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Read through the material below, then test your understanding.
Module Lessons
Hot Water Systems: Planning & Design
Fuels Used in Hot Water Systems
Open Vented Storage Systems
Unvented Storage Systems
Localised Water Heaters
Unvented System Pressures
Secondary Circulation Systems
Hot Water Safety Controls
Functional Controls: Strainers & PRVs
Expansion Devices & Check Valves
Pressure Relief, Tundish & Composite Valves
Discharge Pipework: Sizing & Termination
Design Information Sources
Sizing Cisterns & Storage Vessels
Hot Water Pipework Sizing
Sizing Circulation & Boosting Pumps
Sizing Expansion Vessels & Presenting Designs
Installing Unvented Hot Water Systems
Testing & Commissioning Hot Water Systems
Diagnosing Hot Water System Faults
Component Fault-Finding: Pumps, Vessels & Thermostats
Servicing & Maintaining Hot Water Systems
Lesson Overview
Unvented hot water storage systems operate above atmospheric pressure, requiring fail-safe controls to prevent water reaching 100°C and flashing dangerously into steam.
Learning Objectives
Identify the three tiers of thermal safety required by Building Regulations Approved Document G3.
Explain the operating temperatures and actions of control thermostats, energy cut-outs, and temperature relief valves.
Distinguish between direct and indirect safety interlock mechanisms and understand why pressure relief alone is insufficient.
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