Have to bleed convector every few weeks (#1 on the system)...

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Old 02-15-14, 12:30 PM
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Have to bleed convector every few weeks (#1 on the system)...

Hi guys,

I have a 1960 built house w/ hot water heat. I have what seems to be the original oil fired boiler (Paragon) and recessed wall convectors.

I have been in the house for 2 years, and I have had the bleed the first radiator on the system (my daughter's bedroom unfortunately) every few weeks. I have had my heating oil company out here on many occasions, and they will bleed the whole system, look for leaks, etc, but it always comes back again. There are no signs of a leak. 1 room of my home is on a slab, the tile floor feels warm right where the pipes run, but nothing out of the ordinary (and this 1 room is on a separate zone from where I am having issues, if that is relevant). I guess there could be a leak in there, but it would take other means to find out I guess.

I have started to run out ideas...when I noticed that the last convector in the system (or 2nd to last) has an auto bleeder on it. It looks like the pic below:
[ATTACH=CONFIG]26795[/ATTACH]

Not being an expert on heating/plumbing it just seems silly to me to have the auto bleed valve on the last radiator. Am I missing something? Could this actually be letting air IN to the system if pressure is not high enough to keep it always wet? Is there any way to test if this is the case...or is it worth it to just eliminate it and replace with a normal bleed valve and see what happens? It seems to me like it wouldn't be doing any good being on the last radiator anyway.

thanks for any advice you can give!
 
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Old 02-15-14, 01:02 PM
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More info...

First keeping in mind that boiler gauges are almost never accurate, read this:

http://www.doityourself.com/forum/bo...ure-gauge.html

And then tell us what the pressure and temperature is reading.

What type of expansion tank do you have? Large steel strapped into the joists above the boiler? or the type that looks like a gas grill propane tank?

It is possible under certain circumstances for a float type vent such as you've pictured to 'gulp' air at times...
 
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Old 02-15-14, 01:16 PM
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Hi...thanks for the quick follow-up.

Temperature is 170, pressure appears to be around 12.5 (assuming the gauge is accurate, as the link you included suggested is likely not the case). The heating company never seems to be worried w/ the 12.5 pressure even though I always ask them if it is OK.

I have the old style large steel tank strapped up between the joists. That overflow pipe recently let out a lot of water and spilled over the bucket that was placed below it, so I had my heating company service the expansion tank (let the water out of it?).
 
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Old 02-15-14, 02:01 PM
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Saab,
First of all instead of replacing that self bleeder just tighten the cap for now and it's like making it a manual bleeder.
If you think you may have a leak it doesn't matter what zone it's in, the feeder still replaces the water into the boiler which introduces air into the system.
You can shut off your cold water feed and see if you loose pressure in the system. That's one way of determining if you have a leak.

If the pressure drops, if that zone can be isolated for a while try that and see if the pressure holds.

Lastly, this is just my opinion, 12 psi is a little low for my taste. I like to see at least 15psi cold and even a little higher.
 
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Old 02-15-14, 02:04 PM
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An automatic air elimination device should not be installed on a system with a conventional steel expansion tank. It will cause the tank to become waterlogged and the relief valve to discharge. The air eliminator will have to be removed and the connection plugged.

You will also need to replenish the air charge in the tank. To advise you how, please post good, wide-angle photos of your boiler area.
 
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Old 02-15-14, 02:14 PM
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I'm with spott... pressure is too low (at least let's presume so until the gauge is verified).

The heating company never seems to be worried w/ the 12.5 pressure even though I always ask them if it is OK.
In today's economy, most business models dictate that the tech gets in and out as quickly as possible so if something does not add to the profit, they won't even suggest it.

Bottom line, they don't care.

Twelve PSI should be considered a MINIMUM pressure when the system is COLD for up to a 2 story home. A couple PSI higher for a 3 story... how many floors in your home? Boiler in the basement with 2 floors above?

When system is HOT I would like to see 15-18 PSI.

While there may be other reasons for the air, it is a given that low pressure in the system will contribute to the problem.

I suggest that you verify the gauge accuracy and we'll go from there.

the feeder still replaces the water into the boiler which introduces air into the system.
Because fresh water contains a lot of dissolved air... and when heated it forms new bubbles.

The type of expansion tank you have requires piping that allows air in the system to be caught and sent to the tank where it belongs. Can you show us some pics of the system?
 
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Old 02-15-14, 02:16 PM
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The air eliminator will have to be removed and the connection plugged.
Or just closed... screw the cap down tight.

You will also need to replenish the air charge in the tank.
He said the service company did that... but who knows if they did it right?

It IS something that a homeowner can do fairly easily...
 
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Old 02-15-14, 03:35 PM
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Thanks guys...

The house is 2 stories, about 1900 sq feet. The boiler is in the basement. 2 zones. Levels 1 and 2 are on the same zone (seems silly) and a large den, on a slab behind my garage has its own second zone.

Question regarding shutting that auto bleed valve on one of my convectors - I took a look at it, appears to already be shut...as in "very hand tight". Do I take a vice grips to it, or is hand tight with a lot of force considered "closed"? I just don't want to break it.

Here are some photos of the system that you guys requested...let me know if any other pictures would be helpful.



In the last picture, the valve to the left is what I presume to be a pressure reducer valve...the valve on the right goes to the drain bucket.
 
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Old 02-15-14, 04:00 PM
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Do I take a vice grips to it, or is hand tight with a lot of force considered "closed"? I just don't want to break it.
Heck no! No vice grips! Even a 'lot of force' is probably too much... just snug it on down and it will be fine.

the valve to the left is what I presume to be a pressure reducer valve...the valve on the right goes to the drain bucket.
That's correct, the one on the right is your safety pressure relief valve.

I would not call your expansion tank 'optimally piped' ... but 99.9% of them are not. Installers seem to not understand that those tanks have two purposes, one to provide expansion space for the water as it's heated, and two, to provide a place for the air to reside AND BE ABLE TO GET BACK TO the tank.

Even so, if you have to drain the tank every five years or so, that's not so bad really.
 
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Old 02-15-14, 04:48 PM
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That overflow pipe recently let out a lot of water and spilled over the bucket that was placed below it
By "overflow pipe," I assume you mean the discharge from the relief valve? For that to lift, the system pressure must be over 30 psi, which wouldn't be related to your pressure gauge reading low. I think your problem is a waterlogged expansion tank, probably caused by the air eliminator that shouldn't be there. You'll need to drain and recharge the tank with air.
 
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Old 02-15-14, 04:56 PM
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He did say that the air vent was already closed 'as found'...

and that the service guy drained the tank AFTER the relief valve spewed...
 
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Old 02-15-14, 05:02 PM
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the air vent was already closed 'as found'... and that the service guy drained the tank AFTER the relief valve spewed...
Then why did the system pressure climb right back up to lift the relief valve? Maybe the auto fill valve, which looks newish is leaking"? In which case, isolate it.

If the "tech" drained the tank, did he also vent it to atmosphere to fill it with air? Why do I suspect not?

This whole original system is from the 1960s? I doubt that this problem has been ongoing for 50+ years?
 
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Old 02-15-14, 06:13 PM
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Then why did the system pressure climb right back up to lift the relief valve?
He didn't say it did... says it's sitting at 12.5 PSI now... opened the relief valve BEFORE the service guy supposedly drained the tank, which I'm with you, he probably didn't completely drain it... but ya never know, stranger things have happened!
 
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Old 02-15-14, 07:26 PM
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To clarify the sequence of events...NJ Trooper has it right...where I stand right now is: The expansion tank has been drained by the technician a few months ago (and system has not overflowed again since), apparently the automatic air vent I discovered on the last convector was actually shut all this time, and I still have the constant need to bleed radiator #1 on the system (sometimes #2 as well, but much less so), as I have needed to do for the 2 years I have been on the house.

I am not really sure what technique the guy used to address the expansion tank.

I was reminded of another tidbit just now as I sit here. The den is on it's own zone, and it is traditional baseboard instead of recessed convectors. I typically hear the sound of rushing water. That is usually a sign that air is in the system, right? So I guess just a different "symptom" of the same issue that is causing the #1 convector to get air-locked?

Thanks again everyone for the outpouring of advice so far!
 
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Old 02-15-14, 07:33 PM
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If it's been a couple few months since the tank was drained I think it's safe to assume that he got at least enough air into the tank for the time being anyway.

I typically hear the sound of rushing water. That is usually a sign that air is in the system, right?
Yes.

I guess just a different "symptom" of the same issue that is causing the #1 convector to get air-locked?
Same symptom, no? Yes, you've got air in the system, no doubt.

I suggest that you verify the gauge accuracy and we'll go from there.
 
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Old 02-15-14, 07:44 PM
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Thanks. I will have to get/build a gauge as you described and get back to you.

One last thing I think is worth mentioning... The previous owner of the house was 90 years old...and I am guessing that maintenance sort of fell by the wayside in his later years. From what I have heard, it is normal to have the bleed the radiators on a system like this once a year (please correct me if I am wrong on this). If the previous owner did not bleed the radiators for years and years, could so much air have accumulated in the system that I keep bleeding little bits out as more of the air finds its way to that #1 convector? Would that even be possible?
 
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Old 02-15-14, 08:27 PM
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From what I have heard, it is normal to have the bleed the radiators on a system like this once a year (please correct me if I am wrong on this).
I guess 'normal' is sort of a relative term.

If a 'normal' system is one that is not really designed and piped properly, then yes, it's normal.

If a system is properly designed and piped, it would not be normal.

Properly designed and piped means that the air traveling through the system is caught by a device known as an 'air scoop' and is directed back to the expansion tank through 3/4" piping that slopes upward toward the tank a minimum of 1/4" in 5' so that the bubbles can travel back where they belong.

Even better yet would be if the circulator pump was pumping AWAY from that air scoop that the expansion tank is connected to... Bell & Gossett has only been trying to get installers to put the pump in this location since the mid-50s or so...

Sadly, if an instruction book was ever even looked at, it was only briefly before the workman placed it on the floor to kneel on to keep the knees of his chinos clean. Workmen really liked the nice thick install manuals... more padding for the knees.


If the previous owner did not bleed the radiators for years and years, could so much air have accumulated in the system that I keep bleeding little bits out as more of the air finds its way to that #1 convector? Would that even be possible?
Yes, sure it is. And bleeding little bits at a time is the best way to do it if you don't have an air scoop (which you don't).

If you 'purge' the system by force feeding a ton of fresh water, you are also adding BACK all the air you just took out, and maybe even more... because fresh water has tons of dissolved air in it.
 
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