Can I use a 3 prong to 2 prong adapter?

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Old 07-27-13, 09:47 AM
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Can I use a 3 prong to 2 prong adapter?

Just moved into a house built in the 40's. The refrigerator outlet is a 2 prong. When I meter the the 2 prongs I get a standard 122V AC. When I meter one prong to coverplate screw I get 55V AC. When I meter the other I get 14V AC. Is that "normal"? Is that enough of a ground for me to safely use an adapter until I can rerun that line?
 
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Old 07-27-13, 10:13 AM
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Refrigerators need to be on a grounded circuit. You need new wiring run.
 
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Old 07-27-13, 10:22 AM
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You should remove the cover plate and check the voltage from the receptacle to the metal of the box. There might not be a solid connection to ground through the cover plate screw. If you still get those low numbers, you have a poor ground or maybe not even a legitimate ground. If you can't solve the problem, code allows you to replace the receptacle with a gfci receptacle.

Mod Note: the GFI does not provide a ground and would not meet the Article 250 requirement of having the refrigerator on a grounded circuit.
 

Last edited by pcboss; 07-27-13 at 09:08 PM.
  #4  
Old 07-27-13, 11:24 AM
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Not sure I'd want a fridge on a GFI. Locally our inspectors will allow a non GFI outlet in a garage if they know it's dedicated for a freezer.

Mod Note: the exception for a non-gfi receptacle in a garage has been removed from the code. Now all, including garage door opener receptacles require GFI protection.
 

Last edited by pcboss; 07-27-13 at 09:10 PM.
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Old 07-27-13, 11:27 AM
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Normally.... you would install a single receptacle.... not a duplex....if it were a dedicated circuit for something like a freezer or sump pump.

It would be better to run a new line to the fridge. I wouldn't want to trust mine on a GFI receptacle.

Mod Note: the exception for a non-gfi receptacle in a garage has been removed from the code. Now all, including garage door opener receptacles require GFI protection. A properly functioning refrigerator or sump pump should have no issues on a GFI.
 

Last edited by pcboss; 07-27-13 at 09:12 PM.
  #6  
Old 07-27-13, 12:15 PM
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I agree. Just offering it as a option if there's no ground. Might be the best alternative for someone who can't have a new circuit for one reason or another.
 
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Old 07-27-13, 09:06 PM
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The wiring from the 40's most likely is not listed as a grounding means.

Here is what the NEC says about refrigerators and grounding.

250.114 Equipment Connected by Cord and Plug. Under
any of the conditions described in 250.114(1) through (4),
exposed, normally non–current-carrying metal parts of
cord-and-plug-connected equipment shall be connected to
the equipment grounding conductor.
Exception: Listed tools, listed appliances, and listed equipment
covered in 250.114(2) through (4) shall not be required
to be connected to an equipment grounding conductor where
protected by a system of double insulation or its equivalent.
Double insulated equipment shall be distinctively marked.
(1) In hazardous (classified) locations (see Articles 500
through 517)
(2) Where operated at over 150 volts to ground
Exception No. 1: Motors, where guarded, shall not be required
to be connected to an equipment grounding conductor.
Exception No. 2: Metal frames of electrically heated appliances,
exempted by special permission, shall not be required
to be connected to an equipment grounding conductor,
in which case the frames shall be permanently and
effectively insulated from ground.
(3) In residential occupancies:
a. Refrigerators, freezers, and air conditioners

b. Clothes-washing, clothes-drying, dish-washing machines;
ranges; kitchen waste disposers; information
technology equipment; sump pumps and electrical
aquarium equipment
c. Hand-held motor-operated tools, stationary and
fixed motor-operated tools, and light industrial
motor-operated tools
d. Motor-operated appliances of the following types:
hedge clippers, lawn mowers, snow blowers, and
wet scrubbers
e. Portable handlamps

A properly functioning refrigerator should have no issues with GFI protection.
 
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Old 07-28-13, 05:58 PM
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I agree. Just offering it as a option if there's no ground. Might be the best alternative for someone who can't have a new circuit for one reason or another.
The option for installing GFCI protection on an ungrounded circuit is allowed in order to provide the equivalent protection to personnel that a grounded circuit would provide. Installing GFCI protection is not a substitute for, and does not provide, an equipment ground. It will not provide the independent path to ground that some electronics and other appliances require, especially, in this case, a refrigerator.

Tech Note: The real, full name of the bare or green conductor that folks often refer to as "the ground wire" is "the Equipment Grounding Conductor," or EGC.

EGC = ground. No EGC = no ground.
 
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Old 07-29-13, 09:49 AM
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Nashkat1, I've been told that some electronics do use the ground for a reference, but I'm not an electronics guy, so I can't state that from experience.
But why would you say"especially a refrigerator", unless of course you mean refrigerators with electronics in them?
 
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Old 07-29-13, 12:27 PM
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Gari, answering questions that challenge earlier posts is becoming tiresome. Especially when the answer has already been posted:
Originally Posted by pcboss
Here is what the NEC says about refrigerators and grounding.

250.114 Equipment Connected by Cord and Plug. Under
any of the conditions described in 250.114(1) through (4),
exposed, normally non–current-carrying metal parts of
cord-and-plug-connected equipment shall be connected to
the equipment grounding conductor...

(3) In residential occupancies:
a. Refrigerators, freezers, and air conditioners...
Yes, refrigerators with electronics is part of it. But the more important reason is the reference to

"exposed, normally non–current-carrying metal parts of cord-and-plug-connected equipment..."
 
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Old 07-29-13, 02:00 PM
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Article 406.4 (D) (2) (C) says in part that "A non–grounding-type receptacle(s) shall be permitted to be replaced with a grounding-type receptacle(s)
where supplied through a ground-fault circuit interrupter".
Neither the article you quoted or the one I'm quoting says anything about one superceding the other. So does that that mean we can pick the one that fits our individual situation? I don't have an answer for that.
But knowing how a GFCI works, I feel that if for some reason a new grounded circuit isn't in the cards,that it's a much safer option for the protection of persons that may come in contact with the refrigerator.
 

Last edited by Nashkat1; 07-29-13 at 03:20 PM. Reason: Remove non-beneficial comments
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Old 07-29-13, 03:24 PM
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knowing how a GFCI works, I feel that if for some reason a new grounded circuit isn't in the cards,that it's a much safer option for the protection of persons that may come in contact with the refrigerator.
Yes. As stated earlier in this thread,
Originally Posted by Nashkat1
Installing GFCI protection is not a substitute for, and does not provide, an equipment ground.
 
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Old 07-29-13, 03:53 PM
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As quoted above, certain equipment must be on a grounded circuit. While it is legal to replace a 2 prong with a 3 prong if gfi protected, it does not mean you can ignore the other article. Both need to be considered in conjunction with each other.
 
  #14  
Old 07-30-13, 08:57 AM
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For a fridge a solid ground connection provides two nice features:
1) It allows a path for the electronics to filter out noise generated from the active side of the circuit (compressors = noise makers). While it likely won't harm the fridge, this noise feeds back into the rest of the circuit and can interfere with other devices (I'm assuming that it is likely not a dedicated circuit for the fridge since it's circa 1940's).
2) The ground provides an "exit" path for any stray current that makes its way into the fridge chassis (this current can come from an electrical short that develops, or in some cases the motor or compressor or other components can actually generate an EMF that will charge the exposed metal parts of the fridge). You would actually feel this current if you were touching metal on the fridge and some other grounded device in the area and could get a mild to severe shock depending on how much current is available.

Since this likely does not comply with NEC, I won't suggest simply using copper piping (instead of plastic) to connect an ice maker or water dispenser to the fridge, even though there is a very good chance it would be tied to ground internally. Of course for that to work it would have to be a brass fitting on the fridge side and not a plastic one.
 
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