A UV curing lamp has variable resistive ballast provided by at least one resistance alloy wire and a set of switches tapping varying positions along the resistance alloy wire. The method includes determining a flux bulk temperature from the determined heat flux and determining a flux interface temperature from the determined heat flux. The filter defines a filtered fluid chamber within the internal chamber of the tank. The method also includes forwarding the message from the source node along a path to the external address which includes an intermediate node and a destination node.