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Axiom mini feeder question

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moemah123
moemah123 Member Posts: 55
edited August 2023 in Radiant Heating
I had my heating system modified and axiom mini feeder dmf 150 installed. I was looking at the systems online and I am not sure why it was installed with white pipe in middle of tank. Heater guy pierced it and installed white pipe in addition to the copper. None of systems online I saw installing dmf150 did this. Only see them have the copper part not a pipe in tank.Does anyone have thoughts? 
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  • Jamie Hall
    Jamie Hall Member Posts: 23,433
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    OK, that's different. That looks for all the world like a pressure relief valve, and it looks like your man has piped the outlet of the valve into the tank. Not even sure that's legal, and I'm certainly not sure why he or she would do that.

    Anyone?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    GGross
  • psb75
    psb75 Member Posts: 844
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    I'm not sure you are allowed to use white pvc for that purpose. I believe it is mandated to be copper and with nothing obstructing the "terminus" i.e. end of the "blow-off" pipe. Good news: its not going to affect the "feed water" function of the Axiom. But I'm fairly certain that Axiom would not approve. The plumber purposed the Axiom vessel to be a catch-receptacle for any potential "blow-off" or "leak" event.
  • GroundUp
    GroundUp Member Posts: 1,926
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    He did it so that any glycol loss from the relief valve would be retained in the feeder. It's a fairly common practice, though I don't recommend it. He also installed the relief valve improperly- it should be in a vertical position. It appears to be CPVC, not PVC, which should be acceptable for a low temp system but your local code may differ.
    hot_rodmoemah123rick in AlaskaZman
  • hot_rod
    hot_rod Member Posts: 22,256
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    Its to catch the glycol if the relief pops. Maybe there is a relief on the boiler also? If so it could be piped into the tank too

    Officially you are not supposed to use pvc or cpvc with glycol. But in that case there is only glycol if the valve goes off
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    moemah123
  • Alan (California Radiant) Forbes
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    Brilliant solution to what I think is a below grade installation or a mechanical room surrounded by living space, i.e. nowhere to daylight the relief lines. I don't think any code would cover this as long as there's the required relief valve on the boiler. All except that 3/4" pipe should serve that relief valve.

    Nice, clean work, too! Union, drain, isolation valve.........
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    moemah123
  • moemah123
    moemah123 Member Posts: 55
    edited August 2023
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    Two questions

    I am seeing agreement that this is acceptable. But I am also seeing suggestions, what should be changed about white pipe here and valve?

    I am seeing axiom feeder reading drop 4 psi every hour. (The guy had shut off the loops as he is coming back again to fix manifold) this means feeder is triggering every hour.  How is this possible with hydronic system not pumping/operating 
  • Jamie Hall
    Jamie Hall Member Posts: 23,433
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    moemah123 said:

    Two questions

    I am seeing agreement that this is acceptable. But I am also seeing suggestions, what should be changed about white pipe here and valve?

    I am seeing axiom feeder reading drop 4 psi every hour. (The guy had shut off the loops as he is coming back again to fix manifold) this means feeder is triggering every hour.  How is this possible with hydronic system not pumping/operating 

    There's a leak somewhere...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    GGross
  • hot_rod
    hot_rod Member Posts: 22,256
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    The valve should be mounted vertically as per instructions. This keeps any crud from packing against the mechanism inside.
    I think a relief valve needs to be right on the boiler or piping at the boiler? Is there another valve installed as per the boiler manufacturers instruction? Sometimes the factory installs them, sometimes they ship with a boiler for you to install. Or mis-install :)

    Same with the discharge tube directions. Used to require a metallic discharge tube, but I do see plastic ones sold for water heater relief valves and sometimes with the heater?

    Pressure should not drop constantly. It will vary from a cold boiler to a hot boiler from expansion. But if it keeps dropping, time to look for a leak.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    GGross
  • Alan (California Radiant) Forbes
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    It sounds as though your installer is attending to the problem, that is, by returning. He should be able to explain and fix the drop in pressure problem.

    Someone said the white pipe is CPVC which should be fine. It's a relief outlet and probably doesn't see much use.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    kcopp
  • moemah123
    moemah123 Member Posts: 55
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    hot_rod said:

    The valve should be mounted vertically as per instructions. This keeps any crud from packing against the mechanism inside.
    I think a relief valve needs to be right on the boiler or piping at the boiler? Is there another valve installed as per the boiler manufacturers instruction? Sometimes the factory installs them, sometimes they ship with a boiler for you to install. Or mis-install :)

    Same with the discharge tube directions. Used to require a metallic discharge tube, but I do see plastic ones sold for water heater relief valves and sometimes with the heater?

    Pressure should not drop constantly. It will vary from a cold boiler to a hot boiler from expansion. But if it keeps dropping, time to look for a leak.

    I am slightly confused is the relief valve not vertical, could you show me what expected looks like? Also i have a combicore (bradford white defender that has similar relief valve with same position as this one) So i am seeing 2 relief valve one on axion and one on bradford (domestic water part as i understand it)
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,616
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    I agree that the installation looks good except for the relief valve position. I probably would have used copper but the CPVC (which it is if you blow up the picture and look)

    @moemah123 the relief valve on the water heater is a temperature and pressure relief (T & P) it is allowed to be mounted horizontal

    What you have is a pressure relief which is a different valve. Pressure reliefs should be vertical
    moemah123
  • moemah123
    moemah123 Member Posts: 55
    edited August 2023
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    I agree that the installation looks good except for the relief valve position. I probably would have used copper but the CPVC (which it is if you blow up the picture and look)

    @moemah123 the relief valve on the water heater is a temperature and pressure relief (T & P) it is allowed to be mounted horizontal

    What you have is a pressure relief which is a different valve. Pressure reliefs should be vertical

    Just so i am clear, are we talking about stem part or green area?. Which direction should stem point at? and which direction should green part point at (ceiling or floor?)

    If for some reason it can't be changed whats the worst that can happen here?
  • hot_rod
    hot_rod Member Posts: 22,256
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    Vertical like this
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    moemah123
  • moemah123
    moemah123 Member Posts: 55
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    hot_rod said:

    Vertical like this

    When he visits again, should I push for it to be replaced as it was not installed correctly? What is the consequence if it stays that way?
  • GGross
    GGross Member Posts: 1,069
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    Not to get you all flustered, but the pressure relief valve is a mechanical safety device designed to prevent a boiler from blowing up. Personally I would want it installed correctly per manufacturers spec. I don't agree with piping that relief down back to the fill unit either, I do understand WHY he did that at least, but that relief could blow off and refill the boiler pretty much endlessly without really letting you know there is an issue since it keeps refilling the Axiom, it is a dangerous combination of installation errors in my opinion.

  • moemah123
    moemah123 Member Posts: 55
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    GGross said:

    Not to get you all flustered, but the pressure relief valve is a mechanical safety device designed to prevent a boiler from blowing up. Personally I would want it installed correctly per manufacturers spec. I don't agree with piping that relief down back to the fill unit either, I do understand WHY he did that at least, but that relief could blow off and refill the boiler pretty much endlessly without really letting you know there is an issue since it keeps refilling the Axiom, it is a dangerous combination of installation errors in my opinion.

    From your comment i am reading


    1. You don't agree with piping to feeder
    2. Change value to be vertical

    So my question is

    1. If valve blows off what difference does it make if it is vertical or horizontal? specially with your second concern
    2. If valve blows off what other alternative could he have done instead of installing pipe into axiom?

  • GGross
    GGross Member Posts: 1,069
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    1- If the valve blows off due to pressure it is doing its job but it indicates something is very wrong with the boiler, the issue arises with the installation orientation currently, where it could potentially NOT blow off. Also if it does blow off you may just never know because it is blowing into the fill unit and just refilling itself, which could mean it will KEEP blowing off, and eventually could just not work. Generally if a relief valve has blown off due to pressure, I just change them at that point.

    2- That is the issue, usually you would pipe this to a floor drain, if you have a fill unit like this then you would see the level drop, indicating a leak, or relief valve issue. I understand why they piped it into the tank as this looks like a carpeted closet and there is no floor drain. Depending on the application it may not be a huge issue piping it into the fill unit like this. It is the combination of both installation errors that concerns me. the ability for the relief valve to potentially blow off due to pressure without anyone knowing, and the fact it is installed wrong making it more prone to failure.


  • moemah123
    moemah123 Member Posts: 55
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    GGross said:

    1- If the valve blows off due to pressure it is doing its job but it indicates something is very wrong with the boiler, the issue arises with the installation orientation currently, where it could potentially NOT blow off. Also if it does blow off you may just never know because it is blowing into the fill unit and just refilling itself, which could mean it will KEEP blowing off, and eventually could just not work. Generally if a relief valve has blown off due to pressure, I just change them at that point.

    2- That is the issue, usually you would pipe this to a floor drain, if you have a fill unit like this then you would see the level drop, indicating a leak, or relief valve issue. I understand why they piped it into the tank as this looks like a carpeted closet and there is no floor drain. Depending on the application it may not be a huge issue piping it into the fill unit like this. It is the combination of both installation errors that concerns me. the ability for the relief valve to potentially blow off due to pressure without anyone knowing, and the fact it is installed wrong making it more prone to failure.


    One additional question, with axiom controlling pressure. What ranges of pressure are we talking that it could blow off i.e. if i look at what axiom reader says every day
  • GGross
    GGross Member Posts: 1,069
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    The axiom feeder is keeping your boiler at the correct fill pressure, usually between 12-18 PSI depending on application, but the system pressure will rise a bit when heating. The relief valve generally is set to blow off at 30 PSI. This isn't 100% every install mind you, just typical residential systems tend to be very similar
  • hot_rod
    hot_rod Member Posts: 22,256
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    A tough call. I hate to see glycol go down the sewer if it pipes directly over a floor drain. Its both expensive and it could set panic at a sewer treatment facility

    on solar thermal we always put the relief into an empty 5 gallon bucket

    Typically the valve doesn’t dump the entire system fluid. It gas a delta P built into it
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • moemah123
    moemah123 Member Posts: 55
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    hot_rod said:

    A tough call. I hate to see glycol go down the sewer if it pipes directly over a floor drain. Its both expensive and it could set panic at a sewer treatment facility

    on solar thermal we always put the relief into an empty 5 gallon bucket

    Typically the valve doesn’t dump the entire system fluid. It gas a delta P built into it

    You mention glycol but it seems he used water in my system :D thats another curious thing for me, should we be using glycol?

    Also with the current way things are piped, is it hard to change orientation? I am not even sure how he would do that (assuming he accepts)
  • moemah123
    moemah123 Member Posts: 55
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    GGross said:

    The axiom feeder is keeping your boiler at the correct fill pressure, usually between 12-18 PSI depending on application, but the system pressure will rise a bit when heating. The relief valve generally is set to blow off at 30 PSI. This isn't 100% every install mind you, just typical residential systems tend to be very similar

    Is it too complex to change valve orientation in this design? I should expect him to have known about orientation, he seems very knowledgeable so I am wondering if he was cutting corners due to tight space or something.
  • GGross
    GGross Member Posts: 1,069
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    I'd want to see it located maybe closer to the boiler? it is hard to tell where exactly the boiler is in this setup, usually you see the relief valve piped near, or directly from the boiler.
  • moemah123
    moemah123 Member Posts: 55
    edited August 2023
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    Adding a pic of whole system, you can see the valve on left on top of axiom as first pic (sorry axion got cut out of pic) and another one on right near boiler. With this setup, do we want to change green pressure valve (on left to vertical) and is it hard to do so?

  • hot_rod
    hot_rod Member Posts: 22,256
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    moemah123 said:

    GGross said:

    The axiom feeder is keeping your boiler at the correct fill pressure, usually between 12-18 PSI depending on application, but the system pressure will rise a bit when heating. The relief valve generally is set to blow off at 30 PSI. This isn't 100% every install mind you, just typical residential systems tend to be very similar

    Is it too complex to change valve orientation in this design? I should expect him to have known about orientation, he seems very knowledgeable so I am wondering if he was cutting corners due to tight space or something.
    a 3/4" brass street ell is all that is needed to turn the valve vertical. The pvc may be long enough to reach into the tank still. If you intend to keep it in the tank?

    Really no need to have a tank fill system on a plain water system. A fill valve and a low water cutoff are another option.

    Although fill tanks do get used on system with a suspected leak. It help identify how much the system is leaking over a period of time.

    If that is a combi cor heater, it is not considered a boiler, maybe that is why the relief valve is remote mounted?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    moemah123GGross
  • GroundUp
    GroundUp Member Posts: 1,926
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    Ah, I remember this system now. Did anyone ever lower the pressure in the expansion tank? Did the installer of this mini feeder tell you why he thought it was a good idea to have? As hot rod said, these are typically reserved for glycol systems and a simple auto-fill from your domestic would have been a much better and cheaper option if leak monitoring isn't a necessity. Looking at the supply line and seeing it's pink, are you sure there is no glycol in the system? You say it's dropping pressure- was it doing that before the feeder? It's possible that there is just air escaping- have you added water to the Axiom tank? How much has it used since install? The relief valve can be removed and replaced to the proper orientation with an elbow, nothing too serious. Honestly it probably doesn't need to be there at all since the combi-cor's T&P will do the same job, but a little redundancy never hurts.
    moemah123
  • moemah123
    moemah123 Member Posts: 55
    edited August 2023
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    GroundUp said:

    Ah, I remember this system now. Did anyone ever lower the pressure in the expansion tank? Did the installer of this mini feeder tell you why he thought it was a good idea to have? As hot rod said, these are typically reserved for glycol systems and a simple auto-fill from your domestic would have been a much better and cheaper option if leak monitoring isn't a necessity. Looking at the supply line and seeing it's pink, are you sure there is no glycol in the system? You say it's dropping pressure- was it doing that before the feeder? It's possible that there is just air escaping- have you added water to the Axiom tank? How much has it used since install? The relief valve can be removed and replaced to the proper orientation with an elbow, nothing too serious. Honestly it probably doesn't need to be there at all since the combi-cor's T&P will do the same job, but a little redundancy never hurts.

    I will try to answer your questions and HotRod. I believe you both have helped me alot in the past.

    I had expansion tank removed and he put it again. And same for water side (potable tank) He also said he wants to maintain system at 18 psi. Thats as far as he told me as pressure goes.

    Before this install, my system was losing pressure fast. After he installed the feeder, he did find that manifold (which i mentioned before to him) had small leak of water. He believes it is contributing to pressure loss and air in system.

    Only reason I believe we installed feeder was to help with the system losing pressure and he installed air eliminator to help with air gurgles I have, so i dont have to get maintenance to repressurize system every year (back when there was no leaks i believe), i am seeing online autofill seems to perform a similar function, what then is the purpose of the feeder :(

    I am pretty sure he just added water not glycol in the axiom tank, he filled it from tank and asked me to replinish if needed with filtered water.

    Since install i dont think volume of water lowered ( i only hear machine turn on ) but it didnt lower (he has loops closed at the moment until he is back, if that helps)

    "a simple auto-fill from your domestic would have been a much better and cheaper option" What is a simple autofill system? Unfortunately i asked 2 companies and both suggested feeder due to loss even though i asked to fix leaks first, but he suggested it so i don't have to worry about pressuring system again (as combicor has 3-5 years left on it)

    Finally, are you saying the relief valve horizontal or vertical doesnt matter because it is redundant?
  • hot_rod
    hot_rod Member Posts: 22,256
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    The combicor is a water heater tank with a coil inside for radiant

    The tank needs a T&P valve in the side, which you have. That us a 150lb  210 degree valve

    You also need a 30 lb  relief on the heating side, which you have also, the valve in question.

    The valve should be vertical, I suspect it will work the way it is
    So yes that system needs two relief valves 
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    GGross
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,045
    edited August 2023
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    @GroundUp said:
    The relief valve can be removed and replaced to the proper orientation with an elbow, nothing too serious. Honestly it probably doesn't need to be there at all since the combi-cor's T&P will do the same job, but a little redundancy never hurts.
    The T&P relief valve is for the domestic side. A 30 psi relief valve is still required on the heating side.

    @moemah123 said:
    What is a simple autofill system?
    The benefit you have with the Axiom is that it tells you that you have a leak. That thing is loud when it goes off and you have to do something about it, otherwise you go bonkers. If you have an autofill valve, it's quiet and you may never know that you have a leak.
    Like others have suggested, change the relief valve to vertical with a 3/4" brass street 90.

    As an aside, we use those Axiom PressurePal's in San Francisco. Before these became available, we used autofill valves on boilers and the city required a fancy backflow preventer (RP device) to protect the domestic water supply from any chemical or pathogenic backflow. These RP devices had to be tested every year - $125 a pop. Since the Axiom PressurePal's aren't connected to the domestic system, they require no RP device and the owners save the inspection fee.

    And those cardboard boxes near the water heater are a fire hazard.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    moemah123
  • moemah123
    moemah123 Member Posts: 55
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    Thank you all!! I will let him know that he needs to change orientation.
  • GroundUp
    GroundUp Member Posts: 1,926
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    @GroundUp said:

    The relief valve can be removed and replaced to the proper orientation with an elbow, nothing too serious. Honestly it probably doesn't need to be there at all since the combi-cor's T&P will do the same job, but a little redundancy never hurts.
    The T&P relief valve is for the domestic side. A 30 psi relief valve is still required on the heating side.
    I know. That does not change the fact that the only heat source is the domestic side, meaning that a relief on the heating side is redundant. It literally can not overheat and explode (the reason the relief exists) without the heat source, which is already covered by the T&P.

  • GroundUp
    GroundUp Member Posts: 1,926
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    Did he reduce the air pressure in the tank to 18psi then? If the feeder is running, it's adding water. If the water level never changes, the relief valve is likely dripping back into the tank which is causing the pressure to drop. That little weep you had on your manifold should take months to drop any pressure, unless it got much worse since then- but are you saying they did not fix the leak, AKA the whole reason they were called out there in the first place? I'm sorry, but it doesn't really sound like this technician is very competent.
  • hot_rod
    hot_rod Member Posts: 22,256
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    GroundUp said:

    @GroundUp said:

    The relief valve can be removed and replaced to the proper orientation with an elbow, nothing too serious. Honestly it probably doesn't need to be there at all since the combi-cor's T&P will do the same job, but a little redundancy never hurts.
    The T&P relief valve is for the domestic side. A 30 psi relief valve is still required on the heating side.
    I know. That does not change the fact that the only heat source is the domestic side, meaning that a relief on the heating side is redundant. It literally can not overheat and explode (the reason the relief exists) without the heat source, which is already covered by the T&P.

    If the coil developed a leak then tank pressure would go into the hydronic side. Under a rare condition that could go to 150 psi if a failure in the domestic side caused over-pressurization.
    Components used in the hydronic side may not be rated to the 150 PSI of the tank relief. Like hydronic expansion tanks, for example, usually rated to 100 psi.
    Certainly no harm in protecting the hydronic side with a pressure relief valve.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • moemah123
    moemah123 Member Posts: 55
    edited August 2023
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    GroundUp said:

    Did he reduce the air pressure in the tank to 18psi then? If the feeder is running, it's adding water. If the water level never changes, the relief valve is likely dripping back into the tank which is causing the pressure to drop. That little weep you had on your manifold should take months to drop any pressure, unless it got much worse since then- but are you saying they did not fix the leak, AKA the whole reason they were called out there in the first place? I'm sorry, but it doesn't really sound like this technician is very competent.

    So, after they installed system and ran it. He said that yes manifold has a small leak, said it shouldn't be a big deal as you mentioned and said he will order the part and replace it for me.

    So current state of the system is loops are closed until he comes back (maybe 2-3 weeks) to replace manifold, flush and turn on system.

    The part that i don't understand that you mentioned is the drop of pressure. When i asked him over email, he said that my relief valve was working to let out pressure because axiom was overshooting and asked me to lower psi to 17. However, even though i haven't heard it run (it is going lower in number) does the system loops being closed have anything to do with why relief valve is dripping as you say? or what could cause system to drip. I am not understanding how system is dripping based on current design, fact i don't hear drips and fact it is losing pressure. What could be leaking pressure here?
  • GroundUp
    GroundUp Member Posts: 1,926
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    moemah123 said:

    GroundUp said:

    Did he reduce the air pressure in the tank to 18psi then? If the feeder is running, it's adding water. If the water level never changes, the relief valve is likely dripping back into the tank which is causing the pressure to drop. That little weep you had on your manifold should take months to drop any pressure, unless it got much worse since then- but are you saying they did not fix the leak, AKA the whole reason they were called out there in the first place? I'm sorry, but it doesn't really sound like this technician is very competent.

    So, after they installed system and ran it. He said that yes manifold has a small leak, said it shouldn't be a big deal as you mentioned and said he will order the part and replace it for me.

    So current state of the system is loops are closed until he comes back (maybe 2-3 weeks) to replace manifold, flush and turn on system.

    The part that i don't understand that you mentioned is the drop of pressure. When i asked him over email, he said that my relief valve was working to let out pressure because axiom was overshooting and asked me to lower psi to 17. However, even though i haven't heard it run (it is going lower in number) does the system loops being closed have anything to do with why relief valve is dripping as you say? or what could cause system to drip. I am not understanding how system is dripping based on current design, fact i don't hear drips and fact it is losing pressure. What could be leaking pressure here?
    As we explained to you last time, the air pressure in the expansion tank bladder needs to match the fluid pressure on the other side. Your tank was charged to 50 psi at install. If the fluid is being run at 18 psi, the air pressure in the bladder should have also been dropped to 18 psi. This is a 30 psi relief valve. If the Axiom was set to anywhere below 30 psi, it should not be overshooting. If the relief valve was indeed lifted due to overpressurization, it should be replaced when the position of it is corrected. The only ways to reduce pressure in a sealed hydronic system like this are removal of air and loss of fluid. If nothing is circulating, there isn't likely any air being released. That leaves a loss of fluid, which may be a leak or may be this relief dripping into the feeder and repeating the cycle. Perhaps finding a real technician is in order, because it sounds like this one has no idea what he's doing besides robbing you blind.

    moemah123
  • moemah123
    moemah123 Member Posts: 55
    edited August 2023
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    GroundUp said:

    moemah123 said:

    GroundUp said:

    Did he reduce the air pressure in the tank to 18psi then? If the feeder is running, it's adding water. If the water level never changes, the relief valve is likely dripping back into the tank which is causing the pressure to drop. That little weep you had on your manifold should take months to drop any pressure, unless it got much worse since then- but are you saying they did not fix the leak, AKA the whole reason they were called out there in the first place? I'm sorry, but it doesn't really sound like this technician is very competent.

    So, after they installed system and ran it. He said that yes manifold has a small leak, said it shouldn't be a big deal as you mentioned and said he will order the part and replace it for me.

    So current state of the system is loops are closed until he comes back (maybe 2-3 weeks) to replace manifold, flush and turn on system.

    The part that i don't understand that you mentioned is the drop of pressure. When i asked him over email, he said that my relief valve was working to let out pressure because axiom was overshooting and asked me to lower psi to 17. However, even though i haven't heard it run (it is going lower in number) does the system loops being closed have anything to do with why relief valve is dripping as you say? or what could cause system to drip. I am not understanding how system is dripping based on current design, fact i don't hear drips and fact it is losing pressure. What could be leaking pressure here?
    As we explained to you last time, the air pressure in the expansion tank bladder needs to match the fluid pressure on the other side. Your tank was charged to 50 psi at install. If the fluid is being run at 18 psi, the air pressure in the bladder should have also been dropped to 18 psi. This is a 30 psi relief valve. If the Axiom was set to anywhere below 30 psi, it should not be overshooting. If the relief valve was indeed lifted due to overpressurization, it should be replaced when the position of it is corrected. The only ways to reduce pressure in a sealed hydronic system like this are removal of air and loss of fluid. If nothing is circulating, there isn't likely any air being released. That leaves a loss of fluid, which may be a leak or may be this relief dripping into the feeder and repeating the cycle. Perhaps finding a real technician is in order, because it sounds like this one has no idea what he's doing besides robbing you blind.

    I believe he did remove and repressurized the tank but I will ask when he is here. Unfortunately, pretty much there is like 3 - 4 technicians serving my area. This one atleast installed air eliminator, the others pretty much refused to do it, saying its useless.

    When i say overshooting I meant at time he left it at 23 PSI and it goes to 26 PSI where triggers a warning. So he advised to put it at 17 PSI.

    I have a question (again keep in mind hydronic system loops are closed) I noticed that when my combicor is not running, pressure is dropping, but when it runs (to heat water for shower), the pressure keeps going up. Is this expected? Wouldn't that trigger my relief valve eventually if say i am taking a shower as pressure will build up ? or it won't exceed 30psi? I would have imagined that the combicor wouldn't cause axiom pressure to increase during use of domestic water
  • hot_rod
    hot_rod Member Posts: 22,256
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    maybe lower the pressure to 10-12 psi, and the expansion tank also. No reason to have it at 23 psi, typically. The Axiom should adjust down to 10 or 12.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • GroundUp
    GroundUp Member Posts: 1,926
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    If the pressure is rising and falling with temp, the expansion tank is either bad or not properly pressurized. Its whole purpose is to maintain a constant pressure in the system. Whether the fluid is 50 degrees or 150 degrees, the pressure should always be the same. This would also explain the relief valve leakage, if it is spiking to 30 psi and releasing the relief valve. Try to pull the CPVC line out of the Axiom and run it into a bucket. If any water is ending up in the bucket, there is a problem. If the system pressure is fluctuating under any circumstance, there is a problem. Both of which may be solved by properly charging the expansion tank, and probably dropping the system pressure to 10-12 as hot rod says.
  • moemah123
    moemah123 Member Posts: 55
    edited August 2023
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    Ok so he needs to let out some pressure from expansion tank? I looked up and they use some tool and reading to lower expansion tank pressure. Is that right? 

    In terms of fluid how can he control pressure to 10-12 psi? I assume through axiom?

    One thing not still clear to me. In my system water and hydronics are supposed to be separate. So how did the water tank heating up affect pressure read of axiom ? Since atleast hydronic system knobs being shut at this moment (kind of worried when he turns it back on what will happen) I wouldn't have expected any water to flow into or out of that over charged expansion tank. So I am confused how axiom is detecting pressure change 

    Pics below to show what I mean by system closed

  • moemah123
    moemah123 Member Posts: 55
    edited August 2023
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    Ok I truly don't know what's going on with system. I turned on water again for shower. And this made axiom reading drop (before I saw it rise) but this time it made it drop at rate of 0.1 every couple seconds. What is going on :(  you can see my system closed as per pics above. Why is axiom fluctuating so much.

    Edit: after shower I found it at 29.6 psi reading.

    I will set up a camera to record. But I feel something is wrong here.

    Does this mean for sure given pics above of system closed that my expansion tank is being used and its not correctly pressurized? I feel if this is case how did he miss this step?