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Will a downstream 30A fuse will always blow before an upstream 100A fuse?

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  1. brandonbreon is offline Junior Member Pro Subscriber
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    Will a downstream 30A fuse will always blow before an upstream 100A fuse?

    A downstream 30A fuse will always blow before an upstream 100A fuse.

    False was the answer. Why is this? The article included essentially stated that the 30A fuse will always blow first.

    http://www.cooperindustries.com/cont...ow_to_Read.pdf

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    Quote Originally Posted by brandonbreon View Post
    A downstream 30A fuse will always blow before an upstream 100A fuse.

    False was the answer. Why is this? The article included essentially stated that the 30A fuse will always blow first.

    http://www.cooperindustries.com/cont...ow_to_Read.pdf
    The 30A will always blow first when there is between more than 30 amps and less than 100 amps. However, when there is more than 100 amps going downstream (Let's say 150 amps), then the 100A fuse would blow first before it gets to the downstream 30A fuse. Hope this answers your question.

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  5. gchoquette is offline Junior Member Pro Subscriber
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    Quote Originally Posted by brandonbreon View Post
    A downstream 30A fuse will always blow before an upstream 100A fuse.

    False was the answer. Why is this?
    If the 30 amp fuse is a slow blow type and the 100 amp is fast blow, then when the current exceeds 100 amp, it is possible that the 100 amp will blow first.

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