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Does manifold orientation matter?

Gordan Member Posts: 891
Is there anything in a hydronic manifold that would make mounting it in alternate orientations (say, horizontally, or sideways, or upside-down) inadvisable? The manifold I've got has balancing valves, spring-based flow gauges, isolation valves and temp gauges. None of these components, as far as I can tell, ought to care whether they're pointing up, down, sideways or somewhere in between.

Air vents, yes, but can't the orientation of those usually be changed relative to the manifold?


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Some flow meters depend upon gravity...

    some don't.

    Other than that, and the need to vent the manifold, no reason why you can't mount it in any position that suits your needs.

    Don't forget to take into consideration long term air removal. You don't want to create any air traps that would be problematic in the long run.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • hot_rod
    hot_rod Member Posts: 21,855
    but not on chilled water systems

    we don't like to see the electric actuators facing down on chilled systems. This is to prevent any condensation from running into the actuators.

    I like vertical mounting best. It allows you to loop in with the least amount of tube when some loops go up and some down.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669

    If you mount the manifold vertical with the main on the bottom the top zone will catch all of the air
  • Gordan
    Gordan Member Posts: 891
    That makes a lot of sense!

    I can see what you mean: in the top side of the manifold there will be a localized drop in flow velocity, as the manifold only gets the flow from the top zone and its effective diameter is the same all the way through. This will cause air bubbles to "de-train" and perhaps also air to come out of solution, and that could be a problem if you don't account for it, but wouldn't it also be an asset if you do account for it? I'd think that this would be analogous to what happens in a hydraulic separator, and you mount those vertically and put air vents on top, probably precisely for this reason.

    So it seems to me that it might be better to go ahead and mount manifolds that way, making sure to put a vent on top, than to count on air entrainment to bring everything back to the eliminator at the source. Am I totally off my rocker?

    Mark, HR, Tinkerer - many thanks for sharing your expertise!
  • hot_rod
    hot_rod Member Posts: 21,855
    at some point

    all the air should be removed from the system. With a good micro bubble type purger, in the proper location, within a week or do the system should be clean.

    Hydronic system conditioner fluids are a good idea also, in my opinion. Most contain oxygen scavangers, as hydronic glycols do, to assure a corrosion free, long lasting system.

    But a float vent on the manifolds is not a bad idea, regardless of the mounting orientation.

    I like the float type with a hydroscopic cap for a second level of protection, especially if the manifold is mounted in or above a finished space.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Microbubble air eliminators.

    I do not believe, from my experience in my home boiler system, that a microbubble air eliminator can always eliminate the air from a system in a week. It took me a couple of months to get the air all out of my system, that was filled with all fresh water after it was installed.

    The air eliminator is the 1 1/4 inch version of this Taco one (the one on page 2, a 49-125):


    It is my impression that this is a pretty good air eliminator. In John Siegenthaler's book, he suggests a week or two to get all the dissolved air out of the system. I believe the reason my system took so much longer to get the last little bit of air out is that the water where the eliminator is located never gets above 135F and that these devices work better at higher water temperatures, such as 180F. But since my downstairs zone is 120F maximum (on grade radiant) and my upstairs is 135F maximum (oversized baseboard), that is all the boiler puts out.

    The way I measured the dissolved air is crude: I listened to the circulators. The one to the downstairs is almost impossible to hear (Taco 007-IFC), but the one to the upstairs (also a Taco 007-IFC) made slight "air bubble" sounds. These decreased with time, but it took almost the entire heating system to get rid of them. I assume the air came out of the system in the circulator due to the lower pressure and higher temperature there. And since the temperature was so low, it took that much longer to get the air out. The system had no air sounds anywhere else.
  • hot_rod
    hot_rod Member Posts: 21,855
    air removal depends

    on a number of factors. The initial purge has a lot to do with it. You need 2-4 fps to move air along. Every zone, every loop, every pipe and fitting needs to see that flow rate to push the air along and back to the purger.

    System balancing, an often overlooked part of hydronics, has a lot to do with flow rates in zones and loops. Ideally flowsetters would be installed, checked and properly adjusted on multi zoned systems, and at every radiant loop if they are un-equal lengths.

    How else would you know what flow rate the various zones are actually seeing?

    Oversized piping, especially vertical pipes can hamper the air removal, low velocity again. Commonly seen in solar drainback systems with improper pipe sizing .

    Pump to expansion tank/ air purger relationship can have an effect air removal, especially with remote mounted circs. (see the post about double expansion tank locations)

    Sometimes burping a pump, by loosening the mounting screws will clear a volute that has trapped air. Integral check valves pumps can be tricky to get air out. Air can rise up to high points and trap in the volute. When the pump starts it is trying to pump air, or a mixture of air and water, if the volute has a trapped bubble.

    Pumps with integral check valves, mounted vertically on a header above a boiler are prone to air locking over the off season if the system was not purged completely at installation.

    The fill water has air and O2. Brand new wells can often have a lot of air in the stream until they are pumped hard for a day or two.

    So every installation is different. Generally if ALL the fluid crosses through a microbubble eliminator air will be removed quickly and completely. Pay attention to the flow rate through the eliminator also, they do have a sweet spot :)

    Maybe one small zone is not flowing enough through the purger to do a complete job.

    Watch the clear pipe SpiroVent demo at a trade show some time, it shows how well that type of eliminator actually works. The smallest bubbles and even the cloudy water with entrained air disappears quickly.

    If it took a entire heating season to rid you system of all the air, it probably wasn't the "device's" fault, something else is going on I suspect.

    Often times just raising the fill pressure a few pounds will help "squeeze" those last troublesome bubbles along the path to removal. Adjust the expansion tank pre-charge accordingly of course.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    If it took a entire heating season ...

    My view is that it was not the device's fault. There are probalby several factors at work.

    1.) The one I mentioned before, that the water temperature through the air eliminator was much cooler (at most 135F) that used to be typical.

    2.) The Taco 007-IFC points up, so air could remain trapped under the IFC valve. I do not think this very likely since the pressure goes up very fast after it leaves the main part of the volute before it gets to the valve, so the air should go into the upstairs zone. And there cannot be much air in there because the circulator flow is so high that I get only a coupla degrees drop through the zone. Not enough to get the noise I expect if the flow exceeds 4'/sec. though. Not enough to stop the flow up there either.

    3.) If the air is so slight that it is coming out of solution in the pump, and going back into solution at the pump's exit, it gets another chance the next time around the loop.

    My guess is that I am talking about a very small amount of air, that comes out of solution in the circulator and goes back into solution by the time it hits the exit of the circulator. I.e., in most of the system, it is dissolved in there. And in that condition, combined with the low water temperature, it comes out of the water only very slowly.

    Of course, if that circulator dies next season, it may mean it is cavitating in there. But a problem like that I would not expect to get better by itself. And I would expect cavitation to sound different -- more percussive I guess.
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