Air eliminator location
I am considering re-arranging the plumbing a bit in my setup. Every year in the fall or winter when i start using my heating system i need to purge the lines of air. Not a huge problem obviously but a bit of a pain since there is no drain in the basement near the boiler. The current configuration goes boiler supply —> circulator —> air eliminator —>zones—>return—> zone valves.
I am thinking of replumbing it and switching out the air eliminator to a spirovent air eliminator so the configuration would be boiler supply —> spirovent —> circulator (etc ).
I feel like the biggest issue is going to be supporting the circulator in the new location but i found threaded rod and floor supports that i think will do the job.
The big question to me, will this configuration make a differance? I keep hearing about "pumping away" and that a air eliminator should be close to the boiler yet before circulators and or pumps.
Comments
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draw your proposed system. The best way to keep air eliminated permanently is to get rid of your leaks. air doesn't naturally form in the system, it gets in there from filling. On install the system is purged of air, then an inline air separator helps to remove the entrained air in the system, air vents appropriately located remove the trapped air that can be missed via purging. If air returns to the system it either was never fully removed, or has been introduced via makeup water (ie leaks)
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Any air purger works best when you are pumping away from the expansion tank. The graphic below shows how the pump adds the pressure differential to the system, when pumping away
So boiler, air sep, expansion tank, pump.
Typically the expansion tank connects under the air purger. The fill system connects at the expansion tank also.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
So ya my current setup is wrong for sure, the air eliminator is right after the circulator. Looking at the mfg pdf for the boiler my expansion tank is connected to what is labeled as the relief valve outlet according tohttps://dunkirk.com/wp-content/uploads/2022/03/2304_0.pdf . Which seems odd to me.The more i look at my setup and compare it to the pdf the more i question what the installers did.
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It is possible to have the expansion tank connected into a port on the boiler, with fiill and relief, pump on boiler supply and air purger after the pump.
IF you use a good air sep like a Caleffi Discal, it coulld be after the pump. You are still pumping away from the expansion tank.
Any of the microbubble type air seps can be on either side of the pump with no piping distance required.
Air comes out of solution best at the hottest point and the lowest pressure. So suction or inlet side of pump., is the ultimate
Additionally the expansion tank could be on the return piping, but air sep at the hottest point, supply out of the boiler.
Other options here.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Thank you, i think for what is currently there its a bad configuration since it seems like a relatively simple seperator its a 35$ part at home depot with that tiny connection. I think as much of a pain this will be to do its going to be better if i re-arrange things a bit. The biggest pita is probably going to be supporting the pump right now its just supported by the black iron pipe coming from the boiler.
Also, thank you very much for all the information on this. It think once i re-pipe some of this it will alleviate this annual headache since there are occasions where the pump gets air bound. having a air seperator before the pump i can only imagine helping that issue.
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There are a number of different air removal sdevices.
A simple float type can often be fpound on top of boilers or indirect tanks.
Manual vents on fin tube base boardor hydro coils. Both are for high point air capture.
Back at the boiler use a good brand air separator. These are 95% efficient within a few passes of all the water through them. Within an hours running, up to boiler high temperature a system should be air free. Big bubbles and micro bubbles.
The ramp type are not as efficient as there is no media inside to capture the micro bubbles, and they need straight piping, about 18" upstream.
So the procedure could be.
A purge with hoses and fast fill
Open any manual high point vents.
Once you have circulation in all zones, the air separator takes over.
If the system has leaks and takes on fresh water occasionally air and dissolved minerals are entering. Find and eliminate any and all leaks.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
So, i have a high point auto float type with one of those scoops. But its directly after the circulator. Its also the only air eliminator in the system other than manually opening the drains on the returns.
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I thik this is what you have? It can work ok, ideally you want 12-18" of straight pipe between the mpump and air scoop/ vent.
Also vents do plug or the floats can stick and not do any elimination.
A good air separator can make a difference with air noise, increase system efficiency. You want water with no air traveling through the boiler, pipes, and heat emitters. For top performance.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Thats mostly what it looks like, except that the circulator is vertical ( shaft is horizontal ) and there is probably 6 inches of pipe after the 90 into the air scoop. It might be 18 inches from the outlet of the circulator but i would bet it should really be 18 inches with no fittings at all to let the water "settle" so to say. Knowing my dad ( the previous owner who had these systems installed ) he probably "knew a guy" who might have been kinda skilled, but maybe not really skilled if you know what i mean. Kinda funny saying that because here i am on the internet just gathering information and planning to diy this project. I just looked at my control board and i am thrilled that it has a spot on it to wire the circulator, the original installer did something where the circulator is wired off the burner. Wiring it off the control board will make more sense with the pumps new location. I feel like this will also help with the banging during the winter, almost everything i have read about that says its air in the pipes.
I think my biggest question at this point is, does it make sense to have both an air scoop with automatic air eliminator and a spirovent, or would just a spirovent work perfectly fine solo?
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Is this a Dunkirk cast iron boiler?
Yes you just nerd s good air separator, not both.
I prefer the Caleff Discal, they are more serviceable than other brands.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Yes, its a dunkirk with a tankless coil in it. Its a pretty straight forward system. Even the control board is pretty easy to understand. Only thing i fear with this unit is that it might not last terribly long, it seems to like to form leaks here and there where the coil bolts into the unit and its in the basement so its a long time before its noticed.
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Most manufacturers flow test their air separators at different operating conditions. Results show better efficiency and faster removal with microbubble type seps.
The tiny microbubbles that develop at the boiler wall need to combine it a large bubble before a scoop purger will grab and expel them.
Systems with chronic air problems do well with the microbubble removers. Withinan hour you should have complete air removal.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
I just want to say thank you, honestly you have been an absolute wealth of knowledge here.
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