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Thread: Compact flourescent bulbs

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    Default Compact flourescent bulbs

    I currently have 2 standard style lights that have (2) 60 watt bulbs each. I want to install 10 recessed lights to replace the standard fixtures. I was worried about having to install a new circuit but the electrician says that I can use 60 watt rated compact flourescent bulbs that only use 14 watts each. He says that I would only be using 140 total watts instead of the 240 watts that I am using now. Is this true?

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    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by cathead View Post
    I currently have 2 standard style lights that have (2) 60 watt bulbs each. I want to install 10 recessed lights to replace the standard fixtures. I was worried about having to install a new circuit but the electrician says that I can use 60 watt rated compact flourescent bulbs that only use 14 watts each. He says that I would only be using 140 total watts instead of the 240 watts that I am using now. Is this true?
    No, this is not true.
    When dealing with incandescent bulbs it would be correct to just add the total wattage to determine the size of the circuit but with florescent bulbs the total of the ballasts, transformers, or autotransformers used to power the bulb must be used.

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    Plumber jimbo's Avatar
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    It is approximately true. Rough comparison for simlar light output is to divide the incandescent bulb by 4. So a 14/15 watt CFL is the replacement for a 60 watt. Now, the ballast circuits are not 100% efficent, but they are in the 80s or 90s, so your figures are in the ballpark.

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    would 10 recessed lights with the cfl's and 4 outlets with a plasma tv, stereo, dvd be too much for a 15 amp circuit. The builder of my home (1988) put the entire house on 13 circuits. I wish he would have spread it out a bit.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    The labels of each thing will say how much power they draw...it is simply a matter of adding it up. No circuit should be loaded more than about 75%. volts x amps = watts, so 15A x 120v x .75 = 1350. You'll want a good surge suppressor with noise filtration for your TV and other elecronics...some CFL's can produce a lot of electrical noise and you don't want it getting into the TV.
    Jim DeBruycker
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    Computer Systems Engineer jdoll42's Avatar
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    Quote Originally Posted by cathead View Post
    would 10 recessed lights with the cfl's and 4 outlets with a plasma tv, stereo, dvd be too much for a 15 amp circuit. The builder of my home (1988) put the entire house on 13 circuits. I wish he would have spread it out a bit.
    You may want to check your local codes. When I built my house, they said no more than 8 fixtures/outlets per circuit. If you are adding 10 cans plus outlets for your entertainment center, you might be violating some codes.

    Plus, if it were me, I'd be a bit scared anyway. What's to say you don't sell your house down the road and the new homeowner puts incandescent bulbs in those cans. They are probably rated for at least 75w bulbs anyway. Now all of a sudden you are pulling 750w + entertainment center on the circuit you designed for WAY less. Now imagine if they like it really bright and they put in 100w bulbs. Something's gotta give somewhere and it might not be pretty.....

    If it were me, I'd put a new 20A circuit in for the cans.

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    In the Trades Bob NH's Avatar
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    I would put the new 20 Amp circuit in for the entertainment center and let the cans live on the 15 Amp circuit.

    I see a lot of 1000 Watt surround sound systems operating off the DVD and TV. Add that to 350 to 500 Watts for a big TV and maybe a computer and you are pushing the limits for a 15 Amp circuit.

    I ran a 20 Amp Multiwire Branch Circuit (equivalent of 2 circuits) for my entertainment center when I was rewiring last year. That will take care of anything that shows up in my lifetime. The ceiling in the room below was open and I ran 4 THHN in a 1/2" PVC conduit.

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    Computer Programmer Bill Arden's Avatar
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    Quote Originally Posted by cathead View Post
    I want to install 10 recessed lights{snip} 60 watt rated compact fluorescent bulbs that only use 14 watts each.
    There is a problem in that I have found CF bulbs don't last very long when used in recessed lights.

    You would use less power for the same amount of light if you use 4 foot T9 lights.
    Important note Ė I donít know man made laws, just laws of physics
    Disclaimer: I'm a big fan of Darwin awards.

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    Plumber jimbo's Avatar
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    Like anything else, they are sensitive to heat, because they have electronic components. You are probably OK with 13's. but when you look at the 23 watt and up models, they often say to use base down or horizontal, but not base up.


    A better choice for ceilings are cans which are ballasted and accept the plug in PL bulbs. The heat is not a problem here, and also you do not run the risk that someone replaces all your 13 watters with 100 watt floods!

  10. #10

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    The CFL rating includes the ballast because it is in the base of the bulb. Other bulbs or tubes do not include the ballast because it is separate - in the fixture.

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    DIY Member arfeller's Avatar
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    It was my understanding that when performing load calculations you must look at the wattage the light fixture is rated for and not the light you intend to put inside.

    So, if the cans say "Max 75 Watt" then all the calculations should be done with that value.

    This would address the statements above about new owners not liking the CF and putting in incandescent.

    Anybody know if this is true?

  12. #12

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    you thing 13 circuits is bad my aunts house only has 2

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    In the Trades Bob NH's Avatar
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    Quote Originally Posted by arfeller View Post
    It was my understanding that when performing load calculations you must look at the wattage the light fixture is rated for and not the light you intend to put inside.

    So, if the cans say "Max 75 Watt" then all the calculations should be done with that value.

    This would address the statements above about new owners not liking the CF and putting in incandescent.

    Anybody know if this is true?
    The code 220.12 and Table 220.12 requires 3 watts per square foot for residential general lighting loads. Footnote a of Table 220.12 refers to 220.14(J) which says that in dwelling occupancies the specified lighting load includes the loads of general and other receptacle and lighting outlets specified in 220.14(J).

    Therefore, the circuits and feeders must be adequate to supply 3 watts per square foot for all lights and outlets, regardless of the rating of the general lighting fixtures.

    The often-stated "requirement" that the circuit may only be loaded to 80 percent of the amp-rating of the circuit is not correct. The only situation that requires derating of a general lighting and receptacle circuit is if the circuit supplies a continuous load where the maximum load is expected to the continue for 3 hours or more. In that case, the overcurrent device (the circuit breaker) and the wires must be rated for the sum of the non-continuous load and 125% of the continuous portion of the load.

    For example, one 15-amp circuit (1800 Watts) could permissibly serve all of the non-continuous lighting and general outlet loads in a 600 sq-ft room.

    Notwithstanding the requirements, I would never put a 600 sq-ft recreation room on a 15-amp circuit. If known loads are greater than 3 Watts per square foot it would be stupid to put in circuits that are too small or too few.

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