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SCR dimmer control for portable electric heater??

Discussion in 'Electronic Repair' started by [email protected], Mar 21, 2010.

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  1. Guest

    I have one of those 1500 watt radiator style portable
    electric heaters. Love it

    However, rather than the built in thermostat turning
    the unit OFF?ON every 15 min's or so, I was thinking
    it would be more efficient to use an SCR dimmer control
    to vary the amt or power it gets?

    Does anyone know of an SCR control hefty enough to
    handle this kind of resistive heating load??
  2. Guest

    Yeah that would work also....

    Thing is I was hoping it possible to find such a
    control for maybe $30 or the dang heater only
    cost $40. lol

    Anyway...... just thought controlling heat output that
    way (vary power) better than on/off thermostat.
  3. David

    David Guest

    A TRIAC lamp dimmer is PWM of sorts since it passes only a
    portion of the incoming sine wave. These are readily
    available for at least 1200 Watt loads. I assume this heater
    has no fan.
  4. mike

    mike Guest

    How much improvement are you expecting?
    You're gonna use up the same number of electrons to produce
    the same amount of heat. If the thermal hysteresis is large,
    you might argue that you get a tiny gain from the reduced
    maximum temperature via conduction losses thru the walls...
    but I expect it's less than the loss of a PWM controller...
    for a typical setup. Yes, the controller produces heat
    that you can use...just ain't worth the trouble for the
    minuscule gain you MIGHT get.

    A light dimmer with this capacity ain't gonna be high-volume/cheap.
    No reason it couldn't be, except for volume...

    You don't say how long it runs every 15 minutes.
    Hook two in series.

    Bottom line...relax and enjoy the heat.
    Some problems don't need to be solved.
  5. Or (maybe) better yet, how about some kind of PWM control? Wouldn't that
    be even more efficient (the control device is either on or off, so
    little thermal losses)? Just an idea ...
  6. Another idea, really quick and cheap: how about just a diode in series
    (or maybe several diodes in parallel)? That would cut the power in half.
    I haven't looked but surely you can get some rectifiers that would
    handle it, say 250 PIV and enough current to handle the heater.
  7. Does anyone know of an SCR control hefty enough
    SCR dimmers use PWM.

    I rather like the idea of wiring two heaters in series. This will reduce the
    total output to half of what it was, but it will be better spread around the
    room, which might be a net improvement.
  8. Phil Allison

    Phil Allison Guest


    ** But there are now two heaters in series, R is doubled so the power is

    ..... Phil
  9. I rather like the idea of wiring two heaters in series. This will
    But there are two heaters. Two times 1/4 = 1/2.
  10. Ever build a thing like that as I could not find it on the market at the
    time. Used a 555, a dual pot and an SSR that could handle over 250Vac/20A.
    The SSR had a build in zero cross detector so I could switch on between 1
    and 100 halfcycles within a 50 cycles period. Worked as advertised though it
    was not very cheap mainly caused by the price of the SSR.

    petrus bitbyter
  11. [SMF]

    [SMF] Guest

    The on/off cycling of the device is not only for ambient
    temperature, but is also for device safety. The unit will
    cycle on and off until the thermostat temperature set point
    is reached.
  12. Guest

    The goal was to keep internal thermostat contacts from
    wearing out.....IF and only if I could get a heavy duty
    enough unit at low cost that is

    Plus it seems to me it would help give more even heat?
  13. Guest

    Correct.... no fan at all!
  14. I rather like the idea of wiring two heaters in series. This
    How about four in series-parallel? That would be the same heat output as
    one, but you'd (probably) need to cycle them on less often for the same
    degree of comfort.

    Regardless, I've never understood why radiators and heating fixtures are
    place right next to the windows.
  15. Guest

    Don't want to do that...... just need one heater
  16. mm

    mm Guest

    I've only had one thing where the contacts wore out and that was
    decades old. Not counting engine ignition points.

    Why would it do that.

    If you want more heat, turn the thermostat up.

    AIUI, this should have been cross-posted to, instead
    of asking the same question in two newsgroups. That way everybody
    could have the benefit of what others say, and they wouldn't repeat
    what was said elsehere already.
  17. mm

    mm Guest

    He makes a good point however. By placing them near the window, the
    hottest part of the room is near the window and the most heat loss
    occurs, compared to placing it somewhere else.

    Maybe having the room temperature even is something some people would
    sacrifice to save money, and that pesky old environment and balance of
    payments. And that way the people who like it warm could sit on one
    side of the room and the ones who are hot all the time could sit on
    the other.
  18. mike

    mike Guest

    Interesting that there's no mention of that goal in your original statement.
    Based on what?
    Point your thermometer at the heating surface.
    What's the temperature when it first turns on?
    What's the temperature when it cycles off?
    That delta-t is the measurement of heat evenness.
    This can be a big number with a radiant heater.
    Can be almost zero with a well-designed
    radiator style heater. The whole idea of the radiator
    is to have some thermal mass and keep heat even.
  19. Guest

    there is no thermal mass in this is
  20. GregS

    GregS Guest

    How about warming the whole floor.

    Much less of a problem with efficient windows.

    The upward current warms that ordinary cool downward draft. Drafts affect
    overall rooms comfortability. I installed, or rather insulated my front door,
    and the room is much better.
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