Study these words before doing the exercises.
heat exchanger
the component inside a boiler that transfers heat from the burner to the water
"The heat exchanger has scaled up and needs descaling or replacing."
condensate pipe
the pipe that carries acidic waste water produced by a condensing boiler to the drain
"In cold weather the condensate pipe can freeze and shut the boiler down."
modulating burner
a burner that adjusts its output level to match the heating demand
"A modulating burner is more efficient than one that simply switches on and off."
zone valve
a motorised valve that controls hot water flow to a specific area of the heating system
"The upstairs zone valve is not opening. The bedrooms are cold."
inhibitor
a chemical added to the heating system water to prevent corrosion and scale
"Check the inhibitor level annually and top up if necessary."
power flush
a process that forces water at high velocity through the system to remove sludge and debris
"A power flush will clear the sludge that is causing the cold spots on the radiators."
magnetic filter
a device fitted to the return pipe that captures metal particles before they reach the boiler
"A magnetic filter should be fitted on every new boiler installation."
bypass valve
a valve that maintains minimum water flow through the boiler when all zone valves are closed
"Without a bypass valve the boiler can overheat when all radiators are turned off."
expansion vessel
a sealed tank that absorbs pressure fluctuations as water expands when heated
"The expansion vessel has lost its charge. The system pressure keeps rising."
flue terminal
the fitting at the end of the flue pipe on the outside wall that expels combustion gases
"Check the flue terminal is clear of obstruction. A blocked terminal will shut the boiler down."
interlock
a wiring arrangement that prevents the boiler from firing unless there is an actual demand
"Interlocking the boiler with the zone valves prevents unnecessary heating cycles."
diverter valve
a valve in a combi boiler that directs hot water to either the radiators or the hot water tap
"The diverter valve is stuck on heating, so there is no hot water at the tap."
scale reducer
a device fitted to the cold water inlet to reduce limescale build-up inside the boiler
"Fit a scale reducer on the mains inlet in hard water areas."
programmer
a timer unit that sets when the heating and hot water switch on and off
"Set the programmer to heat the house from six to eight in the morning."
TRV
a thermostatic radiator valve that controls the heat output of an individual radiator
"Turn the TRV down in rooms that overheat."