High Voltage Electricity

Overview

It is important for student filmmakers to develop a base understanding of how to safely work with high voltage electricity when handling lighting equipment and other gear on set. Knowledge of electrical fundamentals is the best method to reducing the risk of electrical shock and damage to equipment.

Electrocution

• If someone is being electrocuted, and possibly stuck to the equipment that is delivering the shock, DO NOT TOUCH THEM! You will also be electrocuted.
• First, try to disconnect the faulty equipment at the outlet, breaker, or switch.
• If that is not possible, use a piece of wood, a broom, or any solid object that does not conduct electricity to push them away from the source of electrocution.
• Once they are separated from the source of electrocution, check their vitals, and have someone CALL 911. If they are not breathing, clear their airways and administer CPR until they begin breathing again or the paramedics arrive.

Follow the instructions outlined in the On-set Emergencies article in this handbook.

Best Practices

Electrical Do’s

• Always wrap electrical cables using the Over-Over Technique in a clockwise motion and tie with a shoelace knot.
• Turn power off before plugging or unplugging equipment.
• Always unplug cables by holding and pulling firmly at the connector.
• Always use strain reliefs for head cables when using lighting equipment.
• Always wear shoes with rubber soles when working with electrical equipment. It helps to isolate you from the ground and reduces the chances of you getting seriously electrocuted.
• Always make sure you are using properly grounded equipment.

Electrical Don’ts

• Never yank on the cable to unplug equipment.
• Do not overload electrical circuits beyond their rated capacity.
• Do not use metal ladders or step stools when operating electrical equipment. Fiberglass ladders are okay.
• Never place your knee or hand on the ground when plug equipment into electrical distribution boxes.
• Do not touch two separate pieces of energized electrical equipment at the same time. If there is a ground fault present, you may close a circuit with your body and get electrocuted.
• Do not leave cables coiled tightly when energized. If left coiled, they can heat up and melt. They can also cause magnetic fields that may affect sound recording

Inspect Equipment Before Using

Always inspect your equipment for damage before using it. Sure, it would be great if everything you received from an equipment supplier was in perfect condition, but it is not worth your health assuming someone else has you covered. Melted plugs, cracked insulation, electrical arc marks, and frayed cables are key indicators that something is wrong.

Damaged equipment should be taken out of service. It should be clearly marked as B.O. (burned out) using white tape and a sharpie to prevent further use. Please also document and report the problem to the Film Equipment Room to help expedite repairs performed by the service technician.

Electricity and Water

Water is a natural conductor of electricity. Keep electrical equipment dry at all times. Avoid setting up equipment in puddles or other pools of water. Never place electrical connectors in or near pools of water. Do not handle energized equipment while standing in pools of water.

Always use Ground Fault Circuit Interrupters (GFCI) when working in or around water with electrical equipment.

Keeping your hands and feet dry also helps to lower the risk of being fatally electrocuted if you handle equipment with a faulty electrical ground. Human skin is not a natural conductor of electricity, when it is dry. Moisture from sweat, oil, and rain can quickly change this.

If rain is coming, turn off the electrical system and cover your equipment before it gets wet. If equipment has to be operated during rain fall, then take appropriate steps to cover equipment from damage. Follow the instructions outlined in the Working in Rain and Thunderstorms article in this handbook for more information.

On Location

Tech Scouts

A tech scout should be performed before principal photography begins. Evaluate the layout of each location and identify where equipment can be staged and where house power can be pulled from. This includes calculating loads and identifying the amount of amperage is necessary to service the production’s needs.

Make sure you always disclose the intention of using house power to the business or home owners in advance of production taking place. Be prepared to cover the additional cost if necessary.

Calculating Loads

Productions should know what their power needs are before arriving to set. This is done by adding up the electrical needs of all the equipment they intend to use at that location. There are two methods of doing this – quickly estimating via “Paper Amps” or precisely calculating via the “West Virginia” formula (Watts=Volts*Amps). Paper Amps works for most general-purpose needs. The West Virigina formula is necessary when calculating heavy loads or when your needs are coming up close to the rated capacity of the available circuits (when using every amp counts).

When calculating loads for available circuits; make sure the rated capacity of a circuit breaker is actually available. Many homes will have wall sconces, overhead lighting, fans, and other fixtures attached to these circuits. Electrical circuits are often shared over multiple areas; do not assume that outlets in a house or office space are on different circuits simply because they are located in a different room.

Read our tech article on Calculating Electrical Loads to learn more.

House Power

Depending on the lighting needs of the production, you may need to pull power from multiple circuits to accommodate the overload electrical load of the combined equipment you plan on using. To do this, locate the circuit breaker panel and identify which circuits are supplying power to which outlets throughout the location. Then read how much power is available on each marked on each circuit breaker.

Use a small low wattage light, a partner, and cell phones (for communicating) to make a guide of what outlets are on which circuit. Have one person plug the light into each outlet as the other person flips the breakers to determine which circuit the light is connected to. Always get permission from the homeowner and/or the business merchant before switching breakers off and on as there could be sensitive electronics or equipment that could be damaged by quickly flicking power off and on.

Typically, bedrooms share a 15A circuit with other nearby bedrooms and/or hallways. This includes all fans and overhead lighting fixtures, so be sure to consider these when calculating loads. Bathrooms have a dedicated 20A circuit and it is a GFCI. Kitchens have multiple 15A and/or 20A circuits available to service various countertop appliances. Living rooms, family rooms, and dining rooms will often have outlets sharing a pair of 15A circuits. Garages have one or more 20A circuits to service power tools.

Antiquated Electrical Systems

The Central Florida area has many older residential and commercial space that have antiquated electrical service. Students need to be more mindful when using house power at these locations. Electrical outlets with just two prongs are a sign of an electrical system that is out of code and does not offer the safety of an electrical ground conductor. If this is noticed during the tech scout, be sure to bring additional ground lift adapters to make sure you are able to plug in all of your grounded equipment.

When shooting at locations that have screw-in-style fuses be careful to not tax the electrical circuits too much, as old wiring may overheat and burn before the protective fuses blow. Keep the electrical load to less than 50 percent of the fuse’s rated capacity to avoid stressing old cabling which may lead to electrical fires.

Cable Management

• Always keep electrical cable runs neat and organized.
• Always tape cables down in high traffic areas or cover with floor mats.
• Cable crossovers must be used if electrical cables span roadways or cross in the path of vehicles

Power Generators

Portable power generators are often used to provide electricity at remote locations or where additional power is needed (e.g., older homes with limited circuits). When considering how large a generator is needed, students should first determine what type of lighting equipment will be used.

Calculate the necessary load capacity needed (See CALCULATING ELECTRICAL LOADS article) and select the appropriate unit. Be sure allow for additional capacity for unplanned needs, such as charging batteries. For example, if you need 2000w (16.67A) of total power then rent a 3000w (25A) generator.

Before hooking up equipment to the power generator, verify that the power you are generating is to spec. Using a True RMS multimeter, verify that voltage is between 110-125VAC and that frequency is 60.00Hz (+/- .1).

It is common practice to try and shield the noise that generators make by placing them away from set and putting something in the direct line-of-site to block the sound (e.g., vehicle, building, etc.). Students should stage generators within reasonable proximity of the set as voltage drop occurs when using extension cables (~4 volts for every 100ft of copper cable).

Students should use a multimeter at the end of any long cables runs to verify that the service is between 110VAC and 125VAC. If it dips too low, it will cause the equipment to draw additional current. Doing this could over amp the cables beyond the designed capacity and cause damage. Supplying low voltage for extended periods can also cause damage to electronic components or reduce the effective output of tungsten-quartz bulbs. If the generator does not have a feature to adjust the voltage output, you will have to move the unit closer to reduce the amount of extension cables needed until the voltage is brought to within spec.

Putt-Putt Generators

“PUTT-PUTT’s” are small, portable power plants that can be carried or wheeled around by a person and typically run on gasoline. Many of these units can fit into the trunk of a car, some must be transported in the bed of truck. We highly recommend renting Honda Inverter Series Generators, as they run relatively quiet (50-60db) as well as provide a very stable 60Hz cycle that minimizes flickering in lighting instruments when used in motion picture photography.

You can rent the Honda EU2000IS and EU3000IS models from Home Depot, but there are other brands and models of inverter generators that are acceptable alternatives. Putt-Putt’s are designed to be consumer friendly and are often rated in wattage instead of amperage. They also often have two wattage ratings – a peak/starting wattage and a running wattage. The peak or starting wattage is a brief allowance for the electrical surge when motors or heaters are first turned on. The running wattage is the actual capacity of generator, inexperienced users should basically ignore peak / starting wattage ratings and just stick to the running wattage to determine a generator’s capacity.

Students need to be mindful when transporting gasoline inside their vehicles. Secure canisters to prevent tipping. Use only canisters approved to transport gasoline and keep away from open flame or sparks. Turn off generators and let them cool down before refueling. Never refuel a generator while it is hot. Be sure to wipe up any spills with a rag.

Only use power generators in well-ventilated areas as the exhaust fumes are harmful to breathe and can led to illness or death by affixation if fresh air is not made available. It should be running at least 20 feet (7 meters) from all doors, windows, and vent openings. Point the exhaust away from set. Never use a generator in an attached garage, even with the door open.

A Class B fire extinguisher must always be on set when gasoline canisters or generators are present.

Tow-Plant Generators and Genie Trucks

Tow-plants are large mobile power plants that are mounted on trailers to be towed behind a vehicle. Genie trucks are vehicle mounted generator sets. They are commonly used by professional productions to power large lighting equipment, base camps, general set power, and area lighting. They are typically powered by diesel engines and have output capacities that range between 250A to 1400A. These are heavy machines that must be moved by a large truck or a commercial vehicle. They are operated by trained individuals and require large feeder cables and distro boxes to provide service to set.

Any student production that seeks to use a tow-plant or genie truck on their set must get additional safety and insurance information from the Head of Film Production Services.