (microbore coil) and R220 (straight lengths)
What is the main advantage of microbore systems?
Lower water content allows faster heat-up times
Higher water content increases thermal mass and slows heat-up
Larger pipe diameters reduce friction losses only
No need for thermostatic controls
Why must joist drilling only occur between 0.25 × span and 0.4 × span?
To avoid weakening structural support
To maximize cable length between joists
To improve room ventilation
To align with decorative floor panels
What is the maximum permitted notch depth in a joist?
12.5% of joist depth
25% of joist depth
5% of joist depth
50% of joist depth
Why must plastic pipe near boilers be replaced with copper?
Plastic cannot safely handle high temperature at boiler connections
Copper prevents all corrosion in the heating system
Plastic causes electrical interference with the controls
Copper is always cheaper than plastic
Why are pipes sleeved through walls?
To allow expansion and prevent wear
To increase water velocity
To improve pipe insulation
To comply with electrical wiring regulations
What is the purpose of insulating primary circuits?
To reduce heat loss and prevent freezing
To increase pump noise
To raise the flow rate through radiators
To prevent limescale formation
Jacob is installing radiators in a new house. Why must he ensure that each radiator is placed 150 mm from the finished floor?
To allow correct convection airflow
To make it easier to paint behind the radiator
To meet electrical equipment clearance rules
To reduce pipe length
What is the purpose of the plastic inserts on radiator brackets?
To prevent metal-to-metal noise and allow expansion
To increase the load-bearing capacity of the bracket
To provide corrosion protection to the bracket
To serve as decorative trim only
What tool is needed to tighten radiator valve tails?
Radiator valve key
Phillips screwdriver
Adjustable spanner
Pipe cutter
What is the test pressure for a 1‑bar sealed system?
1.5 bar
1.0 bar
2.0 bar
0.8 bar
Oscar is performing maintenance on a heating system and needs to do a cold flush. Why does Oscar remove the circulator during the cold flush?
To prevent debris damaging the pump impeller
To increase the flushing temperature
To calibrate thermostats during the flush
To reduce water flow resistance for the flush
What is the main reason for fitting a vent pipe in an open heating system?
To filter impurities from the water
To increase water flow rate
To allow air and excess pressure to escape safely
To reduce the need for inhibitor chemicals
Which component is used to automatically remove air from a sealed heating system?
Pressure relief valve
Magnetic filter
Expansion vessel
Automatic air vent
What is the primary function of a magnetic filter in a central heating system?
To add inhibitor to the water
To capture magnetite and prevent blockages
To regulate water temperature
To increase system pressure
What is the main function of a lock-shield valve on a radiator?
To balance the flow of water through the radiator
To mix hot and cold water
To control the boiler temperature
To vent air from the system
Which component is used to automatically remove air from a heating system?
Expansion vessel
Pressure relief valve
Zone valve
Automatic air vent
What is the primary reason for insulating heating pipes?
To allow for easier pipe installation
To increase water pressure
To prevent corrosion inside the pipes
To reduce heat loss and improve system efficiency
What is the main function of a thermostatic radiator valve (TRV)?
To remove air from the heating circuit
To control boiler firing rate
To increase water pressure in the system
To regulate the temperature of individual radiators
Why is it important to balance a central heating system?
To prevent corrosion in the pipework
To ensure even heat distribution throughout all radiators
To reduce the need for expansion vessels
To allow the use of smaller diameter pipes
What is the purpose of a magnetic filter in a heating system?
To capture and remove magnetite and sludge from circulating water
To mix hot and cold water for domestic use
To increase the flow rate through radiators
To automatically vent air from the system
