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heating element

why? is there no thermostat or timer?

look for "4000w scr" on ebay for $4.

edit: the link still doesnt work.
 
We have an old cottage that had an electric water heater wired with 110 vs. 220. I've been waiting to fix that when the water heater needs to be replaced. Since 1989. That gives you only about 1/4 of the rated amount, though.

If you were to put an appropriately sized diode in the line, it would reduce the wattage to 500.

750W elements are available for purchase. This link doesn't do you any good, as it's from Australia, but it proves that such an item does exist. Since this is for a boat, it is expensive.

Isotherm Immersion Heater Replacement Element 240Volt 750 Watts for Isotemp Slim, Basic Water Heater
 
I think (that's as in think ???????????????? cos I'm no spark) it can be done by reducing the voltage.

Anyway here's an Ohms law calc to help you. Ohms Law Calculator

P.S. If I'm talking bollox, let me know and I'd delete the post
 
dian said:
why? is there no thermostat or timer?

look for "4000w scr" on ebay for $4.
Click to expand...

I think that will work. Thanks!

It’s for an OLD water distiller. Can’t get the correct heating element so I have to improvise. A standard hot water tank element (adapted to fit) works but it burns out after it makes about 15 gallons. So if I can reduce the voltage just enough to boil the water it should extend its life.
Thanks guys, keep up the good work!
 
blueboy said:
I think that will work. Thanks!

It’s for an OLD water distiller. Can’t get the correct heating element so I have to improvise. A standard hot water tank element (adapted to fit) works but it burns out after it makes about 15 gallons. So if I can reduce the voltage just enough to boil the water it should extend its life.
Thanks guys, keep up the good work!
Click to expand...

...and now it finally comes out.

Just doo what the simple room vaporizers doo....put the wall electricity directly into the water.

NO elements to overheat or "burn out".
 
Those humidifiers that run current directly into the water generate both hydrogen and oxygen. I had a small immersion heater that worked on the same principle. you could light the bubbles.

To find the right voltage for a specific wattage: W=V^2/R.
The problem with trying to use that formula is that the element resistance varies with temperature and that varies with applied voltage.
 
Illinoyance said:
Those humidifiers that run current directly into the water generate both hydrogen and oxygen. I had a small immersion heater that worked on the same principle. you could light the bubbles.

To find the right voltage for a specific wattage: W=V^2/R.
The problem with trying to use that formula is that the element resistance varies with temperature and that varies with applied voltage.
Click to expand...

They doo not. they run on a.c.
Unless you, or someone else put a diode in series for "half power"....
 
blueboy said:
I think that will work. Thanks!

It’s for an OLD water distiller. Can’t get the correct heating element so I have to improvise. A standard hot water tank element (adapted to fit) works but it burns out after it makes about 15 gallons. So if I can reduce the voltage just enough to boil the water it should extend its life.
Thanks guys, keep up the good work!
Click to expand...

water heater heating elements don't like to run dry/aka boil.
 
digger doug said:
They doo not. they run on a.c.
Unless you, or someone else put a diode in series for "half power"....
Click to expand...

Where in the hell did I mention direct current. The line current goes directly into the immersed electrodes. During one half-cycle you get hydrogen released at the electrode. During the other half cycle oxygen is released.
 
The power goes with the square of the applied voltage. To from 1000 watts to 750 you need to reduce the voltage by a factor of the square root of 0.75 which is 0.87. If you’re running the heater on 120, the voltage across the heater needs to drop to about 104. If you drop the voltage with a resistor, the voltage across the resistor will be 16. With 104 volts across the heater and heater at 750 watts, the heater (and resistor) current is 750/104=7.2 amps. The value of the resister should 16/7.2= 2.2 Ohms. The resistor must dissipate 16x7.2=115 watts. Wiring two of the 100W 4 ohm resistors in the Amazon link below in parallel with each other and in series with the heater will do the job (760 watts) for less then $10. If you’re running on 220, use two 10 Ohm 100W resistors in parallel) also readily available. Don’t forget that the resistors will get warm.

https://www.amazon.com/uxcell-Mount...resistor+100+watt+4+ohm&qid=1608673827&sr=8-4

Jon
 
blueboy said:
If I had a 1,000 watt hot water tank heating element and wanted to reduce it to around 700, how would I do that?
Click to expand...

As has been mentioned, too much power will cause rapid burnout, so a simple bang-bang thermostat may not suffice. What is the supply voltage?

In any event, PID controllers that use zero-crossing switching (of the 60 Hz power waveform)can modulate such a heating element fast enough to prevent big temperature excursions. But make sure you also have a safety thermostat that will stop the drama if the damn thing shorts on (full power).

Here is a PID controller and a bang-bang/PID controller. You will also need a Solid-State Relay (SSR) to control the heater power.

https://assets.omega.com/spec/CN7200_SERIES.pdf

https://assets.omega.com/pdf/proces...devices/controllers/pid-controllers/CN142.pdf


And here is a thermostat, which may be adequate. This does not require a SSR to control the heater power.

https://assets.omega.com/pdf/proces...evices/controllers/thermostats/FGT100_200.pdf


In both cases, you will need a thermocouple in a well somewhere in the heater. Use heavy-guage thermocouple wire, #16 or #14 AWG, for robustness and reliability.
 
Last edited:
digger doug said:
...and now it finally comes out.

Just doo what the simple room vaporizers doo....put the wall electricity directly into the water.

NO elements to overheat or "burn out".
Click to expand...

You replace a heating element with electrodes with are about equally reliable if both are properly implemented.

Except you lose control of wattage because of variable resistance of the water and deposited minerals on the electrodes. If sufficient arcing occurs to clean the electrodes then sufficient arcing occurs to wear them down.
 
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