Variable AC control (low cost)

Light bulbs are nonlinear, but Nichrome heaters aren't, not to speak of, so let's stick to the problem at hand.

Average power delivered to the load = (integral of V*I over once cycle)/(period).

Since the heater is linear and there's no reactance to worry about, V and I are in phase.

Assuming that the diode is ideal, which it is to within 1% or so in this instance, the average powers with and without the diode are:

Without: P = 60 * integral(0 to 1/60 sec) of

With: P = 60 * integral(0 to 1/120 sec) of

The only difference is that with the diode, you get only one half-cycle's worth of power rather than a full cycle's worth, and the half cycles are symmetrical, so the ratio is 1/2.

Cheers

Phil Hobbs

Not really, it just shuts it off 50% of the time! :)

Jamie

Ok, I see it now. Apologies offered. I sit corrected.

it all goes according to how you perceive it.

Jamie

Not wood-fired? Yuck.

Look for the amperage rating on the bimetal thermostat. Or for a part number and then pull the datasheet.

If that fails you could use a big contactor that is rated for 20A or more and is suitable for the usual switching rate. But make sure it's all installed safe and per code.

In case you just want to throttle it down a bit without regulation John Larkin's autotransformer solution is the best method. But make sure the isolation rating and size of the transformer are ok. Nice thing is, the transformer then only needs to be rated for the power you are taking away, not for 1500W. So it's not going to be very big. Plus safety precautions in case the primary goes open. A primary going open on an autotransformer under load is _not_ a pretty scenario. You could have sparks flying and all that.

Last but not least there's the thermostats of ovens. Most are very powerful and it's usually not difficult to find a discarded oven.

That would be the usenet way.

And come back when ever you want some more slapping around! :)

Jamie

Sure is, why change now!

Jamie

I don't understand the need for such a big heater. I had a full-sized smoker. The firebox was only like 6" x 6" x 6", and was a smoldering fire, not blazing... the temperature in the "bonnet" (about 4' long x

I gave it to Aaron because it was such a pain to stand there all day playing with the vents to hold the temperature constant.

I did contemplate temperature control via propane.

Then we bought all that nice double oven plus warmer stuff for the kitchen :-)

I do a prime rib for 24 hours at 130°F... comes out GORGEOUS! ...Jim Thompson

that formula only works with RMS

The diode divides the average voltage by two, but reduces the RMS voltage by a divisor of only ?2 (sqrt(2))

I've had mine butt kicked a buncha times. Don't feel special.

Here's an easy math-free way to look at it:

AC------+-----|>|--------R---------+-----N | | | | | | +-----|

Our Brinkman smoker was similar, about 10" diameter fire pan, maybe 5" deep. I had to keep it pretty well stoked in order to keep the temps up. Most of the time I had all three racks loaded with goodies. I usually picked a day when I had to work outdoors anyhow, or dragged a laptop outside. But this smoker could run unattended for 1-2h no sweat. Then some more Juniper or Hickory had to be added, and maybe some charcoal. But the smells wafting through the air were torture, made me and the neighbors drool all day log.

Ours rusted out and my wife tossed it. She's the tosser. I thought it could have hung on for another year or two.

Now I do everything in the Weber. Big turkeys, meats, veggies, bread, pizza, potatoes, and so on. Those things are indestructable and last forever. Ours is 15 years old, has weathered numerous storms where it was thrown about, looks almost like new. I remember one night where the wind howled, stuff from other neighbors flew by, and suddenly ... thwock ... *KAINGGG* ... the lid had flown clear into the air and smacked onto concrete. All it needed was a "sit in" to get it from an oval shape back to its circular shape.

Bought a 2nd used Weber that's at least 20 years old, for when we have lots of guests.

Oven? Indoors? How decadent, that's for sissies, tsk, tsk, tsk ...

It doesn't even require an autotransformer. A simple low-voltage transformer's secondary voltage can be connected in phase with the line voltage to "boost", (or out of phase to subtract), its voltage from that fed the heater.

I would suggest a filament voltage transformer, but they are now an endangered species. A once common 12V CT transformer would do as you showed just by changing it's connections. The transformer needs only an output current rating to handle the maximum current drawn by the load. ~1500/(120+12) or about a 140W transformer.

A TRIAC can handle about 20A, but I was unable to find a dimmer rated for over 100W.

Instigating another long and dragged out useless sequence of post, just so that you can visit those "WORD" snack bars on the net, isn't going to work with me.

Your imagination and use of such words that you stumble on, does not do much to repair the fracturing image you have earned for yourself.

And if you think for a moment that you are intimidating any one with your buffet pickings, think again, the joke is on you.

Only a fool or one suffering from senilism would think otherwise.

Jamie

I was thinking where I had connected a 240 volt water heater to 120 volts and that was 1/4 the power.

But Dr Hobbs had the best explanation and I see where I was wrong.

Anyway, thanks all.

be

I call that an autotransformer. But that's just me.

I hooked up my variac to control mine. I was afraid I was going to get too much heat, but found I was not getting enough heat. Thin uninsulated walls suck.

Greg