MHS Boilers Ultramax 115, Operating & Maintenance Manual, Page: 10 / 46

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2.2.1 Description of principal components
The boiler is constructed from the following principal components:
Fan [26]
The DC fan, which is equipped with a speed feedback, draws in the combustion air and increases
the air pressure. The speed feedback signal is relayed to the regulator, which adjusts the speed if
need be.
Gas train
The principal component of the gas train is the main gas valve [25]. The quantity of gas is adjusted
in proportion to the quantity of air being supplied. The quantity of air depends on the speed of
the fan. As an option, the unit can be equipped with a gas filter [27].
Burner [4]
After the gas/air mixture has been distributed over the burner using a distribution plate, the mixture
is burnt on the burner surface such that the flame is directed downward. The burner is both
air and water-cooled. The water headers are constructed of cast iron (stainless steel for water
heater), and ensure a two-pass flow through the burner.
Heat exchangers [6, 7 and 8]
The first heat exchanger is constructed of smooth stainless steel pipes and transfers most of the
combustion energy to the system water. The second heat exchanger is constructed of laser-welded,
stainless steel finned pipes. The third heat exchanger is constructed of smooth stainless
steel pipes. The second and third heat exchanger transfer the heat from the combustion gasses to
the system water. All water headers are constructed of cast iron (stainless steel for water heaters),
and ensure a five-pass or three-pass flow through the heat exchangers (depending on the
type). The space between the burner and the first heat exchanger constitutes the combustion
chamber.
Water headers [21]
The water headers are part of the burner and the heat exchangers.
Water connections
These consist of a flow connection [13] and a return connection [19]. Both of these connections are
provided with a filling/drain valve [18]. The flow switch [20] is fitted on the flow line.
Boiler pump (optional)
The boiler pump must be mounted on the return connection to the unit and must be directly connected
electrically to the supplied lead protruding from the rear of the appliance. The capacity and the working
head of the pump must be sufficient to overcome both the resistance of the boiler and some system
resistance. As an option, the pump is supplied as a separate item with the boiler.
Condensate receptacle [9]
A condensate receptacle is fitted underneath the last heat exchanger. This receptacle is equipped
with a condensate and flue gas outlet.