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Rectifier fuse vs. dual element or time delay

zepfan
zepfan Member Posts: 412
in THE MAIN WALL

does anyone know what a rectifier fuse is, and can a dual element or time delay be used in it’s place even if only temporary? We have a panel pictured below that controls a large number of electric baseboard heaters. The panel has rectifier fuses in them, and four are bad. The issue is that we can not find these locally and I was planning on using 20 amp 600 volt time delay fuses, until we can get the rectifier type. All heaters are 240 volt. I know I would have to install a temporary fuse block as the existing type are bolt in. Any suggestions would be much appreciated. Thanks to all.

75814170577__EB482FE0-FC7A-497B-B3DD-84F1955D2B13.jpeg

Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 9,717

    I can't help you on this from experience, but to tell you that the fuses are probably protecting a circuit that has some sort of rectifier in it. Perhaps to change AC voltage to DC voltage. I would think that a standard fuse may blow prematurely if the inrush voltage spike of the circuit is excessive. A time delay may be a temporary alternative for now. I have a feeling that the standard and time delay or slow blow fuses are not designed for that application and may fail (blow) sooner that the proper fuse.

    I do not think the standard fuse or the slow blow fuse will damage the equipment it is protecting. I think it will just blow before it needs to. That said, you might want to take a good fuse and put it in the failed fuse location and hope that the temporary fuse will work in the place that you swiped the fuse from. the problem circuit may have more duty cycles and will cause the regular fuses to fail, while a circuit that did not have a blown fuse may have less duty cycles therefore the non rectifier fuse may last longer there.

    Just a thought,

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    zepfan
  • hot_rod
    hot_rod Member Posts: 23,816

    did you google that fuse number? Someone must have those on a shelf. Over night shipping if it is critical

    Might check for shorts or other issues that would cause the fuse to fail?

    IMG_9394.jpeg


    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    zepfan
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,848

    I googled "Simply Breakers" they say they have them in stock. Pricy. 24 of them are around 2k.

    Probably can find them elsewhere

    zepfan
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,848
    edited January 10

    Rectifier fuses are used in electrical systems to protect rectifiers from damage. They convert alternating current (AC) to direct current (DC) using diodes. Rectifier fuses prevent backflow of current, protecting the rectifier from reverse voltage and overcurrent conditions12345

    First time I ever herd of them.

    zepfan
  • 109A_5
    109A_5 Member Posts: 1,909
    edited January 10

    Hello zepfan,

    Rectifier fuses are often found on Thyristor (SCR, TRIAC) or IGBT type motor drives and heating equipment that basically works like a light dimmer or Variable Frequency Drives to control motors and/or heat output of resistive heaters. They provide better protection to the equipment.

    You probably can use another type of fuse temporally but if something bad happens it increases the chance of damage to the equipment. Why did the fuses blow in the first place ? Is there damaged equipment already ?

    looks like there is plenty of KAC-20 type fuses on eBay for much better prices than from normal vendors.

    Be safe, wear your PPE.

    image.png

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • mattmia2
    mattmia2 Member Posts: 11,145

    I'd check the heaters on the zones with blown fuses for shorts. Could be the semiconductors failed on those circuits too.

    zepfan
  • zepfan
    zepfan Member Posts: 412

    thanks to all that responded to this. I ended up ordering the rectifier fuses off of eBay (hopefully they are good) they cost a fraction of what I was quoted locally and the lead time was less.
    I went by the building today and could not find anything downstream of the fuse that was any type of an electronic device. From the the fuses they all go straight to a section of resistance heat. I don’t know why they used these specialty fuses. The only thing I can come up with is the panel is a Honeywell pre wired panel that is about 50 years old. Maybe they used those fuses to save room? Thanks to all

  • JDHW
    JDHW Member Posts: 83

    I think fuses to protect rectifiers or other semiconductors are quite fast. If you have a rectifier system powering heating elements there shouldn't be any big surge currents because there are no capacitors to store energy. The key parameter to look for is it it^2 rating of the fuse.

    john

  • Jamie Hall
    Jamie Hall Member Posts: 25,262

    You'd be surprised. The initial surge current into an electric heating element is very large indeed.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England

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