Double Tap Wiring

mattsdni

mattsdni

Active member
I didn't want to revive an old thread from 2006, so...

Has anyone tried wiring a 2k or 5k light to run on 2 or 3 circuits to allow them to be used on regular 15A circuits? Wouldn't it just involve connecting the hot wires together and the grounds together? Or would that just make everything blow up? I'm in the process of building a 2K and don't want to deal with tripping breakers or dryer distros.
 
That is dangerous on several levels and for several reasons. NOT RECOMMENDED! The more common work-around for powering big lights is to use the "dryer outlet" and use 240V bulbs.
 
Thanks for the replies. nwstudios, I thought that might happen. I think I will just stick to 1500w bulbs for now since running a stinger from the dryer would be a hassle. Richard, I hadn't really though of using 240v bulbs. I may do that in the future when I need more power.
 
mattsdni said:
I didn't want to revive an old thread from 2006, so...

Has anyone tried wiring a 2k or 5k light to run on 2 or 3 circuits to allow them to be used on regular 15A circuits? Wouldn't it just involve connecting the hot wires together and the grounds together? Or would that just make everything blow up? I'm in the process of building a 2K and don't want to deal with tripping breakers or dryer distros.
Click to expand...

This subject has been covered extensively elsewhere in this forum (see http://www.dvxuser.com/V6/showthread.php?245070-How-to-fire-up-a-5K-fresnel.) To summarize that thread, you have two options when it comes to running 5ks on common residential 240V circuits. The first is to use a 5k with a 240V bulb. The 5k head has to be specifically designed to operate at 240V with a double throw switch (switches both hot and neutral simultaneously. So before you throw a 240V 5k globe in that 5k, you need to confirm that it has a double throw switch. If not you will have a hazardous situation where the lamp is energized without a return. You don’t want to become the return path to ground. If it does have a double throw switch you will also probably need an adapter to plug into the 240V outlet because most 5ks are wired with a 60 Bates plug.

The second and safer option is to use a 240v-to-120v step-down transformer to power a standard 120V bulb. A transformer will convert the 240 volts supplied by the 240V receptacle to 120 volts in a single circuit that is the sum of the two single phase legs. A transformer can convert a 30A/240V Dryer Receptacle into 60A/120V Amp circuit which will be sufficient to power a 5k 120V globe since it draws 42 Amps.

I regularly use transformers to power not only 5ks, but also big HMIs (2.5-4Kw) 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
 
nejuicer said:
This subject has been covered extensively elsewhere in this forum (see http://www.dvxuser.com/V6/showthread.php?245070-How-to-fire-up-a-5K-fresnel.) To summarize that thread, you have two options when it comes to running 5ks on common residential 240V circuits. The first is to use a 5k with a 240V bulb. The 5k head has to be specifically designed to operate at 240V with a double throw switch (switches both hot and neutral simultaneously. So before you throw a 240V 5k globe in that 5k, you need to confirm that it has a double throw switch. If not you will have a hazardous situation where the lamp is energized without a return. You don’t want to become the return path to ground. If it does have a double throw switch you will also probably need an adapter to plug into the 240V outlet because most 5ks are wired with a 60 Bates plug.

The second and safer option is to use a 240v-to-120v step-down transformer to power a standard 120V bulb. A transformer will convert the 240 volts supplied by the 240V receptacle to 120 volts in a single circuit that is the sum of the two single phase legs. A transformer can convert a 30A/240V Dryer Receptacle into 60A/120V Amp circuit which will be sufficient to power a 5k 120V globe since it draws 42 Amps.

I regularly use transformers to power not only 5ks, but also big HMIs (2.5-4Kw) 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
Click to expand...

I was waiting for Guy to weigh in on this topic. He's the guru on this stuff and you should learn all you can from him.
 
For 110vac you have 3 wires: Line(or Hot 110v), Neutral and ground. For 220vac in houses you have 4 wires, Line 1(hot 1 110v), Line 2(hot 2 110v), neutral and ground.

For 110v lights it's common to have a switch break both hot and neutral. I'm guessing that the 220v switch would break both Line 1 and Line 2?
 
Svart said:
For 110vac you have 3 wires: Line(or Hot 110v), Neutral and ground. For 220vac in houses you have 4 wires, Line 1(hot 1 110v), Line 2(hot 2 110v), neutral and ground.

For 110v lights it's common to have a switch break both hot and neutral. I'm guessing that the 220v switch would break both Line 1 and Line 2?
Click to expand...
Some 240v circuits have a neutral. The neutral is never switched in 120v circuits. 240 switch will break L1 and L2. The Neutral is never switched.
 
120V wiring (at least here in North America) consists of a "hot" wire with 120V, and a "neutral" wire which is zero volts and ultimately tied to ground back at the breaker box.

240V wiring consists of TWO of these 120V circuits on opposite sides of the transformer. So each hot wire back to neutral is 120V, but across the two hot wires is 240V.

Mr Holt (nejuicer) made the vital point that when using the 240V source, BOTH sides are "hot", so they must both be switched for safety.
 
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