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Boiler information
C. Things to be clear
The boiler is not the heating system
As already mentioned the boiler can not be seen as an independent
unit. It is only one of the parts in the global heating system. As
shown in the following figure, a heating system consists of 4 main
parts.
Figure 3: Different parts of a heating system
- Boiler/burner combination: the part producing the
heat
- Piping with pumps and valves: the part distributing
the heat
- Radiators, convectors,…: the part emitting
the heat to the room
- Control equipment as room thermostat, outside temperature
control: the part controlling room and water temperature
The heating system efficiency can be much lower than the boiler
efficiency
Figure 4 shows a boiler with annual losses of 660 Nm³ of gas
equivalent, which is a part of a heating system with global annual
losses of 1289 Nm³ of gas equivalent. In this case the boiler
losses only amount to 51% of the total energy losses.
Figure 4: Losses of the different parts of a heating
system
The different parts of the heating system interact
Convector, radiator or floor heating requires different water temperatures
for their optimal use.
Different water temperatures will be obtained by using different types
of control systems. A control system with merely an aquastat controlling
the burner will cause a constant boiler temperature. A gliding water
temperature control will adapt the water temperature to the heating
demand.
These differences in water temperature will of course lead to differences
in boiler efficiency and in distribution losses.
These are only a few examples of how the parts of the heating system
interact.
The heating system interacts with the building
The main function of the heating system is to compensate for the
heat losses of the building. When the heat losses of the building
decrease, the requirements for the heating system change at the
same time. This has practical consequences.
For instance, a building owner considers carrying out following retrofit
actions for his building: double-glazed windows, new roof insulation,
a new boiler and a new control system for the heating. In this case
it is essential that design and other considerations concerning the
heating system take the new situation into account. First calculate
the new energy demand including the insulation measures and then work
out the heating system. Not doing so would lead to oversizing and
wrong assumptions on payback time.
Simple and cost effective measures can improve the heating system
Improvements of the piping, radiators, control equipment,…
can often be done with simple and cost effective measures. Pump
control, insulation of distribution pipes, installation of a room
thermostat, optimisation of control settings are often easy actions
to improve the energy efficiency.
Source: VITO
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