SCR dimmer control for portable electric heater??

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no fan at all on this unit
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You will have to seperate the motor from the heating element. Probabaly not much differant in the efficency of either. I work on some scr type controls that operate at 480 volts and 600 amps. We also have some that operate on lower voltages, but the control circuits would cost much more than a truck load of heaters like you have.
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Simple... Connect a Diode ( of amperage for more than the heater wattage) across the thermostat connections. This will cut the voltage in half to the heating element. Connect the fan to the hot side of the thermostat so it will still run at the lower heat output when thermostat is "open" "off". WW
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wrote:

That doesn't suggest much knowledge of electricity.

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On Sun, 21 Mar 2010 10:35:15 -0500, Gary H

from ever shutting off. It would switch from high to low - assuming a single pole thermostat.
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On Mar 20, 6:04 pm, snipped-for-privacy@privacy.net wrote:

Andy comments:
There is no difference in the efficiency. 100% of the electricity will be turned into "heat" with either method.
The SCR approach simply means the unit turns on and off 60 times per second instead of every few minutes. It is also necessary to build an interfact to it if you want to control the temp with a thermostat.... Additionally, there will be some interference generated on the power line by the constant switching, which might even interfere with your radio or television....
That being said, it's a do-able idea. But just because an idea can be made to work, it doesn't mean that it is a good idea or that it has any real advantage over the existing way.
Think about it.... What grander, better thing will happen if you go to that trouble?
Andy in Eureka, Texas
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I don't want to control the heater with a thermostat at all cause I come and go so much that I just turn the unit off/on when leaving/coming.
I would turn thermostat all way up.....and control heat with pulses from Triac
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wrote:

would be more even as, if properly adjusted, the heater would be on almost constant and there would not be great fluctuations. A bit like the units that switch from 1 to 2 to 3 elements for low, medium, and high - 500 watts each for 500, 1000, and 1500 watts. There is a radiant heater made in Turkey and sold in North America that DOES have variable heat output - and IIRC (only saw them once) it does use an SCR type phase switching control.
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*Most likely it won't be more efficient because the power not going to the heater will be dissipated through the dimmer. Also the heating elements will not function as well with reduced voltage. You may turn the voltage down to 75%, but the actual heat output may be reduced to 25%.
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Agree with Andy and John. I don't see what the real objective is here regarding the stated goal of efficiency. The existing simple thermostat is just a bimetalic switch that dissipates very little energy. Less energy than the SCR will dissipate. But either way, all that energy is heat that goes into the room anyway.
Also, the heat output is a function of the square of the voltage. So, if you reduce the voltage to 75%, the power will be at 56%.
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On Mar 21, 6:12 am, snipped-for-privacy@optonline.net wrote:

Andy comments:
The heating element may be non-linear, so the current may not be linearly reduced along with the voltage, and will be different...
I did some experiments with an old stove top burner which , the small size, is 1000 watts when powered by 220V..... I found that the current drawn was linear with voltage, which means that running it from 110V made it a 250 watt element.
However, light bulbs, for instance, are not linear, and the same wouldn't apply....
Just felt like typing --- it's easy enough to characterize your heater if you have a voltmeter and a current meter.....
By the way, I have a great application for old stove burners mounted on a metal paint bucket filled with sand..... Really good heaters that don't put out enough light to keep you awake at night.... and keep your coffee warm.....
Andy in Eureka, Texas
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Good point..... could be the case!
I realize it may NOT be worth pursuing.....especially if there does not exist off shelf Triac control at low price.
But since I come and go so much.... I turn the little heater off and on a lot.....so a thermostat does little good for me.....and was thinking a Triac would allow me to "tweak" very small increments of heat....and then just keep at that setting.... and turn heater off/on when leaving
Probably not worth messing with..... but it was an "idea"
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On Sun, 21 Mar 2010 07:57:34 -0400, "John Grabowski"

A dimmer doesn't reduce the voltage. It reduces the duty cycle.
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You can buy a 2000W dimmer. I have one, and I use it to control a 1500W tungsten light bulb (as part of a light bulb collection, nothing more). They were hard to find on the web a few years ago, but search a little and you'll get one. If you want I can look at the brand name on mine.
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On 3/21/2010 11:50 AM, dean wrote:

You can buy them at any real supply house. Had two in an office. They had a large external heatsink. Not as common anymore as we move away from incandescent light.
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Yep, big heat sink! Would look ugly on a wall,
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The 2000W dimmer is made by unenco.
-D
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OK.... was hoping to find something off shelf at Lowe's or Walmart
If I cant do that....will scrap the idea
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On 3/21/2010 11:37 AM, Monty B wrote:

Depends what "voltage" is being discussed. It reduces the RMS voltage. RMS voltage is the voltage displayed by a typical meter. Attach a load to a dimmer and then connect your meter to the load. You will note that the displayed voltage does drop as you lower the dimmer. RMS is used because it approximates the DC value which is what we need to perform easy power calculations.
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YES!!!
I think that is what some people are missing....
The Triac only controls duty cycle...... on/off
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