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Lowering water temps on Viessmann vitogas

jimjim Posts: 68Member ✭✭
Hello

I have a Vitogas 100 with one heating circuit and 2 zones. i have gone to constant circ. Rooms are still too warm. I have vitotronic 200 control with ODR. I have turned the curve down to .08 the water temp is still 133 degrees. Outside temp right now is 37. Does not seem to go lower when turning curve down. Is there a setting or code that reduces minimum water temp. I am trying to get rooms down to 69 but they are staying at 73 or 74. Have also reset the odr damped temp to read every 60 min. Any suggestions.

Thanks

Jim
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Comments

  • sdcsdc Posts: 12Member
    non condenser

    Isn't the vitogas none condensing? If it is the boiler coding card sets a minimum water temp. to save the boiler from condensing. You may needs to add a mixing valve station.
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  • furnacefigher15furnacefigher15 Posts: 470Member
    Shut the pump off

    Why not shut the pumps off and have them turn on when heat is needed? Like the old boiler probably did?



    Not familiar with viessmann controls, but sounds like the same way buderus does likes to do it.



    Makes no sense to run heat when its not needed.
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  • ChrisChris Posts: 2,869Member
    Normal Room Temp

    What is the normal room temp set for? You need to adjust the shift not just the slope. Shift is set to 0 from the factory. Drop it to -3 and let it run that way for 24hrs and see if that works for you. Got to find your sweet spot.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
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  • jimjim Posts: 68Member ✭✭
    Normal Room Temp

    Thanks Chris



    Normal room temp is set at 68. I also found that the installer set the electronic low temp for 133. Called viessmann they suggested i set the low temp at factory default of 68.



    Jim
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  • jimjim Posts: 68Member ✭✭
    Normal Room Temp

    Thanks Chris



    Normal room temp is set at 68. I also found that the installer set the electronic low temp for 133. Called viessmann they suggested i set the low temp at factory default of 68.



    Jim
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  • ChrisChris Posts: 2,869Member
    Min Temp

    Yes set it back. He basically bottomed out the curve at 133.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
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  • Jean-David BeyerJean-David Beyer Posts: 2,467Member ✭✭✭
    Minimum water temperature.

    You cannot go by my numbers, because I have a different boiler and probably different radiation. Also, my insulation and windows may be different from yours. I have two zones, one radiant at grade slab, and one with fin-tube baseboard that is deliberately oversized. (With my boiler, I can control the reset curve separately for each zone.) But they may give an indication of what you might wish to try.



    I heat the house to 69F inside and the design day temperature here is 14F.



    For the radiant zone, my minimum supply temperature is 75F and it starts to increase only when it gets below 50F outside, reaching a maximum of 120F when it gets to 6F outside.



    For the baseboard zone, the minimum supply temperature is 110F and it starts to increase only when it is 52F outside and gets to 134F when it is 6F outside.



    I do not run the circulators continuously; the thermostats turn them on and off. But I have set the reset curves so that below about 50F outside, they run longer and longer as the outside temperature drops. When it is really cold outside, I have seen the radiant zone run 18 hours straight.
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  • croydoncorgicroydoncorgi Posts: 83Member
    Be careful! Condensation causes corrosion

    As far as I can see (Vitogas models don't come to the UK market) this is a cast-iron boiler which should NOT be allowed to condense.  In other words, the flue gas temperature needs to stay above 135F or so.  Return temperature must be kept high enough to ensure this is maintained.  If your FLOW temperature is as low as 133, you're at serious risk of wrecking the heat-exchanger
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  • ChrisChris Posts: 2,869Member
    Not So

    As long as he has the right stainless vent such as "Security Chimmney" and a drip tee no problem with the condensate. Good point though and a question that I should have asked.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
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  • jimjim Posts: 68Member ✭✭
    Viessmann

    I called technical support at Viessmann. They told me to lower the electronic temp to the factory default of 68 degrees. Is this going to cause a problem?

    Thanks
    · ·
  • GordanGordan Posts: 891Member ✭✭
    Wouldn't condensation on the heat exchanger still be an issue?

    Of course, with proper piping (thermal bypass) it should be completely possible to have the boiler run at a higher temperature and the system run at a lower temperature.
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  • jimjim Posts: 68Member ✭✭
    viessman vitoga

    Spoke with another tech support person at Viessmann and shared your thoughts and suggestions. They advised me to set electronic low temp to 104. The system has one heat circuit and two zones along with a Viessmann DHW and ODR. They suggested that I have my contractor install a KW2 mixing valve on heat circuit 2. Then the Vitogas 100 can run at whatever temps and condensing will not be a problem. Does that sound correct. By the way the folks on this board and Viessmann are so helpful.

    Thanks again for taking the time to offer your suggestions.
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  • ChrisChris Posts: 2,869Member
    Emmitters

    You never told us what the emmitters are in the 2 zones. Do you have a need for a 2 temp system?
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
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  • Paul PolletsPaul Pollets Posts: 2,832Member ✭✭✭
    Continuous Circulation

    The mixing valve circuit (Circuit B) in the boiler computer and Pump Control Module(PCM), is only used when a 4-way mixing valve and actuator is installed for a RFH (or low temp) circuit. The "A" Circuit controls the high temp, or in your case, the baseboard zone. To get continuous circulation, wire the pump into the A circuit terminals on the PCM. I advise my customers not to use zone valves, which decrease efficiency and stop constant circulation. My systems use wall panel radiators and TRV's, not zone valves. TRV's can be installed on BB, but it's not as easy. If the BB is piped in series, TRV's won't work. I also prefer a "smart" pump (Grundfos Alpha or Taco equal) for the heating circuit. Especially when zoning is present.
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