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What thermal fuse do I need.

Discussion in 'General Electronics Discussion' started by renerelire, Feb 10, 2021.

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  1. renerelire


    Feb 8, 2021
    Hi !
    I need to replace a thermal fuse (I know what causes the fuse to burnt), but I'm not sure what to buy. For instance, I found some that said on it : "250V". Is that ok for a 120V appliance?

    Electric Hot Plate
    Model : SB-01
    1500W, 120V, 69Hz

    What it is written on the original thermal fuse:
    G A 4 0 0
    TF 216C
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Using a 250 V fuse in a 120 V circuit is o.k., just not vice versa.
    Sure? I find G4A00 type fuses. The one you have is most likely a 216 °C type. See this datasheet.
    ratstar likes this.
  3. renerelire


    Feb 8, 2021
    Thanks Haral Kapp!
    I don't know what to do whit the datasheet.:D
    So, I just need to know the degree, witch is 216C, and the Volts can be 120V or 250V ?
    How many Amps does it needs ? 15A? As 1500W / 120V = 12.5A ?
    I there a side (a direction) I need to solder it ?
  4. ratstar


    Aug 20, 2018
    The amps has to do with the rest of the circuit as well, I think you measure the resistance- and that will tell you how much amps goes through. (I think thats partially wrong tho...)
  5. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    From the datasheet:
    Fuses have no directionality, solder it any which way.
  6. Bluejets


    Oct 5, 2014
    Careful there, need to shunt the heat with needle nose pliers or the like otherwise end up destroying the new one.
    Most are crimped in place.
    Harald Kapp likes this.
  7. renerelire


    Feb 8, 2021
    Thanks to all, but I still don't know what I must use. :)
    Since my voltage is 120V, I can use a 15 amps fuse with 250V if I don't find a 150V one ?
  8. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Of course you can. The higher voltage rating signifies that the fuse can safely interrupt a 250 V line. It will then also be safe on a 120 V line. I stated that already in post #2.
    You never replied to my question about the part number being GA400 as per your original post but me finding only G400A types. The G400A, the datasheet of which I also linked in post #2, is good for 15A @ 120 V.
  9. renerelire


    Feb 8, 2021
    I thought that the G400 data sheet was just explanation about the type of the fuse (for me type means "sort, category") and I said that I didn't know what to do whit it. I think my English is not good enough for this topic.
    Is there something I have to do to mark this thread as closed ?
    Thanks anyway :)
  10. flippineck


    Sep 8, 2013
    Looks like the outer case will remain live after operation if connected one way, but not if connected the other way round. Always wondered what was inside these.
  11. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    No. The main question is: is the old fuse really GA400 as you stated in your post , or is that a typo and the fuse really reads G400A?
    If the fuse reads G400A, then according to the datasheet and my post #2 and detailed in #8 it is a 216 °C thermal fuse, rated 15 A at 120 V.

    I always wonder what it is with the (anglo-saxon?) way of insisting on that distinction between live and neutral when it comes to devices with a cable and plug. That may be a suitable way of looking at appliances that are installed permanently when the correct attachment to live and neutral can be verified. Whenever there is a cord and plug, there are at least two reasons not to rely on this distinction but rather treat both wires as if they were potentially live:
    1. If the plug isn't coded for direction of insertion (as is the case with many plugs following European standards, but also e.g. American two-pronged plugs), it is a 50/50 chance to predict which terminal will be live and which one will be neutral. So for safety reasons both have to be treated as potentially live.
    2. Even if you use coded plugs (as e.g. when an earth terminal is used as in America or GB), you can never be certain that the outlet is wired correctly. If live and neutral are swapped within the outlet, the device will still work fine, but the assumed neutral will be live. So for safety reasons even in this case both wires should be treated as potentially live.
  12. shrtrnd


    Jan 15, 2010
    In support of what Harald said about treating both wires as potentially live:
    Assumedly licensed electricians here in the US wire outlets to the correct standard.
    But a lot of do-it-yourself homeowners here replace outlets in their houses (and probably elsewhere, at work and etc...)
    without regard to hot or neutral wires. As Harald said, the device will work no matter which way the outlet is wired,
    It is unwise to ASSUME live or neutral wires because you can never be sure who did what to the outlet.
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