277 Volt single phase water heater on 240 volts

Merry Christmas
Joethemechanic said:
Do you believe that the 6.28 ohm combined heating elements are going to change by like 1.2 ohms or something. Of course it works by percentages.

This is all basic electrical theory taught in 8th grade. The numbers are all so small as to be insignificant. and if it isn't as hot the resistance will be lower so it will draw more current, but not enough in this application to mean anything.f it was a manufacturing tolerance it woukl

I'll bet manufacturing tolerances are wider than what difference is caused by the small temperature changes in the element cause.

Hell it's so small a difference in percentage of resistance it'd be in the gold

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So now we are comparing the "tolerance" of carbon film axial lead resistors, to an immersion heater? You do realize what that "tolerance" really means, and the dR of even those carbon resistors changes substantially with heat? Like I design PCBs and that is something that has to get factored!

The current in a wound Nichrome element is a function of it't temp. The current in a single piece of of Nichrome can vary by 10% just within a 200*F window of operating temp! That is NOT fluid temp, that is the wire temp. How do you know the operating resistance of a wound element? Precise measurement of applied voltage and observed current.
 
A drop in voltage of voltage of 13% is not going to cause a 200 degree drop temperature in a water heater element unless there is something seriously wrong with the thermal conductivity of your ceramic material

And yeah I know the difference from different types of resistors, I think I said the band was a "manufacturing tolerance"

WTH, even Rudd doesn't take temperature into consideration in their published calculations. Do the math the way Rudd says to and it will agree with my numbers.

You know back when I was in school to pass our electronics class you got a pencil and paper and were expected to draw a schematic of a superheterodyne receiver complete with values right off the top of your head. That was in 1978.

What are they teaching now?
 
ptonsparky said:
The fan is to the upper right.
Fan
140...66.3
140....66.4
No fan
140...66.1 to 66.2
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That is curious. _Lower_ resistance with the fan off, where I would expect higher temperature and thus slightly higher resistance.

It is fun when theory and practice agree. But when they disagree that is a party :)
 
ramsy said:
More like lab VP had high cholesterol, and changed formula to keep sampling the candy at his pleasure.
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Palm oil and palm kernal oil are a lot different. And not just different pour points.

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The palm oil seems to leave a lot more "gunky crap" on everything. I'm sure some of that is tempature related but I'm not sure it's a good thing no matter what the cause. Of course palm is cheaper. And the export product going to Canada is a better formulation. Even Canadian chocolate bars with almonds "MUST" only contain whole almonds. No pieces.

On a positive note, the crispy little wafers are baked on big waffle plates with 100% bee's wax for anti stick
 
For the next experiment, test three standard inverse-time circuit breakers and measure their trip times when a heating element is intentionally shorted to municipal tap water in a tank. The tank should be connected with non metallic piping and EGC size #10AWG. An old electric water heater and three identical used heating elements may be used, with one element dedicated to each test.

For consistency, cut an identical slot in each heating element at the same location to create a controlled short to the water. Cut the slots in the element so its as close as possible to the center of the tank. Use the same temperature water.

Replace the heating element after each test.
Test the following new, off-the-shelf, residential two-pole breakers:
  • 25 A
  • 30 A
  • 50 A
For each test, record:
  • Peak current versus time on the 240 V supply conductors
  • Ground-fault current in mA scale on the equipment grounding conductor
If a breaker does not trip, terminate the test after 10 minutes.
 
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ramsy said:
More like lab VP had high cholesterol, and changed formula to keep sampling the candy at his pleasure.
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Not sure sure of that but he was a hero to many people. He fought in the underground during WW2 and saved the company a ton of money. He hired a company that made asphalt mixers to build three huge chocolate conches. Each had two 100 HP motors on 4' gears to power two Inter winding blades They would run for 8 hours to break down powdery chocolates into liquid chocolates. These machines cost less then a third of ones made in Europe. Years later they made him order a fancy German conche that used twice as much expensive Lecithin. That machine never ran more then a few weeks without breaking down. Company spent a fortune flying in techs numerous times to get it to run a little better. Ended up only running it two or three batches a week while 15 year old asphalt mixers ran 24/5..
 
garbo said:
Not sure sure of that but he was a hero to many people. He fought in the underground during WW2 and saved the company a ton of money. He hired a company that made asphalt mixers to build three huge chocolate conches. Each had two 100 HP motors on 4' gears to power two Inter winding blades They would run for 8 hours to break down powdery chocolates into liquid chocolates. These machines cost less then a third of ones made in Europe. Years later they made him order a fancy German conche that used twice as much expensive Lecithin. That machine never ran more then a few weeks without breaking down. Company spent a fortune flying in techs numerous times to get it to run a little better. Ended up only running it two or three batches a week while 15 year old asphalt mixers ran 24/5..
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Allegheny Iron & Metal got a lot of the machinery when that plant shut down. Got some VFDs out of there that were as big as the cooler I take camping. Maybe 5 hp rated. Of course that was all pretty high tech stuff 30 years ago
 
ptonsparky said:
I don't know. I think we need to delve into Tortuga's request in post #94. That relates. Somehow. I think. Does it matter?
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Seeing as how water by itself is not even conductive, the type of water will change results drastically.

Just as a personally observed case matter, I showed up onsite to see a pump pressure switch and pump pressure tank floating in a pit, very much live, and pump still getting it on. Breaker was a double 20. No trippy whatsoev. this was before GFI breakers. That was well water with documented Iron in it as well as the typical other silicates.
 
I am genuinely curious, running a water-heater in simultaneous mode I have always seen two 25 or 30A breakers, same with electric on demand, some have like four 40A breakers one for each element, but never one 50A for two elements.
They do they eventually trip the breaker when a element goes crusty and bad or do usually people just notice no hot water or?
 
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