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hydronic heater problem

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  • hydronic heater problem

    I have a wierd one, I installed a new water pump on the water heater with a check valve and replaced both gate vales , cir pump pumps water though to the in door coil after I purge the air out of the lines. seems to be working fine. I go inside a run the kitchen sink hot side to check for air bubbles. I notice the pump temp starts to lower and the pump not moveing water anymore. I open the hose bib near the pump and have intermitten air and water comming out. Purge more air and water and it works until I open a inside tap then it starts again more air. Somone has removed the expansion tank years ago , customers says the hydronic heater worked fine until I installed a new water heater. Wheres the air comming frome ? Need help.

  • #2
    Re: hydronic heater problem

    What type of heater is it? Many hydronic units have built in check valves and pumps that can cause problems.

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    • #3
      Re: hydronic heater problem

      Not sure what brand water coil is in the ceiling, going back next week again , will check. I thought the heater coil was just a water coil in and out as there is a built in check valve in the pump assembly. Found out they had 3 different plumbers working on the downstairs condo. Hard to find out what they did. Kitchen faucet that is 40 ft, from the water heater and takes about 4 minutes to get hot water to the faucet. Its got copper pipeing. Still trying to figure out where the air is commong from ?

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      • #4
        Re: hydronic heater problem

        4 minutes for 40 feet? that's a huge amount of time. sounds like a restriction some place. or a cross connection. if there is a severe restriction and the pump cavitates air will be stripped from the water. what did the impeller of the last pump look like? pits, cracks, holes? is there a mineral buildup someplace?
        ~~

        ... it was plumbed by Ray Charles and his helper Stevie Wonder

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        • #5
          Re: hydronic heater problem

          The coil may have an auto air vent nearby. If the pump moves water fast enough past it the vent can draw IN air. Doesn't happen often but I've seen it.

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          • #6
            Re: hydronic heater problem

            Originally posted by plumberscrack View Post
            The coil may have an auto air vent nearby. If the pump moves water fast enough past it the vent can draw IN air. Doesn't happen often but I've seen it.
            good catch. also, if there is no expansion tank - if there is a leak the water leaks out, the leak hole or an autovent can let air in.
            ~~

            ... it was plumbed by Ray Charles and his helper Stevie Wonder

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            • #7
              Re: hydronic heater problem

              Thanks for the replys guys . that some good ideals to check ( auto vent ). I was told the fan coil has a hose bib in the ceiling to connect a hose and bleed off air as the coil is higher than the water heater and pump. I am going back Tuesday to figure it out, I hope. I'll post what I find. Thanks, sewer rat

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              • #8
                Re: hydronic heater problem

                Maybe I am reading this wrong...Something else to consider. You have a hot water coil in an air handler, right. Get a hose and purge the water out of the coil to a bucket st in the tub or outside. This way you will be able to see the air bubbles. Make sure the heater is nice and hot to help get the entrained air out easier. These types of coils take a while to bleed out.

                The pump, I hate integral checks. By any chance is there another spring type check somewhere? These little pumps cannot overcome those restrictions. I would either rip the check out of the pump with needle nose pliers and add a wye swing check or get a new pump with the same check. What is the pressure just before and just after the pump?....may be easier to check amps if you have to add tees at this point. This will help tell you if there is something up within the pump.
                AllurePlumbing.com
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                • #9
                  Re: hydronic heater problem

                  Originally posted by Plumber Punky View Post
                  4 minutes for 40 feet? that's a huge amount of time. sounds like a restriction some place. or a cross connection. if there is a severe restriction and the pump cavitates air will be stripped from the water. what did the impeller of the last pump look like? pits, cracks, holes? is there a mineral buildup someplace?
                  I did see lots of mineral and lime buildup in the old gate valve near the pump. I'll tear the pump down and check it. THANKS

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