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Pressure relief questions ....

Blast
Blast Member Posts: 12
edited December 2016 in Gas Heating
Hopefully someone can help:
My 2 floor plus basement summer house, basement boiler (baseboard hot water system), where the pressure relief valve is on the boiler, has what looks like a "T" fitting at the top of the pipe coming up from the boiler, , 1 part of "T" going to the relief valve, the other end of the "T" going directly to what looks like a steam release valve, which has a small thumbscrew on it.
The pressure release valve has been changed , however it occasionally "goes off", daily, & I notice water on the basement floor under the relief valve pipe. I have been in the basement once where I "caught" the pressure gauge momentarily go way up, & the release valve briefly let out a bit of water onto the floor, & the system pressure quickly go back to normal.
The problem is 90% of the time it is running normally, it is hard to catch it "in the act", & a repair person was not able to duplicate the situation while he was there, he did all the regulr bleeding of system, ect ....
Could it be that "T" at the top of the boiler has a bad steam valve (if that is what that is), would that stop the occasional momentary pressure spikes... ??

Comments

  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    edited December 2016
    I think the valve with the screw is your water feeder.
    What kind of system do you have? I assume it's a water boiler, but do you have an internal coil or indirect for domestic hot water?
    What type of expansion tank do you have?
    If the pressure keeps rising it's either:
    1. Water feeder not closing tightly, adding water to system and eventually blowing out relief valve.
    2. Steel expansion tank water logged, or bladder type expansion tank failed/lost its charge or is undersized.
    3. System not properly bled.
    Or a combination of the three (or all three)
    Can you post some pictures?
    steve
    delta TBlast
  • delta T
    delta T Member Posts: 884
    I think the 'steam vent' OP is talking about is an air vent. I have seen some older boilers that had an air vent on a tee with the relief valve coming out the side of the tee, some CI boilers have baffles built into the boiler kind of like an air scoop. Tapping on top was for the tee with relief valve and air vent.

    Weil Mclain boiler i'm betting.

    Agree with all the above, pictures will help us verify some of this.
    Blast
  • Blast
    Blast Member Posts: 12
    edited December 2016
    Thanks for the replies !
    It's a summer place, so I won't be able to post any pics for about a week or so, when I get there, but here's some additional info based on both your comments:

    * It has a bladder type expansion tank, ( recently replaced), connected up near the ( gas fired) boiler to a pipe, that seems to be in line with just One of the two Zones. I had asked the service person about that, & he said it didn't matter where it was located, as long as it is "somewhere" in the system ... ( if that zone is not running, only the other zone, then how does the expansion tank "work"?)
    * The "bell" looking water feeder ( also fairly recently replaced), enters from a cold water main at a lower point of the boiler.
    * The "Steam valve" on the "T", I'm pretty sure is an air vent, ( as @delta T mentioned above), & that vent has not been replaced recently. ( It reminds me somewhat of the end vents we had on steam radiators in my home as a kid ..).
    * Hot water comes from a separate gas hot water heater, not this boiler.
    * The boiler ( not the pipes/rest of system), was replaced in 2012 before I owned home.. I believe the pipe with the "T" coming off the top with relief and air vent was probably from the old boiler & connected to new, but not sure.
    -- Trying to get to the bottom of why the very occasional bursts of high pressure/ relief valve water release
  • delta T
    delta T Member Posts: 884
    " I had asked the service person about that, & he said it didn't matter where it was located, as long as it is "somewhere" in the system ... ( if that zone is not running, only the other zone, then how does the expansion tank "work"?)"

    This is not true. The placement of the expansion tank relative to pumps has an effect on system pressure when the pump is running. If you want a detailed explanation, someone may jump in, I have to run now. If you are really interested the book 'pumping away' available on this site will explain exactly what the pump/expansion tank relationship is.
    Solid_Fuel_Man
  • Blast
    Blast Member Posts: 12
    edited December 2016
    As suggested for pictures, ( again thanks @delta T and @STEVEusaPA ),
    Here below, is a 2 min video, showing the boiler brand, pump, the mentioned "T" with release valve/airvent, expansion tank , water input, pressure gauge, water on basement floor etc ...
    - Any insights as to why the occasional pressure build/releases would be greatly appreciated.
    Secondary questions are:
    - Do you think the expansion tank is OK where it is?
    - Should I replace the air vent?
    Thaks in advance..
    Here is the video link:
    https://youtu.be/U6Id0V6gSWw
  • Zman
    Zman Member Posts: 7,561
    The expansion tank is absolutely in the wrong place. I don't think that it is completely isolated at any time unless you have check valves on the return that are not visible in the video.

    What I think is going on is that the location of the expansion tank is causing the pressure to fluctuate as the zones open at the point that pressure reducing fill valve is located.This could be tricking the valve to add water when it is not needed.

    Try turning off the water supply to the system and see if the problem goes away.

    As rule, anyone calling themselves boiler technician that thinks that is a good place for the tank should be shown the door.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    delta TBlast
  • Blast
    Blast Member Posts: 12
    edited December 2016
    Zman said:

    The expansion tank is absolutely in the wrong place. I don't think that it is completely isolated at any time unless you have check valves on the return that are not visible in the video.
    What I think is going on is that the location of the expansion tank is causing the pressure to fluctuate as the zones open at the point that pressure reducing fill valve is located.This could be tricking the valve to add water when it is not needed.
    Try turning off the water supply to the system and see if the problem goes away.
    As rule, anyone calling themselves boiler technician that thinks that is a good place for the tank should be shown the door.

    Thank you for the tips, @Zman .
    Where do you think the expansion take should be located / moved to, ( or is it OK only in that single Zone's return, if a check valve is added between it & the boiler), & also, is it generally "safe" to shut off the Boiler's water supply for a week or 2 , if I am not able to get to the house? ...


  • Zman
    Zman Member Posts: 7,561
    The correct location for the expansion tank and fill would be directly upstream (above) the circulator given your present layout.
    I think a better fix would be to move the circulator to the supply side then move the expansion tank to the location of your existing fill valve.
    I would not isolate the boiler and leave it unattended, Particularly since your system is having some issues and does not have a low water cut off.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    delta T
  • john walsh_2
    john walsh_2 Member Posts: 64
    edited December 2016
    It seems to me from the video, that the expansion tank is being isolated from the system when the right hand zone valve closes. In other words, when that zone temperature satisfies the thermostat, access to that expansion tank can only happen through the return line. More than likely it pops the relief valve when , the left zone valve opens on a call for heat but not the right. the rapidly heated water from the boiler just doesn't have time to access the expansion tank from the return before the relief valves reaches it's limit. In short, the expansion tank needs to be on the boiler side of those zone valves. (Just to add, when the either zone valve opens, the circulator calls on, so when the right zone valve is off, the rising pressure caused by the heating water needs to fight against the added circulator pressure and the resistance of the total length of return piping all the way to the expansion tank. The expansion tank should be before the zone valves, and it would be wise to have the feed water connected there as well.)
  • Grallert
    Grallert Member Posts: 643
    To add something. I would bet that circulator still has it's internal flow check. So when the right hand zone closes, and it closes quickly the the other zone is isolated from any expansion room.
    Miss Hall's School service mechanic, greenhouse manager,teacher and dog walker
    Zman
  • Blast
    Blast Member Posts: 12
    edited December 2016

    It seems to me from the video, that the expansion tank is being isolated from the system when the right hand zone valve closes. In other words, when that zone temperature satisfies the thermostat, access to that expansion tank can only happen through the return line. More than likely it pops the relief valve when , the left zone valve opens on a call for heat but not the right. the rapidly heated water from the boiler just doesn't have time to access the expansion tank from the return before the relief valves reaches it's limit. In short, the expansion tank needs to be on the boiler side of those zone valves. (Just to add, when the either zone valve opens, the circulator calls on, so when the right zone valve is off, the rising pressure caused by the heating water needs to fight against the added circulator pressure and the resistance of the total length of return piping all the way to the expansion tank. The expansion tank should be before the zone valves, and it would be wise to have the feed water connected there as well.)

    So is an acceptable "quick fix" here, without redoing/re-designing many of the pipes & parts of the system, (since I will need to call & pay a tech for this), would be to have the service tech just move these 2 zone controls ( which I believe are in the return pipes), to "above" & past the expansion tank, so that the expansion tank is still "hanging down", but no longer in line with just the 1 zone.. ( Am I ASSuming wrong that this type of tank is not meant to be mounted perpendicular off the side of a pipe) ... if so, this , ( I again ASSume :) ), would mean the easiest/least costly way is then putting the zone controls a bit farther from the boiler, in the ceiling on the "other side" of the expansion tank? It would also seem that putting the expansion tank just above the circulator would also be perpendicular.. Again thanks in advance to all & any ideas are appreciated!
  • delta T
    delta T Member Posts: 884
    I think it would be cheaper to move the expansion tank above the pump, than to move two zone zone valves. That should solve your problems, and you shouldn't have any fill valve related problems. The location of the fill valve is not ideal, but I wouldn't expect it to cause any problems, as long as you are pumping away from the expansion tank.
  • john walsh_2
    john walsh_2 Member Posts: 64
    edited December 2016
    Blast said:

    It seems to me from the video, that the expansion tank is being isolated from the system when the right hand zone valve closes. In other words, when that zone temperature satisfies the thermostat, access to that expansion tank can only happen through the return line. More than likely it pops the relief valve when , the left zone valve opens on a call for heat but not the right. the rapidly heated water from the boiler just doesn't have time to access the expansion tank from the return before the relief valves reaches it's limit. In short, the expansion tank needs to be on the boiler side of those zone valves. (Just to add, when the either zone valve opens, the circulator calls on, so when the right zone valve is off, the rising pressure caused by the heating water needs to fight against the added circulator pressure and the resistance of the total length of return piping all the way to the expansion tank. The expansion tank should be before the zone valves, and it would be wise to have the feed water connected there as well.)

    So is an acceptable "quick fix" here, without redoing/re-designing many of the pipes & parts of the system, (since I will need to call & pay a tech for this), would be to have the service tech just move these 2 zone controls ( which I believe are in the return pipes), to "above" & past the expansion tank, so that the expansion tank is still "hanging down", but no longer in line with just the 1 zone.. ( Am I ASSuming wrong that this type of tank is not meant to be mounted perpendicular off the side of a pipe) ... if so, this , ( I again ASSume :) ), would mean the easiest/least costly way is then putting the zone controls a bit farther from the boiler, in the ceiling on the "other side" of the expansion tank? It would also seem that putting the expansion tank just above the circulator would also be perpendicular.. Again thanks in advance to all & any ideas are appreciated!
    Actually, the zone valves are on the supply side of the boiler. your circulator is on the return. I would not move the zone valves. In a perfect world, your zone valves would be on the return side of the boiler and the circulator on the supply pumping away from the expansion tank. But we don't live in a perfect world so we need to work with what we have. So, this is what I would do. Do you see the first elbow coming off the boiler? You have the horizontal pipe coming from the boiler and that first elbow going to the zone valves, see it? Have your installer change that elbow to a tee(with the run horizontal and the bull pointed up, towards the zone valves) so you have a place to hang the expansion tank. It looks like you will need to add a 6 inch nipple to the open side of the run to get past the gas pipe then using a reducing elbow at the end of that nipple, hang your expansion tank.

    But before you do anything, One quick question. When did this problem start? was it when he changed the relief valve? Or is that why he changed the relief valve?
  • Blast
    Blast Member Posts: 12
    edited December 2016
    OK I now have 2 different helpful suggestions for the expansion tank move, thank you both, & please help me clarify:
    delta T said:

    I think it would be cheaper to move the expansion tank above the pump, than to move two zone zone valves. That should solve your problems, and you shouldn't have any fill valve related problems. The location of the fill valve is not ideal, but I wouldn't expect it to cause any problems, as long as you are pumping away from the expansion tank.

    ** If the expansion tank is moved above the circulator pump, & the need is to pump away from the expansion tank, then it would seem to me, in order to be able to pump "away" from an above tank, then the circulator pump in the video is actually pumping "down" to the water fill valve pipe, , not up thru that shut off above the pump, as I had thought. correct?
    This solution sounds good, except for my confusion regarding weather the pump would be pumping up "into" the tank, or "down" & away from the tank.....
    If so, then a simple "T" somewhere above that shut off, above the pump, leading to the expansion tank as a dead end, would be ok?

    Actually, the zone valves are on the supply side of the boiler. your circulator is on the return. I would not move the zone valves. In a perfect world, your zone valves would be on the return side of the boiler and the circulator on the supply pumping away from the expansion tank. But we don't live in a perfect world so we need to work with what we have. So, this is what I would do. Do you see the first elbow coming off the boiler? You have the horizontal pipe coming from the boiler and that first elbow going to the zone valves, see it? Have your installer change that elbow to a tee(with the run horizontal and the bull pointed up, towards the zone valves) so you have a place to hang the expansion tank. It looks like you will need to add a 6 inch nipple to the open side of the run to get past the gas pipe then using a reducing elbow at the end of that nipple, hang your expansion tank.

    But before you do anything, One quick question. When did this problem start? was it when he changed the relief valve? Or is that why he changed the relief valve?

    I will answer these last 2 questions first:

    Home was bought in late 2014, this basement had been completely submerged by Hurricane Sandy in 2012, so prev. owner had new boiler, hot water heater & elect panel among other things, ect installed.
    I had noticed the floor water leak below the pressure valve problem right away, & later in 2015, after weather got warm, I had a plumber ( friend of a friend"), come and replace the dirty looking relief valve, thinking that would solve the problem, & he also replaced the expansion tank & not great looking water fill "bell" valve at the same time ....
    Winter 2015/16 came, & once heat was back on & being used regularly, I noticed the problem still there, did not get solved by these replacement parts, and I started thinking it might possibly be the location of the expansion tank or that air vent .. called in a tech at that time, (he was the one that added those 2 "drain shutoff valves" above the circulator pump in the video, said they should be there for easier flushing), he drained/refilled/tested the system, & could not duplicate the problem, & told me the expansion tank location was fine ...
    Problem was never fixed, & now it's the 2016/17 3rd winter, & this lead me here to this forum, before I call in a tech ( & just tell him what I want done/moved based on these suggestions).
    As mentioned it's more of a 2nd summer place, so I am not there daily . I of course leave the heat set to around 60 when I am away, so the system still runs regularly.

    ** Is your suggestion about tank placement off the zone pipe, being to hang the expansion tank "low" , off a T from that entrance/elbow of the lower zone input pipe , hanging generally somewhere in the area or height of the circulator pump? Also, how do you feel about @delta T 's suggestion of being above the circulator pump?
    For some reason I had thought the zone valves / tank were in the returns, not sure why ....


  • john walsh_2
    john walsh_2 Member Posts: 64
    Either location should be fine. I was just taking the logistics into consideration. Although it's better to have the circulator pumping away from the expansion tank,(for reasons that you can read in Dan's book "Pumping Away") it will still work. Your call.
  • Zman
    Zman Member Posts: 7,561
    How much pressure are you running normally?
    How high is the house?
    I assume the boiler relief is 30 PSI.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    john walsh_2
  • john walsh_2
    john walsh_2 Member Posts: 64
    edited December 2016
    Blast, I had a few minutes to read your questions and I think it would be helpful to review some important points.

    . The circulator "circulates" the water around the system by causing a certain difference in pressure. It will either increase the discharge pressure or decrease the input pressure or both. what it does is directely related to where it is in reference to the expansion tank. No matter where it is in the loop, it's going to move the same amount of water and at the same speed. but it can neither add nor take away water from the expansion tank. The only things that will add water to the expansion tank is the fill valve or the heating(expanding) of the water.

    .The point where the tank is connected to the system is called the point of no pressure change. So if the circulator is located near to where the expansion tank is connected to the piping and pumping away from that point, the intake side of the circulator can't drop and it circulates the water by increasing the discharge pressure. In a nut shell, this is a better way of keeping your system free from air and the associated problems that air causes(air is introduced into the system every time the feed valve adds water). (all this is in Dan's book)

    Soooo, in an ideal world, we would have your expansion tank connected to the supply pipe where it leaves the boiler, then we would have your circulator pumping away from the "point of no pressure change" towards the system, your fill valve would be connected right between the supply and the expansion tank(again at the point of no pressure change). and your system would live happily ever after!

    But that's a lot of re-piping! Maybe your up for it and maybe your not. I'm not sure that I would be. Many boilers are still piped the way yours is with the circulator on the return, pumping towards the expansion tank, and they work. You just have to make sure that the expanding water has access to that tank!!

    Also, Zman's question is a good one because they make pressure relief valves for steam boilers that are rated to release at much lower pressures (15 lbs) More than likely your pressure relief valve is the correct one(30 lbs), but double check it.
  • Blast
    Blast Member Posts: 12


    "...Also, Zman's question is a good one because they make pressure relief valves for steam boilers that are rated to release at much lower pressures (15 lbs) More than likely your pressure relief valve is the correct one(30 lbs), but double check it.

    Thanks, I will double check that when I am there next .. I doubt both the old & new PR valves were both 15 lb instead of 30, but who knows .... I recall the boiler pressure being somewhere in the 'teens, don't recall exactly ( single family , 2 floors above that basement)..
    *** So in the video, is that circ pump pumping "down" towards the fresh water fill valve, or "up" to the pipes above? I think the @delta T suggestion of moving it above the pump sounds the easiest, and least costly, but he did add the mention in his suggestion ".. not ideal, but I wouldn't expect it to cause any problems, as long as you are pumping away from the expansion tank..."
  • bob_46
    bob_46 Member Posts: 813
    It's hard to see the volute of the pump in the video. There is an arrow cast into the volute , the water flows in the direction of the arrow. It looks like it's flowing down but can't be positive.
    bob
  • john walsh_2
    john walsh_2 Member Posts: 64
    Down into the boiler return. Or at least it should be..
  • hot_rod
    hot_rod Member Posts: 22,024
    Assuming the pump arrow is facing into the boiler and the zone valves are flowing out. I think the simple fix is to move the expansion tank to just upstream of the pump. You have an isolation valve there and plenty of room to add a tee between the valve and pump. The zone valves will isolate the other side of the boiler and you should not need to drain down or lose much water to correct this.
    Both the expansion tank and fill valve connect there.

    Air purger always wants to be
    at the hottest going, you have that ok. Expansion tank does not need to be with the air purger, you will have that okay also.

    Pumping into the boiler is fine as long as the expansion tank in in that location also.

    I'd be inclined to install a new relief valve if it had been going off a lot, cheap and easy while the system is down.


    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    delta TBlast
  • rick in Alaska
    rick in Alaska Member Posts: 1,457
    If you do change the boiler pressure, you will also have to match the air pressure in the expansion tank to this new setting. This will have to be done with the pressure in the boiler at zero in order to get an accurate reading.
    Rick
  • Blast
    Blast Member Posts: 12
    edited December 2016
    Great ideas here .. I think I will go with the suggestions of moving the tank to the area before the pump. I will need to call in a service tech & "tell him" what I want done ( hopefully it doesn't turn into "you don't wanna do that..." ) ...
    I did check the newer installed PR valve & it is 30 psi .
    I could not see any arrow on the pump, but all the writing on it's face was upside-down.
    The operating pressure seemed to be about 14 or 15 PSI, not taking into account the very occasional pressure spikes that go past 30 psi ..
    I will have to schedule the work sometime after the holidays, & I will report back here to let you guys know if the problem was fixed ..
    john walsh_2
  • john walsh_2
    john walsh_2 Member Posts: 64
    A simple way to tell what direction the pump is pumping is by feeling the pipes coming out of the boiler on a call for heat from a cold start. Turn up the thermostat(either one), put one hand on the pipe just below the two zone valves and one hand on the pipe just above the pump. The pump will be pumping in the direction of whichever pipe gets hot first. I'm sure it will be the pipe just below the zone valves.
    Blast
  • Blast
    Blast Member Posts: 12
    edited January 2017
    Ok, I finally had the work completed from the above video problem, and I have posted an updated video to show the completed work below.
    The heating guys really did not want to cut/redo all the work to put the expansion tank as in the diagram above, & it was less expensive and easier to simply " T " it off the PR valve with fittings,, where they claim they install them regularly and it should be fine, & no longer in just 1 of the feeder zones .. so I let them do that ,.
    It seemed to be OK yesterday, day of install, & the boiler was running at about 12 psi .. since I'm not there all the time, I will see within a week or 2 if the fix actually has worked ....:
    https://www.youtube.com/watch?v=pJ-pAM3315k
  • Zman
    Zman Member Posts: 7,561
    Well,
    I guess it is better than having it on an isolated zone. You are still pumping directly into the expansion tank which is not ideal. You might want to stop inviting those guys over...
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    BlastCanucker
  • john walsh_2
    john walsh_2 Member Posts: 64
    It will work. Not Ideal, but much better than where it was.
    ZmanBlast
  • Blast
    Blast Member Posts: 12
    It has seemed to have worked .
    Thanks again all.