SCR dimmer control for portable electric heater??

[[email protected]]

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??

 

[[email protected]]

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.

 

[David]

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.

 

[mike]

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.

 

[David Nebenzahl]

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 ...

 

[David Nebenzahl]

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.

 

[William Sommerwerck]

Does anyone know of an SCR control hefty enough

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.

 

[Phil Allison]

"isw"

"William Sommerwerck"


It will reduce the current to (approximately) half, which will reduce
the heat output (power) to one-quarter that of a single unit. Power is
I^2*R.

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


..... Phil

 

[William Sommerwerck]

I rather like the idea of wiring two heaters in series. This will

It will reduce the current to (approximately) half, which will reduce
the heat output (power) to one-quarter that of a single unit. Power
is I^2*R.

But there are two heaters. Two times 1/4 = 1/2.

 

[petrus bitbyter]

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??

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

 

[[SMF]]

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.

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.

 

[[email protected]]

How much improvement are you expecting?

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?

 

[[email protected]]

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.

Correct.... no fan at all!

 

[William Sommerwerck]

I rather like the idea of wiring two heaters in series. This

Why not use 4 heaters in series? Or maybe even 8 or 12 or 16?

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.

 

[[email protected]]

I rather like the idea of wiring two heaters in series.

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

 

[mm]

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

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

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

Why would it do that.

If you want more heat, turn the thermostat up.

AIUI, this should have been cross-posted to alt.home.repair, 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.

 

[mm]

If they are placed along inner walls the room temperature is uneven.
Since heat escapes through walls, windows & doors you need to replace
it. Then, the center of the house will stay warm from convection
currents and the lower heat loss through a ceiling or roof.

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.

 

[mike]

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

Interesting that there's no mention of that goal in your original statement.

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

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.

 

[[email protected]]

The whole idea of the radiator
is to have some thermal mass and keep heat even.

there is no thermal mass in this heater.....it is
mica-thermic

 

[GregS]

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.