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Thread: Rewiring Knob and Tube in Attic

  1. #1
    DIY Member arfeller's Avatar
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    Default Rewiring Knob and Tube in Attic

    Greetings,

    I am purchasing a home that was built in 1922 which has Knob and tube wiring in the attic.

    1. The House has updated 200 amp service with breaker box (a little small, 20 1" slots)
    2. Has open unfinished basement and nice 2' crawlspace. All other knob and tube has been replaced.
    3. When the other knob and tube was replaced, they did not redo the circuits. I will be rewiring the rest of the house after the knob and tube is replaced.

    So... my question is. All the knob and tube in the attic goes to ceiling lights and the switches. My intention is to rewire all the knob and tube for these ceiling lights and put that on 1-2 circuits

    Is it reasonable to take this approach rather then try to incorporate the ceiling lights into the circuits of each room and outlets?

    3 Bedroom, 1 Bath, 1300 ft2 home.
    If all the ceiling lights were on at the same time ~1500 watts ->12.5 amps
    Also there is bathroom fan, stovetop fan, and ceiling fan. I would put on seperate circuit.

    So two 15 amp circuits to replace the knob and tube.

    Comments?
    Last edited by arfeller; 08-25-2007 at 09:29 PM.

  2. #2
    Engineer Furd's Avatar
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    Is it reasonable to take this approach rather then try to incorporate the ceiling lights into the circuits of each room and outlet?
    I prefer that receptacles and lighting in a room are on separate circuits. This way if you need to work on the receptacle circuit you still have lights and if you need to work on the lighting circuit you may connect a portable lamp to the receptacle circuit.

    I would use at least two independent circuits, more is always better.

    The House has updated 200 amp service with breaker box (a little small, 20 1" slots)
    You may be able to use "two-circuit" breakers in your panel which would allow for two circuits in a one-inch space. This is the easiest and least expensive fix.

  3. #3
    Electrician Chris75's Avatar
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    Do a load calculation for the required # of circuits, 3 watts per sq/ft.,

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    DIY Member arfeller's Avatar
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    Thank you all for the responses and Help!

    Quote Originally Posted by Chris75
    Do a load calculation for the required # of circuits, 3 watts per sq/ft.,
    Ok, so here is the calculation

    1300 ft2 * (3 watt/ft2) /120 volts = 32.5 amps

    This is just for ceiling lighting calculation? Or for whole house including outlets?

  5. #5
    Electrician Chris75's Avatar
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    Quote Originally Posted by arfeller
    Thank you all for the responses and Help!



    Ok, so here is the calculation

    1300 ft2 * (3 watt/ft2) /120 volts = 32.5 amps

    This is just for ceiling lighting calculation? Or for whole house including outlets?

    The 3 watts per sq.ft includes receptacles and lighting, (except recess lights and the required bath room receptacle circuit... ) so if you divide 32.5 by 15 you get 2.16, so you would need three 15amp circuits... or two 20 amp circuits...


    You can do what you want with these circuits, but I tend to try and spread them out equally...

  6. #6

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    Are you including the basement in 1300 SF calculation? Will that be included as well?

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    DIY Member arfeller's Avatar
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    Quote Originally Posted by xd2005
    Are you including the basement in 1300 SF calculation? Will that be included as well?

    Good question, it is not included in the 1300 ft2. The unfinished (pretty rough at the moment) basement is ~600 ft2 and would have dedicated 20 amp circuit.

  8. #8
    Electrician Chris75's Avatar
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    Quote Originally Posted by arfeller
    Good question, it is not included in the 1300 ft2. The unfinished (pretty rough at the moment) basement is ~600 ft2 and would have dedicated 20 amp circuit.

    The 3 watts per sq.ft. is for livable sq. footage only... the nec only requires 1 gfi protected receptacle in the basement, unless of course you finish it...

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    Jack of all trades frenchie's Avatar
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    Who upgraded to 200 amp and left you with such a small panel? That must be frustrating... if you start using the double-pole single-slot breakers, careful you don't overfill the panel. They're only rated for a certain number of poles. If you need more spaces than the panel is rated for, consider a sub-panel.
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  10. #10
    DIY Member arfeller's Avatar
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    Quote Originally Posted by frenchie
    Who upgraded to 200 amp and left you with such a small panel? That must be frustrating... if you start using the double-pole single-slot breakers, careful you don't overfill the panel. They're only rated for a certain number of poles. If you need more spaces than the panel is rated for, consider a sub-panel.
    I'm not sure who, but i would like to have a discussion with them

    I am currently looking at a siemens 30 1" slot, 40 circuit panel. Seriously debating whether or not to make the change.

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