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Old June 30th, 2003, 08:04 PM   #1
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Light kit on location - Watt to do?

Let's say you go to shoot something on location in an office or at someone's home... and you pull out at least 1 - 1,000 Watt light, maybe 2 - 500 Watt lights, and whatever else...

... can your average electric wiring handle that? Anything to look out for to prevent burning down a client's place?
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Old June 30th, 2003, 09:52 PM   #2
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Most electrical circuits are 15 amps, kitchen appliance and some commercial outlets are 20 amps. Current north american codes specify that you should not load a circuit any more than 80% of it's rated ampacity (12 amps for a 15 amp breaker and 16 amps for a 20).

Wattage is computed by multiplying voltage times current (amperage) To find amperage simply devide the wattage by voltage. Since you most likely don't have a voltmeter, assume that you have 110 volts.

A 1000 watt fixture at 110 volts ( watts devided by volts) would require 9.1 amps. A 500 watt fixture would pull 4.5 apmperes at 110. For most common circuit size (15 amps) you would be allowed 12 amps legally. At 1500 watts you're pushing the rating and that's assuming there is nothing else on that circuit. Many people including me, have knowingly pushed he envelope, but when you get fully loaded you may trip the breaker and you may suffer from dimming lights when other loads are switched on or off. have you ever noticed the lights dimming when your wife vacuums or when you use your circular saw. A dimming light at a crucial segment could cause grief.

A toaster, hair dryer coffee maker and a few other appliances draw high current but for short periods of time. they are usually on separate circuits though. It's a good idea to scope out what the power layour is. If you do use extensions make sure they are heavy duty. A short 16 guage would service a 1000 watt lamp. 12 and 14 guage cord sets are a good thing to have. (14 guage is good for 15 amps and 12 is ok for 20 amps) I'm too lazy to look right now but there are charts with length versus wire guage versus amperage.

I use a 650 watt HIR tube in my medium softbox. This lamp draws 5.9 amps yet gives me almost the same amount of light as a standard 1000 watt bulb. I believe there are lesser wattage HIR bulbs available as well.

I just open the panel and throw my amprobe (clamp on amp meter) on but then that's my business. Just use a little comon sense. Add up what you think is on each circuit and whenever possible spread the load between circuits. If you turn a light on and everything else dims then you know you're over.

Sorry for the long winded answer. Short answer is to spread the load to as many circuits as possible.
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Old June 30th, 2003, 10:41 PM   #3
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Bryan is right about there being multiple items on a circuit. Typically, you'll find that a number of outlets and lighting circuits will be wired to one breaker (15 or 20 amp). You need to know the total of all the other items on the circuit before you add yours to determine if you'll have a problem or not. A good example of what not to do would be: using mulitple higher wattage lights in the same room where a space heater is already running (not sure why anyone would since the lights ARE space heaters too). Most commercial and residential rooms have all the outlets on one circuit so you could easily overload it. AND, like he says, some of us test by plugging them in and hoping the breaker doesn't trip. Probably not the best way and SURLY not recommended in locations where the wiring/breakers may not be up to todays specs (like where they are still using fuses).
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Old July 1st, 2003, 06:09 AM   #4
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I'm just thinking, that is an awful lot of light and heat for a small location. You may want to cut it down a bit, before you accidently cook or blind the poor soul.
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Old July 1st, 2003, 06:37 AM   #5
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Yeah, be careful. I just blew a fuse setting up light banks in my garage. Everything seemed reasonable until I got hungry.
I popped a frozen dinner into an 800 watt microwave and
searched for something else in the fridge. I think the fuse blew
when the fridge compressor switch on. I had totally forgotten
about the microwave. In my olde home, the garage and kitchen
are on the same line.
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Old July 1st, 2003, 07:53 PM   #6
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Thanks for all the info, guys. Bryan, you've helped me a lot in making a light purchase decision.

I live in Japan and places are generally small here. Plus, the electrical outlets for my entire apartment seem to run on the same circuit (and I'm sure that's the case in many small apartments, small offices here). Add to that that the spaces are very small, and the ceilings are low. The result? A poorly-wired pressure cooker.

For that reason, I can't imagine buying anything but fluorescents. Despite the limitations, I think the heat factor alone precludes me from purchasing non-fluorescents. A 1,000 Watt or 500 Watt hot light setup could be pretty risky. I was wondering if I'd burn down my place (that has a makeshift interview studio), and other locations if setting up, say, a four-light setup (key, fill, hairline, background... that's a lot for a small room, I know, just wanted to hypothesize with a maximum amount of light instead of minimum). I could get by with two lights in most interview situations... but the voltage used is still much higher than fluorescents.

I'm looking into getting a couple of Scandles and probably a Caselight from Lowel. The Scandles say they have 8 24-watt bulbs, and the current here is 100 volt (some U.S. appliances don't require transformers at all here, these lights probably will, though). I'm not sure if my math is correct here... 8 X 24 = 192 / 100 = 1.92? Is that all? And that light output is supposed to be equivalent to a 500 watt hot light? That's pretty amazing.

The Caselight is about the same... 4 X 55 Watts = 220 Watts / 100 Volts = 2.2.

Looks like fluo is the way to go over here.
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Old July 3rd, 2003, 03:20 PM   #7
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Way back when I first started doing video as a sideline I was doing a corporate video that would show new employees how their role fit in with this particular carpet company.

I was setting up to shoot in the warehouse and asked one of the workers where I could plug in my 1000 watt light. He pointed to an outlet, I hooked up to it and started getting my shots.

After several minutes the carpet cutter stopped. The extra load on that circuit knocked out the carpet cutter on a Saturday (one of the busy days) and I don't know if they ever got it back online for the rest of that day.

Surprisingly enough, the president of the company never complained. He liked the video, tho.

I started using fluorescents in quite a few of the shots I'm doing for a home improvement show, especially where daylight needs to be balanced. I know no one will believe this, but they do a great job and they're really cheap lights. It just took a piece of Lee 249 (1/4 minus green) to get them to color balance nearly perfectly. Spent $150 at Sam's Club but that was for six of these things.

We were using a Lowell Light Array but the setup was a hassle, the ballast was heavy and cumbersome to position, and the amount of light it threw wasn't that much more than these cheap, lightweight worklights.

I'll see if I can post a few frames somewhere to show the results.

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Old July 3rd, 2003, 06:55 PM   #8
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Dean,

Supposedly the Scandles and Caselites are supposed to be daylight balanced already...do you think that's not really the case? In your opinion, gel will be required?

John
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Old July 3rd, 2003, 07:09 PM   #9
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John...

The scandles and Caselights are balanced for daylight a whole lot better than the Cheaplights and won't require a gel.

The Caselights look pretty nice as they'll provide a broad source and seem as though they're easily set up. The Light Arrays required the lights to be unfolded and tubes inserted everytime they were transported.

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Old September 28th, 2003, 12:15 AM   #10
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<<I'm too lazy to look right now but there are charts with length versus wire guage versus amperage>>

Bryan...any idea where I should look for this type of information? I'll do the searching...just hoping you can point me in the direction of one of the better sites you've seen for this.

Back when were discussing this thread, I purchased a fluorescent light setup (a 4-bulb Lowel Caselite and a Scandle, used in tandem with other cheapo fixtures I have) and have been using it to shoot some corporate stuff in small offices. The cool lighting and low amperage have been a great relief. For that type of shooting, I've been happy as a clam.

I'm preparing to shoot something now, though, that will require an external crane shot of a house at dusk (shooting into the light part of the sky at the point where the sky is electric blue) and so I plan on using some 1k Arris to fill the front of the house (I've always done small-scale lighting...taking advantage of available light as much as possible...so this is new territory for me). Otherwise, the house will just be a silhouette. The extension cords will have to be pretty long since the power source will be in the house itself.

Any suggestions on this?
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