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 DIY Chatroom Home Improvement Forum Confirming Circuit Load Test
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09-20-2011, 01:22 PM   #1
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Hey all - it's my first post! I have been preparing for a recessed lighting project and doing my homework. I plan to replace a ceiling fan in our master bedroom with 8 new cans.

My first order of business is determining whether I can tap an existing circuit or whether I need to install a new dedicated circuit. The ceiling fan is on a 15-amp breaker. Other loads on the same 15-amp breaker include:

15 cans
3-bulb bathroom fixture
3-bulb chandelier
1 patio light
2 wall outlets

So adding the new 8 cans in the master BR, it would give me a total of 30 bulbs on the circuit. At the same time I install the cans, I plan to replace ALL bulbs in the house to CFLs. For simplicity's sake, I'm assuming 25W per CFL since this is on the higher end of the spectrum for CFLs (right?).

So....based on handy formulas I've found, total load for the lights including the 8 new cans will be about 6.5 amps (assuming 115 volts). Any load from the wall outlets would be extra.

Utilizing the "80% Rule", it appears that I'm within the realm of safety here. Nothing crazy will be run on the 2 existing outlets, but I'm worried that running a vacuum cleaner could put me over.

Are my calculations and assumptions correct? Anything I need to watch out for? Thanks in advance!!

09-20-2011, 01:50 PM   #2
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No, the calculations are based on the max wattage each can is rated for.
Most ceiling fixtures are rated a max of 60 watts per socket.

There is no 80% rule used in residental.

I would install a new circuit.

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 09-20-2011, 03:13 PM #3 Newbie   Join Date: Aug 2011 Location: Southern California Posts: 27 Rewards Points: 25 JB - Thank you for clarifying! So from what I gather......From a practical perspective, I could probably get away with using CFLs without tripping the breaker due to their reduced wattage. But from a safety/code perspective, I would likely be over the 15 amp threshold. In that case, I will install a new circuit! Looks like my project just got a tad more involved. If anyone has a good link to a tutorial on adding a new circuit, I would appreciate it. I've done a fair amount of electrical work but never had to add one. Thanks again.

 09-20-2011, 04:50 PM #4 Member   Join Date: Jul 2011 Location: Canada Posts: 49 Rewards Points: 25 80% rule IS used in Canadian residential, if you happen to be there.
 09-20-2011, 04:57 PM #5 JOATMON     Join Date: Aug 2011 Location: S. California Posts: 11,401 Rewards Points: 1,958 Blog Entries: 2 Even if you use CFL's in the cans....if they have Edison sockets, you will be over. If you sell the house, what would stop someone from filling up all those cans with incandescents? BTW....for load calculations, use 120Vac...not 115. Yea, your actual voltage might be around 115...but 120 is the 'exected' voltage. I don't think there is any code against having lights and outlets on the same breaker.....but I don't allow that in my house. I don't want a tripped outlet turning off the lights....Besides, you typically have lights on 15A breakers...and outlets on 20A breakers. Lights use 14-2 (or 14-3) and your outlets 12-2 wire. __________________ Even if you are on the right track, you will still get run over if you just sit there. My 2-Story Addition Build in Progress Link ... My Garage Build Link and My Jeep Build Link
09-20-2011, 05:41 PM   #6
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Quote:
 Originally Posted by MitNotrof 80% rule IS used in Canadian residential, if you happen to be there.
I'm in Southern Cal....I'll be updating my location shortly in my profile. Thanks.

09-20-2011, 05:43 PM   #7
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Quote:
 Originally Posted by ddawg16 Even if you use CFL's in the cans....if they have Edison sockets, you will be over. If you sell the house, what would stop someone from filling up all those cans with incandescents? BTW....for load calculations, use 120Vac...not 115. Yea, your actual voltage might be around 115...but 120 is the 'exected' voltage. I don't think there is any code against having lights and outlets on the same breaker.....but I don't allow that in my house. I don't want a tripped outlet turning off the lights....Besides, you typically have lights on 15A breakers...and outlets on 20A breakers. Lights use 14-2 (or 14-3) and your outlets 12-2 wire.
Thanks ddawg....I bought the house about a year ago and I too found it strange that the outlets were wired to the same circuit as the lights. Your point is well taken. I will definitely be installing a dedicated circuit for the new cans.

Out of curiosity - what is an Edison socket and how would it increase the load?

 09-20-2011, 06:12 PM #8 Sparky   Join Date: Mar 2011 Location: Central Florida Posts: 706 Rewards Points: 510 if there is an edison socket you have to assume the max wattage lamp the socket is rated for will be installed (usually 60-65W) edison socket is the 'correct' name for a standard screw in light bulb socket
09-20-2011, 08:03 PM   #9
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Quote:
 Originally Posted by Techy if there is an edison socket you have to assume the max wattage lamp the socket is rated for will be installed (usually 60-65W) edison socket is the 'correct' name for a standard screw in light bulb socket
What he said.....

And this is actually a sore point with me....if you look at the title 24 stuff for high efficiency lighting.....then go to Home Depot or Lowes.....you find out very quickly that there seems to be a 'failure to communicate'....all of the 'new construction' cans they sell have the Edison (screw in socket)....but these for the most part do not meet title 24 standards....you can't find a single GU24 light fixture in those stores.....

Just so you understand, GU24 is a pin style socket that will most likely be the standard to replace the Edison....it's not like the pin style you see for the short plug in type of CFL's....do a search....you will understand.

Anyway....if your doing everything permitted....you might have issues if you use Edison style cans.....
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 09-21-2011, 01:02 AM #10 " Euro " electrician     Join Date: Apr 2006 Location: WI & France { in France for now } Posts: 5,369 Rewards Points: 2,000 Ddawgs., IIRC there is a loophole with edison sockets is use the dimmer switch or motion sensor one of the two will take care of it { I know many homeowner rather use the dimmer over the motion sensor } Merci, Marc __________________ The answer will be based on NEC ( National Electrical code ) or CEC ( Cananda Electrical code ) or ECF ( Electrique Code France )
 09-21-2011, 09:00 AM #11 Newbie   Join Date: Aug 2011 Location: Southern California Posts: 27 Rewards Points: 25 Thank you all for the clarification and info. I will be installing a new circuit to make sure it's done correctly.
09-21-2011, 06:34 PM   #12
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Quote:
 Originally Posted by frenchelectrican Ddawgs., IIRC there is a loophole with edison sockets is use the dimmer switch or motion sensor one of the two will take care of it { I know many homeowner rather use the dimmer over the motion sensor } Merci, Marc
You are correct....those are the exceptions.....a more common name for the motion sensor is "occupant sensor"....

I personally like CFL's....I really like my \$45/month electric bills.....and not having to change bulbs.....

My wife has designed most of our lighting so that it makes considerable use of sconces.....nice indirect lighting....we also have a lot of switches....if we want more light...we turn on more lights....

Basically, for soft relaxing light....it's sconces...reflects off the ceiling....works great....if we need task lighting....we turn on the light over the task....works great.
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 The Following User Says Thank You to ddawg16 For This Useful Post: frenchelectrican (09-22-2011)
 09-22-2011, 10:27 AM #13 Newbie   Join Date: Aug 2011 Location: Southern California Posts: 27 Rewards Points: 25 OK, my saga continues.....so based on all the wonderful input I received here, I had decided to add a new circuit. BUT, I inspected my panel and realized that I have no empty spots for a new breaker. So I could be screwed, unless I replace the entire panel with a bigger/better one (which I assume is pretty expensive). In thinking this over, I might have a couple other options: 1) Tap another circuit that has enough capacity to accommodate the 8 new cans. There is one other 15-amp circuit for the downstairs lights (my master BR is upstairs) that could be a possibility, but I haven't considered how to run the wiring to tap it. This is not ideal since I would rather not mix downstairs lights with upstairs lights. 2) Use the same 15-amp circuit that I originally planned to, but install the 8 new cans as GU24 sockets, plus convert several other existing cans to GU24 to limit the load further. I realize these options are not the best route but I am just trying to find a way to make this work without installing a new panel. Any thoughts? Again, thank you all in advance for your infinite wisdom!!
 09-22-2011, 10:49 AM #14 Licensed electrician   Join Date: Sep 2007 Location: Maryland Posts: 10,802 Rewards Points: 1,758 adding a subpanel for more circuit space is an option. You would need to move 2 circuits into the subpanel to make room for the 2 pole breaker that feeds the sub. __________________ Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
09-22-2011, 11:01 AM   #15
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Depending on make and model of the panel, tandem breakers could be an option.

Give us the brand and model number, and someone will tell you.

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