300ft power run

egproductions

egproductions

Veteran
I need to run power to a location that has none for my lights. I'm going to be running about 1300 watts off of a 20amp circuit (running source 4 lekos). Only issue is the length of the run. It would require me attaching 3x 100' extention cords to eachother. According to voltage drop calculators i am going to be left 100.3 volts (16.42% voltage drop)) at the end of the run. Which I beleive is right at the 1300 watts that I need. Does that make sense? Is this a major saftey hazard or am I good if I stay under 1300 watts?
 
Paul F said:
What gauge wire are you using? I think it isn't legal to run that long; checking.

"In the United States the domestic voltage is 120 V, and the National Electrical Code (NEC) prohibits the use of extension cords in a 20 A circuit unless they are of 16 AWG or larger diameter."

It seems extension cords are not allowed to be longer than 100'; I haven't found the reason yet.
Click to expand...

Because of some changes last season at one of the professional sports venues where I shoot, I had to regularly start making 150'-200' runs* to our live shot location from the power box. I use two 12 gauge power cords, usually 2x 100' or a 100' & 50'. While I'm not pulling as much as eg, I am running an 800 watt HMI, 6x Astra and my camera, at a minimum, so close to 1000 watts.

*The linear distance isn't 200', but there is 150'- 200' of extension cord being used.
 
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Cheap inverter generator is about the only answer to that kind of draw. I've run production trucks that far, not fun hauling 00 cables in 50 foot lengths (because you can't lift longer sections), and that of course was 3 phase and ground.
 
Can't say for the US, but long cable runs here would fall foul of our fairly tough electrical regs and the issue for us would be disconnect time in a fault condition. Plus of course our rules on grounding. Personally, however - you're just running lights, and you've created a dimmer in the cable run, so the lights will be under-run and just a bit redder/yellower.
 
The safety aspect is not as critical as you are thinking. If you use dimmers - as has been happening for a long time, then in the old resistance days, you'd have perhaps 70V at the lights on a 115V system - the lights are dimmer, and the colour temperature changes. We moved to clever dimmers, but the average voltage at the light source still goes down - perfectly safe and not an issue. Your extra long power cables simply have resistance, and you are dissipating this as heat in the cable. If the cable cross section is capable of carrying full current, then nothing you are doing increases it, and volt drop due to resistance is measure by each metre/yard of extra cable. Electrically the usual issue is that some equipment doesn't like lower voltages, but lights with real lamps don't care. Some DMX controlled clever ones could get miffed by the lower incoming level, but Source 4's won't be a problem - they just are a tad less bright. in fact the result will be like mixing 3200K sources with older 3000K sources - a small colour shift.

The other possible issue of long lengths of cable is disconnection time in a fault condition when you are getting a shock from touching an accidental live part, and standing in a muddy field - the extra resistance makes the circuit protection slower to trip - or possibly not trip at all. That is the safety side of the question. Linking three cables is a possible hazard if it's raining, for instance, and the connectors are not water sealed. If they are, fine. In the UK we have laws requiring appliances of all kinds to be tested, and using a long cable results in a fail. Idiot testers, who have been on a one day course simply shout FAIL loudly and apply FAIL stickers and sometimes even hack off the connectors. Knowledgeable testers realise the fail is simply due to the cable resistance and make their determination of pass/fail on solid reasons, which often allow the pass sticker to be applied, even though the resistance was over the acceptable measurement. It's context driven.

I would have no problem at all with driving source 4's through 100m of cable. I would happily driver them through 3 33m lengths if the cable used our 16A connectors, but I would NOT use 3 x 33m lengths fitted with our 13A connectors that are our domestic ones - they are not good or safe outside. I'm sure the US have similar codes, or sensible practices. I worry about rain, and people doing silly things - a bit of cable resistance on a halogen lamped profile (what we call your ellipsoid/'leko' fixtures) doesn't bother me at all.
 
Portable genny’s are a good solution in certain situations. I bought one of the 2K Honda whisper quiet generators years ago for situations where we couldn’t get power. I also had a 2K power inverter installed in my truck for similar situations. I’ve actually used the inverter more than the genny.
 
Thanks for the all the info. I'm suprised I never ran into power issues like this until now. I guess we take our power grid for granted. Here is the final video from the shoot I originally posted about:

 
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