Old house, 100A fusebox, should we replace w. breakers?

Discussion in 'Electrical Forum discussion & Blog' started by capecod, Jan 12, 2012.

  1. capecod

    capecod New Member

    Messages:
    38
    Our house is about 60 years old, have 100A service, fuses.
    Its getting more difficult to purchase fuses, and we were thinking of changing to a new breaker box.
    We have 3 220v. appliances, stove, dryer, and water pump. And the rest is all 110v.
    We would have it done professionally, my husband used to do all our plumbing and elec work, but not any more at this age, and there are new rules and regs.

    Wondering if this is actually necessary, if the old fusebox is fine, and we have no plans to add to our house. Doesnt seem to be a safety issue, fuses blow when needed. Like when our cat chewed thru my router wire and shorted it out, the cat was OK. Blew the fuse but not the fur off the cat.
    Thank you.
  2. jwelectric

    jwelectric Electrical Contractor/Instructor

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    I am a firm believer in if it ain’t broke don’t fix it.

    Changing to Type “S” fuses might help the issue. Be sure to replace the fuse adaptor with the proper size according to the wire and this will help
  3. capecod

    capecod New Member

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    38
    Thank you, I think he has some screwed into the old sockets. Its the Knife/cartridge fuses that are hard to find now.
    The big ones that fit into the main fuse thingie are hard to find, and the fuse holder itself cracked one day when the power was whacky when a tree fell on the line and my husband yanked it out. He glued it together, but we could not find a replacement anywhere, Square D. was on the side of it.
    I did find one on ****, but they wanted $100 for it.
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Fuses have both good and bad points...CB are certainly easier to restore power with than finding an appropriate fuse in the dark. Today's homes like electrical appliances, and 100A may not be adequate. If you ever broke down and added an a/c unit or two to the thing, then you'd likely have problems.
  5. hj

    hj Moderator & Master Plumber Staff Member

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    I am not sure where you are buying fuses, but I have never had any problem locating either the screw in or cartridge fuses. They do make "circuit breaker" screw in fuses with a button you push when it trips.
  6. capecod

    capecod New Member

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    We do occasionally use an AC, but rarely do we need one with our constant seabreezes here in summer.
    We do use a dehumidifier most all summer in our cellar.
    Reason its difficult to find fuses, is we are a small town, but could easily get the cartridge fuses in Hyannis.

    Thank you all for this advice, perhaps this summer we will go ahead and upgrade everything. We did get one estimate for about $700 so far.
  7. hj

    hj Moderator & Master Plumber Staff Member

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    quote; We did get one estimate for about $700 so far.

    Wow! That would just about cover the cost of the material and driving to your house. (Just a little bit of exageration there)
  8. capecod

    capecod New Member

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    38
    We used to do all our own stuff, so have not a clue of costs are now.
    Had a new breaker box put in our camp in Maine for under $200 by a friend, so is the $700 bad or good?
    This is MA, not Maine.
  9. drick

    drick In the Trades

    Messages:
    392
    It depends on what you are getting for $700. If it is a full upgrade from the meter to a new decent quality 200A panel with at least 30 breaker spaces, all circuits properly labeled, with arc fault breakers installed where appropriate, and the backer board for the panel replaced if needed than yes its a good deal. We wouldn't touch it for less than $1K.

    And remember, its a good deal only if you are receiving a good installation.

    I would also recommend replacement, if only for the reason a fuse box is red flag for home inspectors. The money you spend you will likely recover partially if not fully when you sell the property.

    -rick
  10. capecod

    capecod New Member

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    38
    Thank you! This really answers my question. Everything is old, and would be nice to upgrade the whole thing.
    We dont plan selling, the kids will inherit this and the one in Maine.

    We also would like to have our generator wired in, as it is now, we plug it in to a special plug after we pull the main, and turn on only selected circuits.
  11. jwelectric

    jwelectric Electrical Contractor/Instructor

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    One thing to keep in mind is that a service change doses nothing for the interior wiring. When all is said and done you still have old wiring and devices with a pretty panel.
  12. capecod

    capecod New Member

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    38
    Very true, but a lot of that wiring has been updated.
  13. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Something else to bear in mind is that a non-time delay cartridge fuse will blow within 6 cycles or 1/60 of a second but an inverse time breaker can carry 6 times its rated current for up to two minutes. The fuse will blow when loaded to 100 amps in less than a second but a 100 amp breaker can let through 600 amps for as long as two minutes but in most cases when loaded to 600 amps will trip in a few seconds, (between 2 and 30 seconds)

    A non-time delay fuse is 6 times safer than a breaker. A type “S†or time delay fuse is 4 times safer than a breaker when it comes to the amount of time it takes to open them.

    It has been my experience over the past 44 plus years that those who had a service upgrade changing from fuses to breakers without addressing All the issues of the interior wiring of their homes have ended up having more problems in the long run.

    Please understand that I am not trying to talk you into or out of something that you desire to have done, I just want you to be aware of the facts. The price you quoted, if the service is being changed for the same size is about a third of my price. I have a hard time believing that the job can be properly done at that price but then again I have never done work in your area nor have I looked at the job. I will say this, it is about what I include in my bid for labor and expenses for a service change.

    Also be aware when you decide to hire someone to do this work one of the most important questions you must ask is about their liability insurance. Should something go wrong and they don’t have liability insurance you might be stuck with a larger bill than what was bid.

    Also for the sake of your homeowners insurance be sure that the job is permitted and inspected.
  14. capecod

    capecod New Member

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    Excellent info! Thank you, I am soooooo glad I found this forum, we started with the plumbing one, as we were replacing a toilet and needed to research a good replacement.

    Your first paragraph is extremely interesting, I had read something about this years ago, and thats one reason that he stuck with fuses.

    My husband said that they used fuses on the ships for some reason, will have to ask him the reason for that(by the way, he is a retired marine engineer), and knows a lot about DC.
    I am learning so much here! From now on, before we do anything elec or plumbing, will run it by you all first.

    We will certainly have to think about this, perhaps we are better off leaving our fuse box the way it is, its always worked perfectly.
  15. jwelectric

    jwelectric Electrical Contractor/Instructor

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    I made a mistake in that paragraph. It should have said one tenth not one sixtieth
  16. DonL

    DonL Banned

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    How did You come up with these figures ?
  17. capecod

    capecod New Member

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    Im reading it now carefully, a lot of bad stuff can happen in 120 seconds, I sure would rather have a good old fashioned fuse blow almost instantaneously than hang around with a circuit breaker for minutes. A lot can happen, like stuff getting fried.
    My brother's house got hit by lightning and his neighbour's got hit worse. Took out everything in the house, but just the dishwasher in my brother's house. Both houses have circuit breakers.
  18. DonL

    DonL Banned

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    I would not take that figure to the bank just yet.

    JW may just need new batteries in his calculator.
  19. jwelectric

    jwelectric Electrical Contractor/Instructor

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    It is a calculus math problem but there are many sites on the internet where this information can be found. I have a book by Cooper Bussmann at school that I use in the class for fuses. I also use the Square “D” trip curve booklet for breakers.

    Fuses and breakers are used to protect electric motors along with running overload protection that is either internal or separate of the motor. Motors in AC and heat pumps will have running overload that is internal the motor and auto reset while motors like garbage disposals will have manual reset overloads.

    Look at your AC or heat pump and find the minimum circuit ampacity. This is used to size the circuit conductors.
    Now find the maximum fuse or HACR overcurrent device. This is what we use to size the fuse or breaker with.

    The overcurrent protective device will always be larger than the circuit conductor ampacity. The reason is because for the compressor to start it must overcome locked rotor ampacity.

    Looking at Table 430.248 of the NEC we can see that the running ampacity for a single phase 5 horse power motor at 240 volts is 28 amps. Table 430.52 says that the inverse time breaker (breakers sold at the supply house, HD, Lowe’s ect) is to be sized at 250% or a 70 amp breaker. Why? Because the breaker must hold until the locked rotor ampacity is over come and the motor reaches full speed.

    Look at Table 430.251 and we will find that this motor will have a locked rotor ampacity that is six times that of the running ampacity or amperage of 168 amps. The breaker must hold this inrush current until the motor reaches full speed. Under load this can take several seconds.

    Using this same rule of thumb we can apply it to the breakers in our home. It will not work out to the exact number as the calculus math but will be real close.
    This same method is used in drivers education. Take the speed of your car and divide by 2 then add it back to the speed to see how many feet per second you are traveling. Example; At 60 miles per hour divided by two is 30, added back to 60 equals 90 feet per second but calculus figures to 88 feet per second.
    A non-time delay fuse on the other hand is a lot quicker to open.

    Edited to add:

    In most cases during a fault condition most breakers will open between 120 and 180 cycles or two to three seconds.

    While teaching at DCC we did a test using a GE 20 amp breaker and a very large rheostat. We loaded the breaker to 30 amps for over two minutes before it opened. We loaded the same breaker to 120 amps and it took just under 10 seconds but over 9 seconds to open. (The watch had 10.2 seconds but we subtracted the reaction time to operate the stop watch)

    We did the same test using Square “D” home line and Siemens breaker with similar results.
    Last edited: Jan 14, 2012
  20. capecod

    capecod New Member

    Messages:
    38
    Maybe the figures arent exact, but I just asked my husband about the difference between CBs and fuses, and he said that it is true. Fuses are pretty much instantaneous unless they are DC and have huge voltages going thru them, then they can fail. But that doesn't pertain to us here with house AC.
    There is a delay with CBs, guess it depends on the current? I dont understand everything my husband was saying, it gets a bit complex.
    I did find this, and it quite explains a lot about what we are wondering, is it OK to put a link to some other site here?
    Hope so, as I did find this interesting,
    http://www.at-ease.ca/articles/fuses-versus-circuit-breakers
    Im sure learning a lot today.

    Edit to add this; I just read the previous post, yes, my husband can do that kind of math, but its a bit beyond me. Thanks for the details. Learning fast, I am.
    Last edited by a moderator: Jan 14, 2012
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