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Thread: Replacing old fuse box questions

  1. #1
    DIY Junior Member paulmars's Avatar
    Join Date
    Aug 2010

    Default Replacing old fuse box questions

    The 2 mains are both 60amp fuses. The power company wont tell me what amperage service I have, They say they dont know. How can I tell? I could just use 60a mains in the new breaker box, but if my
    service supports more, I'd like to get larger. I've never blown a main.

    Also, all 115vac circuits are 15a, is that normal for a house built in 1954? Reason I ask is because I
    have 12awg wires coming out of the box and someone said I could replace all those 15s with 20s.

    Oh yea, the reason I am changeing this is because:
    1-a sub panel was added to the house before I bought it in 1986. It has breakers for the central AC
    and water heater. The AC breaker is loose and sometimes sparks when it cycles on. The bar that the
    breakers attaches to is damaged. It has always made me uncomfortable.

    2-Since 1986 I have spent maybe 100$ in fuses. Less so these last few years since I cut two existing
    circuits in 1/2 and added two more fuses. There were two empty places on the box which is now full.

    3-I want to add another circuit.

    4-I cant use the clothes washer spin cycle when the central heater is cycled on, otherwise a 15a fuse
    pops. The AC is 230, the fan and heater are 115.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    what gauge wire is feeding the panel? That would dictate the main. If you tell the power company, they could tell you based on that. They don't always use the same rules on their supply as you have to inside the house.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    Test, Don't Guess! cacher_chick's Avatar
    Join Date
    Jan 2008
    Land of Cheese


    The wire gauge and type, the rating of the insulation, and even how it is run also must all be factored in when determining if a circuit can be protected at 20A vs 15A.

    A 100 amp main breaker panel is the smallest that most suppliers here carry any more. New houses are all getting 200A or bigger.
    I've been told that insurance companies won't even insure a house with a fuse panel around here anymore.

    As Jim said, the gauge and type of wire installed from the weatherhead to the meter & panel is the common deciding factor in determining the size of the main. Here, the lines from the pole to the weatherhead are the power company's responsibility.

  4. #4


    Sounds like you have quite a mess.

    First DO NOT start replacing fuses/breakers with higher amperage fuses/breakers! Just because you have a 12 Gauge wire in the panel you cannot assume you can put a 20A breaker on it. You need to know exactly what you are doing and the entire circuit must be inspected before you can conclude that upgrading the amperage on a circuit is ok. Yes, possibly some of those circuits could be 20A, but don't just blindly swap out 15A fuses/breakers for 20A.

    Second, replacing your main panel is not a DIY job. Permits must be pulled and the power company must be contacted. The meter must be pulled to replace the main panel. Where I live a homeowner cannot cut the tag and pull a meter themselves, however the power company will do it for you for $50 if you have the permits. They will also inspect the service laterals at that time and upgrade them if necessary. Where you live could be totally different though.


  5. #5
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona


    quote; Where I live a homeowner cannot cut the tag and pull a meter themselves, however the power company will do it for you for $50 if you have the permits.

    In fact, here, it can lead to a $15,000.00 fine if you cut the tag for any reason. I once tapped into a customer's panel to feed power to a new meter socket/panel for an addition, and the power company was getting ready to issue a citation until they saw the tap was after the other meter. The fuse/circuit breaker is to protect the wires, so 20 amp breakers with #12 wire is appropriate, in most cases.

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