Worksheets307 Central Heating System 2 Quiz
Total questions: 20
Worksheet time: 15mins
Which British Standard covers the method for the calculation of design heating loads?
BS EN 12828:2003
BS EN 12831:2003
BS EN 14336:2004
BS EN 1264-1:1998
What is the measurement of the U-value?
w/m²K
kj/m°C
w/kg/K
J/m³/K
What is the correct formula to determine the heat loss from a space through air changes and ventilation?
m² x At x 1.33
m² x At x U-value
m³ x QTY x At 0.33
m³ x U-value x QTY x 3
What are the likely effects of oversizing a heating system?
Reduced energy usage, as systems produce enough heat quickly before shutting off for longer periods
Reduced life expectancy of heat emitters, which often overheat due to higher temperatures
Greater risk of burns/scalds, due to excess temperatures within the system and increased boiler combustion efficiency
Reduced energy efficiency, as boilers ‘hunt’, and greater initial outlay costs
What is the most suitable external design temperature for a house with normal sheltered exposure in England and Wales?
-1°C
-3°C
-4°C
-5°C
What is the correct formula to determine the heat loss through a surface such as a wall or window?
m² x Δt x 1.33
m² x Δt x U-value
m³ x QTY x Δt 0.33
m³ x U-value x QTY x 3
A radiator has a temperature of 70°C at the inlet and 50°C at the outlet. What is the MWT of the radiator?
20°C
40°C
50°C
60°C
A room has an internal design temperature of 20°C. Using the answer from Question 7, determine the Delta T between the room and radiator.
Delta T20
Delta T40
Delta T50
Delta T60
You are trying to determine the correct size of an expansion vessel for a typical domestic central heating system. The system is installed in 22mm and 15mm copper. Which of the following methods could be used to give an approximate system volume?
2 litres per kW of the boiler
4 litres per kW of the boiler
6 litres per kW of the boiler
10 litres per kW of the boiler
What is the term given to the radiator within a central heating system which is the furthest from the heat source?
The content circuit
The shunt circuit
The hydraulic circuit
The index circuit
What is the formula used to determine the flow rate for a circuit?
kg/s = kW / 4.19 x Δt
W = kg x SHC x Δt
kW = 4.19 / kg x 1.33
Litres = kW x SHC / Δt
According to BSEN 14336:2004, what is the minimum test pressure and period for a water-based heating system?
At least 30% greater than the working pressure for a minimum of one hour
At least 30% greater than the working pressure for a minimum of two hours
At least 1.5 times the working pressure for three hours
At least 2 times the working pressure for one hour
What is the purpose of a hot flush of the central heating system?
To remove excess limescale deposits from the system
To ensure that the system flow rates can be achieved throughout the installation
To remove traces of the legionella bacteria from the system pipework
To remove excess jointing compounds, fluxes and oils from the system
What is not an effect of good balancing within a central heating system?
Increased efficiency at the boiler
Reduced fuel costs
More even radiator temperatures
Higher calorific value of the fuel
Which component is initially used to balance the heat outputs at radiators?
Wheel head valves
TRVs
Lockshield valves
Pump speed controller
A radiator has stopped working and is completely cold. All the other radiators in the system are hot and no air is present in the cold radiator. What is the most likely problem?
Pin stuck within TRV
Sludge blocking parts of the radiator
Faulty pump
System needs balancing
Which of the following components can be used to check the charge pressure of an expansion vessel?
Pressure gauge at the boiler when the system is hot
Tyre pressure gauge when the system is hot and the vessel full
Pressure gauge on the boiler when the system is cold
Tyre pressure gauge with the vessel disconnected from the central heating system
A central heating boiler fires on demand for heating. The flame is established for a second or two before ‘locking out’. What is the most likely fault?
Ignition electrode failed
Rectification probe failed
Air pressure switch stuck in the open position
Gas valve solenoid burned out
A customer reports that she needs to top up the boiler regularly but cannot see any signs of leakage. All pipework from the combination boiler is visible and no signs of leaks are present. You have noticed signs of water at the pressure relief valve discharge pipe outlet. What is the most likely cause of the pressure loss?
Boiler pressure gauge is malfunctioning
Both check valves at the external filling loop are passing and the system is backflowing into the cold main
The cylinder coil has failed, leading to central heating water leaking into the secondary water
The expansion vessel has ruptured
You have been called to an old open vented system which has a pumped heating circuit and a gravity hot water circuit. The radiators are cold but the hot water is hot, despite the controller being switched to heating and hot water. No zone valves are installed. What is the most likely cause of the fault?
Failure of boiler thermostat
Failure of circulating pump
Failure of synchron motor
Failure of cylinder thermostat
