Question on bleeding air from convector

veissman_Bob

Good morning everyone, I have a four zone gas hot water system pumped with a Taco Bumble Bee set at at 40 degree delta T.  It generally is running at 7-10 gpm depending on how many zones are running at once.  My zone on the second floor is what I think is a series loop of finned tube baseboard with two convectors in the middle.  I'm not getting any heat in the rooms on the second floor between the two convectors and I think it's due to air getting trapped in the convector piping. 



Is it normal to have to bleed a zone several times before all the air is released, and how exactly do I bleed these convectors?  I've been opening the screw head on the right, but there's also a non-slotted square plug on the right that looks like it could be opened.  I haven't tried bleeding from there yet and I'm wondering if that could be the reason that the zone stopped flowing for the second time this week.  I've got an air separator on the system.



I'm hoping this is just a matter of gradually releasing all the air from the new system, and that the air is just naturally rising to the highest point in the system.



Thanks in advance for your thoughts! 

billtwocase

careful

with those. I wouldn't touch the plug in that. The screw head is the coin vent. The convector should have been pitched upward to the return side when installed. This make bleeding them much easier and more effective. When replacing the coin vents, they can snapped off in those convectors, so work the one you have carefully. I would also clean the fins. You can have an auto vent installed in place of the coin vent also

furnacefigher15

air bleeding

Bleed air with all the pumps and boiler off.



The air is likely settling out during the off cycles.

billtwocase

I always

bleed when water is being circulated. I can see that he needs to lift up the left side so water can enter, and the air come out

Steve_210

Personally

I would not install automatic vents anywhere that a leak could do damage.

They will leak eventually, you could keep the cap closed but that defeats the purpose

furnacefigher15

with water circulating

This can work.



But, I've always found the turbulence can cause the air to move with the water, instead of coming out of suspension and therefor binding it in the system longer, and perhaps somewhere else.

furnacefigher15

with water circulating

This can work.



But, I've always found the turbulence can cause the air to move with the water, instead of coming out of suspension and therefor binding it in the system longer, and perhaps somewhere else.

icesailor

Personally:

I would never install automatic air vents on the second or top floor. When and if the system pressure goes below the pressure great enough to keep the water level above the vent, it sucks air into the system through the automatic vents.

The 3/8" plug on the convector has a greater chance of coming out with a 6 point socket than the 1/8" coin vent removed by a rookie. In the hands of a professional, it would probably come right out.

The nasty dark brown water stains around the coin vent tells me that the system has been leaking somewhere like the Pressure Relief Valve and fresh water is being introduced into the system. Not a good thing. And that isn't a "Cion Vent". It is an automatic air vent. They suck air into the system if the system pressure is loo low and draws a vacuum as the system temperature drops. That vent is part of your problem.

The fact that the system keeps getting air bound says that the system pressure isn't high enough. The convector is connected with steel pipe, not copper tube. Where I work, it is unusual to see IPS piped convectors piped with series looped baseboard. When they are, there are usually mono-flows under the floor. The fact that there is rust scuzz tells me that the con vent is leaking. If the system pressure is too low, air is getting into the zone there.

There's a reason that it is getting air bound. I never see radiators, convectors or baseboard get air in them when the system pressure is correct.

icesailor

Auto Vents:

Those auto vents have issues. If the system pressure isn't high enough and they are always trying to "vent", they will alsolet air back in during a cooling down/off cycle. Hot water will evaporate in the fiber disks making them leak in and out at all times. Butthey will never flood.

They are nice and expensive when new but awful when old and need to be replaced.

billtwocase

Ice

That doesn't look like the Taco auto bleeder, just look like a mongrel bleeder. If I understand him correctly, the zone is mixed zip loop with 2 wall convectors. I have never had a problem with hivents on those, as a matter of fact, I had a house that had 13 wall convectors, and every one had a Taco 400. The house froze that winter. Only damage was all the Taco's split. It saved every one of those wall convectors from splitting. Talk about luck.I can see the low pressure on the upper floor vent taking in air. Having the correct pressure would solve that, and pumping away also. I do like to close the caps on the upper floor, and loosening it to bleed it is OK, and close it back down. It is a safer way to bleed, rather than taking a chance with a coin vent that can leak just as much. I have repaired many a wall convector that the vent snapped if in. No fun, and easy outs rarely are the savior on them.

Big Ed_4

Convectors

Second floor convectors and base board . I would think the convectors where changed out for baseboard in the past. Check the baseboard for bleeders as well. Leave that plug alone. The risers on a monoflow "should " always rise up to the bleeder which does not mean that it does ... questions , are you bleeding out air everytime you try to bleed ? After you bleed out the air do you get a heat flow ?

icesailor

Bleeders:

Bill,

That's an auto bleeder no longer made like a Beacon or a Dole.

If the system pressure isn't high enough to keep water well above the vent, and the level drops, the vent will allow air into the top of the system. You can have a pressure leak but a vacuum leak is a lot worse.

Remember, If you have water at zero (O#) pressure, and there are air bubbles trapped in the water, putting the water under pressure will compress the bubbles and make them smaller. If you take the same water and put it under a negative pressure or vacuum. the bubbles become larger. The higher the vacuum, the bigger the bubble.

If that guy keeps getting air in his system, he needs to raise the system pressure. Especially if the air shows up on the second floor.

How do I know?

Put an oil line under a high vacuum and watch the bubbles form from the entrained air in the fuel oil. Been all over that.

veissman_Bob

very interesting replies

and thanks for all the advice.  This loop is a series loop with two convectors in the middle of finned tube baseboard.  When I bleed the air out, yes, the system flow returns and I get heat in the one half of the loop between the convectos that hadn't previously been working.  Now keep in mind, this only happened twice so far.  But I didn't realize that the slotted vent allowed air back in when the circuit is off....I thought it was merely a bleed only and that it sealed completely once it was tightened back down.  



The boilers a Viessmann Vitodens 200 with a Taco air separator in the basement and a Taco Bumble Bee running on a 40 degree delta T at about 6.5 GPM.  I thought about possibly decreasing the Delta T to mayber 25 or 30 degrees to increase the system flow but haven't done that yet.



Everything's been running fine today but I just rebled both convectors for the heck of it and got no air from one, and very very little air from the other....so hopefully whatever air was in the loop is out?



I'm still experimenting with the delta-T and the boiler curve....trying to reach the point where the zones all run nearly continuously at the lowest temp possible.  But I realize it'll be a bit of trial and error before it's all dialed in correctly.

furnacefigher15

20 degree delta

The radiation was designed at 20 degree delta, a 40 degrees drop is too high for the application.



Try 20 and I'm guessing the problem will solve itself.

icesailor

Pressures:

Crank the system pressure to 20# at the boiler. The air will stop. The flow of the circulators have no effect on system pressure.

Accurately measure the height in feet, from the boiler gauge to the height above the gauge to the convector. Multiply that elevation number by .434. The answer is how much pressure in PSIG you need to keep the water in the convector.

Put 22# pressure in the system and leave It for a week. If you get air up there, tell me and I will say I was wrong. GLADLY.

I learned about auto coin vents years ago. I learned why here.

Today, I close down EVERY coin vent and float vent. I haven't opened a jet tee cap or a coin vent (unless it was a CI radiator) in 20 years. I purge it once and never get a drop of air, later. Raising the pressure compresses the air. Less air means more flow. And I NEVER get an air locked system. Unless the system pressure drops because the PRV isn't working.

Last month, I drained a big gravity system to install a 4-way mixer. One radiator wouldn't get hot. I found under the house that someone had re-piped the radiator and it was absolutely flat and going down hill at the radiator because of foundation and floor settling. I jacked up the radiator. Nothing. The radiator valve had been replaced. The stop was broken. I couldn't tell when the valve was open or closed. Remembering something I read here about high pressure, I decided to crank the pressure in the system to 25# overnight to try to compress the air. I was able to get an exact replacement, made in China valve, and went back the next morning to drain the system and replace the valve. The radiator was working and is still today as of this morning. I returned the valve for credit.

If you can compress the air enough to get the slightest flow, it will absorb the air and start working.

As far as auto vents, my high range hearing is so accurate, I hear air leaking in the other room. I hear the vents vent out air. And suck in air when I am draining a system. 

veissman_Bob

On pressure and Delta T

Good morning and thanks for the replies.



The system's running at about 15 lbs. now.  I'm not sure how to raise the pressue manually but I'll check the Vitodens manuals tonight and see what I can do.



As for Delta T, I'm running 40 to try and force the system to condense as much as possible.  Viessmann recommended a 30 degree delta T.  I'll crank it down a bit in stages and see how that works.



So far though everything is continuing to work after the two purges.  Hopefully it worked its way out.

icesailor

Raise the pressure:

Raise the pressure. 15# isn't a lot of pressure for a two story building if the boiler is below the first floor. Raise the pressure to 20# and see what happens. It will improve.

veissman_Bob

I think I figured it out

Thank you everyone for your replies, I think I finally figured it out.  Changing the delta T on the Bumble Bee didn't do the trick and I couldn't find any way to rasie the pressure on the Vitodens 200.  I tried running the "air purge" function last night and that didn't do it either.  Also bleed air from the convectors this am for like the 7th time this week and got very little air out.....so I don't think it's an air bubble problem any more.



In the end, I think the problem is that my Bumble Bee running in delta T mode is running too slowly to overcome the head on the second floor to push through the two convectors in that circuit.  Delta T has it running at 6.5 GPM which I suspect is pretty slow for four zones across a basement, first floor, and second floor.I switched to "constant speed" mode on the bumble bee and everything seems to OK now.  I'll report back later once I confirm but I think that's the problem. 

icesailor

Pressures and Delta "T"'s"

Don't take this wrong but you do not understand how a hydronic system works.

There is absolutely NO CONNECTION to anything the boiler or circulator can and will ever do to the static system pressure. That is the pressure in the system when it is at rest. Static system pressure is controlled by the pressure reducing valve. It is the "automatic boiler fill valve". It usually comes pre-set to 12-15#. It is adjustable by following the instructions. If the domestic potable water system pressure is 50#, you need a valve to reduce the pressure in the low pressure heating system. Down to 12-15# or more.

Circulators have absolutely no control over static system pressure. They can only add restrictive pressure to the discharge of the pump against the restriction of the piping and heat emitters.

Raise the pressure to 22# and your problems will be solved. Guaranteed!!!

When I fill and purge a system, I don't even go upstairs to vent. I just purge at the boiler. I turn on big houses with cast iron radiator systems. I back feed the boiler or turn on the by-pass on the PRV and do the top floor first. I run down to the first and if the pressure on the air is high, I turn off the fast fill. I vent and I'm done. I never go back. NEVER. If they are convectors like you have, I don't even take the covers off to vent them. When the pressure is up at (anything below 30#) , I walk by and listen to the "hiss". Before I leave, I go by and every convector is hot. Only if the PRV fails, will the second floor heat stop. A sure sign that I need to replace the PRV.

RAISE THE PRESSURE.

STEVE PAUL_3

Not a coin air vent

That is not a coin air vent. It is an old style automatic air vent. It has a series of internal porous paper disks inside. The air will pass through the disks when they are dry ,until the water comes to the air vent, then the water will wet the paper disks causing them to swell and seal off the water flow. When they were newly installed and not compromised by mineral build-up... THEY WERE CRAP!!! As time went by they got worse and leaked. Notice the water stains on the fitting in the picture.

veissman_Bob

Thank You!

Icesailor, no offense taken at all, in fact I absolutely appreciate the fact that you're being so helpful and teaching me the basics.  When my contractor first installed the system, the system pressure gauge wasn't working.  He came back later and replaced it during temperate weather and it wasn't until it started getting cooler that I started noticing a problem on the second floor,

I attached a couple of photos.  One is of the pressure gauge which shows it's operating at 15lbs.  The other is of the fill valve...the tag on it reads "set 12-15 psi" and "range 10-25 psi". 

So my quesiton, please, is this:  To raise the systme pressure, do I just open the fill valve until the boiler pressure gauge reads 20 lbs? 

And thank you very much for your help.



Bob

icesailor

Watts 1156F:

See that "lever" on the top of the valve that is pointing down? Lift it up until it is pointing at 12 O'clock. You will feel resistance at 4 O'clock. You will hear water going into the system. When the gauge on the boiler reads 20#, move the lever into the old position.

To make a permanent adjustment, move the lever out and unscrew the assembly with the lever. You will see a threaded brass hollow bolt with a brass pin in it. There is also a nut under the adjuster. Loosen the nut. Pull the pin out and take a wide bladed screw driver, Turn the threaded bolt/screw down two complete turns. Tighten the nut. Leave it. Put the pin back and re-install the cap. The pressure will go up some. Raise it until you get enough pressure. Adjusting the screw is a permanent adjustment. The other, using the by-pass is temporary.

After you make the proper adjustments, you may find that the system is quieter.

If the pressure on the boiler shown on the gauge goes up when the circulator is running, it is showing flow pressure resistance through the boiler. Depending on where the gauge is in the boiler. I've never looked.

veissman_Bob

Thank you so much

Thank you, thank you, thank you!  I opened the lever and adjusted it up to 22 lbs, and reset the bumble bee back to delta T mode set at 30 degrees.  I'll post again to let you know how it works.



Assuming it's all ok, do I need to make the "permanent" adjustment or will it work fine as is with the "temporary" setting?

furnacefigher15

monoflo?

Resetting the pump for costant speed, and trouble going away makes me wonder if you has a monoflo piping system.



If you take some pictures of the piping near the boiler, and also below the radiators from the basement, I could probably tell.

Paul48

manual

Here's the manual for that auto-fill regulator. I'd also pick up a cheap sillcock pressure gauge to put on the boiler drain to double check the accuracy of your gauge. http://media.wattswater.com/1910265.pdf

veissman_Bob

It's good!

Thank you everyone, especially Icesailor for setting me straight on what I do and don't know!  I came in around midnight and the house was a nice, warm 68 degrees everywhere.  Same thing this morning at 6am - 23 degrees outside, 68 degrees inside.  Three of the 4 zones are running and circulating 120 degree water.  System pressure's maintaining at the 22 lbs. I set it to last night.



Thanks again and Merry Christmas to all! 

icesailor

Bled:

After a few days, if the pressure stays at 22#, if you didn't do what i said on how to adjust the pressure, do it. Just turn the readjusting screw down 2 full turns. And set it. If the pressure isn't high enough and it starts to get air again, do ONE turn. You don't want it to be excessively high, just high enough to keep the water level above the convectors.

There's a minor issue with the Extrol/Expansion tank but that's for another day.

Have a warm and merry Christmas or Holiday.

veissman_Bob

Will Do!

I will, and thank you again so so much!