GFCI with Aluminum wire

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  #1  
Old 02-22-05, 12:56 PM
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GFCI with Aluminum wire

Hi, I just installed a GFCI (where there wasn't one previsouly) and after reading the info booklet I found that it said the GFCI was for use with copper wire only. Why is that?? Am I still protected or do I really need to change it?

The wiriing is old aluminum wiring (the house is 30+ years).

I installed the GFCI in place of one of those old "razor only" outlets. I was wondering, just out of curiosity, how those razor only outlets work?? I realize there's a transformer in them, but what was the purpose of these plugs?

Thanks!
 
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  #2  
Old 02-22-05, 01:32 PM
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It's an easy fix. Buy a few wire nuts designed for connecting copper wire to aluminum, and a bit of copper wire. Splice in a segment of copper wire for connecting to the receptacle.
 
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Old 02-22-05, 07:36 PM
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Thanks. I went to the hardware store today and bought special wire nuts and also anti-oxide grease (the sales guy suggested it). I must say though I had d ahard time fiding the nuts... They had TONS of copper/copper nuts, but for copper/aluminum they only had a few small boxes (only 6 per box)... I'd have thought these would be more common as surely there are many houses with aluminum wiring and mostly all recepticals these days are meant for copper.

Or am I being overly concerned with this whole thing??
 
  #4  
Old 02-22-05, 07:44 PM
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You are not being overly concerned. If the receptacle is not rated for aluminum wire, then you shouldn't connect the aluminum wiring directly to it.

The store only had a few small packages because they don't sell many of them. Most homeowners are ignorant when it comes to aluminum wiring and have no idea that special precautions must be taken.
 
  #5  
Old 02-22-05, 07:46 PM
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So can anyone answer my 2nd question.... How exactly do the "razor only" receptacles work?
 
  #6  
Old 02-22-05, 08:06 PM
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It's an isolation transformer. Both sides are 120 volts, but the output side (where you plug your razor) has no ground reference. That way you theoretically can't get shocked by touching only one side. Don't try this at home. But the transformer has limited capacity, and thus is why it's marked for razors only. Don't plug a hair dryer into it. It's the safety mechanism for bathroom receptacles that was replaced when GFCI was invented.
 
  #7  
Old 02-22-05, 08:23 PM
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I still don't understand 100% (As I'm sure you can tell I'm no electrician.... but I do have a lot of interest in it). And I guess I don't totally understand how transformers work... I always just assumed that they raised or lowered the power (how exaclty they did that, I don't know...)

Before changing it to a GFCI I tested the plug just to see what kind of voltage it gave out. I got a reading of about 136V (though the supplying line is regular 110) between the two plugs. That was not what I expected because I assumed that the transformer lowered the votlage (and rather dissipated the energy through heat, and that's why the "razor only" outlet was always warm to the touch).

But those where all assumptions. Would you mind expaining exaclty what happens in the circuit from where it comes in on the hot wire and leaves on the white wire.

Also, you said that it theorethically won't shock you if you touch only one side... so does that mean it would offer no protection if you dropped your (plugged-in) razor into a full sink of water?

Thannks for the crash course in razor only receptacles!
 
  #8  
Old 02-23-05, 07:50 AM
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Although most transformers do either raise or lower the voltage, this isolation transformer does neither. It is not there to change the voltage. The fact that you read 136 volts may just mean that the transformer is old and not perfectly functioning. Or it could mean that you didn't use your voltmeter correctly.

Think of a battery. Most batteries don't have enough voltage to kill you, but think of a really big battery that puts out 120 volts. So this battery is just sitting there on your workbench. Neither side of the battery is connected to anything. Thus it has no ground. You could safely touch either terminal of the battery, one at a time, without getting shocked. The only time you'd get hurt is if you touched both terminals at the same time. The reason it doesn't hurt you to touch only one terminal is because the battery is "isolated"--neither terminal has any voltage to ground; they have voltage only to each other. The isolation transformer serves the same purpose, only the voltage is AC rather than DC.

If you dropped your razor into the sink, it would still be okay. You'd probably trip the breaker and maybe cook the transformer, but it wouldn't hurt you.
 
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