Logano plus SB315, SB615, SB745 - Buderus

System examples88 System examples8.1 Information regarding all systemexamplesThe examples in this section indicate possible ways tohydraulically connect the Logano plus SB315, SB615and SB745 floor standing gas condensing boilers.For detailed information regarding the number, equipmentlevel and control of the heating circuits as well as on theinstallation of DHW cylinders as well as other consumers,see the respective technical guides.This particular system example does not represent abinding recommendation for implementing a specificheating network. Practical implementation is subject tocurrently applicable technical rules.Information regarding further options for system layoutand engineering aids are available from the staff inBuderus sales offices.8.1.1 Hydraulic connectionSecond return connectorHeating systems with outputs above 50 kW oftencomprise several heating circuits with different systemtemperatures. In general, all heating circuits are broughttogether in a common return. This leads to a mixedtemperature which is higher than the lowest returntemperature. As a result of the raised return temperature,the system efficiency decreases.In order to prevent this unintentional return temperatureraising, the Logano plus SB315, SB615 and SB745 floorstanding condensing boilers are equipped with anadditional second return connector. The system ishydraulically optimised by the separate connection of thelow temperature and high temperature heating circuits.The return from low temperature heating circuits flowsthrough the low temperature return connector (RK 1) intothe coldest area of the floor standing condensing boiler,where maximum condensation takes place. Heatingcircuits with high return temperatures, as with DHWheating or ventilation systems, are connected to thesecond return connector (RK 2). For a high rate of energyutilisation, the flow rate through low temperature returnconnector RK1 should be more than 10 % of the totalflow rate. This optimisation allows the efficiency to beraised further. As a result, additional energy andheating cost savings are possible.Heating circuit pumpsHeating circuit pumps in central heating systems must besized in accordance with recognised technical rules, e.g.the Energy Savings Order (EnEV) [Germany].For boiler outputs from 25 kW, the power consumptionmust be adjusted automatically in at least three stages tothe pump rate required by the operation.Flow water should not be mixed into the return (e.g. with anoverflow valve or low loss header) so that the highest possibleefficiency can be achieved. One possibility is to install adifferential pressure-dependent heating circuit pump.Dirt trapsDeposits in the heating system can lead to localoverheating, noise and corrosion. Any resulting boilerdamage falls outside the warranty obligations.To remove dirt and sludge deposits, flush the heatingsystem thoroughly before connecting a boiler to anexisting system. In addition, we recommend theinstallation of dirt traps or a blow-down facility.Dirt traps retain contaminants and thereby preventoperating faults in control devices, pipework and boilers.Fit these near the lowest point of the heating system in aneasily accessible position. Clean the dirt traps every timethe heating system is serviced.8.1.2 Control systemThe operating temperatures should be controlled with aBuderus Logamatic control unit in weather-compensatedmode. It is possible to control individual heating circuits inroom temperature-dependent mode (with a roomtemperature sensor in a reference room). For this, theactuators and heating circuit pumps are constantlyactuated by the Logamatic control unit. Number andversion of the controllable heating circuits are dependenton the selection and equipment level of the control unit.The Logamatic control system can also take over controlof the burners:• 2-stage or modulating(with single boiler systems)• 4-stage or modulating(with 2-boiler systems)• 6-stage or modulating(with 3-boiler systems)The control and electrical connection of 3-phase burnersand 3-phase pumps must be made on site.For more detailed information, see the technical guides tothe control units.Technical guide Floor standing gas/oil condensing boilers Logano plus SB315, SB615, SB745 – 6 720 802 589 (2012/01) 49