phase 3 mock exam

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

Answer explanation

The correct choice is BS EN 12831:2003, which specifically outlines the method for calculating design heating loads, making it essential for heating system design.

What is the measurement of the U-value?

• W/m²K

• kj/m³C

• w/kg/K

• J/m³K

Answer explanation

The U-value measures thermal transmittance and is expressed in W/m²K. This indicates the amount of heat transfer through a structure per square meter for each degree of temperature difference, making W/m²K the correct choice.

What is the correct formula to determine the heat loss from a space through air changes and ventilation?

• 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

Answer explanation

The correct formula for heat loss through air changes is m³ x QTY x Δt x 0.33. This accounts for the volume of air, the quantity of air changes, and the temperature difference, providing an accurate measure of heat loss.

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

Answer explanation

Oversizing a heating system leads to reduced energy efficiency as boilers cycle on and off frequently ('hunt'), causing higher initial costs and inefficient operation.

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

Answer explanation

The most suitable external design temperature for a house in England and Wales with normal sheltered exposure is -1°C. This temperature accounts for typical winter conditions, ensuring adequate heating design.

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

Answer explanation

The correct formula for heat loss is 'm² x Δt x U-value'. Here, 'm²' represents the area, 'Δt' is the temperature difference, and 'U-value' indicates the thermal transmittance of the surface.

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

Answer explanation

The Mean Water Temperature (MWT) is calculated as the average of the inlet and outlet temperatures. MWT = (70°C + 50°C) / 2 = 60°C. Therefore, the correct answer is 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

Answer explanation

The Delta T is the difference between the radiator temperature and the room temperature. Given the room temperature is 20°C, a Delta T of 40°C indicates the radiator is at 60°C, making Delta T40 the correct choice.

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

Answer explanation

The term for the radiator furthest from the heat source in a central heating system is the index circuit. This component is crucial for ensuring even heat distribution throughout the system.