1957 Cottage Upgrade

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  #1  
Old 06-27-05, 08:34 AM
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1957 Cottage Upgrade

Here's the situation:

1957 home (724 sq.ft.) with a small electrical service. We will be adding about 200 sq.ft. and doing a complete gut and remodel of the existing kitchen and bath plus adding a laundry room.

Currently the house has only 2-20a circuits wired with early NM cable from a small breaker box directly below the meter. Obviously this is inadequate. All of the outlets and switches are designer style with a ground hole but with the old style NM can't possibly be grounded. The breaker box does have a ground but I have not yet been able to determine what it's connected to.

My plan is to have a 125a service installed which will feed the existing circuits plus a new subpanel located in a wall at the approximate center of the house. I plan to run a conduit from the main panel up to the attic so I can feed the new sub-panel. The total calculated load for the house is less than 80a but I assume I should have it connected with wires sufficient for 100-125 amps (#6 ?) All of the remodeled areas will have new circuits per code. Do I need to add outlets in the areas of the living and bedrooms that don't currently have enough outlets? For example, the living room is 12'x17' but only has 1 outlet on each wall and the bedrooms (11x14 and 10x10) only have outlets on 2 opposing walls. SD's are installed but they are just battery operated.

What can I (or must I) do about the ungrounded outlets and switches in the areas of the house that will not be remodeled?

Is the old NM even safe? It would not be easy to replace because it's almost all run thru the 2x4 stud walls. Very little wire is in the attic and the roof has a very low pitch so access to the exterior walls in the attic is difficult at best.

Last but not least - approximately what should I expect to pay an electrician to install the new service main and connect it to the new sub-panel plus reconnect the 2 existing circuits at the new main (San Diego)?
 
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  #2  
Old 06-27-05, 09:01 AM
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#6 isn't nearly enough for 125 amps.

First, calculate the expected load on the subpanel. That will tell you how many amps you need, and thus what size breaker you need in the main panel. This, plus the distance involved, will tell you what size wire you need to feed the subpanel. It seems unlikely that the subpanel needs access to the entire 125 amps. Some of the future needs can be wired from the new main panel.

You probably will not be required to bring the branch circuits in the existing unmodified parts of the house up to code, but check with your inspector to be sure.

If the old cable is in good condition and the insulation is not brittle, then it should still be safe (at least as safe as ungrounded circuits can be).

As to what to expect to pay, that's hard to say. Not only does it vary by area, but there are a lot of variables that depend on what we can't see from here. You're probably looking at somewhere between $1000 and $2000, give or take.
 
  #3  
Old 06-27-05, 09:33 AM
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Originally Posted by John Nelson
#6 isn't nearly enough for 125 amps.

First, calculate the expected load on the subpanel. That will tell you how many amps you need, and thus what size breaker you need in the main panel. This, plus the distance involved, will tell you what size wire you need to feed the subpanel. It seems unlikely that the subpanel needs access to the entire 125 amps. Some of the future needs can be wired from the new main panel.
Total load served by the sub-panel will be less than 10,000 watts.

2 small appliance ciircuits 1500 x 2 = 3000
1 laundry circuit 1500 x 1 = 1500
Dishwasher 1200
Disposal 1000
Basic Lighting & Recept's 1000 x 3 = 3000
------------------------------------------
9700

9700/230 = 42 amps

So I figure a 50 amp sub-panel would be perfectly fine. There will be some exterior loads which can be run from the main as well as the existing general use circuits in the house. I will only need about 8 new 20 amp circuits.

The Water Heater, Range, Space Heating and Clothes Dryer all all NG so there is no large electrical load requirement.
 
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