powering lights from dryer circuits

Jim Feldspar · May 6, 2009

Are there any breakout boxes that can be plugged into a dryer circuit and split 220v

into two 110v legs? I asked the shop guy at rental house today. He thought so but won't sure and are going to check. I know that there are older three wire circuits and newer 4 wire circuits both with different plugs. It seems that for shoots that have to plug in, this could add a lot of power if possible.

Do people do this? Is it safe if done correctly? Is it legal?

Another question is I have a shoot coming up I want to power two 2Ks. Generators are not options for this shoot. I can get power from a building with 20A circuits but the run would be about 200 feet to each unit. I generally use 12/3.

That is a long run. Is there a way to plug into Edison outlet in building and have another length of 12/3 at the light but feeder cable in between? What should I ask for at the rental house for this?

Any help is appreciated tahnk you.

JD Hartman · May 6, 2009

See this thread: http://www.cinematography.com/index.php?showtopic=38565 Use the search function, "dryer outlet", "dryer plug", this question has been answered many times before.

The real answer is, if you have to ask, you don't have a basic grasp of electricity and shouldn't be doing this. Don't depend on some rental house guy to substitute for an experienced set electrician. Read your Harry Box, Set Lighting Technicians Handbook.

Jim Feldspar · May 6, 2009

See this thread: http://www.cinematography.com/index.php?showtopic=38565 Use the search function, "dryer outlet", "dryer plug", this question has been answered many times before.
The real answer is, if you have to ask, you don't have a basic grasp of electricity and shouldn't be doing this. Don't depend on some rental house guy to substitute for an experienced set electrician. Read your Harry Box, Set Lighting Technicians Handbook.

Thanks for the link and the advice, will do.

John Sprung · May 7, 2009

Are there any breakout boxes that can be plugged into a dryer circuit and split 220v
into two 110v legs?

Yes, such things exist, but they're usually home made. You need a plug to go into the big 240 volt socket, a small breaker panel, and whatever boxes/edison receptacles you want to use.

The hole you're plugging into must have four wires: Two hots, Neutral, and Ground. If you don't have a Neutral, you're SOL. If you don't have a separate ground, you're in a dark gray area. NEC allows ungrounded receptacles if they're protected by GFCI's, but only in old work, and they have to be labeled. You might want to go with GFCI's anyhow, the receptacles aren't expensive, and they're safer. Bottom line, four wires or fuggedaboutit.

The wires from the big plug go into your breaker panel just like it was a sub panel and they're the feeder. Be sure to pull out the bonding link. Then you mount your breaker panel and branch circuit boxes to a board and wire them up just like they were part of a house. It's easy, any ordinary residential electrician can do it.

-- J.S.

Paul Bruening · May 7, 2009

Check that first when location scouting. Houses with electric dryers AND electric ranges? That's 160 amps of joy, joy, joy.

Jim Feldspar · May 7, 2009

One of my neighbors is a licensed electrician with 20 years experience. If I do anything, it will be

after running it by him, even on a shoot by shoot basis. I talk to him about them anyway already.

I do ask him a lot of questions so before I ask him about this I've been looking to see what info. I

could bring him about what film people might already do. Was at the rental house today but the shop guy

didn't say anything. I'm not so interested in his knowledge as in whether in the industry any rental houses

have such four wire plug to break out boxes already made up and rent them.

If a box can be made that is legal for me to use then it might be worth doing. If so, I'd hire my neighbor to make it.

He'd probably wouldn't take any money because he always helps me since I'm been a kid. If he thinks that it's not a good idea

he will say so for sure and he won't make the box either.

I know one guy in the neighborhood who has his own home made box for getting more power out to his tools but

he said that doesn't mean that I should do what he does.

I know people do tie-ins. I'm not going to even get into that. If I could find a way to plug in more lights when I really

need to and it's safe and legal that would be good. If not, then I won't.

Jim Hyslop · May 10, 2009

If a box can be made that is legal for me to use then it might be worth doing. If so, I'd hire my neighbor to make it.
He'd probably wouldn't take any money because he always helps me since I'm been a kid. If he thinks that it's not a good idea

he will say so for sure and he won't make the box either.

Sounds like you've got a good plan here. I'm glad you're making sure it's all going to be legal and (more importantly) safe.

--

Jim

Hal Smith · May 10, 2009

An extremely safe way of using residential 240 outlets without fretting about ground versus neutral, etc. is to use what the electrical industry calls a "dry transformer" to step the 240 down to 120. You pass the ground (not neutral) of the dryer/range outlet through to the output ground of the 120 circuit but otherwise you have no direct connection to either side of the original 240. Google "small dry transformers" for some information and/or look at:

http://en.wikipedia.org/wiki/Transformer_types

In a properly functioning electrical service there is no potential difference between neutral and ground. In fact, at the electrical utility's distribution transformer (AKA: pole pig) neutral and ground are bonded together. The reason that modern codes specify separate neutral and ground wires beyond the pole pig is for safety. Since the ground wire itself doesn't conduct power under normal circumstances it is assumed that it remains a good ground when there is a wiring fault or failure. That cannot be said of the neutral under fault circumstances since it's possible that the current carrying neutral wiring and/or connections themselves may be the source of the trouble. In the older systems without separate ground and neutral, if you lose the neutral due to a fault like a short or bad connection, you've also lost your ground...and that's a VERY dangerous situation.

There are workarounds for the situation where you have older wiring without separate ground and neutral but those workarounds are only safe if done by a master electrician or gaffer...not a newbie. To quote one of my favorite sayings: "The difference between a Master and a Jack of a trade is the Master's improvised solutions work."