Help wiring a distro box - 3 phase to single 120v

Looking for some websites or books that will help me learn how to do this. Or if anyone can help, visuals are needed!

I want to learn how to build a distro box for audio. Input will be 3 phase camloc, output will be several circuts of 120v edison. I know the concepts of 3 phase power and transformer architecture (wye/ delta) But I haven't found a resourse that puts all these concepts into a concise explaination of how I can make them work together. I'm looking for a wiring diagram including the necissary circut breakers on primary and secondary sides. Do I even need a transformer? I have no idea. I'm an audio guy. Help me out here.

It's going to be a portable unit in your standard small panelbox size, about 12"x18"

[ship]

I'm a big fan of the NEC handbook, American Electrician's Handbook, but there is lots of other sources such as Comercial Electrical Wiring out there that won't cost a day's pay to purchase.



In any case, a review of the NEC in temporary power distribution and sections on entertainment lighting much less distribution panels would be helpful as this subject has many parts it falls into for guidance.

Having someone build or atleast watch over your shoulder on this box is very avisable if for nothing else but if this box is done wrong you can get fined if not cause a major injury that could put your company out of business if not kill someone. I'm not saying this type of sub panel is not easy to do, just that without lots of experience in building them - get someone that does have that experience. The devil is in the detail and best left not posted as a step by step. There has been past postings either here or on ProSound's Lighting Network on the subject.

Contact your local lighting company brother and see if you can come in for a demo on how to build such a panel, how much it would cost in labor to supervise you in building it or building it for you while you look over their shoulder, or in buying one pre-built from them. Never a bad idea to have such things built by those who do this for a living, it's than their liability also. At very least if they follow the general concepts below in addition to those not thought of, you will see the details of such a thing.


You need to mount the sub-panel to a painted 3/4" plywood mounting as per temporary job site distribution power not only to mount it but since the sub-panel is not allowed to be the means of support for it's outlets, the plywood is necessary to also support the outlets.

You need to keep your neutral seperate from the ground as per a sub panel.

Your tails feeding the panel can not be more than 10' long.

If going CamLoc than you are at 120v per phase if in the US. No need for a transformer but a definate need to meter your service before plugging in and in getting someone to look over your shoulder in building this much less in plugging it in. This for instance will prevent you from hot patching or un-plugging while live - a bad thing.



You either need a main circuit breaker, or the capacity of your breakers cannot be over that of the wire feeding it and such individual circuit's breakers cannot exceed six. In other words, you can go with a main cut off breaker that will shut it all down, or in case of emergency the maximum amount of individual circuit breakers you are allowed to have without the main is six be they double single or tripple - a question of physical levers to shut the panel down down.

Anything with more than one phase in output must be on a tied circuit breaker to prevent half or part of it's power tripping and leaving on the other legs of power. In your case as stated you are no doubt only tapping off it for 120v single phase power - no moving lights. Given this is the case, you might be able to even get away with three individual main breakers, but it's still better to have them at least tied and rated for the maximum amount of load plus some as you expect to see. If you only plan on pulling 40 amps per leg, there is no reason to have a 100amp main breaker - what's it protecting than?

You are not allowed to modify a service panel. Should you wish to install panel mount CamLoc outputs, it needs to be in an appropriate sized wire gutter feeding into the panel. This mean no duplex receptacles punched into the sub panel either. What's in the panel is all that is allowed to be inside of it. No inlet plug or outlet receptacles allowed.

IF you are doing CamLoc (on cord) tails to feed the panel, you can use strain reliefs to attach them directly to the panel as if each wire was it's own conduit or the bundle of them is one as long as appropriate strain reliefs and bushings are used. Also since it's for entertainment in use the wire must by type SC. No welding cable or grade S allowed.

If your panel is feeding 60 amps per leg of power or less in load, you might not be allowed to power it up in CamLoc plugs. The NEC has a guideline about individual pin plugs and conductors in circuits 60 amps and less that I have forgotten the specifics about at the moment. This is somewhat negotable but if your total load will be in the range of 30 amps per leg, you would be much better using a multi-pin plug such as a NEMA L21-30, if not various other 50 and 60 amp multi-pin plugs out of a outlet set up for this. Given you are tapping off a dimmer pack or something like that, many of them have this power source in addition to a CamLoc feed thru. Powering up off the lighting system is bad MoJo anyway, so adding your own tails and using a sub amperage multi-pin plug directly tapped off by way of outlet your own service would be better anyway.


Next problem is in fitting the wire into the circuit breaker. If you have say a 100amp panel you will most likely need to be using #2 SC as tails. This is the minimum size that will fit in a CamLoc plug without some work done to them for filler. Assuming it's #2 SC feeding the long term usage of this panel it's probably not going to fit into a 60amp circuit breaker nor the grounding bar too well. Choices would be in going with a smaller wire such as #4 SC than shimming up the CamLoc plug to fit it, but the panel not having the ability to grow in capacity, or using either larger breaker lugs or sub-lugs and crimp pins to make larger wire fit into smaller terminals. Cutting away at the wire to make it fit is not an option, nor is dividing it up into two and installing it into a double hole. Also Deoxident and ferrules or copper tape is necessary to prevent the strands at the lug from sparking.


Lots of details - this is just getting you from feeder to main breaker. After that it's for the most part just a sub-panel and normal distribution in nature. You want to use conduit fittings to 1900 boxes, 12ga wire etc. Watch your box fill space and bushing requirements. Type MTW is possibly better to use in this panel instead of THHN, but either type would probably be sufficient.

Use all commercial or specification grade outlets because this is a commercial application of them.

When possible go with a magnetic thermal breaker as it offers a better amount of protection, Avoid Homeline type breakers, they are not commercial grade and your application is. Look for type QO or QOU amongst other types as I remember the more commercial types.

also there are some instances per code where GFCI receptacles, if not entirely going weather tight on this panel and outlets is necessary.

Above all, and especially since this is sound, it's going to be necessary to run your ground wire from outlet to ground bar, don't rely on a mechanical ground.


This is but a few details to be looking into and reading about. Lots more such as if I remember correctly your panel is supposted to be thru bolted to the plywood. Lots more I have not thought about for a while either.

[digitaltec]

I don't know if I would mess with making distro's unless your a certified electrician... there is way to much liability. If you do decide to build it yourself, I would make sure you have a electrician look at it. The last thing you want is a huge lawsuit on your hands because you killed someone or burned down a building. Even doing something as "simple" as tie-ins can result in disaster. Working with 400- 600 amps of power, you do one simple thing wrong and you dont have to worry about showing up to work the next day because you won't have a job or even be dead. Power is nothing you want to mess with, Even as many times as you may work with it you never should be to comfortable because then you get lazy. The stories I chould tell about electricians with over 20 years experiance killing themselves.... not going to go there. Just keep it in the back of your mind at all times.

Using 3 phase power presents a rather large problem for someone that does not have enough experience. There a quite a few three phase systems that have a 208v high leg ( called a delta system) that will fry just about any equipment you would be hooking up to it. I have recently seems an audio distro plugged in via camloc and they picked up a high leg and did not meter it first. They lost 8 amps that day. Also, since you do not own the NEC code book, you do not know what requirements you need to meet.( for instance there is a specific clause that prohibits unqualified personnel to do tie ins, although there are exceptions.) I would recommend getting a theatrical electrician or an electrician that specializes in temporary distribution to do this for you. (Most electricians have never heard of cam loc) A cheaper and better choice would be to simply buy a small distro from union conductor or someone like that. If you buy from them then you know it’s going to meet code and you know that it’s going to work.

As for mounting the whole thing on plywood: Its a good idea in theory, but a home made distro looks much better built into an old road case or rack. Just mount the distro on the back side of the rack and put the outlets on the front. I personally mount three meters from each leg to neutral in my rack. An indicator light for each phase is a nice idea. Ground any metal part of the rack.


Bottom line is that if you don't know what gauge cable, type and size breaker to use then you should not be doing this by yourself.

Jay

[Mayhem]

The above posts contain some very good, practical and safe information. However, as I am from Australia, I am NOT going to comment on how to build a distro.

All I am going to say is that I build all my own distro racks and whilst I am not a qualified electrician, I ALWAYS get a qualified electrician to test and tag my work for me.

I think that safety is the most important aspect to remember here.