Central Heating revision notes
System layouts, controls and interlock, emitters and balancing for domestic heating.
- 10notes, free to read
- 106questions; 25 free to try
- 4topics
C&G Unit 206: Central Heating Layouts & Radiators
Choosing radiators from a room heat loss (worked example)
Turning a room heat-loss figure into the number of radiators needed, and why output ratings must be corrected.
How a wet central heating system works
The heat source, circulation, emitters and flow/return loop that make up a typical domestic wet system.
One-pipe and two-pipe heating layouts
How one-pipe and two-pipe central heating circuits differ and why two-pipe is the usual modern choice.
Sizing a sealed heating expansion vessel (worked example)
Turning a system water content into an expansion volume and then a vessel size, with the steps shown.
Unit 206: Central heating layout systems
One-pipe, two-pipe, and fully pumped S-plan and Y-plan arrangements.
C&G Unit 206: Heating Controls, Interlock & Balancing
Balancing radiators with the lockshield valves
Why a heating system is balanced and an ordered way to set the lockshield valves for even heat.
Boiler interlock explained: what it is and how it works
Boiler interlock is the control arrangement that stops the boiler firing when nothing is calling for heat — not a part you fit. What delivers it, and why Part L expects it.
S-plan vs Y-plan: how the valves control the system
Compare the separate zone valves of S-plan with the shared mid-position valve of Y-plan.
C&G Unit 206: Heating Water Treatment & Cleansing
Low-Carbon Heating: Flow Temperatures, Emitters & Efficiency
Follow heat and control signals through a heating system
Sketch the flow and return, emitters and controls before answering central-heating questions. Then explain what should happen when a room or cylinder calls for heat. This connects component recognition to boiler interlock, circulation and fault symptoms.
Use the free central-heating questions to practise those decisions. The radiator BTU calculator adds the relationship between room heat demand and emitter output; the Level 3 heating notes take the design calculations further, and the Approved Document L guide sets out the controls and 55 °C design a boiler replacement must leave behind.
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