Logano plus SB315, SB615, SB745 - Buderus

8 System examplesArea of application• Logano plus SB315, SB615 and SB745 floorstanding condensing boilers (lead boilers)• Logano Ecostream boiler• Logamatic boiler and heating circuit control unitFunction descriptionThe boiler sequence can be switched on the basis of loadand time. The lead boiler starts when the actualtemperature falls below the set flow temperature. Whenthe heat demand increases, the lag boiler is automaticallystarted via return temperature raising actuator SR2.When the operating flow temperature in the lag boiler isreached, the entire flow rate is channelled through theEcostream boiler. When the load falls, the switchingprocesses run in reverse order.Special design information• The boiler sequence cannot be reversed.• Size the heating circuit pumps in accordance with thecalculated maximum pressure drop in the heating andboiler circuit. The pressure drop levels of both boilersmust be reliably overcome.• To keep the pressure drop on the water side low, whensizing the heating circuits maintain a minimum spreadof 20 K if possible.• We recommend distributing the total output betweenthe boilers so each has 50 %.• Design the connections in such a way that the boilerscan be separated, independently of each other, toensure an emergency supply during maintenance work.• Optimum use of the condensing effect in conjunctionwith high temperature heating circuits is possible dueto separate returns on the water side. In such cases, aprimary store system should be connected to the lowtemperature return.You can check the system hydraulics (5-6-1-2-4) in the Buderus hydraulics database atwww.buderus.de/hydraulikdatenbank.64Technical guide Floor standing gas/oil condensing boilers Logano plus SB315, SB615, SB745 – 6 720 802 589 (2012/01)