Pressure Problems

nbroyer Posted By nbroyer, Nov 18, 2017 at 10:58 AM

  1. nbroyer

    nbroyer
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    Apr 30, 2012
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    Hello,

    I've just completed my first week burning with my Eko 25 and 500 gallons of pressurized storage. Everything for the most part is working as expected, and having storage has been a huge upgrade. The problem I am seeing is that as the temperature climbs, so is the pressure. I get that's what's supposed to happen, but I thought my expansion tank would absorb the pressure and keep things mostly consistent. I have an Extrol SX-90 expansion tank which I think should be more than enough for my application.

    I initially filled the system, purged the air, and then set the pressure to 12 psi. I shut off my automatic water fill because it kept wanting to go higher (it's set to 12-15 psi so maybe I should have let it keep going). The first couple of fires I kept small so I could keep an eye on things, and after working out some control settings, things worked great. The pressure did raise up to maybe 15 psi, but that wasn't too concerning at the time. My third fire was bigger and the temperature from the boiler got up to 185, and storage was only about 170. At this point, my pressure gauge got up to 25 psi. I didn't want it to go any higher so I opened all of the zones and my dump zone. I think I may need to replace some gaskets because the temperature in the boiler kept climbing slightly even with the fan off. I panicked a little bit and decided to relieve some pressure by letting air out of the expansion tank. I realize now that was stupid and will probably cause more problems.

    I'm trying to figure out why this is happening. I first suspected the expansion tank, but from what I've read on here, I think if no water comes out when I release some air, then it's still okay? I've tried feeling the tank to see if it is hot all over but honestly I don't feel heat anywhere in it. The pipe into it does get hot. Maybe with my model there is a shell around the actual tank.

    So, I know I need to add more air back into the expansion tank. I have a shut off above the tank and it's hooked up with a union, but I think there's probably a lot of water in it now and it is the lowest point in the system. Do I need to start to drain out my storage tank to release some pressure and then hook up my air compressor to push out the water? What other problems could be causing the pressure to raise so much?

    Thanks!
     
  2. leon

    leon
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    Feb 3, 2013
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    Where EXACTLY is your bladder tank???? Is this bladder tank on the floor or is it hanging under an air scoop? If the bladder was punctured you would have water spitting out at you.

    you need to physically disconnect the tank to drain all the water out of it and then charge the bladder tank to 15 pounds of air pressure in the bladder tank so make sure you have and measure it with a good gauge. After you fill the air back up open the valve back up and run your system. your circulator will create up to 18 PSIG after the point of no pressure change.

    You need to describe fully where your circulator is and whether you are pumping the water away from the boiler or pumping water into the boiler sump

    This is the best reason a person should have a steel expansion tank in their system as it has no moving parts and you do not have to pressurize it as the steel expansion tank will have a an air volume of 1/3 the capacity of the steel pressure tank after the excess water is drained from the the tank using the airtrol valve.
     
  3. nbroyer

    nbroyer
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    Apr 30, 2012
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    Leon,

    Thanks for responding. My expansion tank is on the floor, connected to the bottom of an air scoop. There is a tee under the scoop before the tank where my automatic water fill comes in. The circulator is pumping away from the tank on the return side of the boiler.

    Thanks

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  4. maple1

    maple1
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    If you add more air to the expansion tank that will make things worse.

    Did you check the precharge pressure in your expansion tank before you hooked it to the system?
     
  5. nbroyer

    nbroyer
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    No, unfortunately. I really regret that now. It's supposed to be precharged to 12 psi but I did get it used so who knows.

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  6. maple1

    maple1
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    You can still do it - if there is an isolation valve between it & the system and a way to let pressure off the wet side between it & the iso valve. Or, let the system go cold, down to its cold system pressure, then check the air side pressure. Mine was supposed to be 12 also, but it was 18 when I checked it, straight out of the box new.

    You might also be able to go lower than 12psi cold system pressure depending on your system height.
     
  7. nbroyer

    nbroyer
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    I can isolate the tank from the rest of the system but releasing the pressure on the wet side is what I'm struggling with figuring out. There is a threaded connection at the top that I can't find any information on. My water connection goes in the base.

    Right now my storage temperature after a couple of days with no fire is 110 degrees and it's at 9 psi. I just don't get why there's such a large swing when the temperature rises. I thought it should be much more consistent with this large of an expansion tank. I just don't feel comfortable with it getting up to 25 psi and I don't think going down to 5 psi cold to keep it around 20 psi hot works? Is there something else that could be causing the pressure to build up this much other than the expansion tank?

    My boiler is in the basement of a two story house.

    Thanks!

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  8. Bad LP

    Bad LP
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    How many fires have you had? In my case the pressure changes were scary and getting all the air out was a PITA. 600 gallons of tank water, wood boiler water, LP boiler volume is moot but a few thousand feet of PEX in the floors that was all drained added to the frustrations. After a few weekends of very careful firing and watching the pressures it did come down. I did lower the supply pressure for make up water down to about 12psi and my maximum pressure at 180::F in the tanks is now hovering around 20-22 psi. I've been unable to get my tanks to a higher temp than that to date. Keep in mind all my testing was done in the last couple of months in order for me to be comfortable leaving the house and having the system change over to LP before the cold weather locks in.

    When I first started it would be near 30 and yes, I was nervous walking near the relief valve.
     
  9. nbroyer

    nbroyer
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    Bad LP,

    So your problem was air in your system and over time it has worked its way out bringing the max pressure down? I do hear bubbles occasionally so maybe I just need to keep making small fires until that gets worked out. I thought about upgrading to a spirovent to help. I've only had about 4 fires so far.

    Thanks!

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  10. Bad LP

    Bad LP
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    Nov 28, 2014
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    I wasn't air locked, just took a lot of time to work the air out of the system. I have air vents at the top (on the domes) of both tanks, top of the buffer tank for the RFH, top of the wood boiler, top of the LP boiler, top of the powerless zone and one on the RFH mixing block. I kept pushing water into the system and I think I was just making it worse. I've spent many hours in the basement next to the boiler drinking beer, taking notes, watching and paying attention to every little aspect on what's going on plus tweaking temps, pumps and getting a feel on how much I can load into it without over firing that would require the dump zone to operate. I did this so I can become comfortable going to bed and leaving the house without worrying. I have 100% faith that the 3 relief valves are 100% operational and that they are truly the weak point in the overall system. In fact when the state was powerless a couple of weeks ago I was in front of the boiler when the restored power went out again and witnessed first hand the powerless dump zone operate until my standby generator came on line and everything worked perfectly. I have to admit that was kinda cool to witness and better than just shutting off the boiler switch.

    From what I learned... Yes, keep making fires in it, make sure your zones are getting water (I was just using the manual bypass on the 9 zone valves) and that you feel the hot water on the return side of zone. Keep listening for air escaping and water bubbles in the lines.If after a dozen or more fires you still have pressure problems you are now sure it is either a volume or precharge issue for your expansion tank.

    Good luck.
     
  11. leon

    leon
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    Feb 3, 2013
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    Hello Bad LP,

    Do you have boiler drains on your return lines before they enter the return line header pipe??

    The boiler drains let you power purge the cold water in these loops to push put most all the
    air in these heating loops and after that is done your hot water firing purges the rest of them.
     
  12. leon

    leon
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    Feb 3, 2013
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    ================================================================================

    Hello nbroyer,

    If I neglected to ask this before shame on me, do you have boiler drains on the return loops at the boiler??

    The boiler drains at the end of the return lines allow you to purge most all the air from the individual heating loops with the cold water and then the smaller remaining amount of air in the system can be purged with the automatic air vents.

    I eliminated all my automatic air vents when I installed the Steel expansion tank with the new boiler and the need to crawl around on my knees to bleed the base board heat. I wish I had cast iron radiators instead!!! It would be so much easier to heat my home.
     
  13. nbroyer

    nbroyer
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    Apr 30, 2012
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    Hi Leon,

    I do have drains on the return line and that's how I've been purging all of my zones with pretty good success with my previous boiler. I know I have some bubbles still because I hear some air coming out of the air vents from time to time. I just started another fire so we will see how it goes this time.

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  14. salecker

    salecker
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    When i built my system i had the pressure valve blow out water the first time i really tried to pack the BTU's into my tanks. It turned out my expansion tank an Extrol one was a little to small.
    For a couple of years i would juggle the pressure in the tank and fill the boiler in the beginning of the year.I would drop the residual pressure in the boiler to almost nothing and make sure everything was full of water. I don't have a makeup valve on my system.I could get it close but the first time i would go for maximum BTU's it would still blow off some water.I dropped the pressure in the Extrol tank down quite a bit to make more space in the tank.
    Still could never find the balance where blow off didn't happen.So i added the small tank that came with my boiler,it is an outdoor model that i have installed inside so it came with a small tank under the tin house.
    Now i have no more problems i can start from sitting cold for the summer,to maxed BTU's and don't lose a drop.
    All my expansion tanks are up high and the pumps pump away from them,they are far enough away that they never get warm
     
  15. Bad LP

    Bad LP
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    At that location I do not but I do have a master drain on the return header that will do the same thing but with a small amount of more work. I'm convinced my problem stemmed more from the size and complication of the system as well as the whole thing being filled with brand new water. We relocated manifolds that were built onto the LP boiler moving them to the wall, moved the LP boiler then added the wood boiler and obviously re-piped the whole thing. Thankfully we left the RFH manifold system alone and just tied the supply and return lines to the relocated manifold.

    Can't wait to convert my 3 baseboard zones to panels then add 2 CI units to "man town" but that needs to wait a bit while I recover $$$ from such a large scale project. This project cost a bit more than I expected. We moved all the heating equipment around in order to not ruin my workshop space due to adding the wood boiler plus I added a Bridgeport milling machine into the mix and that takes up a lot of space.
     
  16. maple1

    maple1
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    If your system is at 9 now, check the air pressure in the bladder tank and see what it is. You might have to add more expansion but need to verify precharge first.
     
  17. nbroyer

    nbroyer
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    Apr 30, 2012
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    Unfortunately I had already started another fire when I read this so I didn't get a chance to check the expansion tank pressure.

    Since then I've found that one of my pressure gauges is high by about 4 psi. The one on my storage tank only went to 15 psi so I purchased a new one which is agreeing with the one on my propane boiler. The gauge on my wood boiler is reading high and that is the one that I had been leaning on. So now at 180 degrees both the propane and storage gauges are reading 24 psi. Still higher than I'd like but better than the 28 on the other gauge.

    The strange thing is my pressure relief valve on the propane boiler opened up twice tonight. I think I've narrowed it down to when the main loop circulator turned on when the house called for heat. It looks like when that happens and the storage tank was at 180, the pressure jumped to 27-28 psi at the propane boiler. It may have been higher when it happened the first time.

    So I still think the pressure is raising up higher than it should so maybe I can release some more air from my expansion tank and measure that when it's cooled down. But then don't I have to add more water, especially after losing some from the relief valve?

    Would I benefit from replacing my grundfos 15-58 main loop circulator with an alpha constant pressure circulator?

    Thanks!

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  18. maple1

    maple1
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    You can't randomly let air out of your expanson. Without knowing what precharge is. Or you could make it worse.

    24 is borderline and higher than I would like. You might need another expansion tank.

    Let your system cool off again and check your precharge.
     
  19. maple1

    maple1
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    And a different circ wont do anything about system pressure.
     
  20. nbroyer

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    Okay I will do that as the next step.

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  21. nbroyer

    nbroyer
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    Okay, I wasn't sure if it would help with the 3 psi jump when the main system circulator turned on, but I admit I don't understand it.

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  22. Bad LP

    Bad LP
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    Have you closed your boiler feed? Doing so will not allow your feed pressure to interfere with testing and proving.
     
  23. nbroyer

    nbroyer
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    Yes, I've had it closed since I initially filled it.

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  24. rkusek

    rkusek
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    I don't think your tank is big enough.
     
  25. maple1

    maple1
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    I also suspect more expansion is needed - but you have to check your precharge pressure first to find where you're at now or else it's just a guess. Then settle on a system temp & pressure number for depleted storage as a starting point. I would assume at least 190 for upper temp for sizing purposes. And no more than 20psi for upper pressure.

    How did you come up with selecting the SX90? Did you use a tank sizing app? I just checked a couple of them and the 90 is borderline for 600 gallons depending on how you fiddle with the parameters. Eg., changing upper temp to 190 from 180 took the selection from a 90 to a 110 tank in one case. And you should use caution with the parameters - err on the side of safety.

    It is a very good idea to have multiple guages in the system - they can be inaccurate. I think I have 6 or 7 on mine. Should also consider where all those guages are height wise in the system when you're reading them. Every 10' of water height = 4psi.
     

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