Upgrade to 120 amp service without rewiring?

Discussion in 'Electrical Forum discussion & Blog' started by mckern, Aug 5, 2008.

  1. mckern

    mckern New Member

    Messages:
    30
    I'm afraid I don't know enough about this subject to write an understandable question, so please forgive incorrect terms, etc.

    I own a condo in a 6 unit building with Federal Pacific Electric panels/breakers that we are planning to replace this fall. We are also considering upgrading to 120 amp service at the same time. According to the board, this upgrade would include "redistributing" the load so that running a hair dryer and AC (for example) at the same time won't trip a breaker. Also, all of this work is to be done at the breaker boxes--there is no need to do any rewiring within individual units. Based on my extremely limited knowledge of this subject, I don't understand how this could work.

    Re the existing setup--my breaker box appears to have two 30 amp breakers (which are connected/function as one) and three 20 amp breakers. However, only two of the 20 amp breakers are actually being used (I've mapped the power in my unit). I've always assumed that this meant that there were only 2 "paths" through my place--having replaced or repaired about a third of the switches and outlets, I've never worked on something that was the "end of the line."

    Obviously, there is room in the breaker box to upgrade to 120, but how could the load be redistributed to other breakers without doing some rewiring within my unit? Is my assumption about one path per breaker wrong? Does this sound like a misunderstanding/miscommunication regarding what the electrician said?

    Thank you
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,824
    Location:
    New England
    The sum of the individual breakers in your panel is NOT (usually, anyways) the amount of available power. The sum usually exceeds the total power available. The CB that is ganged is probably for an electric range. The others are for the rest of the things, and two 20A circuits is pretty substandard by today's standards. In today's codes you would need a bunch more, assuming you have a kitchen and bathroom - a kitchen requires several just for counter outlets, not counting appliances, and a bathroom requires an individual circuit. This leaves the rest of the unit lacking. This would exceed the current quantity installed, and would likely require major rewiring to accomplish. Depending on how much work is performed, and your state and local jurisdictions, you are probably grandfathered, but could open up a can of worms trying to bring things up to current codes when you start changing things.

    The determining factor is what is the size of the supply cable that feeds your panel and what size breaker or fuse feeds the entire panel. The fuse or CB are to protect the wiring, and even with say 60A coming in, you could have 100A or more CB branches. Each circuit must have the proper sized wire. Most circuits are not all being utilized at the same time, but if they are then the main would blow to protect that wiring, even though an indivual branch did not exceed its capacity. This is why the individual branch amp total often exceeds the main breaker. If you total anticipated use is bigger than that available through the main feed, you then need to upgrade it. Until that is exceeded, you can add branch circuits as needed. Clear as mud?
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,311
    Location:
    Cave Creek, Arizona
    circuits

    Unless there are dedicated wires back to the panel box from the outlets they intend to split off, which would create their own code situations, then there is no way it can be done without adding circuit wires. Whether that can be done without opening the walls in the unit depends on the physical layout of the unit, but logic says it cannot happen.
  4. Billy_Bob

    Billy_Bob In the Trades

    Messages:
    422
    It could be that currently there are several wires going back to the main panel, but some are connected in that area to the same breaker. If this is the case, they could connect each wire to its own breaker.

    Or it could be that the people on the "board" do not quite understand all this and there was a "misunderstanding / miscommunication" with the electrician.

    So the question for the electrician is: Is each wire going to the panel currently on its own breaker? If this is the case, then new wires would need to be run to offload some of the circuits.

    Sometimes you can just run one or two wires to things which use a lot of electricity, then this offloads the other things on those circuits. An easy one for example is if you have a window A/C. Can run a new wire to this on an outside wall.
  5. mckern

    mckern New Member

    Messages:
    30
    Thank you for the detailed responses and suggestions.

    Re Sometimes you can just run one or two wires to things which use a lot of electricity, then this offloads the other things on those circuits. An easy one for example is if you have a window A/C. Can run a new wire to this on an outside wall.

    This sounds like a good approach for us--most of the heavy use appliances are on outside walls.​

    Or it could be that the people on the board do not quite understand all this and there was a "misunderstanding/miscommunication" with the electrician.

    I don't think my neighbors would object if I said that this is not a particularly house-savvy group. Based on what I've learned here, perhaps the electrician said that he could incorporate the upgrade to 120 amp when he replaced the panels/breaker boxes--implying that the owners of each unit would take things from there (at their own expense)--but the implication was lost in the translation. ​

    RE Unless there are dedicated wires back to the panel box from the outlets they intend to split off... and It could be that currently there are several wires going back to the main panel, but some are connected in that area to the same breaker... and associated code issues--

    Would this arrangement interfere with the breaker's ability to detect an overloaded circuit?​

    Somewhere between the issues associated with the FPE panels/electrical service upgrade; intermittent water pressure problems caused by corroding galvanized pipes; deferred maintenance issues regarding the steam heating system; (not to mention the current housing market) I've lost sight of the reason that home ownership is considered part of the "American Dream."
  6. Billy_Bob

    Billy_Bob In the Trades

    Messages:
    422
    No, you could have 2 wires going to the breaker panel area, then connected together along with a connection to the breaker. And that breaker would be the correct size for each wire. And would work normally. Not likely this was done, but possible.
  7. Alectrician

    Alectrician DIY Senior Member

    Messages:
    689
    .......Yes
  8. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    When an "expert", such as the electrician who is expecting to do the work, is explaning a problem and solution to non-expert owners it can be confusing and at some times intentionally misleading.

    When there is a lot of money involved it is often a good idea to get an independent "expert" who knows that he will not be considered for the job (and who will be paid a fee) to assess the proposal of the "expert" who is bidding the job.

    The alternative is to get quotes from at least 3 suppliers who are legitimate competitors for the job.
  9. mckern

    mckern New Member

    Messages:
    30
    Based on what I've learned here, I've emailed my concerns to the person who is responsible for arranging a another estimate. I'm hoping to see a better explanation of what is to be done.

    Thanks to all for taking the time to respond--you've been very helpful.

    Bridget
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