Baseboard bleeding

dxj100

I have a hot water boiler setup with 4 zones. 1 zone has 2 loops on it. The issue I am having is part 1 of the loops work. There are no valves to separate them or the zones. I do have bleeders on the input side of my baseboards. I have bled them with the system on and off. It will work for about 30 minutes with some gurgling and running water sounds then seems to get air locked again. To me it seems the air is on the return side of the baseboards. How can I get all the air out of the system?  At the boiler side, I only have the auto fill valve, drain valve and expansion tank valve. No valves for the zones to purge the system. Thanks for any help you can provide.

neilc

what pressure do you have at the boiler?
and does it maintain while bleeding?

is this a new problem?

when you had the system off, did you manually open zone valves, and bleed then also?

one big picture showing boiler, circulator, feeder, and tank, floor to ceiling

dxj100

Current pressure is right around 20 on the boiler gauge. When bleeding, I can hear the auto fill valve kicking in and holds right at 20. I did manually open the zone while bleeding.  Issue started about a week ago. Checked all piping for leaks and found none. 

leonz

I see you have beautiful steel compression tank in the ceiling joist in your basement, that is a good thing.

Is the water feed valve shut off?
I hope your beautiful steel compression tank is not water logged.
Is there an airtrol valve in the base of the steel compression tank?? Is it hidden behind the copper pipe in the picture??

What is the purpose of the red casting in the foreground of the picture? Is it an Internal Air Separator???

What is the purpose of the pipe plug in the casting?

More pictures would help as the pipe routing for your heating system is difficult to follow, at least for me anyway.

About bleeding the air have you tried increasing the water temperature in the boiler to help eliminate the air bubbles while keeping the circulator running on an extended heat call??

neilc

are there any auto air vents anywhere?
you do not want them with this type tank.
if you see any, screw their caps down tight.

and it looks like your pumping into the tank,
not pumping away is doing you no favors there.
what changed, or what got changed, that let the air in ?

EdTheHeaterMan

There appears to be a B&G ATF-12 fitting installed in the expansion tank. There is a small section of a red fitting just behind and above the copper Tee right of the gas pipe. Not 100% sure but I believe that is what it is.


The large cast iron blob is a Vintage B&G Airtrol device that is no longer available. Hence no information on the web about it. As I recall from my Hydronics History Class (School of Hard Knocks class of '55) The internal of that part looks like this.


The side opening allows the part to be used on a horizontal inlet pipe, then the bottom inlet would have the plug. By forcing the water to flow downward in a larger chamber, Entrained air bubbles would more easily migrate to the top to be vented to the expansion tank.

But none of this helps to get the air from the loop that is not heating. There are two possibilities. #1 is that there is in fact air trapped in that loop and the pump head is insufficient to force the air to become entrained in the flow in order to return it to the boiler. This is normal, circulator pumps are not designed to do that. A purging at higher pressure is needed to entrain the air for that to happen. And you need to isolate the problem zone/loop in order to force the air out. Otherwise, the water will take the path of least resistance, the loop with water already in it.

#2 reason is that there is no air problem but the path thru that loop/zone is restricted in some fashion. If that is the case, What has changed to cause that resistance? OR Has this always been a problem? Did the zone or loop ever work in the past? If not, then there is a design flaw that needs to be corrected.

If it worked in the past and there IS an air problem, then there was a way to get the air out, that guy who figures it out used an unconventional method, and someone needs to figure it out. I don't see any purge valve setup in the near boiler piping so purging may not be the answer.

What do your baseboard radiators look like? Can we see a picture of one of the air vents?

Mr.Ed

leonz

Your steel compression tank is water logged!

The only time you open the fill valve is when you fill the
system in the event of a leak. when you mentioned you
heard the system filling with water that told me the tank
was water logged.

You need to shut the globe valve off in front of the auto fill valve
and leave it shut off!

The auto fill has to be shut off after you fill the system and
then you open the airtrol vent and let the excess water out of
the steel compression tank.

After the water is drained and you have nothing but air sputtering
out of the vent you need to shut the airtrol drain and then it will
be able to manage the microbubbles in the heating loops.

dxj100

Thanks for all the replies. I shut the feed valve off and drained the tank. My pressure dropped down to around 12. Still working on getting all the air from the loop. It worked fine until about a week ago. Currently warming up the baseboards in that loop with some gurgling. Opened the bleeder and got some air. Seems it will be a long process of getting all the air from the line. When the problem started I did open the fill valve wondering why it was closed but you guys answered that for me. I have been like looking for info on the airtrol system I have and couldn't find anything.
What would the correct pressure be? The auto fill is set at 12 but I have it off now.
Here are a few more pictures.

leonz

From where did you drain the tank down??????????????????????????????????????????

In order to correctly obtain the 1/3 air 2/3 water ratio in the tank you need to open the valve in the base of the airtrol valve(the ATF-12 valve in the pictures) please, please, please, use only a box end wrench to open the valve a small amount(1/2 a turn or so) to drain the excess water out of it. The drain valve is at the very bottom of the ATF-12 valve. When no more water comes out of the drain valve and air hisses out of the ATF-12 valve close it SNUG and no more.

The boiler drain valve in the end of the tank is ment to only empty the tank.


When you see the images with the end drawing of a steel compression tank in the link I provided to you, you will see how it is designed to provide a huge air blanket over the larger water volume in the tank.

The 12 PSIG you have in the system should be fine unless you have a 3 story home.

The only thing you can do now is open the troublesome loop up manually and just let it circulate with hot water. The other two loops should be shut off.

Here is a link for the airtol valve www.highperformancehvac.com/expansion-tank-water-level-valve


You also need to have a low water cut off installed to protect the boiler in the event of a water loss.
I have had a Bell and Gosset/ McDonnell & Miller RB-122-E Direct Immersion Low Water Cut off installed on my coal stoker boiler and it has protected the boiler for the last 5 years without fail.

You will need a plumber to come and install it for you and in so doing your boiler will be up to the national plumbing code standard.

Ask the plumber to install it and wire it as the first electric control for the boiler to assure it shuts the boiler down in the event of a water loss.

The power for the boiler will pass through the Low Water Cut Off wiring connections and then on to the burner and it will shut the power off if it detects a water loss or when you test it occasionally.

I think I have it all right now.