Bulex Thema Condens AS 48-A, Manual, Page: 38 / 199

MAKSİCONDENSE 48-65
Notes
01/2018 32 Training 0020260859_00
3.1.3 Primary heat exchanger
Exemplary image of the primary heat exchanger/front view with insulating plate
The heat exchanger consists of several heat exchanger elements
– the coils. Each individual heat
exchanger element then consists of a stainless steel bare tube coil with four threads. The heat ex-
changer elements that are located upstream of the insulating plate are referred to as the
"non-
condensing level" because only a very low level of condensation occurs here. The heat exchanger
elements located downstream of the insulating plate are referred to as the "condensing level" as
this is where most of the condensation occurs.
First, the hot flue gases from the burner are circulated around the (four or five) heat exchanger
elements upstream of the insulating plate (non-condensing level). The flue gas that has already been
cooled then heats the elements (1 or 2) downstream of the insulating plate. (Cross-flow heat ex-
changing principle). The advantages include very efficient heat transfer and preventing boiling noises
caused by high flow speeds in the bare tubes. A further advantage of this heat exchanger is its very
low tendency to calcify, as the small cross-section of the pipes causes strong turbulence. The return
connection of the heat exchanger is located at the back, the flow connection at the front. A con-
densed water drain is connected to the heat exchanger.
Note: Cracking noises when heating up and cooling down
Cause: As a result of the uneven thermal expansion of the burner flange and heat exchanger, crack-
ing noises may occur in ecoTEC units when they are heated up or cooled down.
The heat exchanger (PWT) that is used benefits from the further developments in
the course of the heat exchanger development (A+ project) and fully complies with
the EU-wide ErP standard requirements.