I believe I have an air lock in my baseboard heat system. Split level house, 5 heat zones, four of which are hot. The one with the problem is on second floor and has all 6 baseboards cold. Zone at other end of house also on second floor works fine.
I checked zone valves. At first one appeared stuck. But when I bought a replacement controller the old one seemed to operate normally so I put the old one back on. Upon repowering, it was immediately powered open – as expected since room was colder than thermostat setting. It also can be opened manually and closes normal. Perhaps it had some dirt sticking it or maybe I was wrong in first appraisal. There was still no heat in that zone’s rooms. To double check I locked the zone valve open and waited. Still no heat. Also when the zone valve controller was off I checked and was able to manually turn the actual valve.
Circulation pump operates normal. Other 4 zones are fine. Pipes out of all zone valves are hot. Weil-McLain Gold CGa furnace, new by last owner in 2000. It’s running at 180 degrees and about 12-13 PSI. I let it cool to about 70 degrees, still about 12-13 PSI.
What else could it be but an air lock? I checked for bleeder valves on the applicable baseboards. Out of 6 baseboard heaters there is only one valve – and it is in the middle one of 3 on one side of the house. This zone covers 3 upstairs bedrooms and 2 baths. When I opened that valve it only let out water – no air at all. I let about 1 tablespoon out. I’m assuming one (or more) of the other baseboards has the airlock.
Now – I am thinking it must be an air lock and that I somehow need to bleed it out. Do I try to attach a small hose to the little nipple on the one air bleed valve and let it run into a bucket. If so do I need to do anything else? Turn on or off pump or furnace? I’m thinking not.
Or should I drain it from down below in the heat room by shutting off all the valves and shutoffs to the other 4 zones and opening one for this one? If I was to do it that way I’m thinking I’d need to shut off all the valves in my diagram (Diagram picture by heaterpics - Photobucket ) except the one just above the applicable zone valve, the one between the furnace and the zone valves and the one inlet from the hot water, as well as manually keep the zone valve open. Then I could drain the zone from the tap just above the shut off on the return line and I assume as I drain it would automatically refill (right?). Or would it be better to shut off the refill while I drain and then open it back? Would it matter if the pump was running or not? I’d think I’d want it not running. Or if the furnace was hot or not? (it seems better to let it cool, even tho inlet is from hot water, I'd hate to crack anything).
Other pics are: Pictures by heaterpics - Photobucket
Thanks in advance for any help.

 

The pump has to be on to push the air out of the system. Open the bleeder valve on that zone. Let more than a spoonful come out. See if it coughs & spits some air.

 

The pump doesn't necessarily need to be running... the system pressure will push air and water out. Whether or not to run the pump depends on WHERE in the system the bleeders are physically located.

If they are at HIGH SPOTS in the piping, it is better to bleed those with the pump NOT running, and after the system has been OFF for a while in order for the air bubbles to float up to those high spots.

If the bleeders are at the DOWNSTREAM end of a horizontal run, just where the pipe turns to go downward into the floor, these are better bled (usually) if this pump IS running.

Think about where you would go in the system if you were an air bubble, and that's where you will find the air.

I'm suspicious of the pressure gauge on the boiler. The fact that it doesn't move at all when going from cold to hot MIGHT mean that the gauge is not functioning properly. You could be operating with lower than optimal pressure and this could be what's causing the presumed air lock.

When you opened that single bleeder, did it just sorta 'piddle' out slowly? or was there a bit of pressure behind it?

I haven't looked at your pics yet, going there now...

 

If you mean that this was actually installed by the homeowner, it shows... there are a number of 'issues' with the piping that I'm not going to go into at this time. I'm just happy to say that _I_ am not the one that has to change that expansion tank when it craps out! (among a number of other errors).

If this was installed by a so called 'perfeshunal', that dude oughta be ashamed of himself for taking someones money.

On the other hand, what IS right about the system is the fact that they knew enough to install 'purge stations'.

These purge stations will allow you to run water through one zone at a time by properly manipulating the valves.

I don't have time right now to go into it, perhaps someone else will... if not, I'll be around maybe later.

 

Listen to NJT about the pressure gauge. I had a similar problem and couldn't figure it out 'cause my gauge was stuck on 15 psi!
Thanks again, Jeff

Steve

 

I just bled about a cup plus from the one bleed valve. Not so much as a burble or spit - just steady flow of cold water. The outlet is what-- an eight of inch and if I open the screw much it leaks up at the screw as well (and hard to catch without running to floor!) - but it's a steady stream. I hear what you're saying on pressure -but seems its OK with another zone on same floor, opposite end of house even further from furnace heating fine. Furnace and accompaning stuff down there new in 2000. (I rapped on the pressure guage with no change to reading.) I assume baseboards and plumbing original from 1970's. I don't know which of the 6 baseboards are at start and which at end of the loop. The pipes from furnace go off into the wall and come out magically through the floor at each baseboard! But this one bleed valve is on the middle of what appears 3 in a row - one in bathroom, then this one just outside of bathroom in MBR the next on other side of doors to sun room. The other 3 are: 1 in each bedroom on opposite side of house and a bathroom in between. House is as level as any. None appreciably higher than another, certainly not by the amount the piping goes below floor level between rising for each baseboard. I would think any air block would be most likely at one end or the other - not in the middle where the bleed valve is. To bleed enough from that I'd have to be emptying piping perhaps all the way around half my house to the far bedroom accross the hall. Kind of tedious through 1/8" hole! Like I said, all the baseboards are cold - I can't think of how to determine the actual position of the air block (and I'm assuming that's the problem) or which is the begining or end of the zone.

And yeah -it was one of them 'perfessional' jobs - but then this house has a few other 'perfesional' jobs too.

Thanks for the attention.

 

Hi Steve! Thanks for the vote of confidence!

Deepee, It sounds as though there are numerous places for an air lock to occur in that zone... and only one bleeder...

Let's first talk about the system pressure. To the right of your boiler, there's the 1/2" water line feeding it. There's a red manual shutoff valve, then a backflow preventer, then your Pressure Reducing Valve. Is there a 'fast fill' lever on that valve by any chance? I can't tell from the pics...

That red valve is open, correct?

From cold to hot, you have to at least see the gauge move. If it's sitting rock steady at one spot, then it's seriously doubtful that it's working properly.

I have a gauge that I hacked together from junque boxe parts, but something similar can be done with purchased parts.

Lawn sprinkler techs use a gauge that can be had at HD or Lowe's for about $10 that screws onto a hose bib. The gauge is a 200 or 300 PSI job though, and the resolution is NG for boiler work. But, the brass fitting that goes on the hose threads of a valve is just what we need... and you can't buy the parts individually to make one for under $10. So, you can pick one of them up and remove the gauge. Go to a plumbing supply store and pick up a 25 or 30 or 50 PSI maximum gauge with the same threads (1/4" I believe) and install this on the fitting. Screw it onto a boiler drain and open the valve. Now you can verify that the boiler gauge is working or not.

Or, depending on how much junque you have in your trunque, you can make one similar to this:



If you do find that the pressure is low, then you need to find out why, and correct that first. With more pressure in the system, the air bubbles will be smaller (compressed) and may just move by themselves.

The location of the air bleeders on the boiler are pretty much useless. When air bubbles are floating along in the stream, there is zero to no chance that they will miraculously decide to go up that little pipe into the vent. No, they'll just whiz right on by...

Your system does not appear to have an 'air scoop' device. This is a part that actually will collect the air from the stream, and pass it to the vent. That's one of the deficiencies... so even if you DO manage to break the bubble free and move it through the system, there is nothing installed to catch it and remove it.

more...

 

Just for illustration purposes, here is a graphic that shows how air can stop the flow in a system.



Here is one type of 'air scoop'. This one is not as efficient as something like the Spirovent type, but properly installed it will do a good job. The automatic air vent screws into the top, and the expansion tank hangs from it, screwed into the bottom:


photo courtesy PEX - Radiant Heat - Radiant Heating - Plumbing Supplies - PexSupply.com

Here's what the Spirovent looks like... much more $$$ than above, but does a superior job.


photo courtesy Love Plumbing & Remodel of Bellevue & Bothell WA, Terry Love

I'm saying all this to get to this... next...

 

Referring to your diagram:



NOTE! Before you attempt to purge the zone, shut the boiler OFF and allow it to cool to 100°F or less! You don't want to shock the boiler!

Those drain valves above the shutoff valves on the return side can be used for more than draining. You can use them for PURGING a zone. By closing ALL the shutoffs on the returns, hooking a drain hose to the one on the blocked zone, manually opening the zone valve on the blocked zone, and opening the drain, you can force the path that the water will take... it will come in the water feed valve, through the boiler, up the supply, through the zone, and out the drain. When you think all the air is out, close the drain valve.

I asked earlier if your feed valve had a 'fast fill' on it. Here's why: the piddly flow that you get through the feed valve may not be enough to dislodge the bubble... (it also may...) if it's NOT enough, and your valve has a fast fill, you can open the fast fill to get more flow through the loop.

Here's the problem with this: Fresh water has LOTS of dissolved air in it that will come out of solution when the water is heated. What this means is that you may actually be ADDING more air than you are removing by purging the zone. And this is where the air scoop would come into play. It would catch that air and expel it from the system, without adding a ton of fresh water to the system.

So, FIRST, determine if your pressure gauge is working, and if you find that your pressure is low, get that part fixed up so you have the correct pressure in the system.

Then, if that doesn't fix you up, try the 'power purge' above.

If you do the power purge first, and the pressure is low, you may get it working for a while, but it will likely block up again soon.

more...

 

Aside from the location of the expansion tank, and no air removal device, another thing that is wrong is the way they 'choked' the flow down through the boiler with those undersize manifolds.

How many zones? FIVE? What happens when all five of the zones call for heat at the same time? (might never happen, but it _could_)... all the flow from FIVE 3/4" pipes is being forced down into a bottleneck. They come out of the boiler with a reasonably sized pipe (looks like maybe 1-1/4" ? maybe 1") and then immediately into a REDUCER that squeezes the flow down. It's like five lanes of traffic going down into one lane for a construction zone.

That should have been done so that the COMMON piping was ALL the same size as the pipes in and out of the boiler.

 

Wow - thanks for great explanation and info. Plenty for me to chew over here and work with.
I assume the little lever is the fast fill? http://s918.photobucket.com/albums/a...essLimiter.jpg
Yes - the shutoff from the fill line is open.
I definately hear you on the air bleeders. And need for air scoop. And the flow bottleneck! I like your idea for the pressure guage too.
Really thanks for all the personal help. I'll let you know how it goes.

 

Yes, that lever on top is a 'fast fill'. Lifting that lever will bypass the regulator portion of the valve and allow water to flow in at full city pressure... so with that in mind, you will want to be careful that you don't go over 30 PSI in the boiler when you open it. This could happen if for example you closed the drain valve before you let go of the lever...

Keep in mind that these things I've mentioned are obviously not URGENT... I mean, the system has worked for nine years the way it is. So the immediate concern is of course to get some heat in that cold zone.

You could also try something else since you do have the fast fill available... lift it for a few seconds to see if your gauge moves. Don't hold it too long, because you don't want too much pressure in the system that would cause the relief valve to open when your system got hot... just enough to see if the gauge moves. OR, get that external gauge set up first, and then:

With the boiler cool, temporarily increase the system pressure to something like 20 PSI and try bleeding again. The extra pressure might just unlock that zone. When you are done, open a drain to drop the pressure back to 12-15 before you heat the boiler, for the reason of the relief valve opening...

Unfortunately though, without an air removal device, you might end up having to do this periodically.

 

Ok. Before you’d sent your last message, I decided to try and purge the zone from the return faucet after isolating all the other zones.
At first it had me a bit perplexed. Nothing happened! No water flow, no sounds of water flow, nothing. Deciding maybe these zones are not so accurately labeled, I proceeded to alternately shut and open each one to see which return line was at the other end of this zone valve. Of course double checked the associated valves open from water line input thru furnace, up thru that zone valve. All others closed. More than a couple times. And double checked upstairs that something hadn’t blown with water gushing. Still nothing came out. Finally sort of trusting the labeling, while scratching my head for 3 or 4 minutes I heard a little water flow. Out comes a light flow – maybe ¼” stream from the 4’ piece of garden hose I’m using. Clear and cold - like tap water temp. I was expecting dirty and at least room temp. No bubbles or sound of bubbles in pipes. Finally after a couple gallons some little bubbles. I rapped pipes and turned the faucet off and on a bunch. With it off of course the pressure built up some and then when it gushed it’d carry some bubbles along. Gradually got a better flow – but never very strong – not like straight from a regular faucet. It maxed to about a gallon per minute. After dumping about 6 buckets the flow got dirty (and warmer) for the next 20 or 30. I got tired of dumping buckets and finally ran it straight to the floor drain.

I must have let it run with the fast fill as open as possible and the return faucet wide open for over an hour and was still getting regular bubbles – one or 2 per second the size of my fingernail. How long should it take? Even if every baseboard was empty except the one with the air release valve it seems it shouldn’t take this long does it? Early on, thinking maybe I could help things along I tried opening the upstairs baseboard air release – it sounded like air escaped, no water. I’m pretty sure it was escaping – not sucking in maybe from venturi effect or something? Pretty small opening to feel. I tried a little soap but still not certain so I closed it – only had it open 10 or 20 seconds. With fast fill and drain shut, I tried again and only got water –no bubbles at all. So maybe venturi sucking in. Seems hard to believe with the low flow.

After an hour plus of this and no change in bubbles or flow, I stopped and reset everything. Refired furnace. Voila! Heat in the zone. Only water out of the one baseboard air release valve. No apparent leaks anywhere. No sounds of water leaking or bubbles in piping. Yet, I’m perplexed why I was still getting air from the drain the whole time? Should I have purged for longer – it didn’t seem to be diminishing any.

I did note while doing all this the pressure gauge reading did vary – low of about 8 PSI when I had fast flow and drain both open. High about 18 or 20 PSI when I closed the drain but left the fast flow open for a bit. It seemed to have a pretty long lag – many minutes, and still no reaction to tapping. I’m thinking I need to finagle a gauge like you described to double check it. I don’t know where this one came from –looks new but pressure reading goes to 75PSI and has a redline set at 60 PSI. Seems a bit high. I note now with the furnace running at 180 degrees it reads about 17 or 18 PSI (versus earlier consistent 12-13, it must have been stuck and maybe still not too reliable). Sounds like Sdodder had some good advice.

The only tire air gauge I seem to have starts at 20 PSI – so I can’t read less accurately but the air tank seems to have pressure –something less than 20. So I guess I can pick up a new low pressure tire gauge too to better check that.

Anyway – heat in the bedrooms and no apparent water leaks or cracked heat exchangers. Success to me. Thanks for the attention and hand holding.

 

It sounds to me as if you had quite a bit of air in the loop... and perhaps your regulator was a bit plugged up too... keep an eye on the pressure now, because if the regulator WAS plugged up, it's possible that now it may leak through if a piece of 'crud' got under the mechanism... that's the trouble with this stuff, that valve basically sits there and does NOTHING most of it's life, then we try to use it for something, and the crud gets in an messes up the works. If the pressure does start to climb, you can close the manual feed valve, as long as you keep an eye on the pressure.

I don't care for the way your valve is mounted. Any 'stuff' that does come down the pipe will tend to build up in that vertical pipe leading to it. In fact, I wouldn't be surprised if that valve was still a bit plugged up. I have the same valve on mine and get more than 1 GPM with the fast fill. Maybe not FULL blast, but definitely more...

Sometimes even the fast fill won't give you all that much flow, but at least it's gonna be ten times faster than if you didn't have it!

As for the bleeder possibly sucking air, that's very possible... you need a certain amount of pressure to lift the water to some 'altitude'. As an example, if that bleeder is 15' above the boiler, you would need a MINIMUM of 6.48 PSI, and with that pressure, there would be ZERO pressure at the 15' level. Any higher than that, you would have LESS than zero pressure, and it would/could suck air. ( you need 0.432 PSI to raise water one foot )

IF that pipe was actually almost full of air, that air would also act as extra expansion capacity, so this could account at least partially for the fact that the gauge didn't move. You removed that air, and now the pressure swing will be a bit greater because of the decreased expansion room.

When you check the air charge on a bladder type tank, you need to have ZERO PSI on the boiler side. If you don't, you will get an inaccurate reading. The expansion tank should be charged to 12-15 PSI with ZERO on the boiler side. You don't have to drain the boiler, only let out enough water to drop the pressure to zero. You might actually want to do that in fact... pump it up to 15 PSI.

 

That 'redline' on the gauge is adjustable. It serves little purpose really. The face of the gauge actually should turn so that you can place that red pointer wherever you want it... it may be hard to move, or it may not move at all, depending on whether or not there is dirt and rust under the 'rim'... it's likely that it was never actually 'set'... it just ended up where it is for no reason.

With the minimal flow you were getting through the fast fill, it's very possible that you would NEVER get all the air out. You need quite a bit of flow to force air downward...

And... I mentioned earlier that you might have to do this periodically, so don't be surprised if the air starts to collect there again.

There's one other thing about your system that isn't helping the situation... it's the fact that your circulator pump is pumping TOWARD the expansion tank. The effect of this is that whenever the pump is running, it SUBTRACTS pressure from the zones above it. If your pump were located such that it was pumping AWAY from the expansion tank, it would ADD pressure to the system when it runs. There's a lot that can be said about 'pumping away', too much for me to go into... just suffice to say that if you did decide to re-do the piping next spring/summer, you would want to change that. Do that, and add an air scoop with an auto air vent, and you would probably never have to worry about having to bleed the system ever again.