Combi boiler

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Across
  1. 1. caused by non-functioning combi boiler
  2. 3. a combi boiler converts chemical energy into...?
  3. 4. regulates the carbon dioxid content of the combi boiler
  4. 6. a pipe for transferring excess gas outside of the boiler
  5. 8. system used to transfer heat between two or more fluids
  6. 10. tank containing both gas and oxygen
Down
  1. 2. used for inflaming gas/oxygen-mix
  2. 5. can be filled with warm water; used for hygiene and relaxation
  3. 7. protects heating systems from excessive pressure
  4. 9. transfers heat to the surroundings