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Bosch Greenstar 151 propane

chuckB523
chuckB523 Member Posts: 5
in Gas Heating
I have a Bosch Greenstar combi The heats side works perfectly . Radiant heat. My domestic hot water shuts off while in the shower. It seems that it is only the shower and is only some times. When this happens the read out on the boiler climbs to 199F and then shuts its self off then the temp on the readout slowly returns to about 140F, with now hot water running. I have flushed with vinegar 30%. Any suggestions, I started thinking antiscald in the shower valve but how would that account for the rise in boiler display to 199F?

Comments

  • hot_rod
    hot_rod Member Posts: 23,408
    You might buy one of the delime kits like Whitlam, with the pump to circulate the cleaner for 1/2 hour or so. The vinegar may not be powerful enough?
    Maybe if you offer to babysit this plumber can help.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Big Ed_4
    Big Ed_4 Member Posts: 3,020
    There is a flow meter on the cold water inlet that may be bad . But I would first check the strainer just before the flow meter . There should have an external water filter on the cold inlet to protect the fine strainer .

    There was an error rendering this rich post.

  • chuckB523
    chuckB523 Member Posts: 5
    checked the strainer. is it possible that boiler side of the heat exchanger is gummed up? I will try to clean the dhw side again.
  • GGross
    GGross Member Posts: 1,295
    edited January 5
    When you flushed did you pump through the heat exchanger for about an hour?
  • chuckB523
    chuckB523 Member Posts: 5
    yes and the 30% vinegar turned greenish color. What do you think about the boiler side of the exchanger. could it get clogged with maybe excess solder or debris that might have been in the heating system, migrated to the exchanger? The tube coming out of the heat exchanger block maintains heat. When the event happens the display temp starts to rise to 199F and then shuts down causing the DHW to go full cold. This is usually started by running another hot water source while the shower is running. it only seems to happen in conjunction with the shower and it doesn't happen every time. I plan to re flush gain with as suggested, delime kits like Whitlam. Thank you for your help
  • dko
    dko Member Posts: 668
    edited January 6
    Is this a very low gpm shower? What kind of shower valve? When it only sometimes has an issue at the shower, is it when you are lowering the temperature?

    Next time this is happening, turn the hot water on full blast at the faucet next to the shower at the same time and see if it continues.

    edit: I see you did suspect the shower valve. it can explain the rise in temperature because the bosch has a pretty low turndown ratio and minimum fire of 36k btu. so the water will still be heated going at that rate no matter how low your demand and will continue to rise a bit after turning off until equilibrium. The bosch turns off with not enough flow demand, which your shower valve can be restricting.

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