Dryer outlet question.

[Scarpozzi]

Using the 4-prong cord would require substantial rewiring of his house...

1-2-3, just swap the cord. It's easy and safe.

http://www.homedepot.com/c/how_to_replace_a_dryer_cord_HT_PG_AP

Yeah....the cords swap out with a few screws.

4 prongs is the new nationally accepted electrical code. It's been a requirement for a number of years on new builds in most places. When you have old wiring, you can use the older plugs. They change that stuff to reduce the likelihood of a fire. I've actually seen dryer cords heat up and smoke because of the large amount of current they use.

 

[iwajabitw]

They have always had a neutral to allow the 120v path for the tumble motor and timer, for US appliances anyways. The 240v is from going hot to hot in a single phase residential service, and is used to get more power, while drawing half the current (compared to 120v), for the heating element.

The 4th prong adds an equipment grounding conductor, which serves as a fault path if the neutral is lost in the machine, which could electrify the metal case. The neutral is supposed to be bonded to the ground in the panel, and as an extra precaution, that ground will be bonded to a ground electrode, or city water pipes.

A 10/2 240v wired dryer outlet from lets say the '80s has 2-120v wires black/white, then a bare ground. The appliance may be using the bare ground as a neutral since it is bonded at the service panel or the terminal block, but I've seen them run with out the bare wire secured in dryer outlet or breaker panel.But I don't repair dryers, except maybe my own. Same with HVAC condensers, this I do repair, I come across many that have never been grounded to the disconnect, when that compressor grounds out it actually puts a charge on the line set before throwing the breaker searching for a ground, makes for a scary situation for the home owner and service tech because sparks fly at the point it finds a ground.



Newer home 240v appliances now have 12/3 or 10/3 gauge wiring pulled to the range or dryer receptacle. The wiring will have 2-120v black & red, 1- neutral white, and one bare/green equipment ground to complete what you describe above.



Seen even crazier stuff in old aluminum wiring.