Steam boiler system comprising: - a steam boiler generating steam from feed water; - a condenser (2; 42) for transferring heat from said steam to said feed water; - a first feed water conduit for connecting said condenser (2; 42) to a feed water source for supplying feed water to said condenser (2; 42); - a second feed water conduit connecting said condenser to said steam boiler for feeding feed water from said condenser to said steam boiler; - a first steam conduit (8; 48) connecting said steam boiler and said condenser (2; 42) for supplying steam to said condenser (2; 42) from said steam boiler; - a condensate reservoir arranged to collect condensate generated from said steam in said condenser (2; 42); - a first condensate conduit for connecting said condensate reservoir to an attemperation unit; wherein said boiler system further comprises: - a second condensate conduit connected to said condensate reservoir and directly to a steam drum in said steam boiler for feeding condensate out of said condensate reservoir and into said steam drum; - a first regulator valve arranged to regulate the flow of condensate through said second condensate conduit; - an economizer unit connected to the second feed water conduit between said steam boiler and said condenser (2; 42); - at least one temperature sensor adapted to measure at least one parameter indicative of the temperature of the feed water in the second feed water conduit; - a control unit adapted to control said first regulator valve at least partly in dependence on information collected by said temperature sensor; and - at least one condensate level sensor (20; 44) adapted to measure at least one parameter indicative of the condensate level in the condensate reservoir, - said control unit is coupled to the at least one temperature sensor and the at least one condensate level sensor (20; 44); wherein said control unit is adapted to control said first regulator valve at least partly in dependence on information collected by said condensate level sensor (20; 44). - a steam boiler generating steam from feed water; - a condenser (2; 42) for transferring heat from said steam to said feed water; - a first feed water conduit for connecting said condenser (2; 42) to a feed water source for supplying feed water to said condenser (2; 42); - a second feed water conduit connecting said condenser to said steam boiler for feeding feed water from said condenser to said steam boiler; - a first steam conduit (8; 48) connecting said steam boiler and said condenser (2; 42) for supplying steam to said condenser (2; 42) from said steam boiler; - a condensate reservoir arranged to collect condensate generated from said steam in said condenser (2; 42); - a first condensate conduit for connecting said condensate reservoir to an attemperation unit; - a second condensate conduit connected to said condensate reservoir and directly to a steam drum in said steam boiler for feeding condensate out of said condensate reservoir and into said steam drum; - a first regulator valve arranged to regulate the flow of condensate through said second condensate conduit; - an economizer unit connected to the second feed water conduit between said steam boiler and said condenser (2; 42); - at least one temperature sensor adapted to measure at least one parameter indicative of the temperature of the feed water in the second feed water conduit; - a control unit adapted to control said first regulator valve at least partly in dependence on information collected by said temperature sensor; and - at least one condensate level sensor (20; 44) adapted to measure at least one parameter indicative of the condensate level in the condensate reservoir, - said control unit is coupled to the at least one temperature sensor and the at least one condensate level sensor (20; 44);