Driving a 2.5kw par off of edison outlets

[M Joel W]

I may be working on a project in which it will be necessary to shoot a lot of night scenes on an hvx200, possibly with filtration/lens gadgets enough to drive its effective ISO down around 100. It's going to be low budget and I'll basically be using my own lights plus a few that are provided...

 

I was going to pick up a 1.2kw par for key (soft flourescents and/or tungsten for fill), but I can get a flicker free 2.5kw par for about the same price as the 1.2kw. Is there any way to buy some magic box to drive it off of two edison outlets (two circuits) or would it need three and a magic box? What kind of generator would I need to run it if no such magic box exists?

 

Also, how much more efficient is a par can than a fresnel? I know (with the right lenses) it can throw light much further, but just in terms of a similar FOV of light, how much more efficient is the parabolic design and seperate lenses?

 

Thanks as always,

 

-Matt

[Michael Nash]

Rent -- don't buy -- a connector that has two male edison plugs wired into a 60A bates connector (female), and plug into two separate 20 or 30A circuits. This what you use to run a 2.5 off a putt-putt with two 30A circuits.

 

In general, pars can focus to a brighter spot than fresnels. Fresnels can give a wider spread and sharper shadow when flooded, but you lose a little "punch" when spotted in, because the light has to go through so much glass. It's not a matter of efficiency, just a choice of which quality of light you really need. A par isn't very "efficient" at filling up an 8x8' diffusion frame!

[M Joel W]

Fantastic, thanks. I already own a Bates to Edison, but I think it's just a single Edison plug so I'll have to call my local rental house. For some reason, I can't get around the idea that fresnels are just more efficient, though. I once used 75w pars from home depot as hair, back, and edge lights and they were every bit as strong as my mole inking spotlight (250w fresnel). A pain to set up, though.

 

By the way, would something like this work? http://www.simoneband.com/ebay/obrazki/a127a.jpg

[Kevin Zanit]

If that connector went in the other direction it would be. What is in that picture is a male 60amp bates to 3-female 20 amp edison connectors.

 

You need 2 or 3 male edison to one female 60amp bates connector.

 

Kevin Zanit

[Hal Smith]

Disaster looms if you plug the two edison plugs into opposite sides of a 240/120 volt residential circuit or 120 volt outlets derived from two different legs of either a 3 phase 240/277/120 volt delta or 208/120 volt wye circuit. You'll probably create a dead short or possibly power up the ballast with 240 volt or 208 volts.

 

You need to first check the outlets with a outlet checker (looks like an Edison plug and has test indicator lights on it - available at home stores) to make certain they're wired correctly. After you know the outlets are wired correctly for hot/neutral/ground then you need to measure the AC voltage between the narrow "hot" blades in the outlets you plan to use. If you measure zero volts (or just a volt or two) then you're looking at outlets that are on the same leg - but if you're looking at outlets on different legs you'll get 240 or 208 volts measured between the hot outlet terminals. I would first measure the each outlet itself between hot and neutral (narrow and wide parallel slots) to make certain my test leads were making a reliable connection.

 

Then when you've done all the above, plug in your Edison to 60 amp Bates adapter and measure the voltage between the outer two terminals in the Bates outlet. If you measure 120 volts you're good to go. Given the possibility of creating a dead short between different legs with your adapter, I strongly suggest installing a 20 amp breaker in the hot leg of each 120 volt Edison plug circuit of the adapter

 

Using two outlets obviously is only going to work if the two outlets are on separate 15 or 20 amp breakers in the panel box feeding them. If you're on the same circuit then you've only got 15 or 20 amps available, not 30 or 40 amps.

 

Incidently, the "wrong" describe above is a kludge for getting 208 or 240 volts from 120 outlets. You deliberately find two outlets on different legs, then between them you've got 208/240 available. I've actually powered up a Senior with a 240 volt bulb in it once with this gag. It was a bit borderline for power capacity (240 volts X 20 amps = 4800 watts) but it worked.

 

And - the usual caveat: If you don't have enough knowledge and experience with electricity to understand all the above - get a real gaffer or electrician to do the above for you.

[Scott Bullock]

And - the usual caveat: If you don't have enough knowledge and experience with electricity to understand all the above - get a real gaffer or electrician to do the above for you.

 

That is the absolute key, in my opinion. Even if you know how to do it yourself, and a lot of cinematographers do, I wouldn't, not when using 3-phase power. It's just too damned much to have to think about as a DP when you've got so much else going on. This is just my own personal safety rule, but if I'm going to be using 2K and above lighting on a shoot, I will insist on hiring a qualified gaffer and/or an electrician. The possible risk to not only you, but others as well, just isn't worth it. So my advice is this: If you can afford to hire an electrician then go for the 2.5 if you feel you really need it, otherwise, just stick to the 1.2 and make it work. I know some will look at that and think, 'no, if I need a 2.5 then that's what I need, period' but many times that's just the nature of the low-budget beast; making it work.

[Michael Nash]

For some reason, I can't get around the idea that fresnels are just more efficient, though. I once used 75w pars from home depot as hair, back, and edge lights and they were every bit as strong as my mole inking spotlight (250w fresnel). A pain to set up, though.

 

I didn't say fresnels are more efficient. The glass in fresnel lenses soak up a bit of light, compared to a par of the same wattage. But again, "efficient" is only part of the equation. A fresnel is generally more controllable and versatile than a par, although you give up a little punch in the full-spot position, compared to a par of the same wattage. When you put a full-wide lens on a 1.2K par, you'll notice its output becomes pretty disappointing...

[M Joel W]

Well, it seems like I'll be renting or buying a 1.2kw fresnel (or possibly par) most likely since that seems to be what's availible and safe off edison power. Thanks for all the advice. Hopefully soon I'll have the money to hire a professional gaffer, but for now I suppose I can make do with +3db of gain when it's necessary.