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Viessmann Vitotronics 100 Fuse

Rob48xx
Rob48xx Member Posts: 26
in Oil Heating

I have a KW10B Vitotronic 100 control and there is a PCB Fuse on the board that blows out every so often. When it was installed brand new 3 years ago, it came with 5 spare fuses. This fuse is listed as a transformer fuse and with out it, the boiler seems to short cycle, going on and off and not adequately heating the home. My problem is the install company doesn't seem to know where to get replacements, Viessmann hasn't answered any Inquiries and there seems to be many models of that particular fuse available. The fuse is made by littel fuse and is labeled as 100mA/250v. T 374. When I look that up there seems to be like 20 different models of the T374 and what I'm worried about is getting the wrong time delay and it either biring too quickly or not fast enough allowing stray voltage spikes to reach and cause damage to the PCB. Viessmann sales finally answered me but they are not technical and provided a part # of 7837269. When I look it up on boston supply and others they show a glass fuse which is not what is bad. Anyone else have this problem with this PCB Fuse and know where to buy them?

Comments

  • GGross
    GGross Member Posts: 1,317

    the part number you listed comes up with a ceramic fuse from viessmann and appears to be the correct specification that you gave

    Rob48xx
  • GGross
    GGross Member Posts: 1,317

    It is number 94 on the breakdown, if your fuse is in a different location let me know which number and I can tell you the part number.

    viessfuse.JPG

    Rob48xx
  • Jamie Hall
    Jamie Hall Member Posts: 24,927

    And try Digikey if your regular suppliers can't come up with it.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Rob48xxmattmia2
  • Rob48xx
    Rob48xx Member Posts: 26
    edited September 17
    https://forum.heatinghelp.com/discussion/comment/1810679#Comment_1810679

    094 is correct. One of the manuals said it was 7837269. however when going to websites they show glass fuses. Here is what the fuse looks like and for scale its on a salt shaker.. I googled the littel fuse and there is like 97 types of the 374 fuse.

    20240712_155605.jpg

  • Rob48xx
    Rob48xx Member Posts: 26

    I'll take a look there too.didnt think about them.

  • Rob48xx
    Rob48xx Member Posts: 26

    https://m.littelfuse.com/search-results.aspx#q=374&first=20&t=PartsTab

  • Rob48xx
    Rob48xx Member Posts: 26

    Good news is I just came across a description of how the model # for the littel fuse is identified. 0374 is the model series, the next 4 is the Amp code in my case 100mAwould be 0100 abd the last 4 are packaging quantities. This in mind it seems I can narrow the list down from 97 to 5

  • mattmia2
    mattmia2 Member Posts: 11,004

    you need the one that is 100 ma and 250v. should find what is shorting and causing it to blow too

    GGross

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