expansion tank - 2 instead of 1?

Jeff Lewis

I am working on an install of a Munchkin boiler to power domestic hot water (80 gal) and radiant floor heat. The boiler supplier says that I need an expansion tank size 60. The radiant floor zones are already done, with an expansion tank size 30 in that loop. Can I just add another size 30 in my primary loop and be OK, or should I go with a 60 on the primary? Can you have too much expansion capacity?

Brad White_9

I use multiple ET's often.

Partially for redundancy and also that two 30's are often less money than a single larger tank. So long as the acceptance volume is equivalent and the pressures in the tanks are equal they will perform as well as a single tank.

I usually manifold them with lock shield valves to prevent tampering and allow change-out should a bladder rupture. But I take a single connection pipe from the common manifold at the ET's to the PONPC connection upstream of the circulator. As I know you will

Not sure what your water volume is, sounds like a lot for what should be small-ish pipe and a lot more tubing. (Not like it is an old gravity system or anything.) Just a thought but no harm in too much tank within reason.