Logano plus SB315, SB615, SB745 - Buderus

Technical description31RK 12RK 2Fig. 9VKFunction diagram of the heating water path inthe Logano plus SB745 floor standingcondensing boilerRK1 Return for low temperature heating circuitsRK2 Return for high temperature heating circuitsVK Flow1 Combustion chamber (1st pass)2 Condensation secondary heating surface(condensing p heating surface, 2nd pass)3 Water guide element36 720 642 881-08.2T3.1.3 Condensing p heating surfaceA special feature of the condensing p heating surface isthe spiral tubes with a reduced cross-section to match thehot gas flow rate ( fig. 10).The twisting creates microturbulence on the inside of thetube walls and therefore a greater condensation boundarylayer. This leads to the hot gas molecules alternately beingvery close to the tube wall and reaching the main flow.This means that practically the entire hot gas flow comesinto contact with the cold heating surface. This results ina very high condensation rate.As a consequence of the reduced cross-section of the spiraltubes, the speed of the hot gas is almost constant. Thisresults in high heat transfer at low flue gas temperatures.Due to the design and layout of the condensing p heatingsurface with a slight fall, the condensate drainscontinuously from top to bottom. This prevents reverseevaporation of condensate and deposits on the heatingsurfaces. The self-cleaning of the condensing p heatingsurface that this achieves promotes trouble-free operation.At the same time, the maintenance required is reduced.51234Fig. 10Structure of the condensing p heating surface using the Logano plus SB615 floor standing condensing boileras an example1 Combustion chamber2 Upper condensing p heating surface3 Water guide element6 720 642 881-09.1il4 Lower condensing p heating surface5 Cross-section of a spiral tube in the condensing p heatingsurface with the schematic passage of the hot gas flowTechnical guide Floor standing gas/oil condensing boilers Logano plus SB315, SB615, SB745 – 6 720 802 589 (2012/01) 13