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Pressure drop with hot water demand

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  • HomerJSmith
    HomerJSmith Member Posts: 2,468
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    That's great, but I want to know what failed in the TurboMax, why there was a failure.
    dkoPalisandr
  • Palisandr
    Palisandr Member Posts: 30
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    That's great, but I want to know what failed in the TurboMax, why there was a failure.

    Yeah, I'd like to know that too. But all indication is that there was a communication between DHW and boiler HW circuits (constant need for water through PRV for HW circuit). There are two more observations once Turbomax was replaced with Vitocell:

    1. This still puzzling me: when a manometer was installed on the domestic water circuit with Turbomax we saw a large pressure drop when there was demand for hot water. Pressure will go down from 60 to ~30 psi instantly and then instantly recover to 60 once the hot water faucet are closed. Pressure stays stable when there is only cold water demand. That still happens with Vitocell.

    2. less calls for heat from Vitocell to the Triangle Tube boiler for sure (boiler does not fire up as often). Would be interesting to see how the gas bills will be affected.

    I guess don't buy Turbomax would be my advice: high price and doesn't deliver on the promises.
  • HomerJSmith
    HomerJSmith Member Posts: 2,468
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    This doesn't make any sense. If the domestic hot water supply drops when you turn on the kit faucet, I would suspect the thermosatic mixing valve isn't functioning correctly, especially so if the cold water supply had good pressure.

    What is perplexing is that the boiler pressure drops and then re-establishes itself. These two pressure gradients are separate, boiler and DHW, and there shouldn't be any interference between the two and can't be as it would be more than obvious.
    SuperTech
  • Palisandr
    Palisandr Member Posts: 30
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    This doesn't make any sense. If the domestic hot water supply drops when you turn on the kit faucet, I would suspect the thermosatic mixing valve isn't functioning correctly, especially so if the cold water supply had good pressure.

    What is perplexing is that the boiler pressure drops and then re-establishes itself. These two pressure gradients are separate, boiler and DHW, and there shouldn't be any interference between the two and can't be as it would be more than obvious.

    No thermostatic mixing valve is installed on the DHW. Vitocell's temperature probe is directly wired into triangle tube and the temperature is set to 120F.

  • dko
    dko Member Posts: 611
    edited April 2023
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    Was TurboMax involved at all in this? If that was a TurboMax near me and it was indeed some problem with the TurboMax itself, I can get it replaced and delivered under warranty the same day. It carries a 15 year residential warranty. Mileage may vary if you don't have TurboMax guys in your area, but just letting you know how strongly they stand by their warranty in a properly installed environment.

    Did the person who installed the Viessmann call TurboMax? Or simply did a tank change and hope it worked? I'm sure there was more explanation than him coming in and saying, "bad turbomax, good viessmann."

  • Palisandr
    Palisandr Member Posts: 30
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    dko said:

    Was TurboMax involved at all in this? If that was a TurboMax near me and it was indeed some problem with the TurboMax itself, I can get it replaced and delivered under warranty the same day. It carries a 15 year residential warranty. Mileage may vary if you don't have TurboMax guys in your area, but just letting you know how strongly they stand by their warranty.

    Did the person who installed the Viessmann call TurboMax? Or simply did a tank change and hope it worked? I'm sure there was more explanation than him coming in and saying, "bad turbomax, good viessmann."

    I am sure there is a rep in Denver metro. The tank we had only was carrying a 10 year warranty, which started to prorate on year 8 I believe. The guy who installed Viessman said that he called, but nobody replied from Turbomax. One problem was fixed for sure though with replacing the Turbomax - pressure in HW boiler supply no longer requires the PRV to be constantly open. Closed PRV maintains 20 psi pressure in boiler water supply contour on hot water demand. While with Turbomax closed PRV with hot water demand saw boiler hot water contour pressure dropping as a rock.
  • dko
    dko Member Posts: 611
    edited April 2023
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    10 year is for commercial installation now, is this a commercial location? Or it was possibly 10 way back in the day.
    Anyway, what's done is done. Can't really figure out what fixed what or what really happened now. I think that's what we were really looking to hone in on.

    But the real problem, you having a problem with your system, has been fixed and am very glad to hear.

    Could we get photos of the new install? See what changed if anything

    Thanks!

  • Palisandr
    Palisandr Member Posts: 30
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    Here is a movie illustrating the pressure behavior on DHW side (manometer is installed right before the tank on the cold supply line into Viessmann. In the garage I have a tap/mixer with separate valves for hot and cold lines. I was opening them alternatively.

    video start - no demand
    5 s - cold water valve ON
    10 s - cold water OFF
    15 s - hot water ON
    20 s - hot water OFF


    https://photos.app.goo.gl/JxffH4bwDSxq5bYg7
  • Palisandr
    Palisandr Member Posts: 30
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    dko said:

    10 year is for commercial installation now, is this a commercial location? Or it was possibly 10 way back in the day.
    Anyway, what's done is done. Can't really figure out what fixed what or what really happened now. I think that's what we were really looking to hone in on.

    But the real problem, you having a problem with your system, has been fixed and am very glad to hear.

    Could we get photos of the new install? See what changed if anything

    Thanks!


  • Palisandr
    Palisandr Member Posts: 30
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    dko said:

    10 year is for commercial installation now, is this a commercial location? Or it was possibly 10 way back in the day.
    Anyway, what's done is done. Can't really figure out what fixed what or what really happened now. I think that's what we were really looking to hone in on.

    But the real problem, you having a problem with your system, has been fixed and am very glad to hear.

    Could we get photos of the new install? See what changed if anything

    Thanks!



    dko
  • mattmia2
    mattmia2 Member Posts: 9,740
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    Look for something coming apart in or caught in the cold water shutoff valve or the check valve (i think that is a check valve at least). Could be the handle is somehow jammed in the cold water shutoff valve or the stem is not well connected to the ball.

    The part that was confusing is that you had 2 problems, you have some sort of restriction in the cold water supply and the coil in the turbomax was leaking so all the boiler pressure was leaving through the domestic hot water and there was no makeup water. This still doesn't explain why the boiler didn't overpresurize and blow off the relief valve when you turned the domestic hot water faucet off, the cold domestic water should have leaked through the coil and overpresurized the boiler.
    HomerJSmith
  • HomerJSmith
    HomerJSmith Member Posts: 2,468
    edited April 2023
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    Here is a movie illustrating the pressure behavior on DHW side (manometer is installed right before the tank on the cold supply line into Viessmann. In the garage I have a tap/mixer with separate valves for hot and cold lines. I was opening them alternatively.

    video start - no demand
    5 s - cold water valve ON
    10 s - cold water OFF
    15 s - hot water ON
    20 s - hot water OFF

    I looked at your video.

    Ok, so the gauge in your video is at 60 psi and when you turn on the water the gauge jumps up and then falls to 40 psi and when you turn off the water the gauge goes back to 60 psi,

    I think you have a pressure reducing valve on the house water supply from the street. I think Jamie Hall suggested this. It is sticking, mis-adjusted or failed. It could also be a partially closed valve (at the street or into the house) or crushed pipe.
    I think maybe you had two problems that was conflated into one problem which was confusing.

  • mattmia2
    mattmia2 Member Posts: 9,740
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    Here is a movie illustrating the pressure behavior on DHW side (manometer is installed right before the tank on the cold supply line into Viessmann. In the garage I have a tap/mixer with separate valves for hot and cold lines. I was opening them alternatively.

    video start - no demand
    5 s - cold water valve ON
    10 s - cold water OFF
    15 s - hot water ON
    20 s - hot water OFF

    I looked at your video.

    Ok, so the gauge in your video is at 60 psi and when you turn on the water the gauge jumps up and then falls to 40 psi and when you turn off the water the gauge goes back to 60 psi,

    I think you have a pressure reducing valve on the house water supply from the street. I think Jamie Hall suggested this. It is sticking, mis-adjusted or failed. It could also be a partially closed valve (at the street or into the house) or crushed pipe.
    I think maybe you had two problems that was conflated into one problem which was confusing.

    Does the pressure fall if you open a cold water faucet? Is your gauge before that check valve on the feed to the water heater (if it still exists)?

    HomerJSmith
  • HomerJSmith
    HomerJSmith Member Posts: 2,468
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    Does the pressure fall if you open a cold water faucet?

    I asked that question a while back and didn't get a definitive answer.
  • dko
    dko Member Posts: 611
    edited April 2023
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    Circled the gauge he is using in the video. It is after the check valve.


  • HomerJSmith
    HomerJSmith Member Posts: 2,468
    edited April 2023
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    dko, thanks for pointing that out. I was wondering where in hades that gauge was. The domestic sys pressure is 60 psi and the Ex-tank should be pressurized to 55 psi. What is happening, I think is that the tank which is set at 50 psi is compressed to street pressure 55 psi and when a hot water valve is opened a pressure drop occurs and the water in the Ex-tank coming out causes the gauge to jump up and then go to 40 psi. The drop to 40 psi is because of a faulty check valve or supply restriction some where in the cold water supply. This theory should affect the cold water supply, too, if the restriction is some where before the check valve.

    I wouldn't have used a Webstone valve where a simple tee would have been cheaper. You already have a ball valve on the Ex-tank. Putting a Webstone ball valve with drain where the red handled valve is would have been better piping.
  • Palisandr
    Palisandr Member Posts: 30
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    Does the pressure fall if you open a cold water faucet?

    I asked that question a while back and didn't get a definitive answer.
    I think the video gives a pretty definitive answer that the cold water demand does not affect pressure. Does it not?
  • HomerJSmith
    HomerJSmith Member Posts: 2,468
    edited April 2023
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    Well, hot water lines and cold water lines can travel different paths. What are you using to measure the pressure on the cold line? If you are using the gauge that you use for the hot line, you are not really measuring the pressure drop on the cold line even tho the gauge is on the cold line. When you open a cold water faucet, that water doesn't travel thru that hot circuit. I assume that the pressure stays at 55 psi when a cold faucet is opened, as it seems from the gauge. That would mean to me that there isn't anything in the cold water supply that is dropping the pressure. Therefore...

    Look to the check valve as the problem as everything before that valve is at 55 psi and the hot water circuit after the check valve drops to 40 psi when the hot faucet in the kitchen is opened. To verify that, put a gauge before the check valve and compare pressures or just replace the check valve with a spring check valve.

    Verify the Ex-tank air pressure to the house cold water pressure which is 55 psi. Of course, the Ex-tank's connection to the Vitrocell is screwed up even tho it does work as piped until you close the cold water feed valve to the Vitrocell.

    I would like to know what that banging and squeak is in your video. At about 5 sec there is a bang like a valve closing and then a squeak, then a rise in pressure, then a fall to 40 psi and then a rise back to 55 psi when the water is turned off. Use a mechanic's stethoscope that you can buy at any auto parts store which might help you locate the sounds.

    Is the banging at 5 sec coming from the Ex-tank or the check valve?

    There is a jump in pressure at 10 sec when the cold water is turned off. This can be the momentum of water hitting a sudden stop.

    Is the squeak coming from the faucet when turning off the cold valve at 9 sec? Sounds far away.

    Try this, shut off the red handled ball valve at the Ex-tank, without the boiler plugged in and go thru your video sequence again. What happens?



  • mattmia2
    mattmia2 Member Posts: 9,740
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    Palisandr said:

    Does the pressure fall if you open a cold water faucet?

    I asked that question a while back and didn't get a definitive answer.
    I think the video gives a pretty definitive answer that the cold water demand does not affect pressure. Does it not?
    Depends on if that is in fact a check valve or not and which side of it the gauge is on. If it is on the outlet of a check valve, if the cold water pressure drops with a cold water demand, the check valve will hold the pressure on the outlet while the pressure drops on the inlet.
    HomerJSmithSuperTech