Hi All,

I have a 5 zone, hydronic baseboard heating system that I have purged several times for air, and after a few nights/weeks after it comes back with the sound of water rushing and gurgling in some of the zones. I put a new pressure gauge on the boiler, and am running about 20psi most of the time.

When I purge the system, I open the feeder valve to increase the flow/pressure, making sure to stay under 30psi.

What could I do to find the source of the air??

Any help would be great!

 

CounterPoint How Hydronic System Components Really Work [pdf]
TECHNICAL BROCHURE FHD-501A

[page 12, pdf] Air Separation
[page 15, pdf] Compression and Expansion Tanks
[page 16, pdf] Closed steel compression tanks
[page 17, pdf] Expansion tanks

 

you are trying to purge with air. H2O. Heat the water and air will leave the water.How do you eliminate air and maintain air free.
Good air separator, circulators on the supply after the expansion tank.
Comfort Calc

 

[page 12, Para. 4, pdf] Air Separation

 

Thank you for the feedback. Where does the separator get installed? It seems to be (according to the manual) on the side of the boiler between the hot output side and the circulator pumps. Do I need 1 for each zone?

 

In the background, on the pipe going to the expansion tank, the grey device is your air eliminator. Make sure the cap is lose so air can escape. Might be in need on replacement too.

 

Move the pumps to supply with an air separator and problem will go away. While the unit is drained down make that relief valve code compliant and stand it up.

 

Moving the pumps is a lot of work and I don't think its necessary.. Pumps have been on the return for as long as I know.. This is a DIY site and dont think the average homeowner is moving pumps...

IMO replace the air vents you have and you should be good to go... They are most likely faulty.. I have used airvents on many many boilers. I think properly placed they work better then the scoops...

Tell us what the temp and pressure gauge read on the boiler...

Also we see the one air vent near the exp tank as quoted by Tom..... Are there any more???

We need more pics please..

 

The air separator should be placed in the system supply riser, where it will see the primary system flow and the greatest temperature.

I don't know if just adding a properly sized air separator on the supply riser would do the job or not, but it appears to be the least change to the system. The return and supply risers are undersized.

Is the boiler piped with a bypass or is the boiler in series, I can't tell without a view of all the piping below the pumps and at the back of the boiler.

 

Apparently we don't understand how circulators and air separators work. DIY or not does not change how things were designed to work.
1958 pump manufacturers suggested placing them on supply after expansion tank connection due to the introduction of one piece circulators.
Air separators eliminate air by agitating the water to release the air instead of waiting to see if the air can find it way to an auto vent

 

What do you mean Rbeck? There are 5 circs there. Do you think wise to tell a homeowner to move 5 pumps to supply side?

Pumps been on return forever.... It works.. Mine is on return. What will moving it to the supply do any different but give you a pump away method of no pressure change... I have no issues pumping to the boiler.. Its a rare phenomena when pumping to the boiler causes issues...

 

Mike, while you are correct that in most systems it makes no difference where the pump is located, in a few it makes all the difference in the world.

My first post to this forum was on just this sort of problem. Rather than advising to move the pump I instead advised moving the "point of connection" of the expansion tank to the suction side of the pump. The point of connection of the make-up water PRV was also moved to near the pump suction and the problem disappeared.

I don't have the bookmark for that post on this computer, I do have it on my laptop and I will post it later tonight. I have NOT read this thread in its totality so I might be wrong in this case.

 

He has an air issue and IMO related to faulty air vents... I am sure that system has worked fine for all those years,,


Fix air vents and all is good IMO..

This issue I am sure did not develop overnight...


[ATTACH=CONFIG]62776[/ATTACH]

 

Mike, you may be correct that in this thread it is a simple air problem related to the vents. Xiphias also had an air problem, although it didn't become a problem until after he added to the system. It is a long thread but please read the entire thing. My comments don't start until about the middle of the second page.

http://www.doityourself.com/forum/bo...baseboard.html

 

RE:repeated air problem in hot water baseboard #55 Furd

 

I did not try to ruffle feathers here but the title of this post is
"Constant Air in Hydronic Baseboard System! ". I made a suggestion that is guaranteed to take care of the problem.
Furd, thanks as that works better then what he has now. Just works better on the hot side due to heat driving out the air but will definitely work better.
I always suggest to follow the manufacturers instructions for what ever product we sold.
A little bit of information....When I was a service manager we had 28 tech's and 27.000 automatic oil accounts. When I took over as a service manager the boos said we were operating at 10.5% callback rate and wondered what we were going to do about it. FYI....average in the US is 10%. I started in-house training every Wed during the summer and every other Wed in the winter. I taught straight out of the manuals from all the HVAC products we sold, controls etc. In a year and a half we were at 2% call back rate but also reduced calls from what I called time wasting problems like purging boilers. We did away with all our air problems by pumping away due to the fact that we pumped away from the expansion on every installation after I learned that it works 100%. Hundreds of jobs later the proof was in the pudding.
I also learned that improperly placed air vents also will take out very little air to none at all and at best slow to eliminate air. I see many placed on the return side of pumps which is the worst place to place an auto vent.
Since I left that oil company I have trained thousands of tech's. I found it is best to always off the best fix. It eliminates doing something more than once.