Discussion

The Boiler

The project house has an older gas boiler which is now comparatively inefficient (70%) for a number of reasons

  • It has a constantly lit pilot light for igniting the main burner
  • The main burner is either fully on or off.
  • The heat exchanger is poor by modern standards 
Modern boilers improve efficiency (90%+) in a number of ways
  • There is no pilot. Main burner ignition is electronic.
  • The main burner heat output is variable.
  • The heat exchanger is highly efficient. So much so that heat is recovered from the water in the exhaust gas causing it to condense. (Hence the term condensing boiler).

The Radiator System

The ideal heating system would consist of
  • Self contained room areas (rather than open plan spaces).
  • A heater in each room connected to one heating system.
  • Accurate thermostat control of the heating in each room.
  • Heating that was aware of the room occupancy. If the room was not occupied the temperature could be reduced. e.g. living room.
The project house has 
  • Separate rooms.
  • A radiator in each room (although one has an independent electric fan heater).
  • The radiators have thermostats.
  • There is a central thermostat in the living room in addition to the room thermostat.
Therefore, most of the criteria is in place but experience shows it is no where near acceptably controlled for the following reasons.
  • The radiator thermostats are often shielded by furniture or general room clutter.
  • The doors to rooms are more often open than shut so heat from one area can move to another. This makes thermostatic control of the individual areas more difficult.
  • The radiators are not positioned to give good overall heating.

The Boiler Control System

  • The boiler is designed to provide a flow temperature of the order of 80 deg C and receive return water from the radiators at 60 - 70 deg C. Over 80 deg C and the boiler will switch off until the water temperature drops to an acceptable temperature.
  • It has a programmable time clock to control when the heating system is operational. This provides two periods per day to be defined.
  • A room thermostat controls the boiler during operational periods to control the house temperature. the thermostat is located in the living room. 
The control system is inefficient or has the potential to be for the following reasons.

  • The flow and return temperature requires checking and if incorrect the radiators should be balanced.
  • The programmer is quite inaccessible. A more accessible and sophisticated programmer would allow for easier control.
  • The single room thermostat is a simple mechanical type offering only coarse temperature control.
  • If the living room is up to temperature, the thermostat can potentially switch the boiler off leaving the other rooms under heated.