How come air in a bb heat pipe stops circulation?

[Mark42]

Went to my sister house to help purge the bb heat. There was some air trapped in a second story zone and the big B&G pump would not circulate through that zone. I purged all 6 zones to be sure there was no air and everything worked fine. The problem is that the air vent is corroded and just drips water. Her husband will put in a new one soon.<br /><br />What I don't understand is why the pump can't push the air bubble through the system. The air is not trapped in the pump, and water circulates through all the other zones. I'm guessing that the air acts like a spring, compressing and absorbing the pressure from the pump so it doesn't circulate?<br /><br />This leaves me scratching my head.<br /><br />Mark.

 

[Ben Konopacky]

Re: How come air in a bb heat pipe stops circulation?

its not a positive displacement pump,its a circulating pump,it needs a full columb of fluid to be pushed thru the boiler.air in the sys. gets compresser and the circulator can't overcome that press.=no circulation.

 

[Mark42]

Re: How come air in a bb heat pipe stops circulation?

I see. Do you have a preference to which side of the boiler the circulator motor goes on? The installer put the Taco circulator on the outlet side of the boiler. In my sisters house, the B&G pump is the return leg. I would think that being on the return side would have an advantage to life expectency because of lower temperaturs of the return water. <br /><br />Or doesn't it matter.<br /><br />Thanks,<br /><br />Mark.<br /><br />Ps, I decided against installing a larger circulator because I discovered that the 4 zones were not balanced and two large zones were not getting flow because of the water taking a "short cut" through the small zones. Simply closing the ball valve 1/2 way on the short zones caused water to flow through the two large zones. Now all 4 zones can be open at once and the return temperature water is hot on all 4 zones. After a full weekend test, the house is heated more evenly.

 

[Ben Konopacky]

Re: How come air in a bb heat pipe stops circulation?

Mark42; If its single zone its in the retutn leg, if its multi-zone its off the manifold header,one for @ zone.BUT in your case its the contractors way to make $$$ One circ.and bal. valves & zone valves. Im not saying its bad!

 

[Mark42]

Re: How come air in a bb heat pipe stops circulation?

Ben Lucky,<br /><br />Thanks for you'r help. Builders are known for skimping on hardware. And if you want something better than "spec" you pay big time for the upgrade.<br /><br />Tonight it's 17* outside and the house is evenly heated for the first time in years. <br /><br />Mark

 

[Winger Ed.]

Re: How come air in a bb heat pipe stops circulation?

Originally posted by Mark42:<br /> I don't understand is why the pump can't push the air bubble through the system.

There is just a big air bubble in there someplace.<br /><br />It lets the pump push water in, then the bubble moves around the water, and lets the water go on by on its way 'downstream'. <br /><br />/////////<br /><br />Imagine taking a 2-3" clear plastic hose that runs uphill, over the top, and back down....<br /><br /><br />Taking mouthfulls of water, blow into it... the lower part fills until you get to the top of the 'hump' right?.......<br /><br />Then, how much, and how fast can you blow mouthfulls of water into your 2" pipe to overcome the air-gap/bubble at the top of the pipe as it goes over the top and dissplaces the air? <br /><br />Pretty hard, or impossible ,, huh?<br /><br />Your circulation pump(if you're not relying on a gravity/convection system) has the same problem.<br /><br />////////<br /><br />I'm a gas-heat, 'scortched air' guy myself. And so far this Winter--- I ain't even spent $75 running it... <br /><br />Hey,,,, <br />I just realized that means I won't have to sell nearly as much blood or pick up so many Al. cans along the hi-way as I'd anticipated last Fall in order to have my Merc.'s heads shaved/cut, and get the new gaskets....LOL... <br /><br />Anyway:<br />With you being a 'hot water' type,,,, it sounds like you need a NEW air vent at the top of your system,,, or a much bigger circulating pump than ya got.

 

[Mark42]

Re: How come air in a bb heat pipe stops circulation?

Winger Ed,<br /><br />Thanks for the explanation. The problem was at my sisters house, and it was caused by a bad air vent as you suspect. Hopefully, her husband has installed a new one by now. <br /><br />BTW, it is 7* this morning, and the pipes have not frozen so I assume that the anti-freeze is doing it's job. And the house is warm. So I am a happy camper!<br /><br />Ed, how cold is it there? Only $75 to heat this year? Sure you don't live in LA?<br /><br />Mark.

 

[MrBill]

Re: How come air in a bb heat pipe stops circulation?

Ben Lucky has it right...the circ pumps should always be on the return leg. Notice the down arrows on the Taco '07' pumps, circ pumps pull rather than push, thus explaining the problem with air in th lines. Without proper air vent operation, the lines will get filled with air, is impossible to avoid when water is heated under pressure. Also, each zone should have a flow check valve which allows the water to circulate in only one direction, otherwise you'll encounter the proble described where uneven flow occurs or happens when it shouldn't. This is more important where the system uses one pump and electric valves to regulate zone flows.