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Unit 216: Boilers Part 2 Combination boilers

Total questions: 25

Worksheet time: 13mins

Name
Class
Date
1.

Which statement best describes how a combination boiler supplies domestic hot water (DHW)?

a)

Rainwater is collected and heated in an external tank

b)

Cold water is heated by an open-vented cast coil

c)

Pre-heated water is stored in a large DHW cylinder

d)

Cold mains water is heated through a plate heat exchanger

2.

Before installing a combination boiler, what should be checked at the property?

a)

Incoming mains pressure and flow rates

b)

Window glazing thickness and seals

c)

Attic insulation depth and R-value

d)

Boiler flue colour and wall paint

3.

Which traditional components are NOT required with a combination boiler?

a)

Sealed system expansion vessel

b)

Cold water storage cistern

c)

Feed and expansion cistern

d)

Open-vented header tank

e)

Domestic hot water cylinder

4.

A sealed central heating system in a combi boiler primarily means

a)

The DHW uses stored water open to air

b)

The boiler has a sealed combustion chamber only

c)

The heating circuit is pressurised and not open to atmosphere

d)

The system automatically vents through roof pipes

5.

Which limitation should be explained to customers about DHW draw-off with combi boilers?

a)

Only one draw-off point should be used at a time

b)

Two taps can run if boiler is set to eco

c)

Multiple showers can run without temperature drop

d)

Unlimited outlets can open at constant temperature

6.

When a combi boiler is providing DHW, what usually happens to the central heating (CH) circuit?

a)

The CH circuit is temporarily cut off

b)

The CH circuit increases pump speed

c)

The CH circuit runs at reduced temperature

d)

The CH circuit continues unaffected

7.

Why can it take time for DHW to reach temperature at a tap with combi boilers?

a)

The loft tank slowly refills before heating

b)

The pump circulates cold water for storage

c)

The cylinder reheats after each use cycle

d)

Water must travel and be heated on demand

8.

In hard water areas, what issue can affect combi boiler performance?

a)

Freezing in the open vent pipe

b)

Corrosion in the loft cold tank

c)

Scaling in the plate heat exchanger

d)

Air ingress via the header tank

9.

Flow rates for DHW in combi boilers are typically

a)

Unlimited when mains pressure is high

b)

Set by manufacturer to achieve a temperature rise

c)

Completely user-adjusted with no limits

d)

Dependent only on pipe size to taps

10.

If the mains water supply is cut off, a typical combi boiler will

a)

Use roof tank to maintain DHW

b)

Switch to stored cylinder operation

c)

Boil CH water to supply taps

d)

Provide no DHW back-up supply

11.

Match each combi boiler internal component to its function.

a)

Diverter valve

1.

Directs flow between DHW and CH circuits

b)

Secondary DHW plate heat exchanger

2.

Transfers heat to mains water for hot taps

c)

Circulating pump

3.

Moves water around central heating loop

d)

Pressure relief valve

4.

Safeguards by relieving excess pressure

e)

PCB control board

5.

Controls and coordinates electronic functions

12.

Which requirement most influences whether a combi boiler can deliver adequate hot water to a large bath quickly?

a)

Sufficient mains pressure and flow rate

b)

Length of radiator pipework

c)

Size of open-vented storage tank

d)

Presence of gravity hot water loop

13.

Which connection is used to fill a sealed combination boiler system?

a)

A filling loop between CWS and CH return

b)

A vent pipe from CH flow to cistern

c)

An open header tank above the boiler

d)

A drain cock on the heating circuit only

14.

In normal operation, a combination boiler’s primary circuit is considered:

a)

Sealed and pressurised circuit

b)

Open and vented circuit

c)

Gravity-fed low pressure

d)

Partly sealed with open vent

15.

Match each item with its role when filling a combination boiler.

a)

Filling loop

1.

Temporary bridge to pressurise system

b)

CWS connection

2.

Supplies cold water to the loop

c)

CH return connection

3.

Receives water back into the circuit

d)

Vented header tank

4.

Not used in sealed systems

16.

What is the overall width of the wall-hung boiler case shown?

a)

390 mm

b)

280 mm

c)

690 mm

d)

325 mm

17.

When fitted to the wall frame, what is the depth from the case front to the wall?

a)

195 mm

b)

690 mm

c)

390 mm

d)

280 mm

18.

The height from the bottom to the top of the boiler case front is closest to which dimension?

a)

325 mm

b)

260 mm

c)

690 mm

d)

390 mm

19.
Question Image

Match each connection on the combination boiler to its distance from the left case edge.

a)

Condensate drain

1.

33 mm

b)

CH flow

2.

65 mm

c)

DHW outlet

3.

130 mm

d)

Gas

4.

195 mm

e)

CH return

5.

325 mm

20.

Which connection uses a 22 mm pipe diameter?

a)

DHW outlet

b)

CH flow

c)

PRV drain

d)

Gas

e)

DCW mains in

21.

From the left case edge, which pair correctly orders the CH flow and gas connections?

a)

195 mm then 65 mm

b)

33 mm then 325 mm

c)

65 mm then 195 mm

d)

130 mm then 260 mm

22.

Which connection is located furthest to the right on the connection bar?

a)

CH return at 325 mm

b)

Gas at 195 mm

c)

DCW mains in at 260 mm

d)

PRV drain at 291 mm

23.

Select all connections that are specified at 15 mm diameter.

a)

DCW mains in

b)

DHW outlet

c)

CH return

d)

Condensate drain

e)

PRV drain

24.

Which statement best describes the relative positions of the condensate and PRV drains?

a)

Condensate is left of PRV drain

b)

Condensate is right of PRV drain

c)

Both share the same position

d)

PRV drain is above condensate

25.

What is the correct pipe size for the CH return connection on this boiler?

a)

18 mm

b)

22 mm

c)

15 mm

d)

28 mm