120V outlets from 2-Wire 240V wires??


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Old 06-29-12, 08:17 AM
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120V outlets from 2-Wire 240V wires??

So I am in this large warehouse which have 2 electrical boxes on every other support beam. We never used any of them before, but we need to now.

I thought they would be empty, but I removed the cover of the electrical boxes and there were thick guage wires inside with caps on them. The wires went from the ceiling into caps, which then connected to wires going into the other electical box o nthe other side of the support beam. The other side just had caps on them also.

There were only 2 wires, one grey and one pink/peach. I took a voltmeter to them and it read around 270V. I am guessing this is a 240V line?
I would like to plug a regular 120V desk fan into it. What would I need to buy and how would I wire it?
If its even possible...
Thanks!
 
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Old 06-29-12, 08:21 AM
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Welcome to the forums.

So you only have two wires total and each of them is reading 270 volts?
 
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Old 06-29-12, 08:42 AM
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This box may be fed from a 480/277Y panel. Do you have access to the electrical room and panels?
 
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Old 06-29-12, 08:44 AM
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I have 2 wires, I put each probe on each wire, and it read 270V.

I do have access to the panel, just not sure which switch it is. There are around 400+ breaker switches.
 
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Old 06-29-12, 09:00 AM
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There were only 2 wires, one grey and one pink/peach. I took a voltmeter to them and it read around 270V. I am guessing this is a 240V line?
Given that one of the wires is grey and the other may be a faded orange, and that your meter read 270V, I'm guessing that this is a 277V single-phase line. You can verify that by reading from each wire to ground.

If it is, you will have to re-feed this box from a panel that's probably on the other side of a step-down transformer in order to have 120V power there.

I do have access to the panel, just not sure which switch it is. There are around 400+ breaker switches.
This sounds even more like a typical 480/277Y service, with 208/120Y obtained from a step-down transformer.

This is probably a job for a qualified professional. Another question is whether you own the property or lease the space.

That said, if you can post some pictures of the electrical room(s), we may be able to give you some further advice. See How To Include Pictures In Your Post.
 
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Old 06-29-12, 10:20 AM
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The voltage reading are no where close to a 120/240 system. A licensed contractor will need to find another source of power for your 120 volt fan.
 
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Old 06-29-12, 11:55 AM
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I would like to plug a regular 120V desk fan into it. If its even possible...
The short answer is that isn't possible at that location without rewiring.

Here's what's interesting about your question, though. I've spent years installing electrical systems fed with 480/277Y power. I've been trying to recall an instance where we pulled 277V power down to receptacle level. It's just not done, because the devices we use - like your desk fan - can't use it. To switch level? Yes, all the time. That's what 277V power is used for: lighting. But we would never pull one hot and one neutral to a switch. So I have no idea why that power is in those two boxes.

Having said all that, here's a suggestion for something you can do before you call a licensed contractor and agree to some work that won't be inexpensive: Keep looking for 120V power at floor level. Notice where you're currently able to plug stuff in - your computers, your printers, your cell phone chargers. Follow the pipes to see where else that wiring might be. Or just go open up the boxes on some more columns near where you would like to have a fan.

Here's what you're looking for: Any combination of black, red or blue wires with one or more white wires. That should be 120V power. Here's what you're not looking for: Any combination of brown, orange or yellow wires with one or more gray wires. That should be 277V power. Carefully close up the 277V boxes -- 120V tickles; 277V bites, hard.

When you find the low voltage colors, test there to see if it's hot and to ensure that it's 120. If so, look in the back of the box for the circuit designation. With more than 400 circuits, you have several panels - probably several for each level of power. So you might see something like "L3-21" written in the box or on the back of the cover, telling you that that box is being fed by circuit 21 in panel L3. (I have no idea what designation system may have been used for the panels, but circuit numbers are circuit numbers. Circuit 21 is the 11th breaker space from the top on the left side of every standard panel in the building). Then you find the breaker for circuit 21 in panel L3, turn it off, test again to be sure that killed the power, and install your receptacle there.

Post back if you have more questions.
 
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Old 06-29-12, 12:09 PM
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Well if you need more then one 120v outlet* depending on the size of the 277v supply you could install a transformer (buck/boost?) and a subpanel. Again wouldn't be cheap and NOT a DIY job.


*Outlet as defined by the NEC.
 
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Old 06-29-12, 04:55 PM
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There were only 2 wires, one grey and one pink/peach. I took a voltmeter to them and it read around 270V. I am guessing this is a 240V line?
Considering your limited knowledge you should do yourself and your family a BIG favor and immediately close up the panel and never ever get into it again. Just two of those wires measuring 270 volts can do tremendous damage to you! Take a look at this and you'll see what I mean.

480 volt 3-phase Arc Flash Demonstration - YouTube
 
 

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