Is my gas boiler configured incorrectly?

Thehellz

I posted a few days ago about having a waterlogged steel expansion tank. I was seeking help how to fully drain it. I have since succeeded fully draining the expansion tank and now I'm still having doubts about if my system is configured/operating as expected. Maybe it's user error, I'm learning as I go.

After fully draining the tank I then bleed every single radiator up stairs while the expansion tank was isolated. Next I unisolated the expansion tank allowing water to flow in. My system was then under pressuirzed so I added more cold water. 

The next part is where my questions come from so here are pictures of my system. 

After adding water to pressurize the system I noticed the pipes get really cold as if the water flowed up and backwards away from the pump and back into the rads. That caused more air to go up into the rads. Bleed rads and the system is at pressure and hasn't ran since.

Does my system have a major flaw to how it's designed? Should the cold water come in next to the expansion tank so any air that comes in goes straight up into it? I have no air separator leading into my expansion tank other than that atf12 but is the way my expansion tank piped even effective? Everything I've read says I should have that. Pump on the wrong side? 

Jamie Hall

Perhaps not the best, but there is no good reason I can see from the photos that it shouldn't work OK, provided that you have no other air removal fittings anywhere. However, it may take some time if you just bled radiators and didn't actually purge the system for all the air to find its way to the compression tank. It will... eventually.

EBEBRATT-Ed

Hard to tell from the pictures so I am guessing a little.

1.Your circulator is on the return pumping into the boiler...correct?

2. You make up water is piped into the return line on the suction side of the circulator.....correct?

3. Your expansion tank is connected to a tee that comes off the supply coming out of the boiler...correct?


So IF 1,2 and 3 are correct then this is what is wrong:


Best practice is to put the circulator on the boiler supply pumping away from the expansion tank. Yours is pumping toward the expansion tank. That is the "OLDER" way of doing it and it will work ok so I wouldn't change it until you get a new boiler or are willing to repipe everything around the boiler.

The make up water connection and the expansion tank connections to the system need to be on the same side of the circulator either on the circulator suction or the circulator discharge. If I am interpreting your pictures right the MU water is on the circulator suction and the expansion tank is on the discharge. That is wrong.

The tee the expansion tank is piped to is coming off the side of the supply pipe riser. It should come off of a horizontal supply pipe and pitch up to the expansion tank


What you have is not horrible and It will probably work the way it is but will probably be difficult to get the air out.


See the attached drawing

Thehellz

@EBEBRATT-Ed 1.) correct 2.) correct 3.) correct

So you've settled my mind about sinking money into it and throwing the correct parts at it. Any suggestion on how to get the air out of the system? Patiently wait and just bleed from radiators over time? 

EBEBRATT-Ed

Raise the system pressure up to 20 ish. Keep the circ off and bleed the rads. Keep the expansion tank isolated. Then start the circ but not the heat. You would have to disconnect the gas valve wire to keep the heat off. Go back and bleed with the circ on if you need to.

To help I would stick an automatic air vent on at the top of your return tee where it drops to the boiler. I would put a shut off valve or petcock under the vent. This is just to get the initial air out. You shouldn't use auto vents with a compression tank so when you get it bled and running with just the circ and you think the air is pretty much out. Drain some water out of the boiler to get to a normal pressure and open the expansion tank and shut off the auto vent and reconnect the gas valve wire.

What model Dunkirk is that? Some boilers have an internal air scoop.

I think your biggest problem is where the expansion tank is connected on the vertical riser. If that was in a different spot connected to an air scoop you would have better luck.

I know Weil McLain Boilers some have an internal air scoop. Not sure with Dunkirk

The pump location and the water MU you could live with if the expansion tank was right.


The other option would be to disconnect the compression tank and install a Bladder expansion tank. If you put a tee in your MU water line and put the bladder tank there you would solve your problems. You would be pumping away from the expansion tank and it would have the expansion tank connected to the MU water as it should be and then you could install a couple of auto air vents and leave them on at least until all the air has been worked out.

mattmia2

You don't have an automatic pressure reducing valve do you? You just fill it with a manual valve. If so i think what happened was the pressure fell while you were bleeding and you didn't get all of the air pocket at the bleeder out. Did you get water out of all of the bleeders? When you the refilled water flowed back to compress those pockets you left in the emitters as well as the compression tank.

Thehellz

No auto  pressure reducer no. When bleeding I bled one rad at a time then re filled to pressurize back to 12 psi. Yes each individual bleeder spit water out after clearing air. Not every rad had air but most did. 

jesmed1

As @EBEBRATT-Ed said above, your biggest problem is how the expansion tank is plumbed. Based on pics #2, 5 & 6, it looks like your line to the expansion tank comes off a sideways tee on the vertical supply line coming out of the boiler. The expansion tank line tees off there, goes horizontal 6-8 inches, goes vertical, and then goes horizontal again into the Airtrol fitting.

Plumbed this way, your Airtrol is useless, because the air bubbles are not going to go sideways into that tee in the supply line. They're going to go vertically up, following the supply into all your radiators.

Here are the instructions for plumbing the Airtrol correctly. The line to the Airtrol must come vertically out of the boiler, and any horizontal run must be pitched minimum 1 inch in 5 feet. More pitch is better.

https://www.xylem.com/siteassets/brand/bell-amp-gossett/resources/manual/s10300h.pdf

I don't see an easy way to fix your expansion tank plumbing, because the main problem is that tee off the vertical supply. Ed's idea to install a diaphragm tank on the makeup water line is probably the best option.

neilc

move the tank connection over to the safety relief valve, add a tee there, and cap the supply,
then move the circ to the supply out of the boiler,

jesmed1

neilc said:

move the tank connection over to the safety relief valve, add a tee there, and cap the supply,
then move the circ to the supply out of the boiler,

Except that the Airtrol instructions say the relief valve must not be plumbed into the same line as the Airtrol, though I don't know the reason or how safe it is to ignore.

hot_rod

wrong post

Thehellz

neilc

jesmed1 said:

neilc said:

move the tank connection over to the safety relief valve, add a tee there, and cap the supply,
then move the circ to the supply out of the boiler,

Except that the Airtrol instructions say the relief valve must not be plumbed into the same line as the Airtrol, though I don't know the reason or how safe it is to ignore.

I would like to understand the Why,
anyone ?

PeteA

@Thehellz
You said in the paragraph below your photos the system "hasn't ran since"? Do you mean that the boiler hasn't fired since you did the bleeding? I can understand the waterlogged tank and some of the other things described by your efforts to remove air but everything in your installation looks like it's been there for years in this same exact configuration. Are you just having heat issues up to the radiators? Is the circulator running? What temp / pressure does the boiler get up to and after how long? What pipes are hot when its running and what not hot? Sorry if I miss interpreted it but those couple of words caught my eye and that's indicative of other things and not a piping or an air issue.
I think a little more detail other that the air bleeding can help the folks on this site get you at least back to where you were before you drained the tank.

Thehellz

PeteA said:

@Thehellz You said in the paragraph below your photos the system "hasn't ran since"? Do you mean that the boiler hasn't fired since you did the bleeding? I can understand the waterlogged tank and some of the other things described by your efforts to remove air but everything in your installation looks like it's been there for years in this same exact configuration. Are you just having heat issues up to the radiators? Is the circulator running? What temp / pressure does the boiler get up to and after how long? What pipes are hot when its running and what not hot? Sorry if I miss interpreted it but those couple of words caught my eye and that's indicative of other things and not a piping or an air issue. I think a little more detail other that the air bleeding can help the folks on this site get you at least back to where you were before you drained the tank.

I didn't force run a heat call immediately after bleeding it as my house was already pretty warm, however, I did force the circulator to run after bleeding each rad then re bled each rad with the pump on. It did run overnight and the prv popped off for some reason (tank was drained and system was bled while tank was isolated, or so I think its fully bled). When I checked this morning psi was ~20 and temp was hovering around 120°F. It did circulate heat up into my rooms as I could feel the pipes were warm. So it's moving the warm water up into the rooms but I have a hard time saying if it's due to circulation or just because heat spreads to cold. When I watched the temp in the past it never has rose over 160 and it's sets to 180. I haven't done anything to the system yet today. Had to work and I won't be home for another 3 hours. 

jesmed1

neilc said:

jesmed1 said:

neilc said:

move the tank connection over to the safety relief valve, add a tee there, and cap the supply,
then move the circ to the supply out of the boiler,

Except that the Airtrol instructions say the relief valve must not be plumbed into the same line as the Airtrol, though I don't know the reason or how safe it is to ignore.

I would like to understand the Why,
anyone ?

I'm just guessing here, but the only thing I can think of is that the flow back and forth from the expansion tank could (theoretically) carry crud from the expansion tank down into the relief valve and eventually cause it to clog.

Thehellz

@jesmed1 your assumptions on how the expansion tank is plumbed is correct. After doing all my research I was beginning to believe the tank was piped incorrectly (which it is) and it did cross my mind just scraping it and go with a bladder tank. Glad you agree that may be the easiest way to go. I know air goes up and so does hot water. I do know heating water releases the dissolved oxygen. Most air won't make a sudden right turn even if that right turn eventually leads back up.

In yalls professional opinion should I spend the money on it or just wait until I have to replace the boiler? My gut leans towards changing it now. I would like to add a purge station so I don't have to manually bleed each rad (some arent ideally located), and since the system would be drained to do that I may as well just go ahead and pipe the system properly. 

jesmed1

Thehellz said:

In yalls professional opinion should I spend the money on it or just wait until I have to replace the boiler? My gut leans towards changing it now. I would like to add a purge station so I don't have to manually bleed each rad (some arent ideally located), and since the system would be drained to do that I may as well just go ahead and pipe the system properly. 

In my non-pro, just-a-homeowner opinon, if you're already going to the trouble of draining the system to install a purge station, you may as well go ahead and install a diaphragm tank on the makeup water line in its present location. As @EBEBRATT-Ed said, if you do that, the circulator is then pumping away from the tank, and with your purge station and some automatic air vents, you'll be all set.

If you don't do that now and instead put it off until you need a new boiler, you may spend the next 10 years waiting for the boiler to fail and wishing you had put the new tank in when you had the chance.

EBEBRATT-Ed

Weil McLain commonly shows the expansion tank and make up water on the return line on the suction side of the circulator and they list it in their manuals as an alternate location.

@Thehellz

I would cut a tee into your MU water below the valve that feeds the boiler and come out of the branch of that tee horizontally put a ball valve on it and then turn down with a 90 degree elbow with a 1/2" copper x female adapter in the elbow and hang the tank vertically with the threaded connection on top.

Put a pipe hanger on the 1/2" copper close to the new elbow to support the tank. Including the tank your probably talking $100 bill for material if you can do it yourself.