WorksheetsMTL2 Hot Water Learner Outcome 1
Total questions: 40
Worksheet time: 20mins
What makes an open-vented system different?
Sealed vessel
Has a vent pipe open to air
Heated by immersion only
Works at mains pressure
Where does an unvented system get its water?
Feed tank
Expansion cistern
Mains supply
Secondary return
How is a direct cylinder heated?
Directly from the heat source (boiler / immersion)
Through a coil
By air
Only by solar
What does an indirect cylinder have?
Two immersions
A heat-exchanger coil
A vented section
A cistern
Why can water in open-vented systems not boil?
It’s open to air pressure
Thermostat stops it
Coil prevents boiling
Vessel absorbs it
What materials are best for direct cylinders?
Iron
Lead
Copper or stainless steel
Aluminium
What is stratification?
Mixing hot and cold
Layers of hot and cool water
Scale build-up
Uneven pressure
Primary flow pipe size for gravity systems?
15 mm
22 mm
28 mm
35 mm
Minimum distance from cylinder to vent pipe joint?
150 mm
250 mm
450 mm
600 mm
What does a feed-and-expansion cistern do?
Feed cold taps
Vent the cylinder
Allow for water expansion
Supply mains water
How does a Primatic cylinder separate water?
Coil
Diaphragm
Air bubbles
Valve
Which system is now banned in new builds?
Double feed
Thermal store
Single-feed Primatic
Combi boiler
How does a thermal store heat domestic water?
Uses stored water
Heats mains water through coils / heat exchangers
Mixes both waters
Uses immersions only
How are Multipoint water heater feed?
15mm from the mains water supply
15mm from the cold water storage cistern
22mm from the mains water supply
22mm from the cold water storage cistern
What does a combi boiler supply?
Heating and hot water
Hot water only
Heating only
Storage water
What part gives combis hot-water priority?
Motorised valve
Diverter valve
Thermostat
Expansion vessel
What does a single-point heater serve?
Whole house
Two sinks
One outlet
The boiler
Why does an over-sink heater drip?
Leak
Air inside
It vents expanding water
Faulty stat
What must an unvented under-sink heater have?
Tank
Vent pipe
Expansion vessel and check valve
Header tank
Normal hot-water storage temp?
40 °C
50 °C
60–65 °C
75 °C
Best immersion heater thermostat setting?
40 °C
55–60 °C
75 °C
90 °C
Water below 55 °C risks what?
Cavitation
Scale
Legionella
Air locks
Max hot-water temp to a bath?
40 °C
48 °C
55 °C
60 °C
What does a TMV do?
Mix cold water
Mix hot and cold safely
Join heating flow/return
Blend primary water
What keeps water hot in a secondary return system?
Gravity
Bronze pump
Air vent
Thermostat
When is a secondary return needed?
Short runs
Long pipe runs
Plastic pipe used
Small house
What main factor affects system choice?
Paint colour
Hot-water use and demand
Ceiling height
Gas meter size
What should system design balance?
Brand of pipes
Cost, efficiency and performance
Labour only
Fuel colour
Cold-feed pipe size?
10 mm
15 mm
25 mm
32 mm
Pumped primary pipe size?
15 mm
22 mm
28 mm
35 mm
Where should the vent pipe end?
Under water
Over cistern, above water line
With a valve
In overflow
Typical F&E cistern size?
5 L
10 L
25 L
50 L
Medium dwelling cylinder capacity?
74 L
98 L
144 L
210 L
Bath draw-off pipe size?
10 mm
12 mm
15 mm
22 mm
What can cause backflow?
Coil
Mixer tap or shower hose
Thermal store
TMV
What does a Type EA/EB valve stop?
Overheating
Hot water returning into cold supply
Scale
Air
Back-syphonage happens when?
Shower hose sits in bath water
Cistern overflows
Pump fails
Vent pipe blocked
How can back-syphonage be prevented?
Gate valve
Retaining ring or double check valve
Air vent
Expansion vessel
Electric shower water supply must be:
Gravity
Cistern-fed
Direct from mains
Hot-feed
A combination cylinder includes what?
Built-in cold cistern above hot cylinder
Instant water heater
Expansion vessel
Boiler and radiator
