18 replies to this topic

[Austin Marti]

Hi,

 

I bought a used 2kW Mole Super Softlite, and it has a 20A plug on it.

 

The max draw of this light is 16.7 amps (2,000 watts / 120v).

 

How can I power this light in my household and/or in other locations?

 

I read Guy Holt's suggestion to use a 240v-to-120v step down transformer. Would this work for my application?

 

Thanks for any help.

[Adrian Sierkowski]

Any location with a 20A breaker and a typical Edison outlet will work, so long as there isn't much else on that circuit. Check the location breaker box before you plug it in and make sure nothing else gets powered from the same circuit (not just outlet) that the 2K is on.

Generally, I don't like using 2Ks when the house is fused -v- breaker-ed, simply because I don't really carry spare fuses anymore.

[Austin Marti]

It has this plug on it and almost all houses here don't use those. Should I or can I (safely) replace it with a typical 15A/Edison plug (keeping in mind I need a 20A breaker with nothing else running on that circuit)?

Edited by Austin Marti, 18 January 2014 - 01:15 PM.

[Austin Marti]

Apparently I can no longer edit either post above (time limit?), so here's a new post.

 

How hard is it to convert 120v to 220v? What kind of transformer would I need? (need one that is rated for certain amount of watts? can someone provide me with a link? Just trying to understand all this)

 

This would allow me to bring the draw down from 16.7 amps to 8.35 amps, correct?

Edited by Austin Marti, 18 January 2014 - 01:31 PM.

[Adrian Sierkowski]

Yes if you double the voltage you decrease the amp draw, however, you shouldn't have any trouble powering a 2K off of normal 120 power. While it's probably not the best SOP i have put on 15A heavy duty Edison on the end of 2Ks-- they used to make 20A edisons, instead of the "T" plugs, but I haven't seen them around in awhile.

[Guy Holt]

 

I bought a used 2kW Mole Super Softlite, and it has a 20A plug on it.

 

The max draw of this light is 16.7 amps (2,000 watts / 120v).

 

How can I power this light in my household and/or in other locations?

 

I read Guy Holt's suggestion to use a 240v-to-120v step down transformer. Would this work for my application?

 

 

Using a 240v-to-120v step-down transformer is without a doubt the most reliable way to power a 2k on wall out-lets. A transformer will convert the 240V output into a single large 120V circuit that is more than capable of powering the 16.8A load of a 2k at 120V. If you outfit the transformer with a 60A Bates receptacle, it will enable you to use a real film style distro system that will minimize line loss over a long cable run, and provide a 20A circuit right at the light. Common 240V sources found on interior locations include Range Plugs, Dryer Plugs, and special receptacles installed for Window Air Conditioners.

 

While you can put a 15A Edison Plug on a 2k, as Adrian suggests, you still have to find a 20A circuit – which is not always conveniently located. You definitely want to avoid long runs of stingers because the odds are good that there will be an old and weak plug end somewhere in the run that will overheat and melt since they too are only rated for 15 Amps.  And, it has been my experience that 2ks with 15A Edison Plugs get really hot and eventually melt because the stranded copper in the plug becomes brittle and breakdowns from the heat over time.

 

2ks, like 1800W HMIs, are in the class of lights that work best on a real film distribution system where every circuit is 20 Amps, you know what is on the circuit because you are loading it yourself, and you are bringing the receptacle to the light because you are distributing the power yourself.  When you can run a 60A whip and drop a Snack Box with a 20A outlet next to the light you won’t have a problem. But, if your style of shooting requires that you run multiple stingers to plug into a wall or generator outlet, you will likely have problems with the plug ends or receptacle overheating and causing the breaker to overheat and trip.  A step-down transformer will enable you to use real film distro and avoid these problems without having to do a dangerous tie-in or rent an expensive generator.  Use this link for more detailed information on successfully operating large tungsten lights on wall outlets.

 

If Austin doesn’t need all of the output of a 2k soft, another option is to swap the 1k FCM bulbs for 750W EJG bulbs. Now a 1500W softlight, the head will draw only 12.6 Amps at 120V and fit comfortably on the common 15A circuit and not overtax Edison plugs and outlets.

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Sales & Rentals in Boston

Edited by Guy Holt, 18 January 2014 - 05:46 PM.

[Tim Tyler]

 

... another option is to swap the 1k FCM bulbs for 750W EJG bulbs. Now a 1500W softlight, the head will draw only 12.6 Amps at 120V and fit comfortably on the common 15A circuit and not overtax Edison plugs and outlets.

 

Great solution.

[Marc Roessler]

Why not lamp it with 230V/240V globes? Then you won't need a transformer.

The lamps should be readily available, because 230V is a common voltage in Europe, and I've even seen some 240V globes.

Edited by Marc Roessler, 18 January 2014 - 06:34 PM.

[Stuart Brereton]

Why not lamp it with 230V/240V globes? Then you won't need a transformer.

The lamps should be readily available, because 230V is a common voltage in Europe, and I've even seen some 240V globes.

Because 240v globes won't run at full power on 120v, so they'll look very warm, as if on a dimmer.

[Stuart Brereton]

Here's a solution for getting 240v from 2 separate 120v circuits.

 

http://www.quick220.com

[Guy Holt]

Why not lamp it with 230V/240V globes? Then you won't need a transformer.

The lamps should be readily available, because 230V is a common voltage in Europe, and I've even seen some 240V globes.

 

The Quick 220 Power Supply is not as straight forward as it appears: the two outlets it uses to make 240V must be on different circuits that are out of phase (opposing legs of the electrical service) and not controlled by ground fault interrupters (GFI's).  And, if the service is 3 Phase rather than Single Phase, you will get 208V without any means of stepping it up to 240V. At 208V a 240V bulb will look quite dim and very warm.

 

There are a couple of good reasons why you may still want to operate a 2k at 120V through a transformer/distro rather than directly into a 240V receptacle. First, a 30A/240V dryer receptacle offers you 60A at 120V through a 240-to-120V step-down transformer. If you plug the 2k in through a transformer/distro and operate it at 120 Volts you still have 43.2 Amps left over to power additional lights through the transformer as well if your. That’s a lot of power in an easily distributed form to not take advantage of.

 

 

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.

 

The second reason is that if the 2k is far from the 240V receptacle you can have appreciable line-loss (voltage drop) over a long cable run. A transformer/distro can be used to compensate for line loss, as well as the voltage drop on a generator from running it near full load. Our transformer/distros provide variable taps on the primary side that enable you to adjust the step down ratio to boost their output above the standard 2:1 ratio. This boost capacity will compensate for accumulative voltage drop and assure full line level (120V) on set.

 

 

Left: Transformer/Distro plugged into a 30A/240V dryer outlet. Right: 4K HMI Par under rain protection powered by Transformer/Distro

 

This feature of our transformer/distros was a real benefit 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: Arri AS18 1800W Par powered from Transformer/Distro. Right: 4Kw and 1800W HMI ballasts powered from Transformer/Distro.

 

The only available source of power for our 4K and 1800W HMIs was a dryer receptacle in the laundry room. Unfortunately, the laundry room was upstairs and in the front of the house and the kitchen was downstairs and in the back. Fortunately, we could use the boost capacity of our transformer/distro to compensate for the 16.5V line loss we experienced after running 300’ of high voltage twist-lock extension from the front to the back of the house. You wouldn’t think there would be that much voltage-drop over a 300’ 10AWG cable run, except that in this case, the electrical service was in the basement under the kitchen where we were shooting. Which means the circuit supplying our lights consisted of approximately 300’ of wire from the electrical panel in the basement under the kitchen to the dryer receptacle upstairs in the front of the house, plus the 300’ of wire we ran back to the kitchen, for a total of approximately 600’ (see voltage drop table below.)

 

 

Note: the voltage drop on a 600’ run of 10AWG stranded cable is 16.497 volts

 

An added benefit to using a transformer/distro in this case was that it enabled us to use a 100A Shock Block to offer GFCI protection for cast and crew. We knew water would get everywhere inside the kitchen, so to protect the cast we put a 100A Shock Block like the one pictured below 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.

 

 

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.

 

I regularly use transformers to power not only big HMIs  (2.5-4Kw), but also quartz 5ks, in situations where a tie-in is not an option and the budget doesn’t permit for a tow generator. Use this link for more details about using step-down transformers on set.  By giving you safe and legal plug-in access to more house power through common 240V house outlets, a transformer can quite often eliminate the need for tie-ins or generators.

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting rental and sales in Boston

[Austin Marti]

Thanks for all the responses.

 

Guy, if I were to go the route of stepping down 240v to 120v to take advantage of a large 120v circuit, is there a transformer on the market that would do exactly this job or is that something I would need to build myself (like outfitting it with Bates plugs like you suggested, etc)?

[Guy Holt]

... is there a transformer on the market that would do exactly this job or is that something I would need to build myself (like outfitting it with Bates plugs like you suggested, etc)?

 

You could outfit one yourself with a Bates, or we rent/sell them already outfitted with Bates and Voltage Select Switches. Contact me off forum for details.

 

Another option that has occurred to me is that, since a 2k Super Soft consists of two 1kw globes on separate switches, you could split the two globes onto separate circuits with separate plug ends. That way you are only plugging a 1kw into each wall circuit.

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston

[Edward Lawrence Conley III]

You might as well re-lamp it or re-wire it as Guy suggested.

Not all locations have the 240v receptacle to use the step down system that Guy uses.

It is a wonderful product but almost useless here because most appliances in Los Angeles use gas so no 120/240v appliance receptacle to use.

[Austin Marti]

I ended up yesterday buying a 15A plug and fitting it with that. I also figured out the circuit layout of my house so I know where I can plug it in and power it safely.

 

Thanks for your responses.

[Marc Roessler]

Hi,

 

I usually appreciate Guy's very well written articles very much, but I fear in this case I'll have to disagree.

 

Operating at 120V through a transformer/distro rather than directly into a 240V receptacle (with 240V globes) does not give you any benefit.

 

Yes, you can compensate for the line loss by choosing different taps at the transformer (like with the old Colortran system). But this will raise power consumption (amperage/current) on the primary 120V side. You don't save any energy. At some point your primary breaker will trip if you keep compensating by upping the secondary voltage by changing the transformer taps. It's really no issue with 240V as long as your cables are thick enough, and that's really the only clean solution to the problem. Long runs? - Thicker cables!

 

Then the transformer itself has losses. Not too much resistive loss (i.e. heat generated), but it is an inductive load (i.e. reactive current, bad power factor!) so you can't make use of all of that amperage. Depending on the transformer, this means that a 30A/240V dryer receptable will NOT be able to power a full 30*240=7200VA lamp at 120V through a 240-to-120V step-down transformer. You can compensate for that with compensation capactors on the primary side of the transformer. But those are big and raise cost of the unit.

 

Also note that that even when you run 2kW 240V lights on a 240V receptable, you can still use those left over amps to power other devices (120V or 240V - your 240V indandescent lamp does not care how the voltage distributes across the legs). So that's not a pro-transformer argument really.

 

You can use GFCI protection with a transformer, yes. But you can also use it when connecting your 240V lamps directly to 240V, right?

 

Kind regards,

 Marc

[Marc Roessler]

Oh by the way.. in my original posting of course I was referring to running 240V globes at the 240V receptable. Not 240V globes at 120V. This would indeed cause very bad performance both output and color temperature wise

[Guy Holt]

Hi,

 

I usually appreciate Guy's very well written articles very much, but I fear in this case I'll have to disagree.

 

 

While Marc makes some very good points, and is even correct in theory on some, in realty things are very different. So different that I do not agree with the conclusions he draws. Where my response pertains to how to access more power through 240V receptacles  using a step-down transformer than it does to the original post, I have started a new thread where I address his points one at a time. The new thread is available  at  Accessing more power through 240V receptacles.

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston

[Marc Roessler]

Maybe this came across wrong, I'm not putting your system down. I was just saying that it comes with its own advantages and drawbacks, and given those for the particular setup presented I felt (and still feel) it'd not be the right choice. Let's recall: it's about a 2kW Softlite! Lamping with 240V globes and getting proper cabling so to keep cable losses low isn't a problem really here. Buying and lugging around an iron core transformer is, to me at least.

 

Kind regards,

 Marc