Air bound hot water heat

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Old 11-01-10, 06:24 PM
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Air bound hot water heat

I had a leak at the outlet flange on my boiler, so I drained the system and replaced the o ring seal between the boiler inlet and the manifold for the two zone circulator pumps. I refilled the system and bled each radiator, the upstairs zone works fine but I cant get the ground floor heat to work. The house is on a slab and the boiler is on the same slab, the heat piping runs around the top of the ground floor and one separate pipe system feeds the upstairs, that works fine: the other piping feeds the lower level. The problem is with the ground floor, the piping runs up high but the radiators are on the floor and have bleeders on them. I have bled them endlessly to no avail. The circulator pump comes on and sounds normal for about 6 seconds, then it sounds like it is cavitating. The output pipe is hot but the inlet is cold nd there is no circulation. If I leave the boiler on the water in the boiler gets too hot but no circulation, I have to turn on the upstairs zone to cool off the boiler. There are no shut off valves and no bleeders installed higher than the boiler on the lower level. The system worked fine until I repaired the leak. How can I get the air out of the lower level, if I leave the bleeder open long enough I get hot water but only from the water circulating the opposite direction of the circulator side. I feel the air is trapped in the last section of piping between the last radiator in the system and the circulator pump. There are no unions in the piping either so I dont know where to go from here.
 
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Old 11-01-10, 07:12 PM
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In this case, it would help us to see the boiler and all the piping around it. Hopefully we will see that you have what we call a 'purge station' that you can use to force water through the zone and push the air ahead of it...

FREE ACCOUNT / Image hosting, free photo sharing & video sharing at Photobucket / Upload pics there / come back here and drop a link to the album. Please make sure the pics are clear, well lighted and large enough for old dudes to see...
 
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Old 11-02-10, 09:54 AM
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Venting air from heat emitters located below the main is often difficult. Pending your posting photos of your system, a power purge setup, like this, may be the answer:



To bleed, shut the ball valve on the return and open the hose bib. The valve on the supply is optional - might be useful for maintenance, but not used for power purging.
 
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Old 11-02-10, 06:26 PM
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air bound heater

I dont have a photobucket acct, nor do I have any valves to close to do a power purge. I was considering removing the flange and pipe from the circulator pump and replacing the elbow at the top with an elbow that I can install an automatic bleeder on it. Does that sound like it will work ? I can send you guys pictures directly if that helps.
 
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Old 11-02-10, 06:54 PM
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Photobucket accounts are free and you can use an assumed name. There is also Imageshack.com which I think is even more anonymous.
 
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Old 11-02-10, 07:16 PM
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I was considering removing the flange and pipe from the circulator pump and replacing the elbow at the top with an elbow that I can install an automatic bleeder on it. Does that sound like it will work ?
If the air is trapped up in the loop, how will an air vent near the pump do any good?

If you want us to help you, please don't rely on our imagination to picture your system. We're not 'remote viewers'!

Set up the free account, and upload the pics, and tell us where they are...
 
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Old 11-03-10, 03:50 AM
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Originally Posted by jimbo327 View Post
Does that sound like it will work ?
No. In fact it will make things worse. Although I too lack 'remote viewer' skills, it's very likely that your circulator is on the return, and your expansion tank on the supply. In this situation, putting an air vent anywhere near the inlet of the circulator will literally suck air backwards through it. Right through the vent valve and everything.

We need to see some pics of the system.
 
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Old 11-03-10, 06:22 AM
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air bound system photos

Hi guys, I hope this link to photobucket works : heater photos pictures by jimbo2251 - Photobucket
 
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Old 11-03-10, 07:48 PM
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Wow... that system is almost a museum piece! Original circs, expansion, relief valve... amazing actually... it looks as though the only thing that has ever been changed is the air vent, and possibly the pressure reducing valve. Not that it's a bad thing, just kinda remarkable is all.

I am actually, as unbelievable as that may sound, at a loss here for suggestions...

We need to know what the pressure and temperature in the system is first... either read both needles and report, or take a close pic of the gauge on the front of the boiler.

In the meantime... The only thing that I can possibly think of is that the 'flow control valve' for that zone is stuck shut. Those flow control valves are the ones in pic 3 of 7 ... there is a knob on the top ... do those knobs turn freely? Inside those there is a 'weighted disc' that is supposed to lift when the circ runs. If that one is 'stuck' of course it won't let any water through. I'm not sure with that 'vintage' valve on the direction to turn it, but first see if it can even be turned without breaking it. Then, note the position that it is in now, either fully CW or fully CCW, and remember that, because you want to return it to the position when yer done. If they will turn, turn it all the way opposite of the way it is now and try the boiler... tell us what happens.
 
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Old 11-04-10, 12:37 PM
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I actually changed the air vent when I moved in 6 years ago and have not had to do any other repairs since. Last year I had to clean the pilot light nozzle but other than that it has worked fine. The flow valve works, I coached it with some WD-40 and I left it open in the hopes that the warm water would creep its way around the system and force the air through, no such luck. The valve does work because if I close it the pipe after the valve gets cold. The pressure at room temp is about 10-12 and water temp around 80, when the upstairs is working the temp goes up to 170 and the pressure to about 15. I was thinking of installing an air vent on the top of the return pipe that is seen in the top left side of the last photo 7 of 7. That is the section of piping that I feel is where the air is trapped. i have already tried to blled it by attaching a hose to the boiler drain and lifting the lever on the pressure reducing valve to increase the pressure in the system to the water line pressure to no avail. Thanks
 
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Old 11-04-10, 07:22 PM
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i have already tried to blled it by attaching a hose to the boiler drain and lifting the lever on the pressure reducing valve to increase the pressure in the system to the water line pressure to no avail.
Yes, to no avail... because there is no valve that you can close to force the flow of water through the zone. All you are doing by your approach is pumping water into the boiler, and right out the drain. The water will always take the path of least resistance, just like 'lectricity. That's why your system is so troublesome to help with, it simply isn't equipped with the proper valves to force the water through the zone.

I'm also not 100% sure that the problem isn't in the circulator pump itself... you described a sound of 'cavitation', but what if that sound is something else? Like something broken in the circ? and maybe it simply isn't pumping any water? (for what it's worth, I tend to think the problem IS air trapped, but needed to mention the 'what-if' scenario)
 
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Old 11-07-10, 03:47 PM
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Hello and thaks for your recommendations, I drained my system and replaced the last elbow in the return line of the system with an elbow with a manual bleeder and I was able to bleed the system and now I have heat again. I had to heat the fittings with a propane torch to get them apart but it was worth the effort. I appreciate all of your input and hope this problem/solution will help someone else in the future. Please review the picture of the manual bleeder at photobucket. heater photos pictures by jimbo2251 - Photobucket
 
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Old 11-07-10, 05:22 PM
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Excellent! Way to go Mr. Jimbo!
 
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Old 11-09-12, 01:00 PM
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I know its been a while since this was posted...glad you got it working. When you get a chance you can replace the pipe on the discharge side of the relief valve...good rule of thumb, don't reduce the size of the pipe going (out) of the relief valve.
 
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Old 11-09-12, 11:08 PM
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Yeah, it has been a while... 2 years!

Which picture are you seeing the reduction in pipe size?
 
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Old 11-11-12, 01:22 PM
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[email protected]@ks like a reducing elbow screwed into the relief valve, but I could be wrong?

 
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Old 11-12-12, 05:23 PM
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Yeah, maybe... hard to see in the pic though.

BUT, it's a good tip for any future readers.

Do NOT reduce the size of the discharge pipe on a relief valve.

For that matter, I would NOT have used an elbow, ANY elbow, reducing or not, at the outlet of the relief valve. I would have turned the valve itself.
 
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