NEW
Font size
WorksheetsHot Water Systems Quiz 4
Total questions: 20
Worksheet time: 10mins
A vented indirect system is overheating. The boiler stat is set correctly, the cylinder stat has failed closed, and the immersion heater is isolated. Which component ultimately prevents the stored water from reaching boiling point?
Blending valve
Boiler thermostat
Open vent pipe
Expansion vessel
A hot water system has a long pipe run to a remote bathroom. Hot water takes over 60 seconds to reach temperature at the bath. Which solution MOST effectively reduces wasted water while maintaining efficiency?
Increase pipe diameter
Fit trace heating to the hot pipe
Install secondary circulation with time control
Raise cylinder thermostat setting
During commissioning, rigid copper DHW pipework is soundness-tested. After stabilisation, the test pressure is held for one hour. What outcome indicates a PASS?
Pressure drops by 0.2 bar
Pressure fluctuates with temperature
No pressure drop observed
Minor seepage at joints
A customer reports water discharging at the tundish only during heat-up. Incoming mains pressure is within limits and the PRV is serviceable. Which check should be carried out FIRST?
Reset the overheat cut-out
Check expansion vessel pre-charge
Replace the T&PRV
Reduce cylinder stat to 50 °C
Which condition MOST strongly indicates a failed heat-exchanger coil on an indirect cylinder?
No hot water at outlets
Boiler short-cycling
Discoloured hot water and F&E overflow discharge
Cold water warming at taps
Why must the secondary circulation return connect in the top third of the cylinder?
To reduce installation cost
To minimise heat loss from the return
To maintain stratification and usable hot draw-off
To increase static pressure
A cylinder repeatedly trips the immersion MCB shortly after energising. Insulation resistance is low. What is the MOST likely cause?
Failed immersion thermostat
Limescale on element only
Failed immersion element
Incorrect cable size
Which regulation primarily governs energy efficiency and heat retention of hot water systems?
Building Regulations Part G
Building Regulations Part L
Water Supply (Water Fittings) Regulations
Gas Safety Regulations
Hot water is stored at 60 °C, but bath outlet temperature measures 54 °C. Which control is MOST likely incorrectly set or faulty?
Boiler thermostat
Cylinder thermostat
Blending valve
Pressure reducing valve
A vented system exhibits parasitic (one-pipe) circulation. Which installation detail MOST directly prevents this?
Insulating the cylinder
Increasing CWSC capacity
450 mm rising hot draw-off before vent tee
Fitting a non-return valve
Which situation presents the highest legionella risk?
Active dead leg to a frequently used basin
Passive capped branch after appliance removal
Secondary circulation on a timer
Short hot draw-off to a kitchen sink
During decommissioning for cylinder replacement, which action must occur before draining?
Open all draw-off points
Remove cylinder stat
Isolate heat source and label
Disconnect cold feed
Cold water at taps becomes warm intermittently. The vent has discharged previously. Which combined cause is MOST plausible?
Undersized cold feed and high mains pressure
Failed blending valve and PRV
Overheating cylinder and hot/cold pipe proximity
Failed immersion and air lock
Which component is common to both vented and unvented DHW systems?
Open vent pipe
Expansion vessel
Cylinder thermostat
Tundish
A stainless-steel cylinder in a soft-water area shows early internal corrosion. Which maintenance item MOST likely prevented this if serviceable?
Blending valve
Expansion relief valve
Sacrificial anode
PRV
What is the MAXIMUM permitted temperature for hot water delivered to a bath?
50 °C
55 °C
48 °C
60 °C
Which fault MOST likely causes steam in the loft and intermittent vent discharge?
Failed PRV
Failed cylinder thermostat
Failed blending valve
Undersized vent pipe
Why are valves prohibited on the open vent pipe?
They reduce flow rate
They cause contamination
They defeat the primary safety relief function
They increase heat loss
A secondary circulation system is installed without time control. What is the MOST likely consequence?
Reduced scalding risk
Increased bacterial control
Increased energy consumption/wastage
Improved draw-off temperature
Following commissioning, which documentation should be completed and handed over?
Manufacturer instructions only
Gas Safe certificate only
Benchmark certificate and system handover information
Water undertaker notification
