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Power in the rain


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#1 Valentin Farkasch

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Posted 29 September 2011 - 02:33 PM

I was just recently working on an exterior (union) shoot where we had some rain and powered 2 12K HMIs and a 1.2 HMI all conections where uncovered lying on the floor and I asked the best boy about it - he said it is all fine other than that he wasn't very talkative but I'm now very curios about how much rain can an HMI stand as well as the connections and the generator?
I'd be very grateful for more informations on the subject to help me keep my sets safe.
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#2 John Sprung

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Posted 30 September 2011 - 07:04 PM

There's a company that shows at CineGear that has a lot of GFCI stuff. I think it may be Bender:

http://www.bender.org/



-- J.S.
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#3 Stuart Brereton

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Posted 01 October 2011 - 02:00 PM

HMIs generally burn hot enough that rain evaporates instantly it touches the lamp housing. If the rain is particularly heavy, you can get 'rain hats' for the lamps, or croc clip a piece of gel over the lamp in a pinch. Ballasts should kept off the ground and covered, as should cable connections. Some sort of GFCI is also a good idea.
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#4 timHealy

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Posted 21 October 2011 - 11:46 AM

There is a lot you can do to keep a set safe. But you may want to be flexible depending on the conditions and severity of rain.

Rubber mats: Great for covering stage boxes and ballasts in the rain. Make sure ballasts still have some air to move around them to keep them cool. You don't want them to overheat. But try and use your head. Maybe a location has a place where you can group stage boxes and HMI ballasts in a dry place and run header out to the light positions. You know a garage, a shed, and unused doorway to the location that will never be in the shot.

Apple Boxes or wood: Great for keeping stage boxes off the ground and out of pooling water.

Rain hats: Made of metal or Cellotex (fiberglass coated porch screening). Metal works great all the time. Cello should only be used when actually raining. The heat from the lamp will burn the fiberglass coating off if there is no water on it. When raining the water boils off as steam carrying the heat away keeping the screen intact. One the fiberglass burns off you have a screen without protection right where you want protection the most: On top of the lamp. Though many lamps are designed for a bit a water protection. Also the rain hat regardless of material should stretch out over the rear and front of lamp a bit to protect the lens.

UV filter or heat shield: Great for protecting the lens of a light. It just takes a mist or few drops of water to crack a fresnel. Even a single scrim in front of a lamp is better than nothing.

Blackwrap: Can keep a small light dry in a pinch, but it will make a lot of noise when rain hits it. So not advisable near the camera.

HMI's when dry: Don't touch two HMI's at the same time. That means the ballasts, stands, heads or metal connections on header cable. HMI's leak voltage all the time.

HMI's when raining and things are wet including people: REALLY DON'T PHUCKING TOUCH two HMI's at the same time. That means the ballasts, stands, heads or metal connections on header cable. HMI's leak voltage all the time.

Use a grounded system from the genny. US fire codes states on truck mounted genny the system should be closed and stages boxes should be insulated and a truck with a mounted genny should should have rubber mat under the tail gate and hitch safety chains don't drag on the ground. Which means no external earth ground. Some argue that a closed system the electricity has no potential if the genny doesn't have an earth ground. I'm not an electrical engineer or anything but anyone who works is wet may think otherwise.

GFCI's: They work great. Sometimes they work too good and they are too sensitive and the larger 400 amp three phase ones will cut all power to a set. I have been on jobs where they were pulled out of line and just used these: They have 100 amp GFCI so you can do a lunch pail near water. You can also easily buy the 20 amp type at home depot for individual 20 amps circuits.

Breakers: Make sure you stage boxes and lunch pails and gang boxes all have breakered circuits.

try and keep you equipment out of pooling water. You can do that for everything but your cable.

I hope that is helpful

Edited by timHealy, 21 October 2011 - 11:48 AM.

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#5 Guy Holt

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Posted 08 November 2011 - 02:40 PM

…. Use a grounded system from the genny. ….
GFCI's: They work great. …. You can also easily buy the 20 amp type at home depot for individual 20 amps circuits…. Breakers: Make sure you stage boxes and lunch pails and gang boxes all have breakered circuits.


While Tim is correct, I would like to expound upon a few of his points.

It is a common misconception that circuit breakers and ground rods are there to protect you. A circuit breaker is there to prevent fire created by heat from an over-current or short-circuit and protect the equipment. The amount of current it takes to electrocute a person is much smaller than the amount needed to trip a circuit breaker. Add the fact that a ground rod will never pass enough fault current to trip an over current device and you realize that they are not there for personal safety.

The only thing that will provide personal safety in wet conditions is a GFCI. To protect against serious harm from electrical shock, the circuit must be monitored by a Class A GFCI (Ground Fault Circuit Interrupter). This type of device will interrupt the circuit if it detects current leakage that is greater than 6 mA. At 6 mA, almost all adults and children can let go of the source of the shock. At higher currents, people are progressively less able to overcome muscle contractions caused by the shock, and therefore less able to disconnect themselves from the fault source. A GFCI will de-energize the circuit in less time than it takes to receive a harmful amount of current.

Unfortunately, GFCIs do not operate reliably on most portable (ie Honda) generators, because they are not neutral bonded, unless they are earth grounded (but who grounds a Honda?) To make matters worse, GFCI test circuits can be misleading when they are used on portable generators that are ungrounded because they will give a false positive - that is indicate that they will work even though they will not. For detailed information on how to use GFCIs to provide ground fault protection with portable Honda generators, I would suggest you read the article I wrote for our company newsletter on the http://www.screenlig...ard Protection' class='bbc_url' title='External link' rel='nofollow external'>use of portable generators in motion picture lighting.

Posted Image


This article is cited in the just released 4th Edition of Harry Box's "Set Lighting Technician's Handbook" and featured on the companion website "Box Book Extras." Of the article Harry Box exclaims:

"Great work!... this is the kind of thing I think very few technician's ever get to see, and as a result many people have absolutely no idea why things stop working."


"Following the prescriptions contained in this article enables the operation of bigger lights, or more smaller lights, on portable generators than has ever been possible before."


The article is available online at http://www.screenlig...generators.html.

Guy Holt, Gaffer, ScreenLight & Grip, Lighting & Grip Rental in Boston
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#6 John Sprung

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Posted 09 November 2011 - 08:15 PM

(but who grounds a Honda?)


It's not unheard of -- A three foot stick of old rebar driven in moist dirt will do the trick. Best is to have one near the genny and another at the far end of your main run.



-- J.S.
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#7 Stuart Brereton

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Posted 09 November 2011 - 10:32 PM

It's not unheard of -- A three foot stick of old rebar driven in moist dirt will do the trick. Best is to have one near the genny and another at the far end of your main run.



-- J.S.


Probably should be done more often. I had an Electrician get a shock from a faulty ballast recently, which was running off a Honda thru a GFCI.
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#8 Valentin Farkasch

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Posted 10 November 2011 - 01:36 AM

Thank you so much for the comments it definitely gave me more insight into the matter
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#9 Alexander Smith

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Posted 10 November 2011 - 10:10 AM

Here in Atlanta riggers put swamp boxes on all of our big distro boxes (600a and up) ALWAYS. Well cover up lunch boxes with rubber matting, plastic, cellomesh, or anything really and try and get it up off the ground if its raining by resting it on a spare piece of 60A cable or something.

6k, 12k, and 18k HMI's and tungsten bigger than 2k get rain hats when it rains, mostly to protect the lens from breaking. In the summer time you have to be really attentive with it because leaving them on in light rain will cause the head to overheat (it gets really hot down here, even when raining).

When the light has to be pointed upwards in the rain a rain hat wont do, well get the grips to give us a 4x4 frame of heat shield to protect the lens.

4k and down, all ballasts, and putt-putts get cellomesh (aka stinky wrap). Stinky wont melt when these things get hot like rubber matting will.

Shockblocks (GFCI's) are occasionally used, but not required with most rain really. Unless you're working near large bodies of water or have lights submerged in water.
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#10 Phil Rhodes

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Posted 10 November 2011 - 10:19 AM

In my view all generators should be grounded, always.

I have repeatedly had problems with video equipment connected to generators which weren't. These problems often manifest themselves as half-inch sparks drawn between the shells of BNC connectors and the back of the monitor, which hurts and can't possibly be good for the gear.

Usually the excuse is that the equipment can't be grounded according to the regulations so they simply don't bother grounding it at all; on the contrary, what's actually happening here is that, say, 20KW of HMI ballasts are actually being grounded by a PCB trace inside something like a Blackmagic HDLink.

Even the most cursory attempts to provide a decent ground - throwing a cable down a rainwater drain, connecting it to a lamp post, throwing the earth stake in a puddle - immediately solves all these problems. Most of the time I get the impression they're just too lazy to bother.
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