Where is the air coming from?!

Brad White

If you relocate the expansion tank to the suction side of the circulators (or you can move the circulators downstream of the expansion tank at probably more hassle) you will solve probably 90% of your issue right there.

STEVE_17

(im a non-pro homeowner)

I have a hydro-air 3 zone system. Last winter, I had a 4th zone added for a radiator (radson) in the foyer. Its been cold enought to keep the circulator for this rad on almost constantly for over 2 weeks. I have bled air out of this rad every 3 or 4 days - I hear a "bumbling brook" sound from the rad and bleed it.

My question: why do I have to keep bleeding a sealed system?

Thanks

ALH_4

questions and ideas

Do you have an automatic air vent in the system? Is there an automatic boiler feed?

Did the radiator zone add much volume to the system? Is the expansion tank still, or was it ever, appropriately sized? You might make a good guess at the system volume and compare it to Amtrol's sizing charts.

How is your expansion tank's condition? What is the static pressure cold? What is the static pressure when the boiler is hot? Does the relief valve ever leak?

STEVE_17

I dont believe the is an auto air vent. I do have an auto feed. the zone added whatever the rad can hold and the piping to it (40' total 3/4 copper). I am not a pro so I dont know if the exp. tank is appropriatly sized.

I will check the static pressure once i get home and post it. I have never seen water around the boiler so i dont think there is a leak.

Thanks for your post.

Brad White_9

Are you

pumping away from the expansion tank connection point or towards it?

Pumping away is the right way to do it. Pumping to it will place all of the circulator's pressure as a negative value on the suction side, often below atmospheric pressure. This sucks in air which sucks.... you get the idea.

Check that first.

STEVE_17

the exp tank is on the supply side and the circulators are on the return. I noticed some sort of air valve right before the tank.

at 135*f the boiler reads: 16psi and at 170*f it reads the same. (notices that thats the low and high ranges even though the dial is set to 180*f the boiler cuts off at 170*f)

STEVE_17

looks like they are on the correct side: they push the water away from the supply - where the tank is and toward the return...

Brad White

Maybe post a photo?

The way I read your first description and your last description are opposite one-another. The way I read it anyway.