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Domestic Hot Water

Exam revision materials for Plumbing Level 2&3 and ACS Gas Safety test

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Hot Water Cylinders

Cylinder Types

Direct Cylinders

  • BS 699
  • no inhibitor allowed
  • MIN primary circuit size - 22mm (28mm for Solid Fuelled)
  • heated by Immersion Heater
  • Shower Connections
    • Surrey Flange connects to the top of a cylinder
    • Essex Flange connects to the side of a cylinder
  • 50°C - required temperature at hot water outlets
  • 22mm - MIN vent pipe size
  • 450mm - MIN offset between HWSC and Open Vent Tee
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Indirect Cylinders

Indirect copper cylinder

  • Has a coil heat exchanger
  • Annulus Type (single feed, 114L ~ £400)
    Annulus rype hot water cylinder
    • NO Inhibitor allowed as it has inside cylinder overflow pipe
    • Restrictions on the size of a primary circuit
    • Air Seal - separates Primary Water from Secondary
  • High Performance Cylinder
    • Heat recovery time is 15min
    • Larger heat exchanger (coil) surface
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Thermal Stores

Thermal Store

  • Also known as Water-jacketed Tube Heater
  • Blending/Mixing Valve is installed at the hot water outlets
  • Store temperature is 70°C
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