Checking Circuit Load For Recessed Lighting - Electrical - DIY Chatroom Home Improvement Forum

 DIY Chatroom Home Improvement Forum Checking circuit load for recessed lighting
 Register Blogs Articles Rewards Search Today's Posts Mark Forums Read

05-07-2010, 11:32 AM   #1
Newbie

Join Date: May 2010
Location: Waltham, MA
Posts: 13
Rewards Points: 10

## Checking circuit load for recessed lighting

I'm planning on installing new recessed lighting in my finished basement this weekend. It seems like it should be easy enough, especially because our ceiling joists are exposed (ugly damaged interlocking cardboard tiles were up there previously). I know how to do basic wiring and have an understanding of basic wiring in general.

The circuit I'm using is from an existing fixture in the basement. I've read on this and other websites about amp ratings for switches, so I understand that I should add together the max wattage of the fixtures I want to install, find the total amps drawn (Watts = amps * 120V), and make sure that the amps drawn are under 80% of the amp rating of the switch (usually 80% of 15 amps). I've taken "switch" in this context to mean the 2-pole light switch that controls that specific circuit, and not the switch on the circuit breaker.

Assuming everything I've written above is true, do I need to think about the increased load on the circuit breaker itself? The breaker that controls the light fixtures in the basement also controls the outlets in my living room, one of which holds the surge protecter that powers my TV, game consoles, DVD player, etc. as well as 2 different ceiling fixtures on other floors. Do I need to worry about not over-loading that particular breaker in addition to not over-loading the specific light switch? If so, how would I check? I don't know much about how individual circuit breakers work and how they are wired to the rest of the house.

Also, does simply adding up the max-Watt ratings of the fixtures work when they will be wired in parallel? And does the fact that the circuit is on a 3-way switch system (two 3-pole switches) make a difference?

Last edited by Nathan0115; 05-07-2010 at 11:34 AM.

05-07-2010, 12:09 PM   #2

Join Date: Sep 2007
Location: Maryland
Posts: 10,810
Rewards Points: 1,774

The breaker is designed to allow a certain amount of electricity to flow thru it. Everything connected to that circuit like the TV, game console etc leaves you less for your recesssed lighting. For example lets say the equipment upstairs is using 5 amps of the 15 amp circuit. This leaves 10 amps of reserve capacity. If you vacuum with a 12 amp machine it will probably hold, but could also trip. It does not matter how that load is switched, regardless of single pole or 3 ways.

I would add a new circuit for the lighting.

__________________
Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.

 05-07-2010, 12:51 PM #3 Member   Join Date: Jan 2008 Location: Alabama Posts: 608 Rewards Points: 500 How much lighting are we talking about? Typical light fixtures today use 60 watt light bulbs, and if you look at dimmer switches, most are rated to only carry a 600 watt load. That's 10 lights (about 5 amps). If you have more than that, it sounds like you have a really large room or you might be putting in too many lights. But even with large rooms, you usually don't have to worry about the switch (if you're talking the basic on/off switch) because they are rated for basically what the circuit breaker is rated... the 15 amps you mentioned. But if you are worried about stressing a 15 amp circuit, you're talking about 25 to 30 recessed lights on one circuit... which really sounds like overkill. I'm in the process of going overkill in lighting up a 19 x 14 room and ONLY have 21 lights. But in my "overkill", I've got layers of lights (i.e. there is the over-head lights I'm setting up to illuminate like a three way lamp, wall sconces on a dimmer to illuminate under the edge of a tray ceiling, extra lights handing from the ceiling fans, a single recesses light for ultra-low light levels. So while I never expect to have all these lights on at once, even if I did, its less than 1400 watts... and that's assuming I use all incandecent lights (but some WILL be CFLs, so my actual load will be much lower).

 05-07-2010, 01:00 PM #4 Newbie   Join Date: May 2010 Location: Waltham, MA Posts: 13 Rewards Points: 10 So you're telling me that the individual breaker only allows up to 15 amps before tripping? That doesn't make sense at all given that a simple device like a hair-dryer (or vaccuum cleaner, like you said) can pull up to 12 amps on its own. The "15amp" number was what I found was the typical maximum load of a LIGHT SWITCH, not the circuit breaker. My light switch is not hooked up to all the other electronics.
05-07-2010, 01:05 PM   #5
Newbie

Join Date: May 2010
Location: Waltham, MA
Posts: 13
Rewards Points: 10

Quote:
 Originally Posted by HooKooDooKu But if you are worried about stressing a 15 amp circuit, you're talking about 25 to 30 recessed lights on one circuit... which really sounds like overkill.
Right. I'm only looking at putting in 8-12 lights. On its own, that wouldn't be a problem. I'm worried because the circuit that I'm adding the lights to doesn't have a dedicated breaker. It's attached to the breaker that also controls the living room, etc.

That is to say, when I flip the circuit breaker switch to kill the power to the basement lights, the living room outlets also go dead.

 05-07-2010, 01:13 PM #6 Licensed electrician   Join Date: Sep 2007 Location: Maryland Posts: 10,810 Rewards Points: 1,774 Twelve 65 watt fixtures would add another 6.5 amps to the circuit when on. __________________ Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
 05-07-2010, 01:25 PM #7 Member   Join Date: Jan 2009 Location: South of Boston, MA Posts: 17,248 Rewards Points: 2,000 Where are you located ?
 05-07-2010, 01:33 PM #8 Newbie   Join Date: May 2010 Location: Waltham, MA Posts: 13 Rewards Points: 10 Outside of Boston, MA.
05-07-2010, 01:43 PM   #9
Member

Join Date: Jan 2008
Location: Alabama
Posts: 608
Rewards Points: 500

Quote:
 Originally Posted by Nathan0115 So you're telling me that the individual breaker only allows up to 15 amps before tripping? That doesn't make sense at all given that a simple device like a hair-dryer (or vaccuum cleaner, like you said) can pull up to 12 amps on its own.
That is why the current code require 20 amp circuits for outlets in bathrooms. When my house was built about 12 years ago, that requirement wasn't in place. If I run the lights in my bathroom at max (500 watts) and crank up the hair dryer, the breaker does indeed trip.

Now we don't know if the circuit you are talking about is a 20 amp or a 15 amp circuit. In all homes, each breaker used to power recepticals and typicals lights is either 15 amp or 20 amp. 20 amp circuits cost more to install than 15 amp circuits because you have to use larger wire for a 20 amp circuit.

Most circuits in a house will get wired with the cheaper 15 amp circuits. Usually only limited circuits, as mandated by building code, will get wired as 20 amp. Today, bathroom recepticals and kitchen counter top recepticals must be on 20 circuits to handle the loads create by hair dryers and kitchen counter-top appliances. (There might be a few others, but if so, they are not comming to mind).

And to give you an example of how crazy some electricians have been in just the recent past, I discovered that the kids bathroom, the hall way (where a vaccum usually gets plugged in) AND the smoke detectors were all wired on a single 15 amp circuit... No wonder it wasn't an odd thing for the circuit breaker to occationally trip when running the vaccum.

 05-07-2010, 01:54 PM #10 Newbie   Join Date: May 2010 Location: Waltham, MA Posts: 13 Rewards Points: 10 That's very interesting. Did some more research this afternoon ... I didn't realize just how much more power devices like vaccuums and hairdryers comsume compared to electronics like TVs and game consoles and computers. My breaker panel appears to have a number of breakers that aren't even used at all. How hard would it be to take the basement lights off of the breaker it's currently on and put it on one of the unused ones *while keeping the living room on the same breaker*? Might seem like a silly question (either because it's really easy or impossibly difficult), but I have no knowledge of how circuit breakers connect to the circuits they control. Thanks for your replies, I very much appreciate it. Last edited by Nathan0115; 05-07-2010 at 02:22 PM. Reason: clarification
05-07-2010, 02:15 PM   #11
Member

Join Date: Jan 2009
Location: South of Boston, MA
Posts: 17,248
Rewards Points: 2,000

Quote:
 Originally Posted by Nathan0115 I've read on this and other websites about amp ratings for switches, so I understand that I should add together the max wattage of the fixtures I want to install, find the total amps drawn (Watts = amps * 120V), and make sure that the amps drawn are under 80% of the amp rating of the switch (usually 80% of 15 amps). I've taken "switch" in this context to mean the 2-pole light switch that controls that specific circuit, and not the switch on the circuit breaker.
Residential lighting is not considered a continous load & you are not required to load only to 80% of the breaker capacity
BUT, you don't want to run all lights that will normally be on at one time off one breaker if it will max out the breaker
I keep my lighting circuits seperate from outlet circuits
Our vacuum pulls 12a

If you are running low on breaker space in the panel you may want to run 12g 20a circuits to Max useage of remaining slots
15a 14g = 1800w - you would be using 780w -(12*65) 43% of the circuit
20a 12g = 2400w you would be using 32% of the circuit capacity - plenty of room to add on more lights

I only run 20a outlet circuits, but the older circuits in my house are only 15a

 05-07-2010, 03:07 PM #12 Licensed electrician   Join Date: Sep 2007 Location: Maryland Posts: 10,810 Rewards Points: 1,774 If you can pull a new circuit from your panel it is possible to sub-divide the LR circuit. Remember, all splices must be in permanently accessible junction boxes. Given that bedroom circuits are normally only used for a TV and clok radio and some lights, that circuit you described does not sound out of the ordinary. It would be hard to predict when and where someone could try and use a plug-in heater and try to vacuum at the same time. __________________ Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
05-07-2010, 03:49 PM   #13
Totally screwed together

Join Date: Dec 2006
Location: Cypress, SoCal
Posts: 325
Rewards Points: 250

It sounds to me that you need to take an inventory of what your breaker panel feeds. Right now you've got one circuit that feeds three floors, but other breakers that don't do anything... that's weird. You should have a better idea of what is going on before proceeding.

I've taken up the checkerboard theory on lights and breakers. If you flip off the breaker to the hall lights, you still have light coming from the bedrooms. You can trip the lights to the bathroom but still see from the bedroom or the hallway.

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post sandyman720 Electrical 6 11-27-2011 03:34 PM fredgmeyer Electrical 11 10-26-2009 12:41 PM travishume Electrical 30 08-01-2008 07:21 PM lapsis9 HVAC 4 12-20-2006 08:09 PM DrP Electrical 8 05-25-2006 10:05 PM

Top of Page | View New Posts