Tow Generators, Cam Locks, and More...Oh My!

[Tommy Kraft]

Hi all!

I'm going to start getting into powering things via generators for the first time and using distro boxes and I wondered if anyone has any advice or tips for me to make sure I don't blow anything up. I have theoretical understanding of how these systems work but no practical experience. The extent of my practical experience thus far involves powering lights no greater than 2000 watts and 16 amps. I'm going to be renting a tow generator and using a distro box in about six weeks. Any tips?

Thank you!
- Tommy

 

[Greg M]

Hire an electrician.

 

[Tommy Kraft]

In any case, even if I were to hire someone, I would still like to learn this stuff and understand how it all works rather just hire someone and be in the dark, no pun intended. So, any thoughts or tips from individuals with experience using this kind of gear would be very helpful and appreciated.

 

[Hugh Scully]

Try this: Set Lighting Technician's Handbook: Film Lighting Equipment, Practice, and Electrical Distribution by Harry Box. There's another one I have in my library. I'll try to repost when I get back.

 

[Nick Gardner]

How much stuff do you want to run? I have two honda 7000s with the parallel box from Guy in Boston. You get I think 120 amps. Plenty for 99% of the stuff I do. You don't need a truck, they can go in the back of a van, and you can split them up to have two power sources far away from each other without cable runs. I am very happy with the system.

Nick

 

[Eric M Hurt]

This is a scary post. You should try and work under people who know what their doing as well as learning as much as you can from books.
There's a reason electricians in training in the real world have to work under an actual electrician, it's dangerous.
My advice is to work as an electrician on set and then work your way up, or at least work long enough to learn a lot from people in the field.

 

[Les Hillis]

Along the lines of what Nick and others are saying, how much power do you need?

I'd say check out the portable generators that can give you up to about 5000W output each, and if you need more than that then get someone else more qualified in to help you.

If it gets more complicated to set up and run and maintain than what you're already managing on household power, it's too dangerous to be learning by trial and error as mistakes can be deadly.

Mentioning tow generators and distro boxes like that, while also saying you're just starting to get into powering things via generators, naturally rings alarm bells with the kind of people who are more familiar with such things.

Probably better to say what/how much lighting you want to run and ask how best to do it.

And then do another really good behind-the-scenes video so the rest of us can learn about it too, lol.

 

[B Kanegson]

Ditto the advice of others to obtain "Set Technician's Handbook" by Harry C. Box (benchmark reference for electrical set operations) and hiring qualified Gaffer/ Genny op. They can tell you how much generating capacity you actually need, based on the devices you intend to use. They will also be able to determine how much cable and distribution you will need to accomplish your agenda.

Once you move above the household current capacities you are accustomed to using, most units run on 220-240v and that is where the real danger lies. The 220v must be reduced through the distro boxes to 110v to run all the other non-lighting devices on set as well as the smaller lighting units. There may be very expensive smoke when 110v devices are plugged into 220v; and serious safety issues arise when very particular protocols with the genny and running of power are not followed.

Although today's system for power distribution is inherently far safer than the 100 amp paddles and spider boxes of 20 years ago and before, it still requires very particular knowledge for safe operation. Location set lighting power is nowhere near as contained as house power. Building inspectors would never sign off on accepted motion picture systems; They are allowed primarily because it is understood that they are operated by qualified technicians.

The Handbook will define basic rule of thumb relationships between watts and amps, line loss in distance between set and generator, safe sequence of cable connection, etc. A good reading of that will give a good foundation and answer the kinds of questions I think you have.

 

[Tommy Kraft]

Thanks, all. I'm looking into finding an experienced gaffer and/or electrician in my area who can work this stuff out and also help me learn about it. I've picked up Harry Box's book and have been eating it up like crazy. Could someone help me understand load balancing? How does that work on a three phase system? It more or less makes sense to me in a regular household single phase 120V system. But, how do you balance a three phase load? Does the distro box handle that?

Also, I'd like to power an 18k as well as a few other smaller lights tungsten and HMI sources.

 

[PatrickFaith]

I was present at one electrical death, and had to sit next to a transformer where there was another one. I really like the hive lights for low power btw, keeping everything at 110 is just so much safer. Otherwise, I am not a big Union guy, but when dealing with the 220 and three phases I would only do that union. Another thing is that fire danger and set safety is a hole lot more complex when going with those big lights, be fanatical on distance between the lights and things like draperies ... And only let experienced gaffers touch the lights(i.e. No interns, students,etc are allowed step in to do help on the lighting).

 

[Brendan H. Banks]

Try this: Set Lighting Technician's Handbook: Film Lighting Equipment, Practice, and Electrical Distribution by Harry Box. There's another one I have in my library. I'll try to repost when I get back.

Not to pile on, but this book is worth its weight in gold. I find myself running back to the shelf after being on set with great gaffers and grips. It's a textbook for sure, but a pure wealth of knowledge. Sorry for the sidebar

 

[Brendan H. Banks]

I was present at one electrical death, and had to sit next to a transformer where there was another one. I really like the hive lights for low power btw, keeping everything at 110 is just so much safer. Otherwise, I am not a big Union guy, but when dealing with the 220 and three phases I would only do that union. Another thing is that fire danger and set safety is a hole lot more complex when going with those big lights, be fanatical on distance between the lights and things like draperies ... And only let experienced gaffers touch the lights(i.e. No interns, students,etc are allowed step in to do help on the lighting).

Wow, I'm sorry Patrick. That's really awful and I hope people take it as a cautionary tale. A lot of people think "safety first" is a suggestion until someone gets really hurt (myself included in the past). What we do is not fun if anyone is in danger.

 

[Robert Hart]

I think you may have reached that point of project ambition where you need to delegate and hire someone in who knows safe power management if not lighting craft. Unless you are a sociopath who gives not a scrap of ordure about the wellbeing of others, you may constantly fret about safety and dive off task to herd innocents from potential harm. This may sap your endeavours with frustration and distraction.

 

[Hugh Scully]

In any case, even if I were to hire someone, I would still like to learn this stuff and understand how it all works rather just hire someone and be in the dark, no pun intended. So, any thoughts or tips from individuals with experience using this kind of gear would be very helpful and appreciated.

This is the spirit around which I recommended Harry Box's book. Curiosity leads to knowledge which is gratifying BUT if you're not an electrician, don't experiment with high voltage or unlimited current. Hire a professional if you're doing tie-ins or working with electrical distribution systems other than edison plugs. It's not just knowing how to do it you need to be steeped in the culture and best practices necessary to remain safe in in most states, gone through a rigorous apprenticeship and have a license. I'm DIY about everything, except this.

 

[B Kanegson]

A little knowledge can be a dangerous thing. That said, believing good judgment will prevail and qualified folks will handle the "big guns", I will address your question about phase balancing.

Systems can be single phase/ 3 wire - that is positive, negative and ground. Or they can be 3 phase, 3 hots (usually black, red and blue), neutral (white) and ground (green). Three phase is used on higher capacity systems and allows for best efficiency from the genny. Each of the hot lines carries 110v. Two hot lines are combined for 220v. Electrical loads/ demands from devices must be divided as evenly as possible among the 3 hots for the generator to operate efficiently. This sometimes requires unplugging and replugging (re-patch) some units as others come on line. Electricians are continually metering the amperage draw of each leg to know which to use as additional units are added. The genny op is also continually monitoring frequency to be sure output is close to exactly 60 hz. Specifics on all of this are outlined in the Handbook.

As the generator spins, power is driven to each of the hot legs during a different part of each 360 degree rotation. Therefore, to keep it spinning smoothly, the 3 legs need to have equal demand for smooth and efficient spinning. You can imagine the generator is akin to a washing machine during the spin cycle. If one item is exceptionally heavy, e.g. one wet sneaker, similar to high demand on one leg compared to the others, centripetal force will make the washer vibrate and, if it gets bad enough, stop or break. Its as if you have 3 heavy wet sneakers in the spin cycle, and they need to be spaced and weighted evenly to get the washer drum to spin at high speed.

Bottom line is that each of the hot legs has a maximum amperage capacity, and you can get much closer to the maximum on all three when the legs are carrying near to equal loads. Even when the 3 legs are not maxed out, the genny is a lot happier and less stressed pushing a balanced load.

Hopefully, when you hear "RE-PATCH" shouted across the set, and then there is an uncomfortable delay while an HMI tries to hot restrike, it will be understood that this is for the greater good of not having the genny quit and make the whole set dark.

 

[Tommy Kraft]

A little knowledge can be a dangerous thing. That said, believing good judgment will prevail and qualified folks will handle the "big guns", I will address your question about phase balancing.

Systems can be single phase/ 3 wire - that is positive, negative and ground. Or they can be 3 phase, 3 hots (usually black, red and blue), neutral (white) and ground (green). Three phase is used on higher capacity systems and allows for best efficiency from the genny. Each of the hot lines carries 110v. Two hot lines are combined for 220v. Electrical loads/ demands from devices must be divided as evenly as possible among the 3 hots for the generator to operate efficiently. This sometimes requires unplugging and replugging (re-patch) some units as others come on line. Electricians are continually metering the amperage draw of each leg to know which to use as additional units are added. The genny op is also continually monitoring frequency to be sure output is close to exactly 60 hz. Specifics on all of this are outlined in the Handbook.

As the generator spins, power is driven to each of the hot legs during a different part of each 360 degree rotation. Therefore, to keep it spinning smoothly, the 3 legs need to have equal demand for smooth and efficient spinning. You can imagine the generator is akin to a washing machine during the spin cycle. If one item is exceptionally heavy, e.g. one wet sneaker, similar to high demand on one leg compared to the others, centripetal force will make the washer vibrate and, if it gets bad enough, stop or break. Its as if you have 3 heavy wet sneakers in the spin cycle, and they need to be spaced and weighted evenly to get the washer drum to spin at high speed.

Bottom line is that each of the hot legs has a maximum amperage capacity, and you can get much closer to the maximum on all three when the legs are carrying near to equal loads. Even when the 3 legs are not maxed out, the genny is a lot happier and less stressed pushing a balanced load.

Hopefully, when you hear "RE-PATCH" shouted across the set, and then there is an uncomfortable delay while an HMI tries to hot restrike, it will be understood that this is for the greater good of not having the genny quit and make the whole set dark.

Thanks so much for the information. I have indeed been eating up that book like crazy, and your explanation helps make things understandable. My following question is...how do you divide up the load between the three hot legs? Suppose I've got my five wires going into a distro box, how do I know which oulets (bates or edison) to use to make sure the load is balanced?

By the way, when I get to using this equipment, I will be hiring an electrician. I've been convinced. But my personal philosophy is that I want to know how it works so I can be as well-informed and good at what I do as I can be.

 

[PatrickFaith]

Thanks so much for the information. I have indeed been eating up that book like crazy, and your explanation helps make things understandable. My following question is...how do you divide up the load between the three hot legs? Suppose I've got my five wires going into a distro box, how do I know which oulets (bates or edison) to use to make sure the load is balanced?

By the way, when I get to using this equipment, I will be hiring an electrician. I've been convinced. But my personal philosophy is that I want to know how it works so I can be as well-informed and good at what I do as I can be.

I think it's ok hiring a electrician, but a normal electrician does not know all the film set safety stuff and best practices that you will need to learn. I'd also get a union grip(check with their IMDb and make sure they were the actual grip on A level films ... Not in bs mode doing some side job then calling themselves a fully rated grip after a b level grip gig), at least till you understand in detail all the safety and best practices.

 

[Elsie N]

A little knowledge can be a dangerous thing. That said, believing good judgment will prevail and qualified folks will handle the "big guns", I will address your question about phase balancing.

Systems can be single phase/ 3 wire - that is positive, negative and ground. Or they can be 3 phase, 3 hots (usually black, red and blue), neutral (white) and ground (green). Three phase is used on higher capacity systems and allows for best efficiency from the genny. Each of the hot lines carries 110v. Two hot lines are combined for 220v. Electrical loads/ demands from devices must be divided as evenly as possible among the 3 hots for the generator to operate efficiently. This sometimes requires unplugging and replugging (re-patch) some units as others come on line. Electricians are continually metering the amperage draw of each leg to know which to use as additional units are added. The genny op is also continually monitoring frequency to be sure output is close to exactly 60 hz. Specifics on all of this are outlined in the Handbook.

As the generator spins, power is driven to each of the hot legs during a different part of each 360 degree rotation. Therefore, to keep it spinning smoothly, the 3 legs need to have equal demand for smooth and efficient spinning. You can imagine the generator is akin to a washing machine during the spin cycle. If one item is exceptionally heavy, e.g. one wet sneaker, similar to high demand on one leg compared to the others, centripetal force will make the washer vibrate and, if it gets bad enough, stop or break. Its as if you have 3 heavy wet sneakers in the spin cycle, and they need to be spaced and weighted evenly to get the washer drum to spin at high speed.

Bottom line is that each of the hot legs has a maximum amperage capacity, and you can get much closer to the maximum on all three when the legs are carrying near to equal loads. Even when the 3 legs are not maxed out, the genny is a lot happier and less stressed pushing a balanced load.

Hopefully, when you hear "RE-PATCH" shouted across the set, and then there is an uncomfortable delay while an HMI tries to hot restrike, it will be understood that this is for the greater good of not having the genny quit and make the whole set dark.

This is more about curiosity rather than need, but if you are only interested in outputting 220 and it takes two leads to get 220, and if balanced is best... what do you do with that other hot lead?

 

[B Kanegson]

"Suppose I've got my five wires going into a distro box, how do I know which oulets (bates or edison) to use to make sure the load is balanced?"

This is where things get dicey and experience is required. The easy answer is: Assuming the box is wired standard 110v, each port will normally have a colored bar above it which indicates the leg it is on. This, for example, would tell you where to plug in 110v tungsten, e.g. a 5k or 10k. BUT boxes can be configured to 220v, in which case they have to be boldly labeled such and the colored indicators are not telling the full story; then you have to know exactly how the box was wired. This is why it is always standard protocol (and prudent) to talk to an electrician before ever plugging anything in. A 110v instrument getting 220v usually will fry. It is also the case that big guns are often wired with cam lock directly off the mains, upstream from or without utilizing a distro box. In those cases, the two least utilized legs are tapped.


"This is more about curiosity rather than need, but if you are only interested in outputting 220 and it takes two leads to get 220, and if balanced is best... what do you do with that other hot lead?"

Assuming a North America shoot, (vs Europe) there will be a lot of 110v monitors, battery chargers, hair dryers, etc that can be applied to the 3rd leg if there is only one 220v draw only on the first two. However, if there is one and only one 220v unit, and that is the only draw... you could run it in 3 phase using only 2 legs, out of balance, without a problem, since the draw is probably relatively small compared to overall capacity. The next 220v load to be added would include the third leg. The overall output capacity of a genny is lower when set to single phase than three phase, but if loads were expected to be light, it is generally also possible to set genny to single phase and then not run the cable for a third leg. This can be a time saver in some scenarios.

 

[Paul Dean]

Systems can be single phase/ 3 wire - that is positive, negative and ground. Or they can be 3 phase, 3 hots (usually black, red and blue), neutral (white) and ground (green). Three phase is used on higher capacity systems and allows for best efficiency from the genny. Each of the hot lines carries 110v. Two hot lines are combined for 220v. Electrical loads/ demands from devices must be divided as evenly as possible among the 3 hots for the generator to operate efficiently. This sometimes requires unplugging and replugging (re-patch) some units as others come on line. ... Hopefully, when you hear "RE-PATCH" shouted across the set, and then there is an uncomfortable delay while an HMI tries to hot restrike, it will be understood that this is for the greater good of not having the genny quit and make the whole set dark.

There is some misinformation in the above posts. Single-phase power consists of two hot legs that are 180 degrees out of phase. It too provides higher voltage, but because they are 180 degrees out of phase, it is at 240V when the voltage of each leg to common is 120V. Single-phase power uses a 4 wire system that consists of two hots, a neutral, and a ground.

The higher voltage provided by any two legs of three-phase power is 208V when the voltage of each leg to neutral is 120V. This is because the phase legs are not 180 degrees out of phase, as they are in single-phase power, and so are not completely additive.

Most film electricians are not licensed. A licensed electrician is required to operate a generator only where the municipality requires a permit to use a generator, and then their involvement usually does not extend beyond setting up and grounding the generator where required. An unlicensed film generator operator usually takes over after the initial set-up. Permits are generally not required to operate generators under 10kVA. You should check with the municipality in which the generator will be operated if a permit is required.

A grip is not a member of the electrical department and should never handle distribution equipment. Load balancing is not done by the generator operator, but by the best boy electric. A good best boy electric will never have to re-patch a light because they will have worked out the even distribution of the load in advance.

Generators can operate in single-phase or 3-phase. While you generally get more power out of a generator operating in 3-phase (the overcurrent breaker remains the same regardless of how many hot legs there are) sometimes Best Boys prefer single-phase power. It is easier to balance single-phase power if your loads consist of only large heads that operate single phase. And, if you have a long cable run to set, with a consequent drop in voltage, large heads will operate more reliably on single-phase power. If you start at 208v and then lose 10V to line loss, you are powering large HMIs right on the threshold of their operating range (195-250V.) Whereas, if you start at 240V and then lose 10V to line loss, you are supplying them with ample power.

Since sustained exposure to only 100 milliamps (.10A) can be lethal, a Honda portable generator can kill you just as quickly as a diesel tow plant if you don’t know how to distribute power safely. While the Box book is a good primer, I would suggest you also read “Portable Generators in Motion Picture Production” by Guy Holt (it is available for free online.)

Paul Dean