In a hydronic system, should the circ pump come before or after the exp tank?

jeremypbeasley

Space is super tight as I rebuild a 100 year old cast iron radiator system into multiple zones. The old circ pump sat between the exp tank and the boiler. I'd prefer to keep it that way, but I've read some places that you want it after before air in the lines can burn up the pump. Is that actually a risk?

Any reason OPT B won't work?

I welcome any other critiques to my drawings and overall setup, too!

mattmia2

The circulator should be pumping away from the expansion tank. You could use a tee to get it there if you have to. There are also vertical versions of air separators and dirt separators that can help you accomplish that. If the circulator is pumping in to the expansion tank, the tank will absorb some of the pressure differential that the circulator has created instead of it being used to push the fluid through the system. It will also reduce the pressure at the inlet to the circulator making cavitation more likely.

hot_rod

Consider one if the electronic ECM delta P circulators. The work nicely with zone valved

The expansion tank could be mounted anywhere as long as it connects into the piping near the pump inlet

It dies nit need to be below the air purger, so you could use a vertical purger, tee the tank into the line before the circ

with a low pressure drop boiler like that, the expansion tank could connect into the return at the boiler also