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  • Water coming out of overflow on boiler....

    I have a Peerless boiler MCB-097. Its about 15 years old and today for the first time about 2 gallons of water came out of the overflow valve into a bucket.
    The valve is set for 30psi and when I turned on the heat to test it the internal water temp went from 170 to 210 and the pressure went from 12 psi to about 29psi and thats when the water started to come out of the valve.
    The expansion take is the old style. It looks like a mini 55 gallon drum located above the boiler attached to the ceiling. I assume the issue might be that the tank needs to be drained. Is this correct?
    The water line in to the tank has a valve to turn the water off so it can't flow into the tank and then their is a drain valve on the other end. What is the procedure to drain this tank? Do I turn off the intake and just open the drain? Do I do it when the water is hot or cold?
    Thanks in advance,
    Joe

  • #2
    Re: Water coming out of overflow on boiler....

    the usual suspect here is the expansion tank, which is most likley full of water. Next cause would be the feeder, which should be set at or near 15lbs. And finally, if you have a tankless coil in the boiler it may have a hole in it.

    Test #1, Expansion tank. Shut off boiler. Shut off water feed. Drain pressure off boiler. (just the pressure not the whole boiler) If you have a diaphragm type expansion tank, slowly unscrew it. If you get it down and it weighs a lot, it's no good, replace it.

    Test #2, Water Feeder. Shut off valve to feeder. Drain enough water from the boiler to bring the pressure to 15 lbs. Wait and see if the pressure stays steady. If it does, replace the feeder. (watch if for about 15 minutes)

    Test #3, Tankless coil. Shut off valve to tankless coil. Drain boiler pressure to 15lbs. Wait and see if pressure satys steady. (15 minutes again, maybe a bit longer) if it does the tankless coil needs to be replaced.
    sigpic

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    • #3
      Re: Water coming out of overflow on boiler....

      There are a number of potential problems that could be wrong.
      I have to say this...this is a boiler, not a faucet or simple pilot light on a water heater.
      If you misdiagnose the problem online and replace the expansion tank, when in fact it's a problem with the gas valve, aquastat, leaking autofeed or any number of other things, you could create a dangerous situation.
      If it turns out to be an indirect leaking back into the boiler, you could be cooking & showering in stagnant water.
      210 is way too high for a hydronic boiler, the relief shouldn't kick off at less than 30.
      If this is a steam boiler, you shouldn't get anywhere near 30 psi under normal operating conditions.
      I might suggest you have a professional take a look.

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      • #4
        Re: Water coming out of overflow on boiler....

        Well I drained the tank till it was empty then I turned on the heat and watched the gauges. The psi was steady at about 12psi (no more leaks from the overflow valve) and the temp went from 120 to 210. What should the normal temp and pressure be???

        This is as far as I am willing to play with it and I will have a professional take a look.

        Comment


        • #5
          Re: Water coming out of overflow on boiler....

          Boiling temp for water is 212, 210 is a problem on hydronic.

          Comment


          • #6
            Re: Water coming out of overflow on boiler....

            Originally posted by DIYourselfer View Post
            Well I drained the tank till it was empty then I turned on the heat and watched the gauges. The psi was steady at about 12psi (no more leaks from the overflow valve) and the temp went from 120 to 210. What should the normal temp and pressure be???

            This is as far as I am willing to play with it and I will have a professional take a look.
            Good idea...boilers are fairly complex.
            Water Heater Reviews & Water Heater Information

            Comment


            • #7
              Re: Water coming out of overflow on boiler....

              Good idea on having a professional check it over. As for temp settings if it's a hot water heating boiler it should run about 160F startup and 180F stop. The limit should be set to do a shutdown at 200F.

              10-15 PSI operating pressure is normal on a residential or light commercial hot water heating boiler.

              As for shutting off at 210F that's just too high and the limit switch may be what's really shutting it off. After cool down then it resets. I recommend changing to a manual reset limit so it it does overheat you'll know it. If there's no load on it and it had been running for some time and did a shut down at close to 180F residual heat may end up with closer to 200F after a few minutes. If you are running above 200F the thermostat needs to be set lower.

              Something you may want to have checked is the accuracy of the thermometer and pressure gauge.

              If you pressure now stays close to 12 PSI then more than likely your expansion tank was water logged. The non bladder type need to be drained or some compressed air added from time to time. Draining it out and flushing out the crud once a year is a good thing to do. In nice weather (please have a pro do this) it's a good idea to drain the boiler a bit with the fill valve open to help keep it from getting lots of rust and sludge in the bottom.

              If you sometime replace your expansion tank, ask about having a sight glass tube installed on the new one so you can see about how much water is in it.

              Special note: Some residential heating boilers were installed without a true overheat limit switch. Be sure to have that checked and added if needed.

              Remember; SAFETY Above everything.
              Last edited by Woussko; 03-04-2008, 01:09 AM.

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              • #8
                Re: Water coming out of overflow on boiler....

                Water boils at a higher temperature when it's under pressure, so though you probably don't need to operate the boiler at 210 it's not a safety issue so much as a fuel economy issue. Pressure should be between 12 and 15 lbs, so that's normal also.
                sigpic

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                • #9
                  Re: Water coming out of overflow on boiler....

                  I shut off the power to the boiler and took the cover off the relay box so I could turn the hi temp limit which is set at 190 down to about 160.

                  Here is a picture of the limiter:

                  http://s251.photobucket.com/albums/g...=IMG_0013a.jpg

                  http://s251.photobucket.com/albums/g...=IMG_0010a.jpg

                  I can't seem to move the pointer off 190. Do I push the dial down away from the pointer and then turn the dial to the new setting or do I somehow pull the pointer away from the dial and turn the pointer. I don't want to break anything but I can't get these 2 pieces apart from each other.

                  Any advice?

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                  • #10
                    Re: Water coming out of overflow on boiler....

                    hey! what do you know! a honeywell L8148E aquastat! i am looking forward to the replies you get to your inquiry.
                    there's a solution to every problem.....you just have to be willing to find it.

                    Comment


                    • #11
                      Re: Water coming out of overflow on boiler....

                      I'm not all here yet from being sick.... Post removed .... I was thinking more of the controls on an older commercial boiler. I need to remember this is residential.

                      More important please call in a good HVAC tech to check everything. Don't risk the safety of your family and/or property.
                      Attached Files
                      Last edited by Woussko; 03-05-2008, 11:33 PM.

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                      • #12
                        Re: Water coming out of overflow on boiler....

                        The high limit is set a 180 which is about where it wants to be. I would leave it alone
                        sigpic

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                        • #13
                          Re: Water coming out of overflow on boiler....

                          i just went through this with my own 4 yr old slant fin hot water standing pilot boiler. the box you opened is the aquastat. it controls the operation of the boiler. it determines, among other things, how hot the water in the boiler can get and when the boiler should fire as the water cools down due to its giving up its heat as it circulates through the radiators or baseboards. the temperature wheel you photographed is used to set the upper end of the temperature range for the aquastat. if it is, as i suspect, a Honeywell L8148E, it has a fixed differential of 15 degrees between this upper limit and its "lower limit". this means that if the temp wheel is set at 180F, a call for heat from thermostats will cause the boiler to fire and the water will heat to 180F, assuming the boiler water temperature was below 165F when the call for heat from the thermostat was initiated. once 180F is reached, the burner will turn off but the circulator(s) may continue to operate, assuming a continued call for heat from a thermostat. the burner will not fire again until the water temperature reaches 165F (180-15=165F), again assuming a continued call for heat from a thermostat. so if you feel the water is being heated to much (210F in your 3/3/08 posting) and you want to save some money, lower the upper end of the water temperature range for the boiler. if you have only cast iron radiators, 165F would probably be high enough. if you have copper baseboard, i am told that 180-190F is preferred. to lower the upper end of the boiler water temperature, just turn the dial so the desired temperature is opposite the pointer shown in your first photo. that's all there is to it. there is no need to pry on anything to set the upper operating limit. i wouldn't attempt to adjust the high limit stop, which is what i think you were referring to, but this link is the owners manual.
                          http://customer.honeywell.com/techli...0s/60-2278.pdf

                          i think the prying referred to on page 12 is the high limit stop setting instruction.

                          i just spent the last hour cycling my boiler through a few operating cycles and confirmed that simply moving the temp. wheel, without prying the limit arm up, successfully changed the upper limit of the boiler's water temperature. and since it has a fixed differential between upper and lower operating temperature, adjusting the upper limit adjusts the operating temperature range of the boiler. just curious..the 210F mentioned in your previous post..is that the temp the burner shut down at or is that the temp after the boiler and circulator(s) stopped operating. i ask because the temp wheel in your first photo was set just below 190F. its at that temp the burner should shut down.

                          as always, comments appreciated.
                          there's a solution to every problem.....you just have to be willing to find it.

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                          • #14
                            Re: Water coming out of overflow on boiler....

                            LOL Finer,

                            You are becoming quite the expert on aquastats lately

                            See?, all you had to do was rotate the dial

                            Sometimes the instructions are there just to confuse you

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                            • #15
                              Re: Water coming out of overflow on boiler....

                              I think I said that about 12 times, but since I am a teacher, I'm used to nobody listening to me
                              sigpic

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