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Selecting MCB
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<blockquote data-quote="tark" data-source="post: 480164" data-attributes="member: 31362"><p>There is a 6mm2 aluminium cable connected with a 4mm2 copper cable in a radial configuration. They are both buried in masonry, their total length is ~10m. I cannot think of any correction factors (no thermal insulation, no increased ambient temp etc.).</p><p></p><p>1. Can I use a 32A MCB to power that cable? From what I understand, 32A is slightly more than it should be, but is it safe?</p><p></p><p>2. Will those cables get extremely hot (like 70C) under full load of 32A?</p><p></p><p>3. Will those cables overheat and possibly catch fire if overload occurs? For example, at 32A x 1.1 = 35A MCB will not trip, at 32A x 1.45 = 46A it will take up to 1 hour to trip. Can those cables handle 46A for 1 hour?</p><p></p><p>4. And one not related to the topic question: Am I right to think that 2.5mm2 copper cable that hangs in the free air can handle 27A * 1.45 = 39A for up to 1 hour without insulation melting given there are no correction factors? It looks like quite a lot of power for such small sized cable. Can Wago 221 connectors that are rated at 32A also withstand 46A for up to 1 hour?</p></blockquote><p></p>
[QUOTE="tark, post: 480164, member: 31362"] There is a 6mm2 aluminium cable connected with a 4mm2 copper cable in a radial configuration. They are both buried in masonry, their total length is ~10m. I cannot think of any correction factors (no thermal insulation, no increased ambient temp etc.). 1. Can I use a 32A MCB to power that cable? From what I understand, 32A is slightly more than it should be, but is it safe? 2. Will those cables get extremely hot (like 70C) under full load of 32A? 3. Will those cables overheat and possibly catch fire if overload occurs? For example, at 32A x 1.1 = 35A MCB will not trip, at 32A x 1.45 = 46A it will take up to 1 hour to trip. Can those cables handle 46A for 1 hour? 4. And one not related to the topic question: Am I right to think that 2.5mm2 copper cable that hangs in the free air can handle 27A * 1.45 = 39A for up to 1 hour without insulation melting given there are no correction factors? It looks like quite a lot of power for such small sized cable. Can Wago 221 connectors that are rated at 32A also withstand 46A for up to 1 hour? [/QUOTE]
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