Pumping Away

D. Brown

I understand why the expansion tank should be upstream of the circulator as in 'pumping away', but in a boiler such as a Weil McClain GV5 that has an internal circulator on the output, where should the expansion tank go? I would think, according to the theory, that it should go close to the boiler on the return so that it's 'upstream' of the circulator but this doesn't seem to be where people put them. Are they wrong or am I? Thanks for your help!

Josh M.

Normally I would pipe both an air vent and the expansion tank out of the baffle port. But I just looked up the GV series boilers on my CD-ROM and they don't have a baffle from what I see. However if it were me I would relocate the pump onto my system piping downstream of the expansion tank and air scoop. It will take some BX cable and labor but that is what I would do. Another thing you might consider is puting the expansion tank on the return close to the boiler inlet. The pump is on the supply so it will add it's presure to the system piping and the boiler will be at or below you point of no presure change. But that is if you have a primary secondary system or you have only one pump of course. Hope this helps...