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From: David Nebenzahl on 20 Mar 2010 21:44
On 3/20/2010 4:07 PM me(a)privacy.net spake thus:

> 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??

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 ...


--
You were wrong, and I'm man enough to admit it.

- a Usenet "apology"
From: David on 20 Mar 2010 21:17


"David Nebenzahl" <nobody(a)but.us.chickens> wrote in message
news:4ba56b15$0$2390$822641b3(a)news.adtechcomputers.com...
> On 3/20/2010 4:07 PM me(a)privacy.net spake thus:
>
>> 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??
>
> 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 ...
>
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.

From: David Nebenzahl on 20 Mar 2010 22:30
On 3/20/2010 5:01 PM me(a)privacy.net spake thus:

> David Nebenzahl <nobody(a)but.us.chickens> wrote:
>
>>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 ...
>
> Yeah that would work also....
>
> Thing is I was hoping it possible to find such a
> control for maybe $30 or so.....as the dang heater only
> cost $40. lol
>
> Anyway...... just thought controlling heat output that
> way (vary power) better than on/off thermostat.

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.


--
You were wrong, and I'm man enough to admit it.

- a Usenet "apology"
From: mike on 20 Mar 2010 21:35
me(a)privacy.net wrote:
> 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?
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.
>
> Does anyone know of an SCR control hefty enough to
> handle this kind of resistive heating load??
From: William Sommerwerck on 20 Mar 2010 22:35
>> Does anyone know of an SCR control hefty enough
>> to handle this kind of resistive heating load??

> Or (maybe) better yet, how about some kind of PWM
> control?

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.


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