No heat on 75% of top floor zone. Cant purge air.

Hi all. I have an old Sears (?) boiler connected to 3 zones. There is a Taco zone valve for each zone and a single circulator pump. The zones are one pipe (not series) system. It has a bladder type expansion tank and an auto-fill valve. There is an air scoop above the expansion tank with an automatic air vent (brass can looking thing) on it. There is also an air vent on the return pipe, after the 3 zone pipes converge, where it 90s down to the circulator.

For the top floor zone, 3 of the 4 baseboards are not getting hot. I can't get any air from the bleed valves on these baseboards. If I open one of the bleed valves long enough to get about 6 cups of water out of it, I will get hot water and it does come from the supply side. However, after I close the valve, the hot water stops flowing and the unit cools even though the zone is calling for heat.

I noticed the last time I tried to get the air out that while I was extracting the ~6 cups of water, I could hear gurgling from somewhere in the pipes. It sounded like it was coming from the vertical run prior to the shutoff valve for that baseboard.

The one baseboard that does get hot is the third one that branches off of the main pipe that runs around the bottom floor - for whatever that's worth.

I have drained and refilled the system and still have the same situation. The system pressure reads about 12# cold and 18-22 pounds hot (190-200 degrees) with the circulator running.

I am certain that there must be some air in the system some where but I can't figure out how to remove it. Can anyone advise me on how to go about removing this air? Thanks.

 

Here are some pictures.... It doesn't "Pump Away".


Pictures by cantstart - Photobucket

Thanks

 

Can you explain what you mean a bit more detail? (see below)

What type of radiation ? is it all fin-tube baseboard? or maybe cast iron baseboard?

But you DO get a good solid stream of water with a bit of pressure behind it, yes?

Where are the bleeders located on the baseboards, relative to the direction of flow? Ideally, IMHO, the best place for them is at the DOWNSTREAM end, where the pipe turns to go down into the floor again, and if this is where they are located, they are best bled with the circulator pump RUNNING.

Do ALL the baseboards have bleeders on them?

This goes back to my asking for more detail on what you are calling 'one pipe'. Do all of the baseboards TEE off one pipe, and TEE back into that same pipe a bit further down the line? If so, you most likely have a 'monoflo' system, and they can be a real b17c# to get the air out of.

Too late now, but 100% counter-productive. By draining, you replaced the water with air, and the air is what you are trying to remove!

Get the system HOT, and the pressure as high as it gets. With the circ running, start on the bottom floor and go to each baseboard in turn starting from the one closest to the boiler. Leave the circ running, and go to the next level up, then the next level up.

I'm looking at your pictures to see if you have what are known as 'purge stations', and I don't see any. They would make your life a lot easier if you had them. They consist of a drain valve upstream of a shutoff valve.

Another thing working against you is the fact that you don't have a 'fast fill' on the water feed. This would allow you to bypass the fill-x-trol valve and get a faster flow of water through the system.

No, of course not, as Holohan would say, "The Dead Men didn't think of it yet".

 

One thing to add... when you do each floor, from bottom to top, you want ONLY the one zone valve for the floor you are working on to be open. You want the full flow of the pump on that one zone.

 

Thanks for the super quick response! I'm going to buy something from one of the advertisers - seriously.

I'll try that bleeding procedure. Should I raise the pressure some first? I won't be able to do anything tonight since the bad baseboards are in the kids rooms and they're all sleeping.

Here are some answers to some of the questions asked in the response.
Yes. I did mean a monoflo system. I thought that was referred to as a single pipe system. My mistake. I'll post a picture of one of the T sets.


The baseboards are fin-tube and I do get a good flow of water from them when I open the bleed valve. If I bleed it long enough, I can get hot water out. All of the baseboards that are not heating have bleeders on them. The one that is heating has a auto air vent and I have added those to the other baseboards. I t didn't do any good since I wasn't getting air out to begin with. The bleed valves are on the end opposite the shutoff valve. The baseboards for the basement have bleeders where they T off of the main pipe.


That's where they are but they don't go back to the floor there. They do a 180 and go back under the fins and then 90 down into the floor a couple of inches from where the supply comes out of the floor. Also, since the baseboards are essentially cantilevered off of the supply and return pipes, the end of the baseboard with the bleeder is slightly downhill from the where the water enters the unit. I put a block under it to raise it up.


The only valves I have is the drain at the bottom of the boiler and the fill valve from the cold water pipe.


Actually, this is the third time I've drained it this month. When I first started it, the air vent on the return shown in one of the pictures was leaking so I had to drain it to replace that. after I filled it up again, the drain valve was leaking so I had to drain it again to replace that. Then I had to replace a leaky air vent on top of the expansion tank. Just to be clear, I did not expect that draining and refilling would exactly fix the problem, but I was surprised that the same baseboard that worked fine before still was good with no bleeding after that.

 

I found the info below on the web somewhere. Could it be that if the zone valve is not opening all the way I am not getting the needed velocity in the system? I know that at the very least it partially opens because I get heat to one baseboard and I get hot water from the bleed valve if I bleed long eough (6 cups or so). Because of the above, and because the main pipe gets hot all the way around to the return, I assumed that the zone valve was working ok. I'll manually open it when I get home and see if it makes a difference.

Pulling the lever all the way down should FULLY open the valve, correct?

Rocky, I'm not familiar with the scoop tees, only the venturi tees. You need to remember that they work on velocity. Kind of like a plane's wing... you get enough speed, the plane lifts. Same deal with diverter tees. You get enough velocity/flow on the main run and you'll get flow through the branch. Not enough velocity/flow and the heated water won't be diverted through the branch, the heat will stay in the main or at least miss a branch or more.

 

It will help to raise the pressure... do you know how your FILL-X-TROL system works? If not, read up on that, cuz it's different than the systems that have 'pressure reducing valves' on them. Very basically, those things set the system pressure at whatever the air charge is on the tank. In order to raise the system pressure, you would need to add air to the tank, and then let it back out again and drain off some of the pressure from the drain valve.

If you do that, the procedure is going to be a bit different. You would not want to raise the pressure to say 25 PSI, and then fire the boiler, because the relief valve will spew. If you raise the pressure, you will have to bleed with the boiler OFF.

It sometimes is, no mistake. I just wanted to be sure we both were talking about the same thing!

It should... and I guess anything is possible... and this is also the reason that I said to only open one zone at a time when you were bleeding, to get the most velocity through the one zone you were working on.

You say there are valves at each baseboard? I'm gonna ask a question that I have to ask... forgive me... but are you SURE that all the valves are open?

 

The radiator valves are open. They only turn about 1/4 to 3/8 of a revolution but they turn relativly freely and it's just like the one that IS working and that one definitly turns on and off with about 1/4 turn. I can't move one of the valves but I know that one is open because when I bleed the heck out of it, it eventually gets hot from the supply side.

 

While I'm not doubting that you are sure it's open, the logic on why so is a bit flawed... here's why:

With monoflo tees, there's nothing to stop the hot water from the main to flow up the return side, if that supply valve is in fact closed. I'm supposing though that you are actually FEELING the hot come up the supply... and this gives me another thought!

What if you brought the pressure up in the system, CLOSED the supply valve, since it appears that the air is beyond that... and forced the water to come up the return side? If the air is trapped in the return pipe _after_ the bleeder, then maybe this would push the air backwards, and out the bleeder?

 

I know that the 'regulars' are probably tired of looking at my pictures, but I don't know if you've seen this one, and it illustrates some of the stuff we've been discussing:



There's another thing working against ya here... in order to move an air bubble, you do need some velocity. The fact is that opening that little bleeder simply isn't going to provide the velocity you need to budge that bubble. These little bleeders are really designed to vent air that is already underneath it. If the bubble is even 1" away from the bleeder, and won't move, then no amount of bleeding is going to help.

 

I tried this and it got two of the three cold baseboards heating. The one that's still not heating is fed from the first set of Ts (closest to the boiler) off the main pipe.

Before I tried bringing hot water up through the return pipe, I closed the valve to the one baseboard unit that was heating. Should this have increased, decreased or had no effect on water flow in the main?

For the one baseboard that's still not heating, I thought about what NJ Trooper said....I went to the hardware store today and bought parts to make a super bleeder valve. I'll have to use it with the boiler off and cold so that the boiler isn't affected by too much cold water at once. I'll post a picture of it when I put it together. You may get a kick out of it - ha ha.

Also, with all of my use of the cold water supply valve from fixing leaks, the cold water supply valve itself now has a leak. I posted a question about that in the plumbing forum. This has definitely been the year of leaks.

Thank you everyone for your help so far. You've been great.

 

GREAT! I love to hear success stories!

Good question! Here's another one of my all too often posted graphics...



I think you've got one diverter, and one standard tee... so imagine one of the tees as a standard.

Think of this as a highway, with a detour. Some of the traffic goes straight through, and some takes the detour. If you close off the detour, and only let the cars through on the main, you would think the volume in the main would be reduced, and you would probably be correct... at least that's the way I see it. It might not be reduced by an equal amount, as some of the detoured cars are going to try to squeeze by and stay on the main, but the end result is that it's reduced.

Sounds like it's gonna be right up my alley! Can't wait.

That's the 'stem packing' leaking. That large nut below the handle is a 'gland nut' and serves to compress the flexible packing material that's underneath it. Most of the time, all you have to do is slightly tighten that nut, just enough to stop the leak. The packing material will be squeezed more tightly around the stem and the leaking should stop. If you can't tighten the nut, it means that it's done squozed all the way, and you either have to replace, or add, a bit more packing.

 

Well, I assembled the super-bleeder and finally got the air out of the remaining non-working baseboard.

The super bleeder was made of a 1/4" ball valve, a 1/8" nipple, a couple of 1/8-1/4 bushings, and a 1/4" hose barb adapter. Below are some pictures of it before it was installed and in use. Before I used it, I bumped up the pressure in the expansion tank to about 25 psi. When I opened the valve, water came rushing out and I got air out after a couple of seconds or so. Fortunately, the baseboard was right by the toilet so I didn't even need to bring a bucket.

Thanks NJ Trooper for your help.

 

I LOVE IT! Great idea! I'm surprised that you didn't mistype PSI with the talk of the terlet... you know, transpose the S and the I ...

I had an idea a while back that I was gonna mention, but then forgot all about it... I was gonna suggest a temporary hookup for a regulator valve to the boiler drain... using hoses similar to what you did, picking up a pressure reducing valve, set it to like 25-27 PSI and hook it to city water with hoses... would keep the boiler pressure up high without having to reset the fill-trol valve.