At 21:26 7/1/96 -0500, Ed Mulligan wrote:
>Let's see if I can send to this list. . .
>
>All this talk about dryer cords and grounding got me wondering. I dug out
>the 1996 NEC, and an article
>about the new 1996 NEC changes, and my 1996 NEC class notes, and the 1993
>NEC Handbook. From
>SNIP
Ed:
Thanks for the info. Seems like I have to go out and buy a new copy of
the NEC now. :-) This change was LONG overdue. I would equate this to the
sea change that required grounded plugs on 110 volt residential circuits. I
have not seen the new 4 wire plugs and receptacles, but as soon as they hit
my local area, I am going to retrofit my 220 volt appliances - grandfathered
or not! Safety comes above a few bucks and a flimsy 18 guage green wire!
Will also make 110 and 220 volt wiring practices consistent and more easily
understood by electricians.
SNIP
this I would guess that the reason your dryer has no separate ground wire is
>that the NEC didn't require it at the time. As I see it, the dryer is OK
>(grandfathered under the revised for
>1996 section 250-60) and the air compressor would never be legal connected
>the same way (section 250-
>61(b)).
> --------------------------------------------------------------------
>From Electrical Contractor magazine, 9/95
> ARTICLE 250 - GROUNDING
>Ranges, Dryers, and Ovens Now Require Four-Wire Receptacles and Cords
>Section 250-60 Clarify intent of Code
>The code no longer permits the grounded circuit conductor (neutral) to
>ground the frame or junction box
>of electric ranges, wall-mounted ovens, counter-mounted cooking units,
>clothes dryers for "new
>installations." Note: This change brings the NEC into alignment with the
>Canadian Electrical Code,
>which has always required four-wire supply cords for these appliances.
>There is an illustration showing:
> "Proper Installation" = a 4-prong receptacle with the 3-prongs straight up
>and down, and a half round
>ground pin (like a regular 3-prong 110V outlet, but with an additional slot).
>VIOLATION = the three prong receptacle with the neutral connected to the
>grounded conduit system at
>the receptacle box.
> --------------------------------------------------------------------
>According to Gregory P. Bierals (my employer brings him in to explain the
>changes to the code every
>three years - he's the only man I've ever met that has actually memorized
>the NEC. Ask him a question,
>and he'll tell you the answer, the section the answer is from, and often the
>page number it appears on in
>the paperback edition.) "A significant modification has been made to Section
>250-60 with regard to the
>use of the grounded conductor (neutral) for the purpose of grounding the
>frame. . . This provision will
>only apply to existing installations and not to new branch-circuit
>installations which will require an
>equipment grounding conductor routed with the branch-circuit conductors as
>the equipment grounding
>means."
> --------------------------------------------------------------------
>Why did the code allow this in the past? This is from the 1993 NEC Handbook:
>"The use of the grounded circuit conductor for grounding purposes is
>contrary to other sections of the
>Code. . . However, it has been allowed for many years because of the good
>safety record of those
>appliances that are grounded through the grounded circuit conductor and
>because an open splice or break
>in the grounded circuit conductor would normally render the appliance
>inoperable. A subcommittee
>reevaluated this requirement for the 1984 NEC and verified the continued
>good safety record." It goes on
>to explain exactly what would happen if this wiring practice should fail -
>fire/injury/death.
> --------------------------------------------------------------------
>What does section 250-61(b) say?
>"Load-Side Equipment. A grounded circuit conductor shall not be used for
>grounding noncurrent-
>carrying metal parts of equipment on the load side of the service
>disconnecting means or on the load side
>of a separately derived system disconnecting means or the overcurrent
>devices for a separately derived
>system no having a main disconnecting means." It lists 5 exceptions - none
>apply to your air compressor.
> --------------------------------------------------------------------
>My $0.02:
>** As always, check this with an actual residential electrician.** We don't
>wire too many dryers or ovens
>in our manufacturing facilities, so I'm no expert.
>I've always understood existing installations to be grandfathered, until you
>start to work on them. If you
>make a change, you have to bring everything up to current code spec. So
>right now, your dryer should be
>legal. Connecting the air compressor this way would violate section
>250-61(b). Spring for a new circuit
>breaker and outlet. Parts and labor are cheap compared to people and
>equipment.
>If the compressor is portable, or at least able to move, I'd use a
>twist-lock plug and receptacle as well. I'd
>hate to be there if the plug gets pulled out or plugged in with the motor
>on. Besides, it promotes domestic
>harmony to not have the cars interfere with the laundry.
>
>Ed
>
>
>Ed & Laura Mulligan mulligan@fullnet.net
> http://www.fullnet.net/user/mulligan
>'92 5.0 LX "I love the sound of Flowmasters in the morning!"
> MOUSE: "You're immune to both romance and mirth, you must be a. . . a. . ."
> DILBERT: "That's right. I'm an engineer."
>
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