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2 Voltage Regulators On A 220V Heating Element

abk111

Dec 13, 2010
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This is for a water heating element that I do not want to run at its full wattage (4500W).
Trying to keep this element cool enough to insulate on one side with silicone caulking.
Specs for the voltage regulators are not that heavy duty:
Reverse polarity protection, high current protection
High temperature FR-4 circuit board
Maximum Power: 2000W
Voltage: AC 110-220V
Voltage Regulation: AC 50-220V​

Assuming that one side of the phase will act as the neutral for the other.
What would be the best way to wire these for the least amount of stress on the voltage regulators?
In parallel or series on one side of the element?
Or one on each end of the element?
Or would it be better to just use one side of the phase?
The voltage at my location is actually ~ 125V / 250V.
Thanks
Pic of voltage regulator:
https://i.ebayimg.com/images/g/iggAAOSwPBFa1DlA/s-l1600.jpg
"AC 110~220V 2000W SCR Voltage Regulator"
 
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Harald Kapp

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This regulator is not suitable for your plan. While you may achieve an average power of ~2000 W at the heater, peak power will be much higher and is prone to burn the regulator. The regulator should be able to handle the full power as it will have to carry a high current especially while the heater is still cold.

A heater is a rather inert system: heating up and cooling down take a comparatively long time. A control circuit for a heater takes advantage of this fact by powering the heater for a short time at full power, then turning it off for a set amount of time. The duty cycle (ratio of on time to length of a full on/off cycle) determines the average power and thus the temperature. Dedicated controllers are available for that purpose.
 

abk111

Dec 13, 2010
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This is a voltage regulator, not a thermostat.
Using these to control the max temp of the element; not the on / off of the element.
Using a separate circuit for thermostat, which is another reason to reduce watts -- to reduce load on relay of digital thermostat.
Thanks
 
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Minder

Apr 24, 2015
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That link shows what appears to be a simple Triac controller.
Not really suitable for temperature control of an element. which are usually controlled by burst firing. i.e. on for a period of many cycles , off for a period of same.
I think this is what Harald was also referring to.
Picmicro have a example circuit of a burst controller that replicates the bi-metal version. AN958.
M.
 

hevans1944

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Jun 21, 2012
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Hows-about a link to the actual device you propose to use? A picture may be worth a thousand words, but maybe a hundred words or less, to describe exactly what you expect that contraption to do, would be better in this case.

It looks like the device whose image you posted is what @Minder says it is: a Triac controller. If so, then it will certainly lower the power delivered to the heating element as a function of the conduction angle, allowing the heating element to operate at a much cooler temperature, suitable for insulation with silicone caulking compound. Why you would want to do that is another issue entirely. There are perfectly good water soluble furnace cements that are electrically non-conductive, and fair thermal insulators, after the water evaporates from the paste you prepare. Short shelf life though.

Silicone caulking is normally limited to a range of 40 to 100 degrees Fahrenheit, although there is "high temperature" RTV (Room-Temperature Vulcanizing) silicone rubber available for temperatures as high as 600 degrees Fahrenheit.

If all you want to do is lower the power delivered to your 4500 watt heating element (which is typical for a residential water heater), just purchase and mount on a suitable heat sink a 600 PIV, 50 A, stud-mounted power silicon diode and wire it in series with one of the heater leads. The heating element will then conduct every other half-cycle of the AC power line, effectively reducing the average power by 50% from 4500 watts to 2250 watts. Of course your power company might get a little pissed at you introducing DC into the secondary winding of their pole pig.
 

Harald Kapp

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Using these to control the max temp of the element; not the on / off of the element.
Turning the heater on and off repeatedly is a common mode of temperature control.
Controlling the voltage is not.
 

Harald Kapp

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The heating element will then conduct every other half-cycle of the AC power line, effectively reducing the average power by 50% from 4500 watts to 2250 watts.
Not taking ionto account that the heating element may not reach its full resistance as it would when powered continuously because it never fully heats up. It will thus draw more power according to P = V2/R. The effect may be negligible, though.
This method also lacks a way of controlling the power.
Of course your power company might get a little pissed at you introducing DC into the secondary winding of their pole pig.
Definitely!
 

abk111

Dec 13, 2010
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Thanks for the AN958 clue, but just trying to keep this simple without having to program anything.

For more info on this Voltage Regulator…
A search on eBay for ‘2000W SCR Voltage Regulator’ will show several examples of the same thing.
https://www.ebay.com/sch/i.html?_fr...lator&_sacat=0&_sop=15&_blrs=recall_filtering
for example
https://www.ebay.com/itm/AC-220V-20...age-Regulator-Dimmer-Thermostat-/262579098319
Also on Amazon and others, but not much better info.

THANKS for the silicone caulking info. I just figured a “100% silicone” rubber would have high heat resistance… thinking of all the silicone used in baking… oops.
Thanks for the “600 PIV, 50 A, stud-mounted power silicon diode” option.

If all else fails, I do have some adjustable mechanical ‘’‘thermostats’’’ from an old electric range; But as Harald mentioned, the full current would still be there for significant time periods and thus not help protect my digital thermostat’s relay – thanks Harald.
 

hevans1944

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I just figured a “100% silicone” rubber would have high heat resistance… thinking of all the silicone used in baking… oops.
You were thinking right. It does have a high heat resistance, but high-wattage heating elements will actually melt if heat is not removed during operation. Silicone rubber will only impede the heat removal process.

We use a silicone rubber sheet on a shallow baking sheet to cook frozen sweet-potato fries and frozen Ore Ida french fries at 450 degrees Fahrenheit for 22 minutes on the bottom rack of an electric convection oven, along with two Young's cod fish fillets (imported from England), dipped in beer-batter and frozen, and placed on a wire rack over a Pyrex baking dish lined with aluminum foil. Not sure what the maximum temperature of our silicone sheets is, but so far so good. Add a little cole slaw and a beer or two and you have a quick meal with no messy cleanup.

You can buy silicone rubber heating pads of various sizes, but I don't know what their absolute maximum working temperature is. Watlow is a reputable manufacturer and they recommend that 500 degrees Fahrenheit is the maximum temperature for their heaters embedded in silicone rubber and woven fiberglass fabric.
 

Harald Kapp

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The voltage at my location is actually ~ 125V / 250V.
How is the heater currently operated? from 250 V or from 125 V? If from 250 V, you could simply change the wiring to operate it from 125 V for ~ 1/4 of power - still not adjustable though.
 
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