Buffer tank and air vent together?

MikeyB

Does it make any sense to install a buffer tank(boiler buddy) and an Sprio Vent in the same system? I know the Boiler Buddy comes w/a high capacity air vent, but will that vent do as good as a job as a Spriro Vent would? Is it a waste of material/money to install both? thanks guys

Jean-David Beyer

Spirovent location.

I am not a professional, but I have a boiler and an indirect-fired hot water heater. Weil-McLain for both. The water heater is not used as a boiler buddy, but it is a tank-within-a-tank design with an automatic air vent at the top. The boiler has a fancy air extractor, a Taco 4900 series that is a lot like a Spirovent. The Indirect did vent some air when the system was first installed. Since that time, I have checked the vent about once a month for a while. The first time, I got a little air, but now all I get is water from the vent. I infer that all the air that will come out that way is out.



It was pretty clear that this did not remove all the air from my system. (I did not expect it to.) The fancy air extractor eventually got the rest of the air, but it took about 2 months. I believe it was this slow because the water to heat the house is only about 135F at most, and usually much less, and those air extractors work best if they are hotter (to drive off the dissolved air). But eventually it got the rest of the air.



So my answer to your question would be to use both, but put the spirovent immediately after the boiler (after the relief valve, too, I suppose) so as to deliver the hottest water to it. This will get rid of the dissolved air and possibly the microbubbles that will probably not come off in the hot water tank.

hot_rod

maybe

it depends on your system mostly.



Operating temperature, amount of fluid, type of distribution, elevation changes in piping, etc.



Basically how much air is left in the system after the initial purge. How much air and O2 is in the fill water and how much comes out when heated.



Lots of tubing? Small diameter tube, lots of hiding places Vents on the terminal units, radiators, manifolds, etc.?



There is no question micro bubble resorbers function much better than a "wide spot in the road" with a float vent up high. That is what they are designed to do and our lab tested most of the brands available and they all work in the 90% efficiency range. This type of remover will get the problematic microbubbles quicker and more efficiently than a float vent only.



When you look at the cost, life expectancy and increased system performance relating to heat transfer in the boiler and heat emitters, I would say micro bubble resorbers are an excellent investment.



Unless someone builds the resorber into the buffer tank, stay tuned for that coming soon.



hr

MikeyB

buffer and air eliminator

Thanks guys, HR the system will be a small one, mostly bb w/a mod-con and an  indirect, the system will not contain much water at all. looking in adding a Boiler Buddy to give the  the  Mod Con something to "Chew On"  want to avoid any potential short cycling. Having been a big fan of the Spiro Vent I'm thinking of adding one any way for the extra insurance. A resorber in a buffer tank sounds like a real good idea.

Jean-David Beyer

I am curious.

When you say "they all work in the 90% efficiency range" about the microbubble type of air extractors, I wonder what you mean by efficiency. It seems clear to me that they must be more effective than the simple air scoop design.



They seem to be more effective at microbubbles, and probably effective at removing dissolved air as well. By efficiency, do you mean the fraction of dissolved air that remains in the water? In Chapter 13, page 482, of John Siegenthaler's book, he suggests that a microbubble resorber can remove 99.5% of the dissolved air. I would think that would be in the 99.5% efficiency range. I do not know at what temperature he bases his number, however. I would guess 180F.



This is of some importance to me because my contractor put in no vents in my system, other than the float type air vent in my indirect hot water heater and the Taco microbubble resorber in the secondary loop of the heating system. In particular, there are no vents in my radiant slab (below the bubble level) and in my finned-tube heating zone (above the boiler. Now the finned-tube zone would worry me, because any air remaining in that zone would just accumulate until the zone quits because the circulator might not be able to push that much air out. So far, in a year, this has not happened, so I infer that any residual air dissolves in the water and comes back out in the microbubble resorber. Which is fine with me.

hot_rod

micro bubbles

generally do not make much noise and largely go un-detected in hydronic systems. But they tend to gather on the surfaces of heat exchangers, boiler walls and distribution surfaces. When they do they can limit the fluids ability to "touch" the surfaces and transfer the energy, insulation if you will.



IF the bubbles combine and grow large enough they may be pushed back to the "wide spot" purgers.



This link below shows some of these concepts at work.



There are a lot of air elimination devices, they all have a place and pros and cons. It can be as simple as an 1/8" coin operated manual vent, up to 12" pipe sized separators.



Even the small brass air vents with floats are built to do certain jobs. Rated by operating pressure and the amount of air they can remove.



Specialty vents and eliminators. like solar specific, need to be able to withstand temperatures of 300F or more.



And proper pipe sizing, component location and pump sizing are all part of air elimination.



www.caleffi.us/en_US/caleffi/Details/Magazines/pdf/idronics_2_usa.pdf



hr