Product specifications

5. Operation and Construction
The Atmos Multi is a fully automatic, gas fired, high
efficiency central heating boiler providing unvented
domestic hot water at mains pressure via an integral 80
litre copper hot water storage tank.
5.1 Appliance construction
A heat exchanger consisting of three concentric
channels is positioned in the centre of the boiler's
integral hot water tank. (Fig.1).
 Hot flue gas released from a fully modulating, pre-
mix burner positioned at the top of the heat
exchanger, is driven downwards through the heat
exchanger's middle channel.
 The second surrounding channel is divided into
eight smaller central heating water channels,
which together promote the transfer of heat from
the heat exchanger to water within the boiler's
primary circuit.
 The third surrounding channel is divided into
small air channels. These together with the
inner copper wall of the hot water tank form a
double partition between the central heating and
stored hot water.
While the hot water tank is completely insulated by
means of insulation shell sections, the hot water tank
itself along with the boiler's other components is
housed behind a removable outer steel appliance
casing, constructed in such a manner to ensure the
enclosed appliance space is ventilated.
Operation of the Atmos Multi boiler is controlled and
monitored by an electronic control unit that sends and
processes information to and from the boiler's various
temperature and control components. Along with
controlling the boiler's operation, the control unit also
provides a diagnostic programme that simplifies fault
finding by automatically sending a fault code to a
'Status/error code display ' window located on the
control unit's fascia.
Central heating & Hot water circuit
When there is a demand for domestic hot water or
central heating, the water within the boiler primary
circuit is pumped through the heat exchanger from the
bottom to top via the central heating water channels to
a three way valve.
If there is a demand for hot water only, water within
the primary circuit circulates through the heat
exchanger only.
If there is a demand for central heating only, the three-
way valve changes position allowing the heated
primary water to flow from the heat exchanger to the
central heating system.
Where there is a demand for both domestic hot water
and central heating the three-way valve stays in a mid-
position, supplying heated water to both the heat
exchanger and the central heating system.
Flue gas circuit
The burner’s combustion air fan drives hot flue gases
produced by the combustion process from the top to
the bottom of the heat exchanger. Cooling of the flue
gases occur as they flow through the flue gas channels
towards their point of exit. On cooling, the water
vapour suspended within the flue gas condenses,
transferring its latent heat as sensible heat to the cooler
water within the heat exchanger. The resultant
condensate then falls to the bottom of the heat
exchanger where it is automatically discharged via the
boiler's condensate drain point.
Due to the thorough premixing of gas and air, the
burner has a very low flame height, which results in a
very low NOx emission.
ATMOS MULTI Mk 2 version 2008
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