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Theoretical Idea

Discussion in 'Electrical Engineering' started by Den, Apr 22, 2004.

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  1. Den

    Den Guest


    I have a some European (i.e. 230V) kit that is frequency independant. In my
    house (120V) I have the usual split-phase arrangement (i.e . +/- 120V off
    the pole, some circuits fed with -120V and neutral, some with +120V and
    neutral, net effect is 120V where it's needed). I don't have any 240V
    outlets (i.e. -120V and +120V). If I wanted to run this kit is there any
    theoretical reason why I shouldn't wire it to each of two hots on separate
    120V circuits (obviously making sure one is +120V and one is -120V). What
    about practical reasons?


  2. No theoretical reason, other than 240V is not 230V. Also, you could get
    inductive heating and choke on the circuits you use, due to the unbalanced
    load situation you will cause in each of the two circuits.

    For safety's sake, have a 2 pole breaker and 240 volt receptacle installed.

    Mitch Thompson
    Electrical Panel Schedule software for use with AutoCAD

    For safety's sake, get a two pole breaker and a 240 volt receptacle
  3. Den

    Den Guest


    I *wasn't* going to do it!

    Can you explain why there would be inductive heating (I guess I'm unclear as
    to what induction and choke are). I don't see why the circuits would be
    unbalanced. I sorta checked out of physics somewhere between DC electricity
    and AC and thermionic valves and electronics!!


  4. Den

    Den Guest


    I hadn't thought of that angle ... it's obvious when you state it clearly as
    you have done.

    I'm going to be using a step up transformer ... it's just I wondered if it
    could be done this way ... I wasn't going to actually do it as it would
    clearly be (at best) bad practice ... and as you have demonstrated


    D |
  5. ns

    ns Guest

    Doable, if you use the 2 hot circuits from a split-plug circuit (i.e.,
    protected by 2 ganged circuit breakers).

    I've been using this approach for the last 17 years for a counter top
    mixer/blender (Kenwood Chef) that is rated as 240 V.
    It worked just fine using the voltage range of 208 (from an apartment
    split-plug feed) to 240 V (from an detached house split-plug feed). 230
    rated is really 230 +10/-6% (or is it +6/-10%?), so if you use the above
    approach, you should be OK.
  6. bushbadee

    bushbadee Guest

    Very often laundry rooms have 240 volts to run driers and they use both
  7. KR Williams

    KR Williams Guest

    Sometimes. Sometimes not. I believe my laundry room is a three
    wire connection (I know my last house was, and I didn't buy a new
    cord). All would be well if the appliance manufacturers didn't
    cheat with 110V components. Even as is, it's not a big deal (but
    not pure either).
  8. Guest


    A GFCI is not intended to prevent the use of a ground wire as
    a current conductor. It is intended to protect you, by
    interrupting the circuit if there is an imbalance (of about
    5 mA or more) in current flow on the hot vs the neutral wires.
    The idea is that a short in something you are holding runs
    current through your body to ground, which could kill you.

    It is specifically allowed by the NEC to be used where no
    ground wire exists - thus can't be intended to be used to
    make sure no one uses the ground wire as a current conductor.
    See 406.3 (D) (3) in the 2002 code.

  9. KR Williams

    KR Williams Guest

    No, the "cheat is that there is a ground (no neutral) and the
    120V motor uses the return through the *ground* (it's wired to
    the case). AIUI, the later codes require the fourth wire
    (neutral), like they do with kitchen ranges.
    Given the volume of widgets sold, I can't see it costing a dime
    extra. There is no way anyone is going to use a drier on 120V
    (well my MIL tried for a while, but that's another scary story).
    I don't see the point. Very few appliances need the higher
    voltage and the ones that do should have a separate circuit
    designed for the higher load. I don't see the need for a 240V
    circuit to power my bed lamp, alarm clock, cell-phone charger
    (the only things normally on my bedroom circuit). Ok, there is a
    1/2 ton AC on there for a couple of weeks in the summer too (were
    I wiring the house it would have its own circuit - wire's cheap).
    Big deal.
    Too complicated. Why bother. I rather like things the way they
    are. It's simple, cheap, and easily expandable (for values of
    easy approximating the ease of opening a wall ;).
  10. KR Williams

    KR Williams Guest

    Could be. They are the same lug in the entrance panel. I guess
    you can call it a neutral, since it is carrying current. ;-) It's
    bonded to the case though. my MIL found out.
    Not sure. I've only seen the thing twice (when I bought it and
    when I moved).
    I didn't say you did. My point was that a 240V motor, given the
    volume of driers sold, shouldn't be any more expensive than a
    120V motor. I have no clue why they use a 120V motor. Seems
    pretty stupid to me, but there must be a reason.
    Sure, my point is that most rooms have nothing in them that takes
    any significant power, so 120V is good enough. Kitchens,
    I don't see many appliances in the home that need higher power
    than can be delivered now at 120V. AC units, sure, but they
    usually have dedicated circuits. I have a small window unit, but
    it works fine off 120V too.
    Sure, but I don't see this as a significant issue in a
    residential dwelling.
    The advantage of the system as it stands is that I can use 120V
    for small things and glue two together for the biggies. That's
    about as simple as it gets.
  11. KR Williams

    KR Williams Guest

    Entrance panels *DO* do that. The ground and neutral are bonded
    in the entrance panel. In this particular case the *RED* wire
    was connected to the ground-strap and the white was hooked to the
    hot. exciting when you touched the drier case! I found out jut
    how exciting when I hooked a ground strap to the cold water pipe,
    an zapped a 60A fuse.
    Not necessary. In the entrance panel they can all be wired
    together. Certainly in a sub-panel they're separated (I just had
    to separate them in her house so we could sell it).
    I can do that, but I'm not about to pull our laundry room apart
    to measure. ;-)
    IIRC 600V wiring is required for all residential circuits. I
    thought this was true for appliances too, but I could be wrong.
    I'm not a power expert, as you've noted.
    I don't buy that argument. The gas/electric argument seems to be
    better, but even that falls short. Motors wound for both are
    ubiquitous. It's not rocket-surgery to have motors strapped for
    whatever voltage.
    Maybe that's a good idea. Overkill, and you'll never get your
    money back, but if that makes you happy... My father did the
    equivalent sorts of things, though no one else cared.
    I don't agree at all. Who needs more than a kW for a hair-
    drier?! I'd rather *not* have 240V anywhere close to water. I
    had 240V to my pool pump for the obvious reasons, but poolside
    appliances ran off 120V. The 240V GFCI breakers were nutso too.

    ....and you want 240V to the bathroom? My built-in
    microwave/convection/range-hood is 120V. I know because I
    replaced the thing a couple of years ago. No big issue there.
    I don't (prefer). I'd rather leave things at the lowest voltage
    possible. 120V is just peachy for 90% of my uses. Dedicated
    outlets (240V) work for the rest.
    Obviously. The IR drop on most residential circuits is trivial,
    IMO. My cell-phone charger isn't causing too much in the way of
    global warming, the wires in the wall feeding it far less so.
    No, I wouldn't have had any such thought. I don't want 240V to
    supply a tenth of an amp. There are so few places in my house I
    need such huge power (and those have dedicated outlets) that I
    see wiring 240V everywhere as a complication.
    Obviously, but now I need both 120V and 240V lamps. No thanks.
    Leave the trivial loads at 120V.
    Huh? That's the whole point. We don't have any "shared-
    neutral" loads. THe ones that are shared are designed to do so.
    Of course. Why are you bringing in this strawman??

    THe system works remarkably well, and has for many years. Many
    smart people have done much to make it safe. I'm not about to
    throw out all that's been learned over the last century and do
    something different because I *THINK* I know better. I'll trust
    the NEC, thanks.
  12. KR Williams

    KR Williams Guest

    Really? I thought all wiring hat to be rated for 600V. If
    you're right, this isn't goodness. Again, if I'm wrong, I
    appreciate you pointing out my errors!
    I see others who have raised that argument here. It makes sense,
    sorta, but multiple windings (series or parallel) aren't a biggie
    either. All the stationary power-tools in the same cost region
    have such taps, including those with the cheap universal motors.
    This is the only "reason" I've seen, but it's hard to buy this
    one too.
    Of course. Tell me something I don't know. That is indeed the
    beauty of the system. One can split off the low-power circuits
    from the high-power circuits and they all play nice.
    Nothing, except the expense. 2-pole GFCI breakers are
    *expensive*. 120V GFCI outlets are dirt cheap. ...and work just
    as well for small loads.
    Are you talking about US 240V or the Europen 240V? I wouldn't in
    either case, but for different reasons.
    ;-)) I have more hair than my wife, which pisses her off
    constantly. I cannot stand hair dryers, but she insists on using
    them. Go figure.
    I think mine could be wired for 240V, but that wasn't of interest
    since the house is already standing. I wasn't about to re-wire
    the place.
    Absolutely. I see no reason for 240V anywhere that massive loads
    aren't. AC units, sure. Hair driers, please.
    I have a beard too. Gotta plug that Wahl-wart in somewhere! ;-)
    Absurd. The occasional vacuum cleaner would object.
    ....which is exactly what I've been arguing! I much prefer the
    "Edison-connection" to what the right-pondians use. Pehaps we're
    yelling past each other?
    Because perhaps it would make a mess of 240, when it's needed?
    I'll bet half my line cords don't use too much more than this.
    Certainly if you go to 100W there are only a *few* widgets over.
    ....and I think you're nuts. ;-)
    Now you're demanding that I need four-wire 240V to every outlet
    in my house? I don't think so!

    I think you're wandering around this whole issue, so perhaps
    you'd better define what exactly your "perfect" house would look

    Good grief!
    You just said you did above. You are wandering again.
    The neutral wire is a wonderful thing. It allows us to have both
    120V and 240V, where it's needed. ...and both at the same time,
    where needed. ...another great invention of "Edison".
  13. Den

    Den Guest

    Hmm, it certainly wouldn't require a dedicated circuit in the UK! 2400W at
    240V is only 10A. Standard British sockets are rated to 13Amps (each plug
    has a replacable fuse - so the fuse rating may be 1A for a lamp, but 13A for
    a microwave). Circuits are often rated at 30A. I used to run a 3kW (i.e.
    12.5A) electric kettle quite happily off the standard wall socket and
    another 3kW heater off another on the same circuit.

    I was gobsmacked at the limitations of the standard outlets when I moved to
    the US - 15A at 110V - 1.6kW.



  14. DarkMatter

    DarkMatter Guest

    The 120 to 230 volt step up transformer IS the way to go for safety,
    AND for proper operation. The only difference will be what frequency
    your 230 volt device was intended to be operated at.

    Learn why top posting is such a bad thing in Usenet. Then refrain.
  15. DarkMatter

    DarkMatter Guest

    A dryer element is purely resistive, and it wouldn't make a shit.

    That element could easily be driven in such a way. The motor and
    timer are driven off one 120 volt side, and use the neutral.

    The heating element would not need it were it a single element, but
    they are rarely anything other than split pairs with the center on

    You seem drier than you were a few minutes ago. Perhaps you should
    go check your clothes dryer to see if it has finished its cycle. :]

    BushLAMEEE's use of that "b" in front of his posts has to be one of
    the most lame behaviors in any professional group I have yet seen.

    Topic header appropriately trimmed. Assholes appropriately ignored.
  16. DarkMatter

    DarkMatter Guest

    There are UL ratings for PVC, THHN, and various other wire
    sheathings. The military rates teflon wire of a particular type at
    1000V, whereas UL only gives it a 600V rating.

    I see 300Volt PVC wiring in device chassis all the time.

    Even the national laboratories buy COTS now, and all that mil
    scrutiny is gone, or much of it, anyway. The EIA standards used in
    most commercial electronic labs allows for 300 volt PVC. I think that
    baseline NEMA is 600V, and perhaps that of THHN or better. Baseline
    NEC is for PVC, but I don't know the ratings scheduled. As far as I
    know, the UL boys are the folks that do the insulation ratings though.

    Bush Boy's "B"s are lame. As is he.
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