Hot water line in steam boiler flashing fix

NHPResident

Hello heating experts,

I read this before posting this: https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler/

I have a hydronic system added to a steam boiler and whenever both steam (first floor)and water zone (2nd floor) are on I hear "kettling/gurgling" noise from my hydronic pipes on the second floor as well as from the circulator next to the boiler. I believe this is due to flashing, which for whatever reason still happens when circulator is on, because when steam is off, the issue stops.

Question to you all, I don't have space to add bypass line without major change, can I connect the bypass after the circulator?

ethicalpaul

You would like to pump after the bypass "recycle" joint because then the water you are pumping is cooler and less prone to flashing to steam due to the low pressure generated by the pump.

You would also like to run that outlet down to the floor where the pump should be sitting so it has a little more "head" (pressure) going into it I think. You are really close to the water level there.

I think you know this since you mentioned Dan's article which goes into all this, so all you have to do now is to move the stuff around to where it should be. Once begun, it's half-done.

pecmsg

Steam on the 1st floor and hot water on the second?

That’s going to be tough

mattmia2

I assume that the circulator direction is pumping out of the boiler. The bypass has to connect to the suction side of the circulator because you are cooling the water entering the circulator so it doesn't cavitate with the pressure drop in the circulator. You could remove that boiler drain and add a tee and connect the bypass and drain to the tee or to the fill connection or to the aquastat connection.

you could also close the valve out of the circulator or at the return a little to throttle the pump a bit to keep a little more pressure at the pump but ultimately if the boiler is steaming you will need a bypass to keep the water cool enough to not cavitate.

NHPResident

@pegmsg, the house was built with steam and for second floor addition, the previous owner added hydronic...

Thanks ethicalpaul for confirming.

Thank you mattmia2 for your ideas, will try to close the valve a bit and see how it goes before I move the pipes around.

I should be good, thank you!

EBEBRATT-Ed

You could easily take the elbow off under the pump and put a tee in its place.