venturi system

Paul S_3

Hey everyone...I went to a call and the customer just had there boiler (hot water) replaced by a different company....they couldn't solve this issue....before boiler was replaced everything in home worked fine....they have a diverter tee system with venturi tees with 3/4 inch baseboard.....one baseboard in the second floor bedroom does not heat up....there is a elbow on the return side of the baseboard with a bleeder vent...at first I tried to bleed the baseboard some air came out for a little but then just water......I know Dan h says " if you don't get air it ain't a air problem"....but I think there is air trapped somewhere in that loop because it worked fine 3 days ago....thisbaseboard loop comes off of a regular tee then goes up about twenty feet onto baseboard 9 ft long then returns another twenty feet into a venturi tee.....Does anyone have any ideas on what to do....I was thinking of re filling the system floor by floor like you would do on a gravity hot water system to get the air out...or simply put a purge set up on that loop.....any ideas???

Alan (California Radiant) Forbes

Monoflow system

Monoflow systems are well known for being hard to bleed.  Try increasing the water pressure which will make the air bubbles smaller and easier to move around. If this doesn't work, you might need to put a bleeder on the supply side.  If that doesn't work, add a little bit of liquid soap to the boiler water which reduces water surface tension and will allow the air to mix with the water to be carried away to a venting location.

Paul S_3

alan

So the soap will drive the air into solution slot better....I'll add another bleeder on the supply side....stupid question but how much is a little?

Ironman

Worked Fine 3 Days Ago

What's changed. If nothing's different in the piping or pumping, then it's probably air. Try a table spoon or so of Dawn as Alan suggested. If that doesn't work, you could put a ball valve between the Tee's of the problem rad and close it to force all the flow through rad and purge it that way. Then open it back up.



The piping to the rad sounds like it might be an issue also. 20 feet up and then down may be offering a little too much resistance; add some trapped air and flow stops. It may need a diverter Tee on both supply and return.