I've noticed a bit of confusion lately with new requirements for 4 wire dryer circuits.
#1 a Store employee told a customer that was looking for a dryer outlet that He had to install a 4 wire receptacle (& cord/plug) even though He only had a 3 wire cable there now. - "Just put a Jumper" (I made a point to correct him)
#2 I've had the task of installing several 4 wire dryers recently and noticed that the labels on the Appliances give instructions on where to connect the 4 wires (including ground) but do not inform you that the Factory-Installed bond from neutral to frame has to be severed. Only after digging into the manual did I find a Fuzzy description of what had to be done. (Bad picture too!)
A lot of sparky's are getting into it with appliance peddlers, most of whom are not versed in the NEC,yet may suggest, or even install. I find a lot of outdated reference to the old 250-60. In trying to explain the need for a 4-prong pigtail, i've been simply pointing out an average receptacle's separation of N & G, as relates to recent code practice concerning dryers, ranges etc. One has to have a shred of sympathy for the appliance man here, who has been pedaling 3-prongs forever.
Until the 50's, equipment grounding was not considered a big deal. Washing machine outlets had 2 wire receptacles. Machines came with a jumper and clamp to connect to the cold water pipe. Electric dryers were treated the same. The problems developed when the appliances were on a concrete floor, and the jumper was not connected. To avoid lawsuits, the manufacturers grounded the neutral to the frame. Many are still in operation. It will be a long time before homes catch up with the four wire connections. I don't think material shortage had anything to do with the three wire circuit, it was just the thinking at the time, face it, they work, and don't appear to be a problem, other than the discomfort of the customer, when the plug won't fit. My personal opinion is; There was nothing dangerous with the three wire connection, and it should have been left alone.
Wouldn't bonding the frame of a clothes dryer to the neutral on a three-wire be similar to bonding the Green Screw of a 125V receptacle to the neutral on an old two-wire circuit to achieve a "grounded" plug?
I don't see the difference especially considering that most, if not all dryer motors run on 120V, unbalancing the loads a significant amount. So either I'm missing something here...or...?
I've been known to insist upon four-wire installations if I have my name associated with it, am I justified in this thinking? Or have I been "just hard to get along with"?
Thanks for your comments, and don't be afraid to correct me! I'm always learning...
-Virgil Residential/Commercial Inspector 5 Star Inspections Member IAEI
I heard exactly the same rumor about the copper shortage in WW2 & I believe that is the reason that the 3 wire installation was allowed. As a side note, the Manhattan Project would have used so much copper for transformers that it would have actually hurt the war effort. The treasury ponied up several million ounces of silver which was made into wire for the required transformers.
As Bennie pointed out, the 3 wire installation has had an excellant safety record. However, the jacklegs in this business started to think that neutrals (wahatever they are) and equipment grounds were interchangeable. I think it is best that we have now gone to a 4 wire installation.
Few things are harder to put up with than the annoyance of a good example.
My concern regarding the change, is it is too little too late. There is many more older homes than new ones. Homes far outlast the appliance. Homeowners will often change the attachment cord to a three wire, now there is no ground at all. Should they change the receptacle to a four wire, they do not have the fourth wire, again, no ground at all. This is not increasing safety. Very bad decision, in my opinion. It was not broke until the fix was in.