The one in the back has the boiler feed pump bypass feeding into it, not sure it the intake for the feed pump could go in there also but it would make sense as no point in wasting water. Also a convenient way to just add water to the pan as needed. The front one seems to have no function. There are some running on yutube, this one specifically, but I cannot tell what's going on with the pump. Someday it may be operational then see how it all works. A set of instructions would be a real find.
Gen