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Check valve adventures...

TomatoTomato Member Posts: 9
When this high efficiency hydronic heat and DHW-coil boiler system was initially installed, the domestic hot water would become suddenly ice cold for a few seconds while taking a shower. The boiler was cycling off because of the heat exchanger temperature. A stainless-steel insulated 20 gallon tank was added between the boiler and the domestic hot water line to temper the cold pulses. Ah, bliss. And the teens loved the infinite hot showers. Of course, every night the water in the tank with cool off and we would have to run hot water in order to heat it up again.
A hydronic circulator pump was connected to the stainless – steel tank with a rising-plug or piston type check valve between the pump and domestic cold water supply line to the boiler. The pump was controlled by an aquastat which was sensing the temperature in the insulated stainless – steel tank. This worked very well for many years. Then the check valve failed.
When the valve was replaced, the carbon steel pin which acted as a guide for the piston was found to have corroded away. This obviously was a poor design choice because it was a very small amount of wet carbin-steel in electrical contact with a very large amount of brass. The same thing happened with the replacement check valve.
Discussing this with a manufacturer of the valve, we found that this type of valve was not designed for potable water (lead eek) and therefore it should not have been installed in the first place. A swing check valve was installed in its place because it was impossible to find a potable water rated rising plug check valve.
After that, the swing check valve would chatter constantly whenever hot water was being used. In hopes of improving the installation, the check valve was moved further downstream from the pump to avoid turbulence. That did not help.
A normally closed solenoid valve (controlled by the same aquastat as the circulating pump) was installed in the same pipe. The chattering stopped as long as the pump was not running. However, as you can imagine, when the stainless – steel tank got cold and hot water was being used the valve would chatter.
Subsequently, the swing check valve was replaced with a spring-loaded disc check valve. The chattering was somewhat less noticeable but still present.
Thank you for reading this far.
Can you recommend a solution to the chattering?
The https://photos.app.goo.gl/QYBY3VQ7YwSUX8XF8 sketch illustrates the schematic layout of piping. Controls, and safeties are not shown.
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Comments

  • STEVEusaPASTEVEusaPA Member Posts: 2,441
    You can post attachments directly here. How about a make/model of all components?
    steve
  • HVACNUTHVACNUT Member Posts: 1,729
    > @Tomato said:
    >
    > When the valve was replaced, the carbon steel pin which acted as a guide for the piston was found to have corroded away. This obviously was a poor design choice because it was a very small amount of wet carbin-steel in electrical contact with a very large amount of brass.

    ???? Electrical contact with who????

    Which circulator is used?
    The Taco 006 has been a trooper for years.

    The Internal Flow Check (what you call a piston) itself is offered by most circulator manufacturers for the light residential stuff.
    I believe the 006 IFC has the check valve in the volute. Just like everything else, they dont last forever.

    After a few attempts over many years, the teens having to basically deplete the tank in order to get hot water, the correct piping and wiring of an Aquabooster has been known longer than since you first started having insufficient hot water.

    Check figure 2 in the manual. That's the way to do it.
  • TomatoTomato Member Posts: 9
    Gosh, I should have proofread twice... When this high efficiency hydronic heat and DHW-coil boiler system was initially installed, while taking a shower, the domestic hot water would become suddenly ice cold for a few seconds. The boiler was cycling off because of the quickly rising heat exchanger temperature.
    A stainless-steel insulated 20 gallon tank was added between the boiler and the domestic hot water line to temper the cold pulses. Ah, bliss. And the teens loved the infinite hot showers. Of course, every night the water in the tank would cool off and we would have to run hot water in order to heat it up again before morning showers.
    A hydronic circulator pump was then connected to the stainless–steel tank with a rising-plug or piston-type check valve between the pump and domestic cold water supply line to the boiler. The pump was controlled by an aquastat which was sensing the temperature in the insulated stainless–steel tank. This worked very well for many years. Then the check valve failed.
    When the valve was replaced, the carbon steel pin which acted as a guide for the piston was found to have corroded away. This obviously was a poor design choice because it was a very small amount of wet carbon-steel in electrical contact with a very large amount of brass. The same failure happened with the replacement check valve.
    Discussing this failure mode with a manufacturer of the valve, we found that this type of valve was not designed for potable water (lead eek) and therefore it should not have been installed in the first place. A swing check valve was installed in its place because it was impossible to find a potable water rated rising plug check valve in one-half inch.
    After that, the swing check valve would chatter constantly whenever hot water was being used. In hopes of improving the installation, the check valve was moved further downstream from the pump to avoid turbulence. That did not help.
    A normally closed solenoid valve (controlled by the same aquastat as the circulating pump) was installed in the same pipe. The chattering stopped as long as the pump was not running. However, as you can imagine, when the stainless–steel tank got cold enough to start the circulation, and hot water was being used, the valve would chatter.
    Subsequently, the swing check valve was replaced with a spring-loaded disc check valve. The chattering was somewhat less noticeable but still present.
    Thank you for reading this far.
    Can you recommend a solution to the chattering?
    The https://photos.app.goo.gl/QYBY3VQ7YwSUX8XF8 sketch illustrates the schematic layout of piping. Controls, and safeties are not shown.
  • TomatoTomato Member Posts: 9
    @STEVEusaPA,
    Attachments are not working with my Android 8.0.0 Samsung galaxy Note 8. Nothing happens.
    @HVACNUT,
    1. Electrical contact = steel pin is pressed into the brass/bronze valve body makes it a good electrical connection for galvanic corrosion. The small steel pin is doomed with the aeration of the potable water.
    2. Taco 006-B4
    3. The original check valve was a https://encrypted-tbn2.gstatic.com/shopping?q=tbn:ANd9GcSQlkRK2VI6pJmajaN8B-LrZxzpeiQCkhP51R2sN2nGif6yP7S1eSYPZrZUj4MCUHQgGIGAjeaH&usqp=CAE Watts hydronic check.
    4. I think that figure 2 looks like my sketch, only much nicer.
    5. The instructions above Figure 2 say "NOTE: The check valve can often be noisy and cause
    reduced supplv pressures.". So they don't have a solution to the chattering problem.

    I think that the solution is out there somewhere - Scully. (Fox Mulder) https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQhjkr6DGpKizfRVE2u7rRNjjbsOOhghzgahOHfZlMclQpR3w
  • HVACNUTHVACNUT Member Posts: 1,729
    Other than an EK water heater, it has a 006 IFC, a standard Aquabooster usually has a swing check. I dont think I've ever responded to a call for a chattering noise from a swing check. Stuck, yes. Chattering, no.
    Again, the figure 2 diagram is tried and true.

    BTW, theres no such thing as a high efficiency boiler with a tankless coil. You're better off with an indirect.
  • TomatoTomato Member Posts: 9
    @HVACNUT What is the definition of the the boiler which I have? It is a MZ25S.
  • HVACNUTHVACNUT Member Posts: 1,729
    Well I had to Google that one and apparently apologies are in order, albeit a little back handed.
    In your very first sentence you said "high efficiency hydronic heat and DHW- coil boiler system". I thought it was a standard atmospheric boiler with a tankless coil.
    What you have is a Combi, so now I have go back and read it all over again.
    Your killing me!
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