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Will air in line effect heat output of BB

tom3holer Member Posts: 45
I have have a new installation with 3 zones all fed with their own zone pump. It seems that in the upstairs zone there isn't much heat comming out of the BB even with 160* water. I am thinking that perhaps there is air in the line. I do not hear any noise of water running. I just cleaned all the BB removing dust and dog hair,etc. The BB are in the order of 30-40 years old. Do they tend to loose the ability to raidiate heat with age?



  • Jamie Hall
    Jamie Hall Member Posts: 22,934
    Yes and no

    that is, yes -- air in a line can reduce the heat output from baseboard (or any other hydronic radiation!).  Biut there should be a way to bleed it out...

    And no, they don't lose the ability to heat with age -- except for getting so dirty that the air can't circulate.  And you've taken care of that.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • tom3holer
    tom3holer Member Posts: 45
    edited April 2013


    Thank yu for the reply. I am surprised that there is no noise if it has  air. I did see the bleaders on  couple of the BB's and will crack hem later today and see if there is any air.

  • Paul48
    Paul48 Member Posts: 4,469
    edited April 2013

    Air usually migrates to the top of the system. It will stop circulation in the affected loop, and you should be able to tell easily. They transfer heat readily and if after the circ runs for a few minutes, the baseboard isn't hot, end-to-end, you most likely have air. They can be a P.I.T.A. to bleed,and may require that you power purge them. Sometimes when you open the bleeder, the water pushes the air away, and only water comes out. Try boosting the static pressure on the system to about 20 psi, leave it over night, and the problem may rectify itself. Does the sytem have a means of automatically removing air?
  • heatpro02920
    heatpro02920 Member Posts: 991

    is the element hot? Any new carpet or furniture? I have seen baseboard too close to the floor or people that add carpet to a room that was never carpeted, not heat correctly, because there is no air gap under the board to allow for convection....

    If the zone leaves hot and comes back hot the heat has to be somewhere, if you think there is air in the loop a simple feel test should confirm it....
  • CMadatMe
    CMadatMe Member Posts: 3,086
    Isn't Much Heat


    The emitter is only going to pull out what it needs. What's the temp difference between the zone supply and return? How many feet from the outlet of the circ through the system back to it's inlet side?
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • bill_105
    bill_105 Member Posts: 429
    edited April 2013
    Air in line affect heat output?

    Of course I'm in agreement with every written up top.

    Back to orriginal queston. After a good power purge it now has a fresh jolt of oxygen. And from this gas comes microbubbles wanting to wreak havoc on the iron stuff.

    It's my understanding that these microbubbles do in fact provide insulation causing the emmiters to not release as many BTU's. Of course this would need validation in a Lab.


    Will air in line affect heat output of BB? Yes,final
  • icesailor
    icesailor Member Posts: 7,265
    Other worlds:

    All those micro-bubbles and such work In your world.

    In my world, the only reason I put jet tees on the ends of baseboards is to keep big mouths from yapping about my not using Jet Tees and how do you get the air out. You purge it out.

    The house I built in 2000, and have lived in since then, has never been vented since it went into service. No Spirovents or unusual air elimination devices. All Taco #400 float vents are screwed down tight. Every job I do has generous purging built into it. I have a ball valve on the return with a drain above it. I put a hose into a bucket, close the ball valve, open the drain and purge away. I turn the fast fill by-pass and let it rip. As long as the water is flowing, it can be up to 28#. I don't care. When the water comes back hot, I know it is going. And also that the air bubbles stop coming. On to the next zone. I leave the pressure at a minimum of 20+#. It will settle out in time.

    I drain and turn on a lot of houses every year with heat. I have not ever been through the aggravation I've seen here. And if you feed the cold into the bottom of the boiler, you always know when the hot water is coming back. I don't have any, but if I had a system that fed through the expansion tank and then only fed cold water into the system, I'd be putting a back feed on the bottom of the boiler so I knew for sure that the zone was working. Put your hand on the return and you can feel the temperature going up and down until it goes up and you can't hold on.

    Keep it simple.

    And even if someone tucks carpet into the baseboard, the pipe still gets hot. If it's working, you shouldn't be able to hold your fingers on it. If you can't, it's working. If you can, it isn't working.

    If you hear air running through the top floor, raise the pressure. Squish the bubbles. The hot water will absorb the bubbles.

    Don't turn it into a project that needs numerous conferences.
  • heatpro02920
    heatpro02920 Member Posts: 991
    I never put tees on

    each piece of baseboard? Unless I think for some reason I will need it, like a split loop or if there is a trap somewhere, v-system, ect... I do however always install a water feed bypass ball valve on my 1156 {even with the fast fill up its slow}, this way I can really get flow through....

    As far as waiting for it to come out hot, that doesn't always work, sure years ago when we all put the feeders in the return after the purge station it would come out hot, but now a lot of systems have the feeds on the supply, and you wont get hot water through no matter what you do...

    Try shutting all the other zones, get the pressure up to just under 30#s, and at the same time open the purge valve and fast feed, keep the hose in the bucket under water so you can see if there are a lot of bubbles, this works better with 2 people because buckets fill fast and pressuring it out all at once works best...
  • tom3holer
    tom3holer Member Posts: 45

    Thank you all for the suggestinons. There are no bleeders on the top floor zone as there is on the main floor. I will increase the pressure and flush that zone. The new installation has the zone pumps on the return line and NOT pumping away from the expansion tank as I understand it should be. When I called the installer back over he agreed it was easier the way he did it but said he would chnge it.

  • icesailor
    icesailor Member Posts: 7,265
    Air vents:

    I thought of this one while flying home tonight.

    Six years ago, I got a call from the cousin of a customer. His plumber had fired him because his house was an old antique  crib. It is a two story house. The front part is heated by 1950's Cast Iron radiators on one zone on two floors. The back part is heated by fin tube baseboard. Series looped through two floors. The boiler had been replaced a number of years ago by the biggest boiler hack that ever picked up a roll of solder. Clutter is a kind word. I guess that there are vents on the baseboards and I'm sure that there are jet tees on the ends of the baseboards. The act of draining and venting this fiasco drove the last plumber away. The way the boiler is piped would make many here suffer from head explosion. But it works fine.

    The first Fall, I "Purged" all the water from the system with compressed air. I did NOT open a single jet tee or low point drain. In the Spring, I tested it with compressed air and the system is tight. I purged the baseboard part through the return. When the water starts purging back hot, I stop the flow to see if the circulator will do it. If it does, I'm done. I vent the CI radiator with a radiator key.

    If it didn't work, I wouldn't be saying that it works if it doesn't.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    Magic fluid

    Is this a job for Dawn dish washing liquid, and higher pressure?--NBC
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