Level 2 · Plumbing revision
Central Heating revision notes
System layouts, controls and interlock, emitters and balancing for domestic heating.
- 13notes, free to read
- 82questions; 25 free to try
- 4topics
C&G Unit 206: Central Heating Layouts & Radiators
- Basic heating controls: room thermostat, TRV, programmer and zoningWhat a room thermostat, TRV, programmer and heating zone each control, and how they cut wasted heat.
- 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 worksThe heat source, circulation, emitters and flow/return loop that make up a typical domestic wet system.
- One-pipe and two-pipe heating layoutsHow one-pipe and two-pipe central heating circuits differ and why two-pipe is the usual modern choice.
- Open-vented and sealed systems: cisterns, vents and fillingWhat the feed and expansion cistern, open vent and filling loop do, and how a sealed system replaces them.
- 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.
- Trapped air, sludge and bleeding a radiator safelyReading a radiator's cold spot, bleeding it safely, and telling trapped air apart from settled sludge.
- Unit 206: Central heating layout systemsOne-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 valvesWhy 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 worksBoiler 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 systemCompare 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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