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    harvestnet's Avatar
    harvestnet Posts: 1, Reputation: 1
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    #1

    Jul 24, 2010, 03:39 PM
    Can a 20 amp fuse be use on 14 gauge knob & tube wire for airconditioner?
    Can a 20 amp fuse be use on 14 gauge knob & tube wire for air conditioner? The 15 amp fuse breaker pops after use for an hour or two?
    Missouri Bound's Avatar
    Missouri Bound Posts: 1,532, Reputation: 94
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    #2

    Jul 24, 2010, 03:45 PM

    NO! 14ga wire requires 15 amp protection, not 20 amp. Over-fusing a circuit could very easily lead to wiring overheating, and that can cause an electrical fire. Try eliminating other loads from that circuit, or run a new circuit with the proper wire and ampacity.
    ma0641's Avatar
    ma0641 Posts: 15,675, Reputation: 1012
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    #3

    Jul 24, 2010, 05:32 PM

    Noting that it is knob and tube tells me you have a very old house. Insulation breaks down, wire connections get oxidized. How many watts does the AC draw, it should be on the device plate? 15 Amps may be satisfactory for the AC depending on the wattage but you may have other devices on the tlne too. Do not put a 20 Amp breaker in.
    vandallen's Avatar
    vandallen Posts: 11, Reputation: 0
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    #4

    May 14, 2013, 11:27 AM
    You should use 12 gauge wire.
    Stratmando's Avatar
    Stratmando Posts: 11,188, Reputation: 508
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    #5

    May 14, 2013, 12:08 PM
    All above is good advice. The least you shold do is a dedicated 20 amp circuit using #12's as mentioned.
    It is cheaper than replacing everything(fire). The voltage was likely dropping as well, which is not good for the AC.
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
    Electrical & Lighting Expert
    		  
    #6

    May 14, 2013, 01:35 PM
    You should use 12 gauge wire.
    Was this that important that you needed to make this suggestion nearly three years after the OP posted?

    Besides, it's old knob and tube. I have a feeling it is already in place.
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