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temp. drop overnight w/my indirect water heater

iz Member Posts: 10
I recently installed a new mod-con boiler (viessmann vitodens 200) and an paired it with an indirect hot water heater (triangle tube SMART).  My observation over the last few nights (outside temperature ranging from 45-58F) is that my hot water tank temperature is dropping about 8-10F overnight (8 hours).  I have the tank set at the boiler for 140F.  the tank sometimes reaches 144F as the pumps run for a time period after the boiler gas supply shuts off.  this morning the tank read 135F (a 9F drop in temperature).  This seams to be a high rate of loss but not sure.  can someone chime in and let me know your thoughts?

some criteria:

location of hot water heater is in the basement with the boiler.  the basement is unheated (but right now the temp down there is approx. 65F....gets colder during winter months). 



  • Gordan
    Gordan Member Posts: 891
    Can you post a picture of the piping around the indirect?

    Is it insulated?

    Much of the loss could be through the piping, rather than the indirect itself. Even so, 1/2 - 1 F / hr seems to be within common specifications for indirects.
  • CMadatMe
    CMadatMe Member Posts: 3,086
    edited September 2012
    Domestic Hot Water

    Is factory set to shut down at 10:00 at night until 5:30 in the morning. You need to change the DHW time program. Boiler also goes into reduced temp mode. When you push the moon/thermometer what temp is it reading? Factory default is freeze protection..You need to read the operating and user information manual..


    There was an error rendering this rich post.

  • iz
    iz Member Posts: 10

    I found in the specs that the heat loss is about 1 degree per hour which would indicate the temp drop I'm experiencing is about normal. I know the boiler will create DHW on a schedule, that's what I want. I don't want it to turn on in the middle of the night when I won't be using hot water. Initially thought the temp drop was high but it's not.
  • Zman
    Zman Member Posts: 7,573

    Be sure to insulate your piping. It is also helpful to pipe heat traps and or check valves. Keep in mind your sensor is only reading one specific spot in your tank. The reading will change when the circulator turns off and the tank stabilizes.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
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