4-prong to 3-prong dryer power adapter??

[tortuga]

You are asking contractors to approve un-listed adapters

I dont know where adapters are required to be listed, I have wondered this before.

RE OP question #1 Although I would never recommend using this, the device might technically the requirements of 250.130(C)(4)

An equipment grounding conductor that is part of another
branch circuit that originates from the enclosure where
the branch circuit for the receptacle or branch circuit
originates

 

[tortuga]

3. This gets me thinking if one bonded the chassis of a dryer and the chassis of a washer (plugged into a 20-amp outlet) sat next to each other (e.g., with a 10 AWG wire), would it accomplish #1 the same?

Assuming you have the 4 wire cord installed correctly with the neutral floating, and you installed a 4 wire receptacle with the ECG floating yes.
However that would be an illegal install.
What I do as a legal install is just run a #10 to the closest accessible point on a grounding electrode conductor, and install the 4 wire receptacle.
The idea is to keep the neutral floating.
There has been much debate as to what type of cables you can do this with. But if you have 3 wire ungrounded NM you safe. SE cables get more complicated.

 

[ramsy]

I dont know where adapters are required to be listed, I have wondered this before.

Every adapter should have NRTL listing stamped right on it.



I thought missing NRTL's are either from Amazon.com, counterfeits, or otherwise illegal?

 

[mtnelect]

Sections 250-134, 250-138, 250-140, and
250-142(b). Receptacles and cord sets must be 4-wire (three
circuit conductors plus equipment grounding conductor).

 

[mtnelect]

Clothes dryers are available in many models.
Electric clothes dryers have an electric heating element
and a motor-operated drum that tumbles the
clothes as the heat evaporates and expels the moisture

 

[retirede]

Sections 250-134, 250-138, 250-140, and
250-142(b). Receptacles and cord sets must be 4-wire (three
circuit conductors plus equipment grounding conductor).

Did you read all of your attachment? That’s not what it says at all regarding existing 3 wire installations.

 

[mtnelect]

Did you read all of your attachment? That’s not what it says at all regarding existing 3 wire installations.

Yes, it is confusing! It mixed in the SE cable with the 4-wire ...

 

[tortuga]

I should have clarified in my post I only do that 250.130(C) to upgrade an old existing installation to a 4 wire. Anything new is 4-wire of course.

 

[mtnelect]

Prior to the 1996 National Electrical
Code,® it was permitted to ground the junction box to
the neutral only when the box was part of the circuit
for electric ranges, wall-mounted ovens, surface cooking
units, and clothes dryers, Section 250-140

 

[mikeames]

I always wondered why they didn't just install a 240-volt motor and eliminate the need for the fourth wire. It's certainly not because the volume of electric dryers being manufactured is too small to justify it. Anybody have the inside scoop?

Because they had an incandescent appliance lamp in there along with all the "who has" and "do dad" electronics. Of course that coul all be 240 as well but...

 

[mikeames]

Tying the ground wire to the grounds of two circuits (end in same breaker panel) appears safer than just the ground of one circuit for 30-amp fault current... did I miss anything here?

A 12awg conductor will trip a 30A with no problem, trying to parallel another would not make it safer.