Constantly having to bleed system. What gives?

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  #1  
Old 03-18-19, 06:01 AM
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Constantly having to bleed system. What gives?

Hello all,

I have received some great advice from the members of this forum in years past. I am hoping I can dip into the well once again.

I have a 1951 single story home with a basement. The boiler is in the basement. I have a combination of radiant pipes in the walls, ceilings, and fin tube heaters in the form of cabinets and baseboards throughout the house. The house has two zones.

For some reason I am having to bleed air out of the system every couple of weeks from the fin tube heater in the bathroom, and very rarely other fin tube heaters. Since the bathroom heater always fills with air first I assume the others that fill with air do so when the amount of air in the system is greater than what the bathroom fin tube can hold.

I hoping someone can help me understand how a closed system can constantly be producing air. The odd thing is that I don't remember this happening when we first moved into the house. It seems to have started after I have had to do work on the system (installing an drain valve so that I could screw a pressure temperature on it when I want to check the systems vitals, removing sand from the fill pipe connected to the domestic water system in the house, change out propeller (?), etc.).

Years ago I complete drained the system so I find it hard to believe the tank that captures air bubbles from the system could be full. Even if it is, what keeps producing more air in the system. By the way, I do not rely on the auto fill valve. I have the manual valve upstream from the auto fill valve turned off.

Do the experts here have any idea what is causing this?

Thanks in advance,
Blane
 
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  #2  
Old 03-18-19, 06:56 AM
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What is your normal system pressure? When bleeding, temporarily jack it up to, say, 25 psi.
The question is how air is getting into your system. A heat emitter located below the elevation of the main can be tricky.

When you completely drained the system, the water you used to refill it was loaded with dissolved and entrained air. What type of air elimination devices and expansion tank do you have? Please post some photos of your system.
 
  #3  
Old 03-18-19, 07:13 AM
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Thank you for your reply.

Whenever I fill the system, which hasn't been in a few years, I put in 12 psi.

I don't believe there are any leaks as all pipes are inside the house and because so I would think that I would notice moisture somewhere if there was a leak.

The autofill valve is shut off and I have a manual valve upstream that is also turned off in the event the autofill valve malfunctions.

Thanks again,
Blane
 
  #4  
Old 03-18-19, 03:39 PM
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With the auto valve shut off how do you maintain 12 PSI every time you remove the air which also would drop the pressure. Ho do you get it back up to 12.
 
  #5  
Old 03-18-19, 05:38 PM
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My pressure drops of course when I release air. I just checked it and it was 10 psi so I added water to get it back to 12 psi. As soon as I did the pressure relief valve starting dripping and continues to drip.

When it drips at 12 psi when it is cold I assume when the boiler kicks on again tomorrow morning and the pressure goes up to 20 psi or so I am guessing the pressure relief valve is going to drip even more.

Blane
 
  #6  
Old 03-18-19, 06:02 PM
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B,
If your relief valve is dripping at 12 then you either have a bad gauge or a defective relief valve. Those relief valves are set to go off at 30 PSI.

Next if you have 12 PSI cold pressure you should not be getting up to 20 or over hot. That is too much of a swing and is a symptom of a filled conventional steel tank or a defective extrol tank that has lost some or all or its air charge and the system water when hot has no place to expand.

Finally, your air problem. Every time you add fresh water to your system, which you do after bleeding, it brings air with it just like in a faucet only in a closed loop the air cannot escape by itself other than venting. By running your boiler at 12 when bleeding you are just recreating the problem with a never ending cycle.

Before you bleed your system the next time bring your pressure up to at least 25-28 PSI but under 30 so the relief will not go off. After bleeding your emitter drain excess water out until you reach 20 PSI. This will be your cold operating pressure. From cold to hot boiler temp. pressure should not vary more than a couple of pounds if everything is sized right.

I would verify your gauge for proper operation and if so then turn your attention to your relief valve and expansion tank and then fix your air problem which is really no problem at all when bleeding properly at the right pressure.

Hope this helps a little.
 
  #7  
Old 03-18-19, 06:13 PM
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If you have both the pressure relief valve discharging when the boiler is on and the system pressure dropping to near zero when the boiler is off then the air cushion in the expansion tank may be too small.

If the system including the expansion tank is drained completely then long horizontal expansion tanks may require a few weeks of alternately bleeding air from an upstairs radiator and adding more water down below and then things should settle down with little or no air needing to be bled for a long time.
 
  #8  
Old 03-19-19, 06:13 AM
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Thank you spott and AllanJ for sharing your expertise.

Years ago I followed NJtrooper advice and made a screw-on pressure gauge that I attach to the drain valve when I want to check the system pressure. I do not rely on the one installed permanently on the boiler.

I just went through another heating cycle this morning and found the following.

Yesterday I filled the system to 12 psi. This morning I ran both zones (granted the basement valve was turned off so there was still some cold pipes in the system) and the pressure went up to 15.5 psi. I was mistaken in my previous post where I thought it would go up to 20 psi. Based on this it seems that my expansion tank is working properly. (Years ago the system pressure went up into the 20's when the expansion tank filled up. It filled up after a service technician left the autofill valve in operating mode with the upstream valve open. It took a couple years but it eventually filled the tank.)

Yesterday when I filled the system to 12 psi from 10 psi I mentioned the relief valve started to drip. It didn't drip long (the floor is dry) and when the system ramped up to 15.5 psi it did not drip. I don't understand why it would drip for a short while at 12 psi when additional water was added.

spott wrote:

Before you bleed your system the next time bring your pressure up to at least 25-28 PSI but under 30 so the relief will not go off.
I am to do this by adding water correct? (I just want to be sure.)

After bleeding your emitter drain excess water out until you reach 20 PSI.
Is the emitter the fin tube heater in the bathroom (where I first get an airlock)?

This will be your cold operating pressure. From cold to hot boiler temp. pressure should not vary more than a couple of pounds if everything is sized right.
For my two level house (basement and ground floor) I was told that my cold pressure should be 12 psi by one of the experts here. Is this incorrect? If so I have doing it wrong for years.

AllanJ wrote:

If you have both the pressure relief valve discharging when the boiler is on and the system pressure dropping to near zero when the boiler is off then the air cushion in the expansion tank may be too small.
My pressure drops to 10 to 12 psi when the boiler is cold and 15.5 psi when hot. I don't think the pressure tank is too small. It was working great for years when we moved in and it has been in operation since 1951.

If the system including the expansion tank is drained completely then long horizontal expansion tanks may require a few weeks of alternately bleeding air from an upstairs radiator and adding more water down below and then things should settle down with little or no air needing to be bled for a long time.
After my expansion tank filled as described above I drained the entire system including the expansion tank. You guessed it, the expansion tank is long and horizontal. I have been bleeding the system for a couple years but I have not added water until yesterday, hence the 2 psi drop.



Thanks again guys/gals for the help. I really appreciate it.

Blane
 
  #9  
Old 03-19-19, 11:07 AM
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B,
1) You increase pressure by adding water. Add water until you get to 25-28 PSI. The reason you do this is so when you are finished bleeding the pressure is high enough and no fresh water will feed in to bring air again. Every time you add fresh water, weather it be a cup or a gallon it has air.

2) Emitters are your heating units. It could be baseboard, radiators or in your case fin tube heaters.

3) Auto feed valves come preset at 12 PSI and if you go by the math of basically every pound of pressure will give you 2 LBS of lift. The exact math is "Every foot of water (i.e. foot of head) equals 2.31psi."
That being said 12psi is the minimum for heating systems and acceptable for up to 27 ft on paper but 18-20 I believe is better and Taco even recommends running 20psi with wet rotor pumps such as the 007. I believe you will see a difference in operation and quietness and prevents pump cavitation.

As to the point of 12psi being wrong, on paper you fall within that range but as you said you are continuously bleeding so you be the judge.

For my opinion on Allen's statement about the tank and bleeding, if the tank was drained completely empty which it must be when it needs it there is nothing else that has to be done with. Upon refilling the system the water will reach its own level in the tank with plenty of room for expansion so there is nothing more to be gained by continuously bleeding you emitter and is unnecessary.

Just my thoughts.
 
  #10  
Old 03-19-19, 03:09 PM
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A FHW (hydronic) system should be drained as seldom as possible. If you do drain it then when it is refilled there will be some air at large inside that will require bleeding from the emitters. Larger amounts less frequently for old fashioned radiators, smaller amounts more frequently for baseboards. When you bleed out air you have to immediately add water to get the system pressure back up to where it should be (if the system did not autofill). After awhile the need for bleeding will stop and air in the expansion tank will stay in the tank.
 
  #11  
Old 03-19-19, 04:33 PM
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As previously requested, please post photos of your system. With a conventional steel expansion tank, Airtrol tank and boiler fittings are needed to continuously return air to the tank.
 
  #12  
Old 03-20-19, 06:15 AM
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Also, the pipe from the system must slope upwards toward the expansion tank.
 
  #13  
Old 03-22-19, 06:37 AM
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Thanks much for all the helpful information.

I'll follow spott's advice and bring my pressure up in the system by adding more water. I'll add water to bring the pressure to a little over 20 psi so that when the bleeding is done I'll be near 20 psi. To clarify, with all the bleeding I have done over the past 3 years I did not add water to the system during that time yet I was continually having to bleed air (and lost 2 psi in the process). It doesn't make sense to me why this was happening.

I learned when I first moved in the house and hired a commercial heating company to give me a primer on the system that I was not to replace the water except when a repair was needed. He said the blackish water that he observed draining when he was here (replaced a stuck valve) was the color I wanted to see.

The pipe does slope upwards to the expansion tank. I am confident the system was designed and built properly as it was working flawlessly until I had to drain the system to replace a part.

Here are some pictures of the system. If there is anything else anyone would like to see please let me know.

Boiler by BW Swede | Photobucket

I think the pictures show the expansion tank and the fittings that pull bubbles out of the system and send them to the tank.

I can't remember the purpose of the vertical turquoise colored devise in the attic at the highest point in the system (see photos). It has a copper tube attached to it that runs down through the first floor walls into the basement at dumps out in the boiler room so that if any water comes out it drains to the floor drain. Does anybody know the purpose of this device?

Thank you very much for the information being shared.

Blane
 
  #14  
Old 03-26-19, 09:28 PM
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Hello all,

I had some time tonight to spend on the heating system. I thought the first thing I would do is add water while the system was cold. I was back down to 12 psi so I added water with a goal of getting it up to at least 20 psi. I got as far as 16 psi and the pressure relief valve opened up and started leaking water in a constant stream.

Before I go through the effort of draining the system and purchasing a new pressure would someone please confirm that what I experienced is indeed a bad pressure relief valve.

Thanks in advance,
Blane
 
  #15  
Old 03-27-19, 12:03 PM
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I would conclude that either the relief valve or your boiler pressure gauge is wrong.
 
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Old 03-27-19, 01:16 PM
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B,
As gil said it's either your gauge or you relief valve but one of them is off by 14psi since the relief valve went off at 16 and it's rated for 30psi.

What you can try is lower your boiler pressure below 12psi and see if it feeds automatically. Feed valves come preset at 12psi so below that point it should feed fresh water into your boiler. If you get it below that point and it doesn't feed, keep draining a little at a time until it comes on. If it doesn't feed until 8 then your gauge is off by 4. If it feeds at 2 then your gauge is off by ten or you can just get another gauge with a hose connection and screw it on to a boiler drain, open the drain and compare it to your boiler gauge.

If you PRV stops leaking when you let a little water out I would suspect your gauge is off.

https://www.supplyhouse.com/Winters-...auge-0-160-PSI

https://www.supplyhouse.com/sh/contr...ressure+gauges

An example of some gauges. You don't need high pressure for boiler so if you can find one with a 100 psi it might give you a clearer reading.
 
  #17  
Old 03-28-19, 05:35 AM
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spott, gilmorrie,

Thank you once again for your replies. I failed to mention that the reason I assumed it is the PRV is that I have two pressure gauges. One that came on the boiler and one I made to fit the boiler drain valve (per njtrooper instructions) as spott described in his last post. These valve measure within 2-3 psi of each other. Granted, they both could be wrong but when I combine their readings with increased water noise in the system when the system approached 10 psi I am tending to believe the PRV is bad.

Thanks again for replying to my question. I'll start looking for a new PRV.

Blane
 
  #18  
Old 03-28-19, 11:37 AM
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Below is a sight and options of PRV's.

https://www.supplyhouse.com/Pressure...alves-17144000

Hope this helps a little.
 

Last edited by spott; 03-28-19 at 12:16 PM.
  #19  
Old 03-31-19, 07:20 AM
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Awesome! Helps a lot!

Thanks spott.


Blane
 
  #20  
Old 05-08-19, 02:21 PM
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Now that our heating season is over (mostly) I am looking to replace the pressure relief valve. I have started looking and I can't seem to find one with a side inlet and bottom drain like my current B&G setup. All that I have seen so far are the opposite.

Does anybody have any suggestions for me? I called the company that now owns B&G and the local reps were not any help. They gave me a model number but it turns out it is a pressure reducing valve which I don't think is what I need.

TIA,
Blane
 
  #21  
Old 05-08-19, 03:35 PM
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I am not sure what you are looking for but check out these part numbers to see if this is similar to the item you are referencing; B&G model #110197LF or 110198LF. If these are not what you are looking for please post a picture. There are a lot of good guys that monitor this site.
 
  #22  
Old 05-08-19, 04:48 PM
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These look like your other options.

https://www.supplyhouse.com/Pressure...alves-17144000
 
  #23  
Old 05-10-19, 06:57 AM
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Spott, Steamboy,

Thank you for the replies. As long as the units are not orientation sensitive I suppose I could use one from the page linked by Spott. What I am looking for is shown in the attached picture. BTW it has a 3/4" threaded connection.

Thanks again,
Blane
 
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Old 05-10-19, 10:19 AM
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BW,
It is orientation sensitive and must be facing up as yours is now. You can add an elbow and a nipple if you get a female thread. They also make a male thread if you want. They come in different size threads but for residential boilers they are mostly 3/4. Never saw one like that except on a combo that SB posted.

It's strange it's not installed on the boiler itself.
 
  #25  
Old 05-11-19, 04:01 AM
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Wow, I haven,t seen one of those in many years. It may drip at certain pressures but I have never seen one mounted like that I believe that yours is mounted backwards and is piped to the valves discharge port and not the inlet port. Look at the valve closely; some had markings or arrows indicating direction or mounting ports. (inlet) . As far as a new valves mounting position, most are not position sensitive but the preferred mounting is in an upright position. Most relief valves are mounted on the boiler however sometimes you had a 2nd relief valve mounted on the piping as long as there was no isolation valve between it and the boiler. It all depended on the pressure vessel code in your area. (remember, I did mainly commercial and industrial boilers) hope this helps.
 
  #26  
Old 05-18-19, 05:34 AM
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Steamboy,
For some reason a post that wrote several days ago didn't get posted. I'll try again.

The PRV in the picture is mounted correctly as there are not threads on the bottom of the unit, only on the side. I checked to be sure and there is no isolation valve between the PRV in the photo and the boiler. I also have a standard PRV (like on a residential water heater tank) mounted on top of the boiler.

The system has been operating since 1951 and is pretty low maintenance. I wish I could find a direct replacement for the PRV so I can keep the system as original as possible.

Thank you,
Blane
 
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