I'm going to try my hand at lighting and shooting a shower scene ... I'm worried about are getting electrocuted ... I have about 4 feet between my shower and where I'd like to place the lights - do you think that's safe?
No. The National Electrical Code requires receptacles within 6ft of a shower be equipped with Ground Fault Circuit Interrupters (GFCIs). For the same reasons behind this code requirement you should use GFCIs on all the cables supplying your lights – whatever size they happen to be. GFCIs are a must when working around water in order to avoid someone taking a potentially lethal shock. If you stick with smaller quartz lights, you will be fine with the hardware store variety of GFCI cords. But, if you use HMIs, or even Kinos, you will need film style GFCIs, like Shock Blocks, that are specifically designed for motion picture lights. To prevent the nuisance tripping that electronic Kino & HMI ballasts can cause with standard GFCIs, film style GFCIs sense on an "Inverse Time Curve." And, to deal with the harmonics that non-PFC Kino & HMI ballasts kick back into the power stream (that will cause other GFCIs to trip), film style GFCIs include a harmonic filter with a frequency response up to 120 hz. 3rd harmonics are attenuated by 50%, and by 500 Hz are down to 20%. Attenuated by the filter, the harmonics generated by dirty loads such as non-PFC Kino & HMI ballasts, pose less of a problem.
A single 100A GFCI "Shock Block" can provide ground fault protection on wet locations for the entire distro system of a Honda 6500 portable generator when used in-line with a Step-Down Transformer/Distro.
One problem with Shock Blocks is that they don’t come smaller than 100Amps so if you are shooting in or around a house you will need to do a tie-in or use a step-down transformer, like the 60A Full Power Transformer/Distro we make for our modified 7500W Honda EU6500is generator, on a 240V range or dryer receptacle. A transformer will step down the 240V output of these receptacles to a single 60A 120V circuit that you can put a Shock Block on.
A 100A GFCI used inline with a transformer can provide safe and secure ground fault protection for an entire distribution system consisting of Bates Extensions, Splitters, and Break-Outs to Edisons – eliminating the need for hardware store 20A GFCIs that are not designed to be used with harmonic generating loads like non-PFC HMI & Kino Ballast, & LED Power Supplies. Used in-line with a transformer, a 100A Shock Block will provide a larger GFCI protected circuit than is commonly available in homes.
Master shot of an iRobot commercial lit with a 4kw HMI Par (outside) & 1.8kw HMI Par (inside) powered from a 30A/240V dryer outlet through a step-down transformer/distro. Note: Sunny feel created by 4k Par on an overcast day.
I used this approach on a recent commercial for iRobot (see production stills attached.) The spot contrasted the iRobot Scooba designed to clean kitchen floors to the old mop and bucket approach. For the mop and bucket approach we had a haggard looking Mom slopping water all over the kitchen floor as kids ran slipping and sliding across the floor.
Left: Transformer/Distro plugged into a 30A/240V dryer outlet. Right: 4K HMI Par under rain protection powered by Transformer/Distro
Because we knew water would get everywhere we used one of our 60A Transformer Distros on a Dryer Plug to power a 4K HMI, a 1800W HMI, and some Kinos. We put a 100A Shock Block like the one pictured above on the load side of the transformer/distro to provide Ground Fault protection inside around the wet kitchen floor. It was a good thing that we did, because it ended up pouring rain that day and so the Shock Block did double duty for the 4k that was outside the kitchen window.
Left: Arri AS18 1800W Par powered from Transformer/Distro. Right: 4Kw and 1800W HMI ballasts powered from Transformer/Distro.
For more detailed information on using Shock Blocks to provide Ground Fault protection on Dryer/Range plugs or with portable Honda generators, I would suggest you read the article I wrote for our company newsletter on the use of portable generators in motion picture lighting.
Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston
Edited by Guy Holt, 18 October 2014 - 10:04 AM.