linking lights question

[Steven Lee, NC]

I am looking to add some lighting to a garage.

http://www.costco.com/4%E2%80%99-Lin...&storeId=10301

With the above light, I wanted to verify that I could replace the current light in the garage with one of these and then start linking additional lights to it so they are all controlled by one switch.

Question now becomes how many can I link.

Is Max wattage for the above light 42W? And based on what I pulled from googling, 1440 / 42 = 34 lights all linked?

This is way more than I need, prob 8 at most.


googled info:

If you are following the NEC code (most popular in the USA) 14 guage wiring for general purpose lighting can not be protected at 20 amps. 15 amps is the maximum.

Designing for constant loading, a 15 amp circuit would allow for a total of 1440 volt-amperes (roughly equal to wattage)

The amount of fixtures that can be connected to this circuit depends on the MAXIMUM wattage rating of each fixture. For example, if the fixtures you are using are rated max 150 watts (even though you are only putting in 75 watt lamps for now) you must perform the calculation based on 1440 divided by 150 which is 9.6, or 9 fixtures.

[Dan Friedrichs]

Yes, assuming a single 120V, 15A circuit loaded to 80% capacity, you could install 1440W worth of lighting (or 34 of the fixtures you linked to).

[Steven Lee, NC]

awesome, thanks.

[Charles Lent]

My reply is YES as well, but you might enjoy having only half of the lights, every other one for lower light levels, or just half of your shop lit sometimes. My shop is wired with half of the lights, (one end of the shop) on one switch and leg, and the other half of the shop lighting on a second switch and leg. It takes two breakers this way, but also makes both circuits extendable for adding additional lighting in the future. There is also a slight cost benefit if you run half of the lights from one leg of your 240 volt service and the other half of the lights from the other leg of your 240 volt service. Connecting to either service leg and neutral will give you 120 vac. The electric meter charges you for which ever leg is drawing the most current, so it's cheaper to divide the 120 volt loadsas equally as possible between them, and they draw roughly equal amounts of current from both legs. The savings dollar wise isn't very large with only 15 amps of total load, but the lighting is a constant load and it does pay off to balance the loads in the long run. Still, it takes another breaker, more wiring, and labor to do this. So it kind of boils down to what you are willing to do, to eventually save a little at the electric meter.

Charley

[Dan Friedrichs]

The electric meter charges you for which ever leg is drawing the most current, so it's cheaper to divide the 120 volt loadsas equally as possible between them, and they draw roughly equal amounts of current from both legs. The savings dollar wise isn't very large with only 15 amps of total load, but the lighting is a constant load and it does pay off to balance the loads in the long run.

This is not true.

[Jim Becker]

That's a nice price for those, Steven. They are the functional equivalent of the non-linking ones I have in my shop and I love the lighting. Given the low draw, you can likely put quite a few together. I have the equivalent of about 8 on each of my lighting circuits and that still leaves lots of room electrically, AFAIK.

[Earl McLain]

That is a very good price. I've got several linkable LED's from Home Depot (http://www.homedepot.com/p/Commercia...3161/205331022) in both the shop and our basement. The draw is listed at 36 watts/0.3 amps in the manual, but it also says the maximum link is 9 fixtures. My guess is that even though 9 would only be a cumulative 2.7 amps, the power is flowing relatively light wire for what gets to be a pretty good distance (at least 50 feet of the equivalent of lamp cord!!)

My garage install is 7 fixtures on a switched circuit, and the basement is 2 on one switch, 1 on anther--but both of those will be added to in the coming year. They have been great. In the unheated garage/shop--I had been using 2 fluorescent and 8 incandescent fixtures, world of difference. The LED's actually light up in the winter.
earl

[ryan paulsen]

i couldn't tell from the picture, how do these link together? do they literally have am outlet on the end like a Christmas light?

[Jim Becker]

i couldn't tell from the picture, how do these link together? do they literally have am outlet on the end like a Christmas light?

Bingo! I believe that is the case.

[Robert Engel]

I would get 1 or 2 and test out the lighting level first not go by what you might see in a store.

I would be concerned about 42w. I've tried a couple led light not impressed with light but could be brand
I just replaced a few indoor floods in my kitchen and the light is actually "white" in comparison. Grand is Cree IIRC.

I have an 8' T8 fixture 6 feet above my workbench and scattered thru the machine shop and they are very good.

[mark mcfarlane]

I am looking to add some lighting to a garage.

http://www.costco.com/4%E2%80%99-Lin...&storeId=10301

With the above light, I wanted to verify that I could replace the current light in the garage with one of these and then start linking additional lights to it so they are all controlled by one switch.

Question now becomes how many can I link.

...

Steven, It is quite possible that there are already other loads (light fixtures, outlets,...) on the same circuit that your current shop light is on. You need to figure out what is already on that circuit before you can determine what can be added to it. Also, the safety of daisy chaining multiple fixtures will depend on the gauge/insulation quality of the wiring inside the light fixtures themselves.

[Eugene Wigley]

What Mark said is probably the case. Few builders will pay extra to get the garage lighting on a circuit alone. Usually other lighting and receptacle loads are on the same circuit. That is a great price on those fixtures. I glanced at the specs. I did not see a reference to any 3rd party listing. If you are planning to get a permit and have this work inspected by the local Inspector in Raleigh, NC, State code says they will need a 3rd party listing. (usually UL) They probably are listed. I would confirm that.

[Scott Brandstetter]

I have used a few of these exact lights in my shop and love them. It is now my go to, in fact, just installed two of them in my motorcycle garage and couldn't be happier.

I will let the experienced guys and gals discuss the load and how many can hook together.

[Nick Boehm]

Hey there,

I do electrical design for an engineering firm. I'd first figure out how many outlets are currently on the same circuit that will be feeding your LED lights. Once you know how much power is on that circuit, then you can determine how many LED strips you can put in. To calculate the load on the circuit take each duplex receptacle you have on the circuit and multiply that time 180. (if you have any quad receptacles you would multiply those by 360). Assuming you have no hard wired equipment on the circuit you can then add those 2 numbers up and divide by 120 to get you current load in amps. So let's say you have 3 duplex receptacles and 2 quad receptacles.... Doing the math you'd get (3 x 180) + (2 x 360) = 1260. Divide 1260 by 120 and you see that you would already have 10.5 amps on that circuit. To figure out how many LED strips you can add to the circuit you would take the 1260 and add 42 to it for each LED strip you would add. Per NEC code you can't put more than 16amps on that 20amp breaker. So using the above scenario you "could" add roughly 15 LED strips to the circuit. As for the light output these lights appear to be 3700 lumens which will be plenty of downward light depending on the size of your shop. If you are unsure what else may be on the same breaker I recommend you get an electrician to come do some panel readings for you. My calculations above are the simple way and do not take into account any large equipment you may be running off those receptacles.

***EDIT*** Sorry I forgot this was residential so you should only have a 15amp branch circuit so you could only have a 12amp load on it.

[Mike Henderson]

The electric meter charges you for which ever leg is drawing the most current, so it's cheaper to divide the 120 volt loadsas equally as possible between them, and they draw roughly equal amounts of current from both legs.

Charley

Absolutely, positively false. The electric meter is a watt meter and it measures the total amount of watts flowing through the meter. And it's really watts. If you have an electric motor and you run it unloaded, the current will not be in phase with the voltage. The electric meter does not measure the voltage times the current, it measures the product of the voltage and current that is in phase.

There are reasons to try to balance the 120V loads between the two sides of the box, but it has absolutely nothing to do with the electric meter.

Mike