Hot Water Systems revision notes
Vented and unvented hot water, safe delivery temperatures, expansion and secondary circulation.
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C&G Unit 205: Vented Cylinders & Vented Layouts
Direct and indirect hot water cylinders
How a direct cylinder differs from an indirect one, and what single-feed and double-feed mean.
Hot water systems: vented vs unvented
How vented and unvented hot water systems differ and why scald safety matters.
Hot water: open-vented vs unvented cylinders
How vented and unvented cylinders manage pressure, expansion and safety.
Stored water temperature and Legionella awareness
Why hot water is stored hot and cold kept cold, and how dead legs and stagnation raise bacterial risk.
Vented versus unvented hot water systems
How open-vented and sealed unvented hot water systems differ and why unvented needs layered safety controls.
C&G Unit 205: Hot Water Temperature & Scald Safety
Blended (mixed) outlet temperature (worked example)
Using a simple mixing balance to work out how much hot and cold water gives a safe delivered temperature.
Scald risk and the thermostatic mixing valve
Why hot water is stored hot but delivered cooler through a TMV.
Scald risk: temperature versus contact time
Why hot water scald risk depends on both temperature and contact time, and where the tension with hygiene sits.
Thermostatic mixing valves: where and why
What a TMV does, why hot water is stored hot but delivered cooler, and where one is expected.
C&G Unit 205: Hot Water Distribution, Dead Legs & Secondary Circulation
In-depth guides for this module
Longer walkthroughs that sit alongside the revision notes.
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