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Re: [TenTec] High speed washer hum/whine

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] High speed washer hum/whine
From: Carter <k8vt@ameritech.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sat, 06 Feb 2010 11:16:17 -0500
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
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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