Range to 15amps


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Old 12-26-06, 04:44 PM
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Smile Range to 15amps

Hey I have a question I have a DJ business and we're growing and we're finding more and more schools we go to dont have enough power so I want to build a box that goes from a Range Plug down to 2x 15AMP breakers I do have some experience working with electrical equipment but have never done something like this before wondering if someone could point me in the right direction so in short what were going to do is have range plug into a mini electrical panel with two 15AMP breakers that both run to normal wall outlets that willl be mounted to a piece a plywood with the panel. Any help is appreciated THANKS!
 
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Old 12-26-06, 08:53 PM
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You don't want to build this yourself.

This is known as a "temporary power distribution center", and you buy them. You'll probably need to hunt around to find one at a reasonable price, they tend to be expensive.

http://www.jon-doninc.com/catalog/product_info.php?products_id=16915

You should know that 'range receptacles' come in all shapes and sizes, and in schools you may even find three phase power. Until recently ranges were permitted to be wired _without equipment ground wires_, and the plugs have only three holes -hot, hot, and neutral. If you try to use this sort of receptacle to supply 120V, then you would not have a proper safety ground at your 120V receptacles. I don't know if this is considered a problem with the power distribution centers, since they have GFCI protection.

-Jon
 
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Old 12-26-06, 09:12 PM
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Well I know other people who are in the business and I don't know anyone who bought one and they don't look to tricky to build. Anyways all the wiring stuff I would get has a ground and the school board around here is very picky making sure things are to code and all (at least most) have four prongs/holes. I know they're common like that because people aren't switching them around anyways I know I can get one built for about $120.00 and I just wanted to make one to learn a little more. Now im not an idiot im not going to plug it in I have a friend who is an electrician I will have him check it before I blow my hands off
 
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Old 12-27-06, 11:32 AM
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Frankly, I don't believe that you could put together a _safe_ system for less than you could buy one, but that is my gut opinion. I am sure that you could cobble together something that _works_ but that isn't all that safe for a couple hundred $$. The problem with electricity is that it does work, even if rather precarious situations, and when something fails it can fail bad.

I cannot provide you with a complete design to build your own, as I am not a suitably licensed engineer, and if I were I would charge for the design. Below are my comments which should help you do your own design work. I still recommend that you purchase something suitable, but if there is a market here, then maybe you can design something, get an engineer to refine the design, and then get it produced.

1) The overcurrent protection for your 'cord' will be the breaker that supplies the range, and that probably means a 50A breaker. I would use no smaller than #6 SO cord for this application.

2) The finely stranded wires in SO cord don't do well in the screw lugs in panels. You will need to get 'wire ferrules' and a crimp tool. These are metal sleeves that fit over the wire, you crimp them down, and then you have what is essentially a solid wire as far as the lug is concerned. McMaster-Carr sells these

3) 'Strain relief' is critical for the SO cord. You want something that will grip the cord and hold it to your 'box', without putting strain on the conductors, and supporting the cord against sharp bends. You can buy fittings that screw into the box, and then compress a rubber ring onto the cable. Some of these have spring that grips the cable and protects it. These are called 'cord grips', and come in waterproof and regular versions. McMaster-Carr also has these.

4) 'Knockouts' are often a problem. OSHA doesn't like extension cords made with 'handy boxes', because the knockouts can get punched by accident; these things are made for installation in a wall. Ideally get boxes without knockouts, and then punch your own holes where needed. Or you could mount your whole system in a box rather than on a simple panel.

5) Remember that this will be a subpanel. Ground and neutral must be kept separate. If you don't have a 4 wire plug with separate ground and neutral, then don't attempt this at all.

6) While range plugs are generally 50A devices, they are often on 40A circuits. I would design my loading with this in mind, say 6 separate 15A breakers each feeding a single duplex receptacle. (Remember that you have 2 120V legs, and that 15A plugs should only be loaded at a maximum of 12A continuously.)

7) Don't 'cheap out' on any portion of this. When you buy a manufactured, Listed product, you are paying for both material and _knowledge_. If you want to save cash, then you must make up for it in knowledge. There is no way that I can tell you everything that you need to know to get this job done correctly; you will need to research this design on your own. The best that we can do is help you to avoid pitfalls that we happen to know about.

Good Luck!
Jon
 
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Old 12-28-06, 08:04 AM
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One thing I need to do is get it to down from 240V to 120V which is really where im stuck im going to talk to a friend of mine who built one who is an electrician I know these are fairly simple to build I know tons of people who have done it I will just keep researching but thanks for the tips.
 
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Old 12-28-06, 08:26 AM
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I recommend that you get the book 'wiring simplified' and read it through; this will provide you with some basic background.

One of the problems with a site such as this is that we don't know each other's background, and don't know what knowledge to simply take for granted as known, and what to explain. This can be extremely dangerous, because I might leave out a detail that is critical, expecting you to know it.

Since you have access to an electrician, I suggest that you go over your plans with him/her. However since you are doing the internet research, you may come up with a few improvements or details that they've not thought about.

On getting the 120V: residential electric supply is almost _all_ done at 240V, with a 'center tap'. You have two 'hot' wires and a 'neutral' wire. The two 'hot' wires are 120V with respect to the neutral, and 240V with respect to each other. You additionally should have a 'ground' wire which is at 0V with respect to the neutral, and which in general shouldn't carry any current.

At a proper 4 wire range outlet, you will have access to all four of these wires. By going from either hot to the neutral you get your necessary 120V. In a subpanel, the two hots connect to the two bus bars, the neutral goes to the neutral bar, and the ground goes to the ground bar. The circuit breakers provide your protected connection to the hot bus bars, and you run your 120V circuits between circuit breaker and neutral.

I've greatly simplified this, and jotted a note off in 5 minutes. Get the book(s) and read, and the above will become much clearer.

-Jon
 
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Old 12-28-06, 08:41 AM
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Not an electrician here. Would tend to believe that anything that you use that is electricall would have to be UL approved.
 
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Old 12-28-06, 10:45 AM
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Well technically this wouldn't be legal if I did it because im not an electrician but at least locally as long as an electrician did it its fine.
 
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Old 12-28-06, 11:38 AM
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I completely agree with Jon's assessment. You would be legally liable for any damage, fire or injury caused by the malfunction of homemade electrical equipment. If your school board is truly concerned with following safety codes, they would not allow you to use unlisted equipment (assuming they know about it).

Even if an electrician builds the box it is still illegal, because you are using the equipment in a manner inconsistent with its listing without the approval of an engineer or AHJ (building inspector).
 
 

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