Logano plus SB315, SB615, SB745 - Buderus

System examples8Area of application• Logano plus SB315, SB615 and SB745 floorstanding condensing boilers (lead boilers)• Logano boiler• Logano Ecostream boiler with high system pressuredrop on the water side (alternative to the systemexample on page 63)• 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 andboiler circuit pump PK.When the minimum return temperature or the operatingflow temperature in the lag boiler is reached, the entireflow rate is channelled through the boiler. When the loadfalls, the switching processes 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 additional boiler circuit pump PKovercomes the pressure drop on the water side of thelag boiler at the maximum calculated boiler flow rate.• We recommend dividing the total heating output sothere is 50 % to 60 % for the floor standingcondensing boiler and 40 % to 50 % for the floorstanding residential conventional boiler.• 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 (5-6-1-2-6) in the Buderus hydraulics database atwww.buderus.de/hydraulikdatenbank.Technical guide Floor standing gas/oil condensing boilers Logano plus SB315, SB615, SB745 – 6 720 802 589 (2012/01) 67