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??
Ive built them before. Check with someone who sells stage lighting. They have some humongous dimmers.
Jimmie
Ive built them before. Check with someone who sells stage lighting. They have some humongous dimmers.
Jimmie
Probably only cost about $250 to regulate the $30 space heater. Diminishing returns, arrgh.
Yeah.....that's what I was afraid of..... the control would be way too expensive
The stage lighting idea is a good idea
I had hoped it might be possible to get such a control for $30 or so
Build it yourself for a few bucks, assuming there is not a little fan inside the unit (in which case you'd have to find a way to feed the fan whatever constant voltage it wants).
Or spend fitty bucks:
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.
YOu can try something like this:
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
Problem is the size of heat sink the SCR will need to handle 1.5KW.
The SCR is not the component dissipating 1.5KW, the heating element is doing that. Assuming 120VAC, the SCR is required to be able to handle 12.5 amps, which would put it as a basic stud-mount SCR, which can be expected to dissipate about 20 watts (as heat) with the device passing the maximum load.
Jon
Hmmm, So ever took a look at actual heat sink in those applications? I even saw a SCR melted and falling off HS like a melting candy stick.when it got over heated.
SCR don't work like that
no fan at all on this unit
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
*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%.
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%.
Since it's a filament heater (I think?) maybe a light dimmer knob would work. I don't have any specific information. Seems like a good idea, to run the wattage up and down with the heating demand.
well a rheostat type dimmer will burn up quickly if used in that manner... I'm assuming that that's why the OP mentioned "SCR."
nate
use a diode, it will run at 1/2 power... or buy a stage type dimmer, unless you are an electronics engineer you will not be able to design an SCR circuit, also many SCR circuits will generate radio interference Try the diode first...
CAUTION, when you wire it up, think about what might happen if the diode shorts, you don't want this thing to ever be stuck in the on mode such that the thermostat can't turn it off..i.e fire hazard..
Mark
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