7 years of air and hell

Nick6960

HI everyone, I'm reaching out to the forums because no one we have had come by can figure out the problem. I run a 20 unit appartment complex which relies on hot water heating with electric furnace and oil furnace after - 12 degrees. The same appartment on the third story constantly gets air trapped in the line. We have installed a junior Spiro vent on the system in the basement hoping it would do the trick. We changed the watts air vent on the riser which supplies that appartment and the air vent on the line itself in that unit. In that unit we have a water valve on the line for bleeding water and when we bleed from that valve air will come out 20 feet further down the line from the air vent which I find odd. It usually fixes the problem for a few week.
We have the pressure set to roughly 28 during operation. From basement to top line is roughly 30 feet. On that units heating line, in the last 6 feet there are many 45 and 90 degree bends so it runs along the wall and loops up to return back in the opposite direction. Any tips or advice? I can take pictures of the system in the basement if needed and what type of burners or boilers we have setup. Thanks greatly
Nicholas

hot_rod

A pic that shows the pump and where the expansion tank connects into the system. Many times stubborn air removal problems are related to the expansion tank pump relationship.

In some cases those high point air vents can allow air into the system!

Nick6960

The air vent in the high points are new from September, we changed the whole floor before starting the systems. I'll take some pictures for sure. This problem stems literally from 7 years ago, she's the only one getting trapped air every winter.

john walsh_2

The air seems to be accumulating in an area that isn't vented. Probably close to where you are bleeding manually. How much water are you bleeding before the air bleeds out? Is this a monoflo T system? And is there any way to install an automatic air vent close to that point?

Nick6960

Pics added

EBEBRATT-Ed

It's hard to tell from the pictures but I believe @hot rod is correct. I think your pumping toward the expansion tank if I am following the piping correctly.

This needs to be repiped by someone that knows hydronic piping and you need to pump away from the expansion tank

In addition your system pump looks pretty hefty, I have little doubt that air probably is being drawn into your air vents

Nick6960

They installed an air vent on that riser, an air vent 3 feet after zone motor that's inside the appartment, another 2 air vent near the end of the line where air stalls. The weird thing is when I bleed the water the air comes out of aor vent that's 20 feet after that point.

Nick6960

Monoflow? Our return line in the boiler room will mix with the newly heated water.

Nick6960

The pump is a 1/2 horsepower, that could cause air coming in through the vents?

john walsh_2

Can you post a few pictures of the radiator and piping in the apartment?

GW

If it was a matter of my own sanity I might cut in some valves and tees with hose connections and purge that sucker with street pressure. Bang, no more air. Are you absolutely sure your apartment loop doesn't split? Is this zoned or one stat kicks the whole building on?
Another trick may be getting a gauge installed on the highest point of the apartment with a needle that shows how low it got. I'm wondering if you're somehow dropping pressure, maybe a dumb question.

Why have electric tied into the oil boilers?

Solid_Fuel_Man

If that large red circulator is indeed pumping toward the expansion tank, then you will be pulling air in through those newly installed auto air vents. On residential sized jobs installers get away with this, but when high head circulators and long restrictive pipe runs come into play in commercial applications, the point of no pressure change really becomes critical.

It is my honest experience and opinion that auto air vents are one's own worst enemy. I like manual coin vents used sparingly. Pumping away from the expansion tank and a quality air vent really makes most systems almost self purging. When I started pumping away, commissioning and chronic air problems literally went away.

Taylor

Nick6960

Ok, so we control the on and off of the whole building and the tenants have one t-stat that opens a valve at the beginning of the appartment. Each line goes up 3 stories and branches off to its respective appartment.
As for the flow toward the exp. Tanks, if you follow the line after the motor, it will go up roughly 4 inches when using the electric furnace then come back on itself and get mixed in the mixer you can see behind the red valve which is the return. After that it goes through the Spiro vent and up into the units. There is a line that ties under the Spiro vent to the expansion tanks.. Any use to this?

Nick6960

I will add that this appartment is literally the last place that receives heat in the 20 units, being at the end of the line and a top corner unit. Would there be an advantage of installing a small circulator on this line in the appartment?

hot_rod

That is some crazy boiler room piping. Looks like someone has spray painted black spots to use an infrared temperature gun?

There could be some cross connections preventing high temperature to all the emitters? if someone has been using those points for temperature checks?

It is hard to trace the line from the expansion tank to its connection point in the system.

With a good, working central air eliminator, like that Sprio vent, assuming it is not stuck shut, you should not need all those auto vents scattered around. At the most a couple high point vents to catch an air that rises up and cannot circulate back to the Spiro.

Puge the system at the high temperature and lock all the vent caps.

I'm still betting that you are pumping towards the expansion tank if this is an ongoing problem.

Here is a graphic of what happens with a high head circ pumping towards the expansion tank, you essentially pull sub atmospheric conditions and those numerous vents will pull in air. The more vents you add, probably the worse the problem

We make a check cap for air vents to treat a symptom like this until a correction can be made. It fits most brands of vents.

Nick6960

Interesting, anti suction caps.after relooking at the piping, after the motor it goes straight then vertically up and down and the half moon shape you see is actually pushing towaeds the expansion tank. I have a feeling this was never piped correctly since day 1. We've had the place 7 years and this may be the reason is was never resolved. They just kept on adding air vents everywhere.

hot_rod

Nick6960 said:

Interesting, anti suction caps.after relooking at the piping, after the motor it goes straight then vertically up and down and the half moon shape you see is actually pushing towaeds the expansion tank. I have a feeling this was never piped correctly since day 1. We've had the place 7 years and this may be the reason is was never resolved. They just kept on adding air vents everywhere.

It may be a simple fix to finally rid the air issues.

A few other piping details that could be optimized some day..
Not a great idea to bull head piping with pumped flows, weird things can happen in those bulls:)

I'm not a fan of swing checks in hydronics. Swings need a pressure differential to close, and in hydronics that is not the case, the pressure is the same on both sides when it's closed.

Great for sump pumps however.

Then tend to get oversized by the installer sizing them by pipe size instead of CV and flow rate. This can cause clanging, and flow restriction.

The Cv of a swing check is in the full, wide open position. When they are under flowed the swing is sort of floating somewhere between open and close.

A hydronic spring check is a better option, the spring is the close pressure and it has a cone shape for friendlier flow.

Mark Eatherton

Classic case of not pumping away and throwing automatic air vents at the alleged problems and actually compounding the problem... I think I'd consider Sawzall surgery and start from scratch. I know that's not what you want to hear, but everything will be much better off if you do it right. Hydronics, when done right, are virtually silent and relatively trouble free.

Done wrong, well you know from personal experience what happens...

Few people understand the importance of doing it right. Most of them reside here.

ME

Nick6960

You guys are truly amazing, after 7 years and numerous plumbers, heating specialist and various installations I finally find my answer here. So now, is anyone in the Montreal, Canada area? Haha

Canucker

@Henry might be near you

hot_rod

Nick6960 said:

You guys are truly amazing, after 7 years and numerous plumbers, heating specialist and various installations I finally find my answer here. So now, is anyone in the Montreal, Canada area?

I was in Montreal last week doing training at Tecnico Chauffage, a wholesaler.

Call there and ask for Pierre or Luigi they can steer you to some competent hydronic guys

514 444 2126

Mark Eatherton

Henry Nachaj is your man.

Henry Nachaj email address is hnachaj@plomberieDOTcom

I guarantee you once he's done, your system will be right.

ME

Nick6960

Thanks everyone for the help. I'll try and post up when the problem is fixed.