In a direct DHW system, there are chances where precipitation of limestone will occur when heated. This precipitation will then clog the boiler and the nearby pipework. Therefore, direct system is only suitable to be used in areas of “soft” water. This

system could lead to damages or even explosion and is not suitable for hot water central heating.

Direct Hot Water Supply

system

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Types of Direct DHW system: Various fuels and systems of design can be used to heat the water in this system, including the following •  Electric Water Heating •  Gas Storage Heaters •  Boiler-Cylinder System •  Instantaneous System

Inst

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The indirect dhw system is probably the most common form of dhw and allows a

boiler to be used for central heating purposes

Water from boiler in primary pipework

passes through cylinder containing heat exchanger to heat up water

The closed circulation of water can prevent clogging. Secondary circulation is required

to prevent dead legs.

Indirect Hot Water Supply system

Indi

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Types of Indirect DHW system: Various fuels and systems of design can be used to heat the water in this system, including the following •  Vented Storage Hot Water Supply

System (Indirect/Direct Heated Cylinder)

•  Unvented Storage Hot Water Supply System

•  Indirect Hot Water system with Expansion Vessel

Vented Storage Hot Water Supply System  

Unvented Storage Hot Water Supply System  

Indirect Hot Water System With Expansion Vessel  

These   heaters   are  fuelled   either   by  gas   or   electricity  a n d   h e a t   t h e  water   only   when  required.

These heaters are located near a sink a n d h a v e a capacity not more than 15 litres. The stored water is h e a t e d b y a n electric element until the water has expanded enough to discharge from t h e d i s c h a r g e spout.

INSTALLATION  Considera>ons:  •  Type  of  materials  for  pipe  •  Type  of  hot  water  supply  system  

Types  of  Pipe  materials  available:  •  Copper  Pipe  •  Cross-­‐Link  Polyethylene  (PEX)  •  Polybutylene  (PB)  

W  Maintenance  •  Temperature  check:                  -­‐  principal  loops                  -­‐  subordinate  loops                    -­‐  localized  loops                  -­‐  monthly  inspec>on    

• Water  soNening                  -­‐  removes  minerals  from  hard  water    

• Water  sample  inspec>on                      -­‐  to  ensure  no  contamina>on                      -­‐  weekly  inspec>on    •  Chlorine  inspec>on                      -­‐  disinfec>on  of  bacteria                      -­‐  annual  inspec>on    •  Calorifiers  inspec>on                      -­‐  removes  inspec>on  hatchs                      -­‐  annual  inspec>on  

Vented  Water  Hea>ng  Systems  

Advantages   Disadvantages  

Less  complicated   Requires  the  support  of  cold  water  storage  tanks  

Low  cost  upon  purchase  

Easy  to  maintain  

Unvented  Water  Hea>ng  Systems  

Advantages   Disadvantages  

Doesn’t  need  cold  water  storage  support   Incompa>ble  power  showers  

Provides  hot  water  to  any  draw  off  points   High  installa>on  cost  

Direct  Solar  Water  Hea>ng  Systems  

Advantages   Disadvantages  

More  efficient   Cannot  be  used  with  hard  water  

Flexible  collector  installa>on   Requires  an  automa>c  drain  valve  

Less  risk  of  overhea>ng  

Indirect  Solar  Water  Hea>ng  Systems  

Advantages   Disadvantages  

Good  freeze  protec>on  system   Risk  of  breakdown  at  high  temperatures  

Less  problem  with  hard  water  

CASE  STUDY  1  

PROBLEMS  FACED    •  Pipe  leakage:                                        Common  causes:  PH  value  of  water  (only  affects  metal  pipes)  Water  velocity/pressure    •  Check  valve  failure:                                            Common  causes:  Water  velocity  Back  siphonage    

FUTURE  IMPROVEMENTS                                      recommend  the  hotel  to  s>ll  keep  the  previous  water  hea>ng  systems  just  as  a  back  up  for  when  it  is  not  sunny,  thus,  giving  the  hotel  an  interchangeable  water  hea>ng  system.    

CASE  STUDY  2  

Initially, this hotel uses an electrical water heating system. But after some time, due to some inefficiency due to the electrical water heating systems, the hotel manager decides to upgrade its system by replacing those electrical heaters with 21 thermosiphon solar water heaters, which in turn, •  reduces the hot water demand by 50%. •  it also reduces the overall energy consumption by a stunning 80% •  also adds up to approximately 1200 litres of additional storage capacity Due to its success, the hotel, later adds another 4 additional units.