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# how many fluorescent lights off on existing switch?

#1
08-15-05, 09:29 AM
JamesG
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how many fluorescent lights off on existing switch?

Hi, I have a light in my basement. Its just a junction box with a single incandescent light bulb. I had it changed it to a fluorescent light (big white box with two long bulbs - I don't know the terminology, it was done for me by a 'handyman'. He also spliced the wire to 2 other fluorescent 'boxes'.

I'm wondering is there a maximum # of 2 bulb fluorescent boxes that can branch off of one previous incandescent light bulb junction box?

Maybe the better question is, regardless of the fact that they would be on the same switch, how many regular incandescent lights or fluorescent lights can be attached to the same circuit assuming a new construction house.

Feel free to share with me the terminology because I feel pretty stupid right now

Regards,

James...

#2
08-15-05, 09:58 AM
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It all has to do with watts. A 15-amp circuit can provide up to 1800 watts, and a 20-amp circuit can provide up to 2400 watts. So it's just a matter of adding up all the watts currently on the circuit and subtracting from the circuit capacity. That gives you the number of watts you can add. Whether those watts are incandescent or fluorescent makes no difference, although you get more lumens per watt from fluorescents.

If there are receptacles on the circuit, it can be difficult to figure out how many watts to add for it. If there is something plugged in all the time, then you can just add the actual watts of that appliance. But if a receptacle is used for a variety of things, then you should probably add the largest one. For many receptacles, that largest load is often the vacuum cleaner. If there are multiple receptacles on the circuit, you of course don't need to plan for a vacuum cleaner to be connected to more than one of them at the same time (unless you're really a clean freak).

It's unusual to overload a circuit with lighting alone. Things plugged into receptacles are often the big power users on a circuit. Give a lot of respect to the power-hungry appliances such as hair dryers, vacuum cleaners, microwave ovens, space heaters, tanning beds, treadmills, etc. Each of these can easily use up the entire circuit capacity all by themselves.

#3
08-15-05, 10:17 AM
JamesG
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John, thanks for replying so quickly!

Basically it's an unfinished basement. There was 3 junction boxes with 3 incandescent fixtures. That's how it was when we moved in. We changed the 3 incandescents to 3 flourescent, and spliced in (without addin extra junction boxes) so that now there is 8 2-bulb fluorescent fixtures.

This circuit, as far as I know, only handles these lights (all controlled from the same switch at the top of the stairs).

So each bulb is 40w, so that means I can have 20 fixtures? wow

Thanks again,

James...

#4
08-15-05, 10:31 AM
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Join Date: Sep 2000
Location: United States
Posts: 18,497
as far as I know
That's not too comforting. You should map out everything in your house to see what circuit it is on. Shut off the breakers one at a time and check everything in the house to see what's dead. When you get done, do an audit to make sure that everything is on the list for one of the breakers.

#5
08-15-05, 11:20 AM
JamesG
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John, can power outlets be on the same circuit as the lights? If so, how much power drain would a standard PC always on take? How much would a water heater or water softener or sump pump? I'll follow the wiring to see if I can tell if they're on the same line.

James..

#6
08-15-05, 12:56 PM
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Join Date: Sep 2000
Location: United States
Posts: 18,497
In all but high-end homes, receptacles are very often on lighting circuits. It's rather expensive to dedicate a circuit only for lighting, so it's rarely done by electricians on a tight budget.

Sump pumps are almost always on a dedicated circuit by themselves.

Water heaters are always on circuits by themselves.

Water softener...who knows?

A PC doesn't take much power (although not trivial either), but when you add peripherals like printers and scanners, and large monitors, it starts to add up. A laser printer is a particularly power-hungry appliance.

#7
08-16-05, 05:59 PM
JamesG
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John, i remembered after posting that I had an electrician run 2 separate circuits from the panel because there weren't enough outlets when we moved in (2 computers in home office downstairs). At this point all I want is to add one more 2-light fluorescent fixture so I think i'll be fine We want to get another dedicated outlet for the treadmill so i'll have the electrician check things before he leaves.

Thanks for the help!

James...

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