Re: Does any wall dimmer have overload protection?

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"Marc_F_Hult" <MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote in message
news:mr7nv3p4mgol76p1d7q5luoavtkc5bo4ei@xxxxxxxxxx
> On Tue, 8 Apr 2008 10:49:50 -0400, "Robert Green"
> <ROBERT_GREEN1963@xxxxxxxxx> wrote in message
> <VPydnedJd6PvFWbanZ2dnUVZ_saknZ2d@xxxxxxx>:
>
> >I don't think there's any way to prevent plugging a vacuum cleaner into a
> >dimmer unless you made the outlets and plugs incompatible.  An easy way
to
> >do that with a lamp outlet is to replace it with an ungrounded outlet and
to
> >make sure that the vacuum cleaner has a grounded plug.
>
> Just so that we are clear, IMO this suggestion is _also_  a violation of
the
> US National Electrical Code (NEC) .
>
> (But don't take your NEC advice from a geologist! ;-)

It's also not a very good solution for the reasons I noted, mainly that
plenty of seriously "dangerous to dimmer" loads come with an ungrounded
outlet.  I offer it only as stopgap and as being marginally safer than the
current situation of the OP.  It's akin to the little protection X-10
provides against plugging in non-lamp loads into dimmer modules.  It may be
for him that the only dangerous load likely to be plugged in *is* his vacuum
cleaner and eliminating that threat eliminates 96% of the problem.

But you're absolutely correct in pointing out that it's not codeworthy to
downgrade a grounded outlet to a two pin device.  The only way to be
absolutely sure is to use a specially keyed plug and outlet that will allow
nothing but the dimmed device to be plugged into the dimming outlet.  X-10
"avoids" this problem in two ways with their modules.  First, they use a
bright red label at the device outlet that says "Lamps Only" and the second
is two make their lamp modules all two pin, at least AFAIK.   For me, both
the red label and the two pin outlet actually do serve as a good reminder to
use lamps only,

> That way, you
> >couldn't accidentally plug the three-pronged vacuum cleaner cord into the
> >two pronged lamp outlet without a three-wire adapter plug.  That's pretty
> >easy to do with plug-in lamp dimmer modules, because (IIRC) the X-10
> >versions are all two pin devices.  That's not a complete solution,
though,
> >because more and more heavy duty appliances are double-insulated and do
not
> >use a three-pronged grounded plug.
> >
> >As Marc has noted, it's precisely this situation that makes dimmer
> >controlled outlets "against code."  It's just too easy to make a mistake
and
> >plug in a motorized device, often with serious consequences.
>
> Specifically supplying 'dimmed' power to a standard Edison AC power outlet
> (eg "duplex" ; NEMA 5-15) is, in this geologist's opinion, a violation of
the
> National Electrical Code (NEC) 110-3(B) and 404.14(E) (and maybe others)

And even if it's not against code, it's certainly NOT a good idea to do so,
as many melted dimmers can probably vouch for.  (-:  The problem, of course,
is that many, many houses have been wired so that a wall switch controls an
outlet, and when upgraded to nearly *any* kind of wall-box dimmer, such
wiring becomes a potential hazard.  I'll bet a lot of wall switch dimmers
are controlling switched outlets. )-:

> Lutron makes an specialized connector set (eg NTR-15-HFDU outlet and
> RP-FDU-10 plug ) that has UL listing for dimming, but ABIK it is only UL-
> listed for use with Lutron dimmers -- of course ! ;-)
> www.lutron.com/pdfspecs/novatb.pdf These dimmers may very well also "make
> smoke" when used with the inductive load presented by a vacuum-cleaner
motor.

However, it sounds like the connectors might be used, unlisted, with the
OP's X-10 setup.  All that's really required is to insure that the lamp plug
and outlet are not compatible with normal AC sockets.  I've seen some
specially-keyed 110VAC outlets that might work (they had curved prongs and
receptacles) and if I get a moment, I'll try searching them out.

Since you've got a lot of dimmer experience this might be a good time to ask
what's involved, technically, with building a "wrong load" protection
circuit into a dimmer, to get back to the OP's original subject?  We know
that excessive heat is a product of plugging in the wrong load, but surely
there must be some other way to detect a non-resistive load other than
self-immolation!

--
Bobby G.