The controller on my BioMax is a model RK-2001UA. Its very similar, maybe even identical to the EKO. The manual says that terminals #1 and #2 on the back can be used with an optional module to fire an additional boiler if there is no fuel. Anybody have or better yet use these terminals? If so what is the output when there is no fire, 24V? I think I'll check it out tonight and see what I can find out, but some of you may already know. Thanks, Rob.