Fuse Blowing Expansion

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Old 12-21-13, 06:39 PM
Gen
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Fuse Blowing Expansion

Hello,

I have a house, friends house that is, and he has a certain fuse that keeps blowing because the kids turn on too many portable heaters at once. Info on this from another source stated roughly......if the fuse keeps blowing and you keep resetting it....essentially what happens is that the wire to that circuit heats up slightly before the fuse blows, then cools off.....so there's expansion and contraction from the heating and cooling. Over time this can cause the breaker wire contact, or any other connection on that circuit to become loose as a result.
Can anyone confirm or comment on this???
 
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Old 12-21-13, 07:02 PM
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The fuse, or breaker, if properly sized will trip before the wire is damaged. Yes, some heating occurs, but the breaker/fuse is supposed to trip. Now, with that said, the load must be reduced, as constant tripping of the breaker can affect its ability to remain on under moderate loads. Things wear out. Why do they have so many portable heaters? Do it mathematically using Ohm's law. Voltage x potential amperage will give you the maximum wattage for a certain circuit. For instance, 120 volts x 15 amps will limit you to 1800 watts. Check the wattage on the heaters and you'll be surprised what load they were putting on the circuit.
 
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Old 12-21-13, 07:13 PM
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"as constant tripping of the breaker can affect its ability to remain on under moderate loads." Well OK I see what you're saying, and they are working on properly correcting the loads. Meanwhile, any comments about the expansion/contraction theory?
 
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Old 12-21-13, 07:36 PM
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In theory, the breaker will trip before the wire has a chance to heat up. Theory. You will find that receptacles with wires backstabbed, have a propensity of heating up and the wires losing their perfect contact. We always recommend removing backstabbed wires to the screws for a more solid connection. The expansion and contraction you are mentioning should be at a minimum, PROVIDED, the wire is sized correctly, placed on the screws of the switch/receptacles, and the breakers are sized to the wire.

A 14 gauge wire connected to a 20 amp breaker, and loaded to where it will trip the breaker can cause the 14 gauge wire to become the fuse, heat up and cause a fire. Thus the importance of proper sizing of wire to breaker.
 
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Old 12-21-13, 08:00 PM
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By far one of the biggest causes of fires we respond to in the winter are caused by space heaters and old wiring.
 
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Old 12-21-13, 09:09 PM
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That would be mostly electric space heaters I'd bet. Gas space heaters are relatively safe in old houses if you don't try to seal it up like a new house. There should never be more then one electric space heater per circuit and they should never be used as the primary heat source.
 
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Old 12-21-13, 09:48 PM
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Meanwhile, any comments about the expansion/contraction theory?
If the circuit is constantly run near it's tripping point then yes.... the wires do heat up and cool and there is expansion and contraction going on. There are a lot of things going on... high current across a loose terminal will heatup faster causing the connector to fatigue to the point of failure.

Your "friend" should rectify his problem before it heats up to the point of no return.
 
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Old 12-22-13, 08:34 AM
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I agree, adding hard-wired supplemental heat or a new circuit or two is definitely the right answer. Consistently tripping breakers/fuses is definitely not something I'd want in my house. While they should always protect the system and prevent a fire, I wouldn't want to stress the system unnecessarily. Who knows when something might not work as it should and cause a much bigger issue?
 
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Old 12-22-13, 04:04 PM
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Excellent thanks for all the replies, I understand the issue at a deeper level now
 
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