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Expansion tank issues

KCAKCA Member Posts: 285
Hi Everyone...

  Take a look at the drawing...  While the boiler is running at +- 18psi, all on a sudden within 2-4 seconds the pressure raises to 30psi and blows the pressure relief.  Temperature doesn't appear to have any bearing....  Not sure what does....  The system acts as if expansion tank " isn't there....  I temporarily installed Expansion tank "B" and all is well...  Even if I turn expansion tank "A" off so it acts as if "A" weren't there.. .    I have switched tanks with Expansion tank "A" and it doesn't matter....  So I believe that Ex tank "A" is good...

I have the indirect shut off both the coil & the domestic.

This happens when the temp is 180degF or 120degF...  doesn't matter.

It seems that installing the expansion tank "B" solves the problem..  which is great but I wanna know why...  :)


1.  Why am I getting pressure spikes? in the first place...

2.  Why doesn't expansion tank "A" seem to be seen by the system?

3.  How come installing expansion tank "B" solves the problem even with "A" off?

I've rounded the system off to be +- 18 gallons...

Expansion tank "A" = Extrol #30

Expansion tank "B" = Extrol #30

Oh...  one other thing...  I didn't install the system...  I'm just there to fix it..  :)

Thanks for all your help!!  I really appreciate it...

  :-)  KCA


  • furnacefigher15furnacefigher15 Member Posts: 502

    You are pumping into the boiler.

    When there is some more distance between the tank and the pump the pressure will drop a little more between the tank and the boiler pump then it did before, causing a lower output pressure from the boiler pump.

    If you don't need 18 psi, lower the pressure.
  • IronmanIronman Member Posts: 3,436
    Move The Tank...

    And the SriroVent into the primary loop where the flow switch is located. The way it is now, the PONPC is in the secondary.

    Pumping into the boiler is the proper method with this arrangement as long as the boiler pump is downstream from the PONPC.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • LarryCLarryC Member Posts: 331
    edited March 2012
    You are making steam.

    " While the boiler is running at +- 18psi, all on a sudden within 2-4 seconds the pressure raises to 30psi and blows the pressure relief.  Temperature doesn't appear to have any bearing.... "

    I am guessing you are making steam in the boiler.  The expanding steam bubble raises the pressure and pops the relief. 

    Is a Taco 014 a small pump?  Is that pump recommended for the boiler circulator in a primary secondary set up?

    If that is the correctly sized pump, then I would look for a hot spot.  Perhaps a blocked water passage, improper firebox conditions, or improper flame size.

    Be aware I am not a heating professional and my advice is worth exactly what you paid for it.

    Good Luck.
  • icesailoricesailor Member Posts: 7,265
    Checks & Balances:

    If those circles with diagonal lines denote check valves next to the secondary loop, the fill is in a locked loop between two check valves, the second being the rotten IFC's in the check valves. It you had a real wet head check valve, you would be able to manually open the check and see if the problem would stop. As it is, you can't. The first tank, tank "A" is being hydraulically isolated from the system and the system can't "see" what the tank (A) is doing. Not so with tank "B". It is on another side of the rotten IFC's.

    It seems to me but I can't "see" the drawing that well.
  • KCAKCA Member Posts: 285
    edited March 2012
    The system is piped

    according to Weil McLain specs...  The circulator 0014, is actually shipped with the boiler...  It's a pretty big head circ..  I'll grant that the secondary lines are too small...  But that shouldn't matter with regard to the ex tank...  The pressure differential between the two pressure gauges on either side of the Taco 0014 is +- 3 psi...

    I always like to put the spiro & expansion tank in the primary but....  It doesn't have to be...  It would seem that the ex tank "A" can be seen from any part of the system..  So why doesn't it act that way?

    The valves off of the primary & on the secondary branches are ball valves..

    The pressure at 12 would do the same as 18...  except that you need at least 14 for NPSH and now Taco requires 20 for systems above 5000 feet...  so..  18 seems like a good middle of the road number...  I don't agree with the 20psi requirement.....

    :-)  KCA
  • Paul48Paul48 Member Posts: 4,240

    piped to W/M's specs at all.
  • Mark EathertonMark Eatherton Member Posts: 5,582
    What happens if you shut off the make up?

    What you are seeing is what Siggy calls "droop". With the pipes being undersized between the Primay and the secondary pumps, when they kick on, they create a significant drop, or droop in pressure that the PRV sees and sends water in. Moving the PONPC to the secondary circulators inlets, or as close as you can get it to that point should stop the problem. The exp. tank doesn't HAVE to be connected at the air separator.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • SWEISWEI Member Posts: 7,356

    3 PSI is about 7 feet of head, at which a 0014 moves around 26 GPM.  At full output at sea level, the Ultra 230 should give you 14 degrees of delta-T (and as it modulates that number will drop.)
  • icesailoricesailor Member Posts: 7,265
    Pressure Issues:

    The pressure at 12 would do the same as 18... except that you need at least 14 for NPSH and now Taco requires 20 for systems above 5000 feet... so.. 18 seems like a good middle of the road number... I don't agree with the 20psi requirement.....

    Funny thing about that pressure thing. I was talking to a gas and heating professional that does a lot of troubleshooting about such things. I told him about raising pressures on systems where there were high parts in systems and air being sucked into can or auto vents. I don't remember when this conversation occurred. Last week, he told me that after I told him that, he went to their office and raised the pressure to 20#, For 17 years, the air handler in the attic of their two story building would get air bound, and for 17 years, he would need to go up there multiple times during the heating season. Since he raised the pressure to 20#, he hasn't had to go up and vent it once.

    I remember things like that.

    Do you understand why you need to raise the pressure above 5000 feet? There's an explanation
  • ZmanZman Member Posts: 3,479
    Keep us posted

    This is an interesting one. I think Mark is on to something, although I would expect the problem would occur on pump shutdown. The flashing to steam would make sense but only if you were pumping away from the high head loss boiler.

    Icesailor, could you please explain pressure over 5000 feet? Since the pressure is relative to the atmosphere,I am not sure what you are saying. Your example of air locking makes sense. You should have the pressure from the building height + a safety margin. The building you describe would need 15 to 20# depending on the height.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • KCAKCA Member Posts: 285
    edited March 2012
    I shut the PRV off Mark...

    I thought of that and killed the make up..  But that's a good idea...  :)

    :-)  KCA
  • KCAKCA Member Posts: 285
    That doesn't have anything to do

    with a circulator....  They want 20psi on the circs...  They usually are around the mechanical room...  I was told that it was because flashing in the cartridge...  But why 20psi & why above 5000ft?   That is something else altogether..  But thanks for bringing it up..

      :-)  KCA
  • KCAKCA Member Posts: 285
    edited March 2012
    Here is a drawing

    from the WM manual...  It's piped like this..  I left the sidearm out because I isolated it during this issue...  and the flow check isn't installed..

    KCA  :-)
  • ZmanZman Member Posts: 3,479
    Water off?

    Sorry I did not see you had tried to turn off the water. Was the expansion tank functioning correctly with the water off, of was the level changing? Have you tried isolating the secondary loop and just running the boiler loop? It seems the problem must be related to the 0014 in relation to the high head boiler. I assume you have triple checked your pump directions?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • KCAKCA Member Posts: 285

    I triple checked the direction...  & I've isolated the secondary..  to a point..  Because the expansion tank is there..

    :-)  KCA
  • ZmanZman Member Posts: 3,479

    Humm! Do you have a photo. Maybe there is something you are missing that someone on here can find? Double check valve?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • ZmanZman Member Posts: 3,479

    Humm! Do you have a photo. Maybe there is something you are missing that someone on here can find? Double check valve?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • KCAKCA Member Posts: 285
    That would be great

    but the mechanical room is like...  5' across by 6' deep & it has (besides the boiler & sidearm & secondary..)  two gas fired furnaces..  as well as a whole house filtration (hepa) system...  so I couldn't get a good pic...  Some of the pipes are up in the joists..  etc...

    There has got to be something that I'm missing...  I even thought that the diaphragm was stuck to the inside of the ex tank so I changed it...  No difference..

    You can see the ex tank "A" from everywhere in the system..  so I don't understand why it doesn't work..  Yet installing one in position "B" works great..  Hmmmmm....  I guess I may never know..  But then what a waste of time...

      I appreciate everyone wanting to help...  You're great..

      :-)  KCA
  • Steve WhitbeckSteve Whitbeck Member Posts: 669

    What is the pressure on EXP A when the boiler pressure is at 0  ???

    Try installing tank B where tank A is now and plug the fitting for tank B.

    You may just have a bad tank. Piping shouldn't be a problem.
  • icesailoricesailor Member Posts: 7,265

    Bingo !!

    You hit it on the head. "Flashing in the cartridge." Flashing into what? STEAM.

    Try resettng the pressure to 20# and then turn on the boiler. If the problem goes away, it's the pressure. All those pumps trying to do their thing can and will become willful children and creat havoc in the system.

    Do you understand need to raise the pressure in the system when the system is at a higher level above sea level?

    Its important.
  • icesailoricesailor Member Posts: 7,265
    As I see it,

    As "I" see it, 0 (zero) PSIG at Sea Level isn't the same as "0" at 5000 feet. Therefore, when the water in the system gauge says  "0" at 5000', it isn't the same as "0" at sea level. Therefore, the boiling point is lower at 5,000 feet.

    On Mt Everest, climbers have a lot of difficulties. One is that a lot of food needs heat to release nutrients that the body can take up. The product may need to be heated to 175 degrees for the nutrients to be released. Especially in dried or dehydrated foods. But water may be boiling at 150 degrees at higher altitudes. You can't get the water/liquid hot enough without it all boiling away.

    Taco is recognizing what some of us have felt for years that cavitation in pumps was a big problem. But we are considered "contrary".

    Consider this. If you had a system that you filled to 12# PSIG, and you moved the entire system to Denver Colorado without opening it up, what would happen to the pressure?  (Hint: It doesn't go down.)

    What happens to a system filled to 12# PSIG Gauge in Denver Colorado and you move it to The Island of Long?  (Hint: It doesn't stay the same.)

    As I see it.

    Those climbers on Mt Everest could put their food and water in a pressure cooker. But if they tried to open it, it would explode if the water temperature was higher than the outside pressure keeping the boiling point down.

    Isn't this sort of how vapor/vacuum steam systems work?
  • ZmanZman Member Posts: 3,479

    Boiling point at 10,000 feet is around 190 degrees. It does effect cooking and requires boiler temps to be set a bit more cautiously. I agree that the system pressurized at one altitude and moved to another would read differently. However if you charge the tank and fill the system at a given altitude, What is the difference? Perhaps ME will weigh in on this?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • icesailoricesailor Member Posts: 7,265
    Extrol Tank Precharge:

    That's easy enough to check without doing that. Drop the system pressure to zero and check both tanks with a tire gauge. They both should show pressure and the same amount..
  • icesailoricesailor Member Posts: 7,265
    Heating Extrols Vs Well Extrols:

    I've not seen this answered.

    On Well Extrols, the instructions tell you to set the tank pressure at 2# PSIG below the "Cut-In" pressure . Ie: If the cut in pressure is 20#, (20/40# pressure switch) set the tank pressure at 18 PSIG. Cut in at 30#, (30#/50# switch)  set it at 28#. I find that it is better to set them at 3 to 5 pounds below the cut-in pressure to stop any possibility of the water stopping while the pressure switch closes, the pump starts and the water gets going. I can't remember how many years I have followed this rule. But it was shortly after the first complaint of the water pausing while the pump built pressure.

    If you look on the Amtrol Website, there are no instructions on what to set the pre-charge pressure to for heating Extrols. We are left in the wilderness.  And the instructions in the box is no different. To my aged and deteriorating brain, the heating Extrols come pre-set at approximately 12#. If the system pressure is at 15#, you have a 3# cushion. If it is at 12#, you have no cushion. If you set the system pressure to 18#, you have a 6# cushion. It is suggested by some to raise the precharge to equal the system pressure. That would give you no "reserve" if the system cooled and the system water contracted.

    On systems I see with air problems, the PRV is usually stuck and the system is 10# or below. Hit the by-pass and the system may not ever stop filling.

    If the system is precharged to 12# and you run the system pressure at 18# with a 6# differential, it works fine and you have more room for expansion.

    On a well Extrol you cannot set the pressure the same as the cut-in pressure. It must always be lower than the cut-in pressure. Why is this not so in a heating system?

    An inquiring mind is asking.
  • icesailoricesailor Member Posts: 7,265
    Spaced Out:


    Does the primary/secondary loop configuration in this system that you did not install conform to this?

    Note especially the part about distance for closely spaced tees AND the distance from the closely spaced tees to turning ells?

    It does make a difference.

    When using an iSeries-R Mixing Valve, the following piping requirements

    must be considered for proper operation.

    1. In order to hydraulically isolate the boiler loop from the injection or system

    loop primary/secondary piping must be used. There must be no

    more than 4 pipe diameters between the tees in the boiler loop (Note 1).

    2. There must be at least 6 pipe diameters of straight pipe on either side

    of the tees (Note 2) in order to prevent the momentum of water in the

    boiler loop from pushing flow through the injection loop.

    3. There should be a minimum of 1 foot drop on the return pipe of the

    injection loop, in order to create a thermal trap (Note 3) and prevent

    unwanted heat transfer.

    4. When using a 2-way iSeries-R Mixing Valve, a balancing valve must

    be located between the tees in the system loop, in order to provide a

    pressure drop to induce flow through the mixing loop.
  • icesailoricesailor Member Posts: 7,265
    Another thing on that boiler/system.

    Here's another thing on that system. It is becoming common knowledge where I work that they are often way over fired in some applications. If anything is incorrect in the piping, and you have diminished flow through the primary loop and by diminished flow, I mean returning cooler water going into the boiler, it will do what you describe, flash into steam. I have a friend who is constantly down-rating these boilers because they are too big and you can't get enough flow through them to cool them. Once they start to steam, the flow stops.

    A question for Steamhead, if a teapot boiler starts to steam, will the circulator pump be able to push the "bubble" out? Wondering.

    Why I like Low Loss Headers or Hydraulic Separators better than improperly spaced and installed tees.
  • furnacefigher15furnacefigher15 Member Posts: 502
    Well verse heat diaphragm tanks

    They are not doing the same job.

    A well tank uses the air cushion to stabilize water pressure, not to account for thermal expansion.

    The reason the heating diaphragm tank should be set the same as the water pressure is to maintain a place for the water to go.

    At balanced pressure the diaphragm will have not allowed any water into the tank.

    Once there is more water pressure then air, water will push into the tank.

    If you start out with a lower tank pressure then fill pressure, then there will be less room for the water to expand because it has already started to fill the tank before it even got hot. The result is a reduction in the capacity of the tank.

    If the pressure of the tank is high then the system, the result will be that the expansion tank won't accept water until the water has heated and pressurized enough to match the pressure of the tank.

    So the thing to do is match the pressures, that way the water will have a place to go when it heats and expands, and the tank will have its full potential for expansion capacity.
  • KCAKCA Member Posts: 285
    The Ex Tank "A"

    is at +- 18psi when system is at 0psi....  I already tried exchanging tanks with tank "A"...  The tank is OK...

      Thanks for the thoughts...

       :-)  KCA
  • KCAKCA Member Posts: 285
    No I don't

    Explain why you should have 20psi in the system when it's over 5000 ft ASL...

        I don't know...  :)

       KCA  :-)
  • KCAKCA Member Posts: 285
    edited March 2012

    is the same at sea level or at 5000ft above...  PSIA is different...

    Boiling point at 15psiG is the same at sea level and at 5000ft above... 

        :-)  KCA
  • KCAKCA Member Posts: 285
    When I run an injection

    loop...  I tie into the space between the expansion tank & the primary circulator...  You excape the ghost flow issues as well as the primary pump pushing unwanted water into the injection loop..  Has always worked well for me..

      Just an FYI

     :-)  KCA
  • bobbob Member Posts: 808

    I suspect what is going on is with the tank at A, fill pressure drops from the tank to the zone pumps. From the zone pumps back to A the pressure will increase . With three pumps in parallel the GPM of the pumps will add. You are pushing all that water through a 1" pipe causing the pumps to ride up their curves towards max head. This increase in pressure is seen by the boiler loop and is added to the 014. When you move the tank to B the head of the zone pumps is below fill pressure from B back to the pump inlets and reduces the pressure in the boiler loop. Try turning some of the zone pumps off and on with the tank at A and watch the pressure.
  • bobbob Member Posts: 808

    KCA, Question . if you hook a manometer up to a gas burner at sea level and it reads 3.5"WC and do the same in Denver and it reads 3.5" WC is the pressure in the burners the same?
  • KCAKCA Member Posts: 285
    edited March 2012
    I think what you are asking is....

    Does a manometer (and I'm assuming that we're talking about a digital one) take into consideration atmospheric pressure in the readout...  I don't believe so... I believe that a manometer reads out in PSIA...

     Regardless manifold pressure isn't a closed system...

    Interesting question I had to think for a minute...  So that means that the answer may not be correct...  Lol...

     :-)  KCA
  • icesailoricesailor Member Posts: 7,265
    Air Head:

    When you take a Well Extrol or a Heat Extrol out of the box, and it is precharged to whatever it is precharged, the pressure inside the bladder has pushed  the bladder to the bottom of the tank. It is pushed off when the incoming pressure is greater than the pre-charge. There is no pressure range when the pre-charge is higher than the set system pressure. In Hydraulics, the difference between zero and 100# is a drop. It can't be compressed. The fill valve will add water, like the water on  a pump will stop.

    But that's not the cause of a problem you didn't create and are trying to solve.

    Did the original installer make the closely spaced tees 4 pipe diameters?  That's 5" center to center on the 1 1/4: primary loop. A 6" nipple isn't 4 pipe diameters. The closer the tees, the better the mixing. If you don't get good mixing in the zone between the tees, you may not get as much return water as you need to keep the boiler cool.

    Its not the tanks.
  • KCAKCA Member Posts: 285
    The space between the tees

    is about 5" I would guess...  He used a 3" nipple on two 1 1/4 x 1" tees so they are close...

    :-)  KCA
  • bobbob Member Posts: 808

    The pressure in the sea level burner is 14.825 PSIA the pressure in the Denver burner is 12.325PSIA that is why the btu content of nat. gas is 830 /Cu Ft in Denver and 1040 at sea level. Manometers use atmospheric pressure as a reference just like pressure regulators.

    I use to wonder if bourdon tube gauges used atmospheric pressure as a reference so I took two high quality 0 to 10 Lb. gauges at sea level both reading zero and capped one. I drove to Denver, the capped gauge read 2.5 Lbs the un-capped read zero. Two boilers one at sea level one in Denver both with gauges reading 12 Psi will have different boiling points.
  • KCAKCA Member Posts: 285
    edited March 2012

    OK...  I looked it up and here is what I found..

    PSIG is the pressure read from a gauge which reads the difference

    between the pressure in the pipe and the pressure of the atmosphere.

    PSIA is the total pressure including the pressure of the atmosphere.

    That being the case then you are right...  the water at at 12psig at sea level would boil first......

    I thought that PSIG was the pressure in a pipe read from a gauge regardless of atmospheric pressure...   I knew that PSIA was ...  what it says...

    :-)  KCA
  • Big EdBig Ed Member Posts: 863
    edited March 2012

    I was thinking the same as I read down this post ... Breaking in to steam ? You would know by the hammering noise …Nothing was mentioned .

    I am thinking the change from the recommended piping to what was install which puts the circulators in series which adds up into the boiler . they are all pumping away from the tank . by relocating the tank on the heating return... The boiler circulator is pumping away as the heating circulator is pumping toward the tank... Hmmm.... Which takes them out of series

    I see the difference between the two diagrams . The heating zones are injecting in to the primary loop rather then the primary injecting into the secondary ..
    I have enough experience to know , that I dont know it all
  • icesailoricesailor Member Posts: 7,265
    edited March 2012
    Over matched boilers:

    You don't always hear the sound of steam being made in a boiler like this like you might be used to hearing.

    If the rise in pressure is during high fire in the boiler, it's probably steam. You should be able to turn the fire down by modulating the flame to  low fire. Turn it down. Does it still rise in pressure and pop off? If it doesn't rise in pressure and pop off, there's part of the problem.

    I still saw that part of the flow issues are in the closely spaced tees. How far apart are they? Pictures? If the spacing isn't correct, it will act like Mark Ethertons notorious former BIL. He has his foolish friend with him. One will go around the lake in one direction. And his foolish pal will to but at a different speed. If they went at the same speed, one could ride the wake of the other for a better ride. Instead, they will have to cross each others wake. For a bumpy ride.

    They are using a 014 pump for the primary for the high flow through the boiler that is one inch through the boiler. Increased to 1 1/4" and reduced again to 1" through the closely spaced tees.

    Put your hand on the supply/primary pipe before it goes through the closely spaced tees. Run the boiler and if the boiler temperature rises to where you can't hold your hand on the primary side and you can (more or less) on the secondary side supply but the return of the secondary side isn't as hot, it's not mixing. If they all get hot together, the boiler is firing too high. Like many over-sized teapot boilers will do.

    The boiler is the engine. The heat emitting units are the radiation. If the engine is bigger than the available emitting system (radiators), the boiler will over heat.

    And I have said over and over, YOU didn't install and pipe it. HOW would have you done it differently. And that includes WOULD YOU HAVE USED THAT BOILER IN THAT APPLICATION???????

    Don't fall into the trap that the first installer made and don't use their logic on what they did. Use your own.

    Do you have enough installed radiation to cool 230,000 gross input into that boiler to cool it?  Turn it down to low-fire and see what happens. I told you, someone where I work has downfired a bunch of these boilers that were doing this. If you set it to low fire, and it stops, consider that.
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