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Burnham Boiler pressure woes

Japus Member Posts: 7
Before I go into deep detail here I am putting this question out just in case there may be something I overlooked.

I installed this boiler and controls (complete) 35 years ago and maintained it ever since, I am familiar with pressures, flows, etc.

Last winter after replacing air expansion tank I noticed this problem... after shutting off my supply valve to the regulator 12#,   and  shutting down the boiler my pressure dropped off to 0 psi. This happened continuously and still does although not

dropping to zero, just 5-7 #

I visibly checked through 2 zones (operating temps and press)  and found no leakage, it kept doing this and still does.

I removed  the automatic vent valve above the flow valve, also removed the expansion tank.

Plugged the 1/8th inch outlet and used the 1/2 inch to connect a line adding 21# of air. This kept solid for 24 hours, with no  drop in air pressure.

 after visual checks and pressure test I am 100 % confident no leaks in the system are present

There is also no indication of leakage in the boiler, I removed skin, cleaned and checked all I could see,

I did not want to remove the flue outlet hood above the boiler tubes as it was cemented to the water jacket.

I have been hearing a slight gurgling for sometime, inside the boiler. I am aware noises can travel, however I am certain this gurgling is from the boiler internals.

All air has and is purged from all the vent valves in the system. along with the automatic vent valve.

Now here's a kicker that just happened today. Yesterday I add water to bring up pressure to12#  (from 7#)   it went down to 7 again as it has been, and then it actually went back up to 10lbs...(30# gauge accurate)

Pressure is now falling and rising with no input, and no heat

My understanding is a leak can occur at 180 deg @12 psi...and not  noticeable at lower air pressure..let me emphasize  there was no apparent visible water leakage at  this temp and press. only when the boiler cooled down to 80 deg at 12 psi did I lose pressure

Valves around regulating valves are closed and do not leak through..

Is it possible I somehow have air trapped in the boiler cavity that will not vent?.

Would this be the cause of my pressure drop ?

 Yes I am of the conviction...water pressure drop = leak...still very puzzling

I am trying to keep from spending  $3- 4000   for another boiler unless absolutely necessary.

If I need to my next question I will post in greater detail

Many thanks for your help



  • Steamhead
    Steamhead Member Posts: 15,892
    Is that a diaphragm tank?

    If so, remove it from the system and check its pressure. I bet you find it's low. 
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • As Frank says,

    check that tank,,, after 35 yrs. it will lose the pre-charge by osmosis,, consider yourself lucky as most do not last that long nowdays!
  • Japus
    Japus Member Posts: 7
    Burnham Boiler pressure woes

    Pressure shot up last winter , tank was full, so I replaced it..new tank (5 months old)

    12# air pressure inside...I also replaced the automatic bleed valve, however that needed to be replaced also because it leaked water when in operation.

    water not air and would not stop...is it possible the new expansion tank could be defective also ? no water is getting into it .

    Pressure maintaining 12 #...

    maybe I should do an air pressure check with the expansion tank in place ?
  • Steamhead
    Steamhead Member Posts: 15,892
    Did you

    remove the tank from the system before checking its pressure? This is extremely important to do........
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Japus
    Japus Member Posts: 7
    edited August 2010
    Burnham Boiler pressure woes

    Yep, I double checked this just before logging on here, removed tank and air pressure was 12#

    Strange thing tho, instructions on this tank indicate the tank should be installed on the inlet side of the pump.

    Instructions for the boiler is on the outlet side of the boiler just before the zones valves..

    Been working since 77 and I have replaced  one tank in 99, which worked fine till last may.
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,250
    Tanks have always preferred

    being on the inlet side of the pump. Thats same as it has been. can you isolate the boiler from the system and pressure test it alone?
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Japus
    Japus Member Posts: 7
    Isolate boiler?

    I was going to do this, however I thought I'd pressure check the system as a whole, intact and in operating condition, after draining both zones I had 21# in it for 24 hours with no loss.

    Yes I could isolate the boiler by  capping the inlet and outlet side of the boiler. That would mean cutting into both zones which is not a problem, I respectfully see no sense in doing this since I had no pressure drop in my original test....am I missing something?

    And as far as where the expansion tank was to be placed, I still have Burnham's installation guide,  installed as indicated  and it has been running great for the 35 years it's been in service.

    Only since I installed this new expansion tank have I had this pressure drop problem.

    I am considering trying another ex tank, kinda crazy since this one seems ok..
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    It's not your boiler....

    and it's probably not your distribution piping. I suspect that you have a defective make up valve and or a defective expansion tank.

    On occasion, the rubber diaphragm becomes stuck to the face of the tank and allows for ZERO acceptance volume. This will cause the pressure to deviate significantly above and below the normal set point.

    Pull the expansion tank out. Put a FIP to female hose adapter on it, and charge it with street pressure water using a garden hose. Let it sit for a few minutes with street pressure on it. Shut off the source and pick up the tank. Does it feel real HEAVY? If yes, you dislodged the diaphragm. If no, the diaphragm is stuck and the tank needs to be replaced. If yes, be prepared to get wet when you disconnect the hose... There is a BUNCH of water under pressure in the tank now. (best done outside)

    After you put the new tank in and open up the make up, does the auto fill take the pressure up to 12 PSI and then shut down? If no, you need a new auto fill valve.

    The deviations you saw with no heat going to the system (other than ambient heat) indicates a stuck diaphragm. No place for the expanding water to go to.

    BTW, the Burnham drawing was and is wrong. In their most recent installation drawings, they still show the improper installation method, and have an "Alternative" method. The reason that it use to show it that way was because there are generations of heating men installing their products, and back in the days of rag style pump seals, THAT was thought to be the best and most proper way of doing things. "That's the way we've ALWAYS done it, and other than having to bleed Mrs SMiths radiators once a year, we haven't had any problems..."

    We don't use rag seals on pumps any more, and their old drawings create more air problems than what they are worth. Done the right way, air problems are non existent.

    To learn more on this subject, purchase Dan's book "Pumping Away and other neat piping tricks". Well worth the time and money spent.


    There was an error rendering this rich post.

  • Japus
    Japus Member Posts: 7
    Mark ...thanks

    The make up valve is new and does stop at the set pressure of 12psi

    I am going to do the street pressure check tomorrow on the expansion tank..

    The center of the tank is right up at the opening, so that's a distinct possibility.

    Went down to the supply shop today to check out a new and boxed tank, same as this one I am using, up  close to the opening.

    As far as Burnham's installation being incorrect. if I resolve this problem I'm not changing it, let the next guy do it when a new boiler goes in.

    I don't think the pipes would welcome any change after such a long period of time.

    Will let you know here how this made out, again thank you for the great idea.
  • Japus
    Japus Member Posts: 7
    Tank pressure check ok

    Hooked up 90# street pressure to expansion tank, that really weighted it, removed pressure and checked bottom, which was still at 12#.

    Reinstalled expansion tank

    Started up boiler again, starting pressure was 13#

    pressure at 160 deg.....161/2 #

    pressure at 180 deg....17 #

    I have the upper limit set at 180 deg

    shut off fuel and allowing pump to run while temp dropping..

    Still hear the gurgling down in the boiler, once I replace the regulating valve with a new one I am going to open up the relief valve line and drain valve line in order to be sure all air is purged out, this gurgling sound has been going on a long time before my pressure drop problem occurred .

    Once the gas flame is out the gurgling ceases immediately while the pump keeps running
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    The gurgling...

    is steam bubbles, which are not the norm.

    It sounds as if possibly there is a circulation issue, which is not allowing the cooler water to wash through the sections to cool the heat exchanger down. That, or the boiler is over fired.

    The increases in pressure, related to increases in temperature are normal. When all zones are extremely hot, you should not be more than 27 PSI.

    Is there glycol in this boiler? If yes, you may have to treat it with a chelate to get rid of the surface boiling issue.

    Also, by having the pump pumping towards the expansion tank, the pump has no option but to create all negative pressure. I have seen this negative pressure actually cause boiling even when the water is nowhere near boiling.


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  • Tim McElwain
    Tim McElwain Member Posts: 4,580

    statement: "Also, by having the pump pumping towards the expansion tank, the pump has no option but to create all negative pressure. I have seen this negative pressure actually cause boiling even when the water is nowhere near boiling."

    I have seen this happen and what it is a partial vacuum is being created and the water at around 180 in the vacuum flashes to steam, steam occupies 1700 time more space than water hence the gurgling and increase in pressure.

    Try moving the pump and reconfiguring the piping also make sure there are no restrictions on the return piping as it enters the boiler.
  • Japus
    Japus Member Posts: 7
    Mark & Tim

    your answers have been very helpful to me, Mark my pressure is holding now on ambient temp, after I performed the pressure test on expansion tank. Could it have been possible diaphragm was stuck a little ?

    Now before I go further, a few questions that may put this to rest (or maybe go on)

    I have 1-1/4 blk steel pipe in and out of my boiler. To place my circulator on the outlet side of the boiler and expansion tank would not be a major project, well it would be major however I believe I could do it.. (arms still in good shape)

    In your opinions if this was your boiler would you make this change ? or  install a new boiler?

    I installed this  33 years ago in Aug.  1977 and been running fine till this problem, except for a few pumps, regulating valves, and  ex tanks  I am wondering if I should have it replaced.

    I have contacted a few local heating co's and price range is between $3-4000. for a Burnham, or  Lenox  hot water boiler.

    At this point in my life I am not going to tackle this myself for obvious reasons.

    I do realize this boiler could run much longer, however just give me your ideas if you would please

    Many thanks again
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    As with any hydronic heating question, the only correct answer is.....

    It DEPENDS!!

    What are your wishes, wants needs, goals and (budgetary and physical) capabilities?

    If your goal is to reduce your carbon footprint as significantly as possible, consider upgrading to a modcon boiler. It WILL cost a lot more than what you've been quoted. Like maybe 2 to 3 times as much depending on what has to be done. You should see a 30% reduction in energy consumption with this retrofit. But 30% of nada is not a whole lot of money, so the economics depends on what your current annual energy consumption patterns are. (expectations)

    The cast iron vessel in your boiler will (should) out live all of us. 30 years ago, casting technology required a much thicker casting than they do today, so it is quite robust, and assuming that it hasn't seen much fresh water induction, or thermal stress, it will last forever.

    Burner technology has changed fairly significantly in the last 33 years. You might be able to purchase a burner replacement kit that will reduce your energy consumption, and should slide right into place. Personally, I'd stick with the standing pilot. They have yet to come out with a good, reliable spark ignition module, and keeping a flame lit in the box keeps the spiders and moisture at bay.

    If you keep your current heat source, replace the burner, and re-pipe it to reflect current recommendations, replace the pump with a variable speed pump, and install a simple outdoor reset controller, you should be able to realize a 15 to 20% reduction with a higher R.O.I. than the complete replacement with a modcon boiler.

    If everything (boiler vessel) goes to hell in a hand basket, most, if not all improvements you will be making can be applied to the conventional replacement boiler.

    So, now you see the options. You need to do some minor math homework, and see what fits your budget and wishes, wants and needs.

    Quite honestly, and I know NOTHING about your situation, but money spent on legitimate energy conservation efforts will SIGNIFICANTLY increase your comfort and reduce your utility bills, and show the best return on the investment.

    As they say in the solar thermal biz, "Insulate before you Insolate"

    Did I miss anything (other than the required biannual service requirements for the newer equipment)?


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