3
Grant Euroflame Condensing External Modules
During the combustion process, hydrogen and oxygen
combine to produce heat and water vapour. The water
vapour produced is in the form of superheated steam in
the heat exchanger. This superheated steam contains
sensible heat (available heat) and latent heat (heat
locked up in the flue gas). A conventional boiler
cannot recover any of the latent heat and this energy is
lost to the atmosphere through the flue.
The Grant Euroflame condensing boiler contains an
extra heat exchanger which is designed to recover the
latent heat normally lost by a conventional boiler. It
does this by cooling the flue gases to below 90° C,
thus extracting more sensible heat and some of the
latent heat. This is achieved by cooling the flue gases
to their dew point (approximately 55° C).
To ensure maximum efficiency, the boiler return
temperature should be 55° C or less, this will enable
the latent heat to be condensed out of the flue gases.
The boiler will achieve nett thermal efficiencies of
100%.
To achieve maximum performance from the Grant
Euroflame condensing boiler, it is recommended that
the heating system is designed so that a temperature
differential of 20° C between the flow and return is
maintained. The use of modulating circulating pumps
(now widely available) and effective control systems
should be considered.
The Grant Euroflame condensing boiler will however
still operate at extremely high efficiencies even when
it is not in condensing mode and therefore is suitable
for fitting to an existing heating system without
alteration to the radiator sizes. The boiler is capable of
a maximum flow temperature of 75° C.
1 - INTRODUCTION
How a condensing boiler works
1.1
Heating system design considerations
1.2
To achieve the maximum efficiencies possible from
the Grant Euroflame condensing boiler, the heating
system should be designed to the following
parameters:
Radiators:-
Flow temperature 70° C
Return temperature 50° C
Differential 20° C
Underfloor:-
Flow temperature 50° C
Return temperature 40° C
Differential 10° C
1 Size radiators with a mean water temperature of
60° C.
2 Design system controls with programmable room
thermostats or use weather compensating controls
to maintain return temperatures below 55° C.
The boiler should not be allowed to operate with
return temperatures of less than 40° C when the
system is up to operating temperature.
3 The use of a pipe stat is recommended to control
the return temperature when using weather
compensating controls.
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