Hydronic Heating Wont Purge Air Out

[SeattlePioneer]

I was called out today on a boiler in a hydronic heating system that was limiting out.

The house was being remodeled, and a plumber had emptied the water out of the system while doing some work on the baseboard heaters. He didn't bother filling the system.

This system had probably never been opened since it was built 17 years ago. I couldn't get the water to circulate in either of the two upstairs zones (bad zone valve wouldn't open for the basement).

I purged all the air that would come out of the purge points until I got all water. The B&G 1/12 HP pump was cranking away fine. The isolation valves are all open, as far as I can find them anyway.

I'm wondering if it needs more places to bleed out air? There were a couple of purge points on each pipe run.

This has stumped me so far. I invite comments on what I may be missing.



Thanks ---


Seattle Pioneer

[karsthuntr]

You need a purge valve and a boiler drain.

You can use a small sump pump to circlate water through the boiler.

I will post a pic tommorow if you need one.

[simpleman]

Sometimes it not a air problem,flow could be the problem.

I would go and check just what the plumber did to the distribution system.

Did he remove any baseboard,did he add any baseboard.One
of my favorite.. they piped the series loop up and over a doorway then back down.

I agree with capt kman a purge scoop is in order and,you
need to look at the distribution and see where you can offer some improvement where money spent now will save plenty of dollars on the service side.

Seattle If I may offer just two books that will help you gain the knowledge to spot the things or problem with h20
heating system.Also keep in mind not only do they help you
there but,they bring money in as well.

Howe Come? This book has brought me in 2000 time more money then it ever cost me.

Pumping away..this one I'm very fond of because a good friend gave it to many years ago when I very depress with spending to much time chasing air problem.

Seattle if your money tight I'll make you a deal.I'll send you both these books if you promise me you will send me two
dollars on every upgrade or time save on every job you do.

Heck being I'm so kind I'll place a limit on it of lets say seventy five dollars.

http://www.heatinghelp.com..books and more.

[eagle1154]

You might also check to see how much water pressure you have in the boiler.You'll need a minimum of 18 pounds to get the water up to the second floor.There is a formula to use on how much water pressure you need to reach 2nd floor,but it escapes me.I usually use a pump to push the water up to the second floor,then when I get good flow,I open the auto-feeder wide open while purging to make sure I got all the air out,then let the auto feeder work until I reach at least 18lbs.

[johnsp]

Maybe a stuck flow check?

[glennwith2ns]

I backflushed a mouse out of a 3/4 copper zone to an addition once. Musta crawled in while pipe was open.

[anonymous]

sounds like a blockage

[tinman]

Does that B&G pump have a pump coupler? I had a job that the coupler was cracked and looked like the pump was working but it was not.

[SeattlePioneer]

Thank you all for the generous comments.

I've visually inspected the B&G pump carefully, and it's turning fine. Always aim for the easy fix first, right?

Simpleman ---I wanted to check out the book you recommended, but your link doesn't work.


I checked out the system visually, and couldn't detect damage done to the system by the plumber. But it's not wise to underestimate the creative genius of a plumber, so almost anything is a possibility. Based on the comments received, that's the thing that's most likely to be the cause of the problem, I'm guessing.

Another thing is that there are three zones, none of which are passing water. One zone had an obviously defective zone valve, the other two valves open without passing water. Even the mouse would get through the 1.25" or larger pipe and plug up one or the other zone valves I'd suppose, rather than both.


One other thing struck me as peculiar. There is no automatic water feed using a regulator and no check valve, just a water stop directly off the domestic water line. When I open that valve, I'd expect to hear water running strongly into the system, pressurizing it to the point that a relief valve would open.

Instead, there is sometimes some water flow, but it stops as if the pressure on the system is equalizing with the domestic water pressure. I verified that there is good water flow through that valve, but I didn't measure the pressure on the system at that point.

Both pressure gauges on the system appear to be frozen up and don't move under any conditions, limiting the information I have while working on the system.

As I think about it, I could have installed a gauge on the water stop beyond the water fill valve, but I didn't think of that at the time. That would have given me the actual pressure on the system at that point.

Fun, eh?

Thanks for the comments so far.



Seattle Pioneer

[tinman]

Maybe the plumber has the loops tied back into themselves so there is'nt a way for the fluid to circulate.

[tinknocker service tech]

there may be some shut of valves down stream that are closed on the zones. i have seen a lot of older systems where the installer would put stops in some very strange places. if gate valves were used the gate may not be opening and or is broke off the stem. you may also find a feeder installed down stream also. check the pipeing again real closely.

[Christheheatingdude]

This link should work.

http://www.heatinghelp.com/shopcart/...cfm?category=2

The "pumping Away" book is on the third page, just scroll through the items.

[krd]

You should purge one zone at a time to minimize air entrapment. Hook a hot water pressure guage to the boiler drain to get actual pressure on the system. I have mine hooked to a washing machine hose so I don't have to strain the old bifocals standing on my head to see what is going on. Heat up the system then shut it off to bleed I've found this gets more air out Quicker.

[simpleman]

Say what no water feeder??? I sure hope it at least has a low water cutoff on it.If not stop right there and offer one or the other infact offer both.


It sure sound like you only have water on the boiler in not in the distribution system..as in no pressure.

I too would have to agree with you if the boiler pressure
was the same as the domestic pressure then the relief valve should open.

It sure sound like to me you have a boiler that has no pressure on it.

Dryfiring a boiler is bad news.I would make it top pritory
to get back over there with a pressure/temp guage and see
what going on.

Lets us know what you find.

[markwolf]

Originally posted by eagle1154
You might also check to see how much water pressure you have in the boiler.You'll need a minimum of 18 pounds to get the water up to the second floor.There is a formula to use on how much water pressure you need to reach 2nd floor,but it escapes me.I usually use a pump to push the water up to the second floor,then when I get good flow,I open the auto-feeder wide open while purging to make sure I got all the air out,then let the auto feeder work until I reach at least 18lbs.

one psi is equal to 28" of water columb,or for a rough estimate one pound for every two foot of piping heigth.12psi would be more than enough for most two story homes I have worked in keeping in mind the baseboard is at floor level.

[markwolf]

hahaha reminds me of a true story.A plumber made repairs to a frozen piping loop & it would not work when he was done.When I got there I asked where the repairs were made?I cut open the pipe & found a slug of bread to stop the water when he soldered.OOPS!

[Collin]

Originally posted by SeattlePioneer
There is no automatic water feed using a regulator and no check valve, just a water stop directly off the domestic water line.

No check valve means the possibility of boiler water getting into your domestic.
Bad, bad, bad.

[clyde1]

Looking for help related to this subject:

I'm trying to get a system my father installed working (~31 yrs ago).

I just sarted up the system after it has sat for the summer. My problem is similar in that the upstairs isn't working (the radiators aren't warming up). I'm not sure if there are truly defined purge points, but I see places I could use.

As I'm studying his work, he does have the supply line going into a pressure regulator going into valves that can be oppened to feed into the system. He does have an expansion chamber in place. He has numerous valves on the supply and return sides. He had converted an old steam/condensation system into a circulating system with an American Standard water/boiler system. He ran copper return lines from all of the radiator lions back to the furnace room. Looking back it's pretty remarkable what he did.

Right now I think there is a little air in the system, because I can hear a little trickling as the water is circulating. I'm not sure which pressure valves are working. But if the one right off the boiler is correct, then I'm only seeing 5 lbs when the boiler is running, and I don't really see any change between when the boiler is running and not running. This boiler is in the basement, so it seems like closer to 16 lbs is what is needed to get to the 2nd floor. Shouldn't I see some increase in the pressure on the output of the boiler when the pump is running? Or is the idea that once the system is purged of air, we just need a small pressure differential between the input and output of the pump to cause some flow through the whole system.

The radiators on the 1st floor are warming up nicely. Regarding purging the system of air, I was thinking of using small, what looks like a steam valve, near the top of the radiators. I was thinking of opening these valves slightly on the 2nd floor while someone in the basement allows a little domestic water to enter the system until I see some water trickle out of these points. I just hope they close tightly when done so not to have a source of air going forward.

The other thing I was thinking about was closing as many valves to the 1st floor radiators as possible in order to force as much flow through the 2nd floor radiators as possible. However, if it is air that is preventing the flow upstairs, and I've got the 1st floor radiators closed, then I'm concerned of having the boiler on when water is not actually flowing.

Anyway, my bottom line question is if the small steam valves at the top of the 2nd floor radiators would make a good purge point? Thanks for your help