Paul Christensen wrote:
> The reference to that is NEC Article 250.140. Specifically, it
> address the use of an external grounding conductor to the frame of a
> 4-wire dryer on legacy 3-wire service when several conditions are
> met:
>
> (1) The supply circuit is 120/240-volt, single-phase, 3-wire; or
> 208Y/120-volt derived from a 3-phase, 4-wire, wye-connected system;
> (2) The grounded conductor is not smaller than 10 AWG copper or 8 AWG
> aluminum; (3) The grounded conductor is insulated, or the grounded
> conductor is uninsulated and part of a Type SE service-entrance cable
> and the branch circuit originates at the service equipment; and (4)
> Grounding contacts of receptacles furnished as part of the equipment
> are bonded to the equipment.
>
> The 1996 NEC revision had much to do with this change. However,
> nowhere in the NEC does it state that a new dryer connection must be
> 4-wire. But since many dryers need 4-wire connectivity, the NEC
> indirectly compels the use of a 4-wire branch and receptacle because
> as of 1996, the neutral and ground can no longer be shared at the
> dryer.
>
> Some imported Korean laundry dryers do not require a neutral since
> they only utilize the line-to-line 240VAC circuit. Hypothetically,
> under new construction when using one of these new dryers only 3-wire
> branch and receptacle service is required ( L1-L2-G, no neutral).
> That's what the NEC says -- or rather doesn't say. Local codes will
> vary.
>
> The days of "big iron" motors and blowers in appliances running off
> of 60 Hz are coming to a close. My own dryer uses switch-mode
> direct-drive motors (one for the drive, the other for the exhaust
> blower) running at close to 100 kHz. Of course in the name of lower
> production costs and energy conservation, we then have to contend
> with the RFI/EMI issues, especially from direct-drive washers.
From the "For what it's worth" department, we just bought a new GE
electric dryer a few weeks ago and it came equipped with a three wire
power cord and three wire plug that plugged right in to the three prong
socket installed when the house was built in 1968.
I haven't been on the air since we got the new washer (direct drive) and
dryer, so maybe I'll be in for a big surprise! <grin>
Carter K8VT
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