← Energy H61-05 · Module 5 of 7 · Pages: 18 · Worksheets: 5

Solar thermal and hot water

Work out how much hot water your house needs, choose the collector and cylinder, and join sun, range and boiler into one system without frost damage or Legionella

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Solar thermal and hot water

In short

  • One person uses roughly 40–60 L of hot water a day (45 °C, 113 °F), which is 600–800 kWh a year.
  • In the UK and Ireland count on 1.2–1.6 m² of flat-plate collector and 50–80 L of cylinder per person. The sun covers roughly 50–60 % a year, almost all of it in summer (in most of the US, 60–80 %).
  • A collector in a frosty climate must have frost protection: glycol or drain-back. Water in a collector bursts it in one frosty night.
  • In summer a collector reaches 150–200 °C: a safety valve, an expansion vessel and a mixing valve on the outlet are a must.
  • Legionella likes lukewarm water: heat the cylinder to 60 °C (140 °F) regularly.

What's inside

Chapters

  1. How much hot water you need
  2. Flat-plate collectors and evacuated tubes
  3. Thermosiphon or pump
  4. How much collector and cylinder
  5. Frost, overheating and scalds
  6. Legionella and water hygiene
  7. Sun, range, boiler and electricity together
  8. Home-made collector and summer shower
  9. Installation and maintenance
  10. Common mistakes
  11. Printable checklist

Worksheets

  • Collector and cylinder size
  • Savings and payback
  • System sketch
  • Temperature and pressure log
  • Questions for the installer and calendar

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