Question 1

What is central heating?

Accepted Answer

A system providing heat to an entire building from one central source. Central heating heats the whole building from a single source (boiler/furnace), distributed through radiators, UFH, or ducts.

Question 2

What percentage of UK homes have central heating?

Accepted Answer

97%. Approximately 97% of UK homes have central heating, mostly traditional boiler and radiator systems.

Question 3

What are the TWO categories of domestic central heating systems?

Accepted Answer

Open-vented and Sealed. Open-vented (fed from F&E cistern, open to atmosphere) and Sealed (fed from mains, expansion vessel). Every system falls into one of these.

Question 4

An open-vented system is fed from:

Accepted Answer

A feed and expansion cistern in the roof space. Open-vented = F&E cistern in loft. The system is open to atmosphere via the vent pipe. Pressure is controlled naturally.

Question 5

A sealed system uses which component instead of an F&E cistern?

Accepted Answer

An expansion vessel. Sealed systems replace the F&E cistern with an expansion vessel (steel cylinder with neoprene diaphragm) to absorb expansion.

Question 6

Why are sealed systems considered more modern than open-vented?

Accepted Answer

Greater flexibility in boiler/cylinder positioning. Without gravity circulation requirements, the boiler can be positioned anywhere. Sealed systems also heat up faster and offer better control options.

Question 7

What is the purpose of the open vent pipe in a vented system?

Accepted Answer

To allow expansion to escape and release air safely. The vent pipe rises from the system and turns over the F&E cistern. Expanded water rises into the cistern; air escapes to atmosphere.

Question 8

What happens if the open vent, cold feed, and pump are incorrectly positioned relative to each other?

Accepted Answer

The system may not work properly and corrosion from constant aeration may occur. Incorrect positioning can cause the pump to push water up the vent/cold feed or create circulation between them, introducing air that causes corrosion and noise.

Question 9

What is a semi-gravity system?

Accepted Answer

Gravity for HW and pumped for heating. Semi-gravity = gravity circulation for hot water (no pump on primary) + pumped circulation for heating radiators.

Question 10

What pipe sizes are typical for semi-gravity primary flow and return?

Accepted Answer

28mm flow, 28mm return, 22mm vent, 15mm cold feed. 28mm primary flow and return, 22mm vent pipe, 15mm cold feed. The large bore pipes allow gravity circulation to work.

Question 11

In a one-pipe system, the last radiator is approximately how much cooler than the first?

Accepted Answer

15 deg C. ~15 deg C cooler. Water loses heat at each successive radiator. Last radiator must be larger to compensate for the lower temperature.

Question 12

What is the advantage of a two-pipe system over a one-pipe system?

Accepted Answer

All radiators achieve approximately the same temperature. Each radiator has its own flow and return to the boiler, so all receive water at approximately the same temperature. No need to oversize distant radiators.

Free heating systems exam questions

1. What is central heating?

2. What percentage of UK homes have central heating?

3. What are the TWO categories of domestic central heating systems?

4. An open-vented system is fed from:

5. A sealed system uses which component instead of an F&E cistern?

6. Why are sealed systems considered more modern than open-vented?

7. What is the purpose of the open vent pipe in a vented system?

8. What happens if the open vent, cold feed, and pump are incorrectly positioned relative to each other?

9. What is a semi-gravity system?

10. What pipe sizes are typical for semi-gravity primary flow and return?

11. In a one-pipe system, the last radiator is approximately how much cooler than the first?

12. What is the advantage of a two-pipe system over a one-pipe system?

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