Film-Tech Forum ARCHIVE: Concession Trailer Wiring

This is topic Concession Trailer Wiring in forum Film-Yak at Film-Tech Forum ARCHIVE.

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Posted by Barry Floyd (Member # 385) on 02-01-2007, 08:55 AM:

Maybe someone with some 12 volt technical knowledge can help me on this.

I've got a 20 foot concessions trailer we use at the theatre (drive-in) on busy weekends to help alleviate some of the crowds at the main concession stand. I'm trying to figure out a way to illuminate the exterior 12 volt running lights on the outside of the trailer when it's UNPLUGGED from the tow vehicle.

I'd like to find some type of 110 volt AC to 12 volt DC power converter to use so I won't have to rely on a big 12 volt deep cycle battery. When I get it figured out, I'd like to be able to go inside the trailer, flip a switch and control the exterior lights that way.

I have an existing 12 volt power supply that I use in my garage for smaller things, but I think it just doesn't have enough power output to run all of the lights. The trailer probably has 15-18 exterior lights, but I have no idea what type of amperage they draw.

Currently the trailer has no 12 volt power supply of it's own, only a 50 amp 240 volt shore power panel to feed all of the equipment inside.

Any suggestions??

Posted by Dave Macaulay (Member # 813) on 02-01-2007, 12:44 PM:

If they are just normal light bulbs, then they don't know the difference between AC and DC... just buy a 120V to 12V transformer and connect it to the "running lights" terminals on the trailer plug. You could test the required current with a jumper lead and multimeter if you have a 10A or higher meter. If you install the transformer inside the building and run the 12V power out to the trailer you can avoid outdoor shock hazards (and lawsuits...) and quite a few wiring code issues too, 12V wiring is relatively unregulated.
If it has LED lights you should use DC power (attention Strong, LEDs don't like high reverse voltage). If there is any electronics (like a tail/stop light decoder) in the trailer wiring you need DC. It doesn't have to be regulated, a battery charger might be all you need.

Posted by Barry Floyd (Member # 385) on 02-01-2007, 01:35 PM:

Thanks Dave,
There are no electronics anywhere in the trailer wiring harness. We bought the trailer new in April of last year, and it has been an on-going project ever since.

I have a 110volt to 12volt step down transformer out in my garage/workshop that I'm not using for anything... I guess I could try that. I'm just assuming that since there's AC power going in, there's AC power coming out.

One thing that worries me with the AC, even only 12 volts is the potential to end up creating a "HOT SKIN" situation with the trailer. All of the running lights on the trailer only have one wire coming from each of them, and they are grounded to the trailer frame and skin.

Posted by Kenneth Wuepper (Member # 1174) on 02-01-2007, 03:28 PM:

Barry,

Use the proper grounding stake beside that trailer and bond the body to the ground stake.

If you use an Isolation transformer, you can ground one lead of the transformer output to the ground stake and have the other lead of the 12 Volt AC go to the running lights terminal. Be sure to check the transformer for excessive heating if you are not sure of the load currnet.

If you really want DC current for those lights, maybe you can scare up an old exicter lamp supply and use it. Many of those supplies give out enough current to run those lights. Be certain that your lights are not LED operated.

KEN

Posted by Jason Burroughs (Member # 68) on 02-01-2007, 05:44 PM:

Check out a RV parts dealer. Surely they'd have something that would meet your requirements.

Since they are a fairly common item, the costs should be manageble. Maybe something in the used/refurbished market too.

Such a power supply should be able to provide proper grounding, and circuit protection.

Posted by Louis Bornwasser (Member # 3063) on 02-01-2007, 06:55 PM:

12 volt isolation transformers are available at any Home Depot or Loews. They are used for wiring garden lighting.

If current is insufficient, try an industrial electrical (conduit, Allen Bradley) dealer in any city. They can order 12 v trans in any current, even big stuff. DO NOT allow an autotransformer; they are not isolated.

How many bulbs? All the same? Easy to look up the bulb specs and add them up to get current draw for the trailer. Louis

Posted by Jack Ondracek (Member # 1466) on 02-02-2007, 01:01 PM:

quote:
12 volt isolation transformers are available at any Home Depot or Loews. They are used for wiring garden lighting.

If current is insufficient,

... go back to Home Depot, get another and hook 'em both up.

Posted by Barry Floyd (Member # 385) on 02-02-2007, 01:47 PM:

So you guys are talking about a standard 12 volt power pack that powers low voltage landscape lighting?? I've got one of those at the trailer pad down at the theatre. Where we park the trailer at the drive-in, it sits on a 30 x 30 pad surrounded by 10-15 3-teir low voltage landscape lights powered by a 300 watt transformer. I'll give it a try this weekend and see if I blow anything up. [Big Grin]

Posted by Phil Hill (Member # 371) on 02-02-2007, 09:03 PM:

While I agree the landscape transformer is a good solution, I would be leery of the do-it-yourself aspect.

In a commercial biz, I would hire a licensed electrician to install the solution. The $$ spent for him is cheap insurance for any possible litigation should something go wrong down the road with the do-it-yourself thingie.

Posted by Bill Enos (Member # 440) on 02-03-2007, 12:46 PM:

How about a 12 volt battery charger on a switched outlet? Correct voltage, D.C. in case there are any l.e.d.s, inexpensive.