My Kenmore (Sears?) electric water heater stops to works (not more hot water), but the light is on. I supposed it is the thermostat. I removed the 2 front panels from the boiler and check with ohmmeter the 2 resistors (elements, I think 3300 watts each) and the 2 thermostats. The resistor on top shows infinite resistance (I suppose is broken), but the second one shows continuity. When I measured voltage with voltmeter, the resistor on the top (which is broken) has 240v, but the resistor down (with continuity) shows zero voltage. I did suppose one of the thermostats is not more working. There is a "Reset" red button, I did push it but nothing. What is the purpose for this button? The labels on 2 thermostats are "7135" (on top - many wires) and "7059" (on down - 2 wires). Following the circuits, I noticed the thermostat and resistor on down (2 wires) is supplied with voltage from the box (thermostat) on top (more wires). May I put some wire in direct to provide voltage to the resistor on down? And another question: What happen if the resistor on to is broken? May I live it like this? (supposing the resistor on down will work).
You have diagnosed it correctly, from a "cold start" the upper heating element runs until the water at the top of the tank reaches the setpoint of the upper thermostat at which point power is removed from the upper heating element and directed down to the lower heating element through the lower thermostat. That element remains powered up until the water at the bottom of the tank reaches the lower thermostat's setpoint at which time it opens and no power is consumed until the water in the tank cools through heat loss or someone uses hot water.
You won't kill anyone if you rewire things so that power only goes to the lower thermostat and thence to the lower heater, and you will get hot water to use, but you probably won't pleased with the "recovery rate" for hot water.
If you decide to do that, please disconnect and safely cap off the leads going to the upper element just in case that elemen is rusted through its outer sheath.
Running on just the lower element and thermostat may just get you by until you can fix things properly, but it's no way to leave things now.
As someone already said, replace the upper heating element, they are really inexpensive. And do spring a few bucks for the "socket wrench" sold specifically for grabbing the big hex on those elements. It'll make you job much easier.
The thermostat has lots of screws, and the heating element is usually below it. You're calling it a resistor because you have the schematic and it uses the symbol for a resistor??
The heating element has only two or three screws. I have Kenmore too, but I think all the brands are alike, insofar as, if the heating element has two elements in one, it will have three screws, and a jumper was originally provided so that one could connect two of them to one wire, and the third screw to the other wire, so that both ran at once. Then one is supposed to note this on the spec plate that is on the outside of the water heater.
You understand why, right?
Well, you noted that the red light was on. That only goes on when the top thermostat is closed, which should cause the top element to make heat, but you've shown that it is broken.
When the top thermostat is closed, the bottom thermostat is always open on Kenmore and most wh's. So that's why there is no voltage on the bottom resistor/element.
The thermostat is connected to but separate from the heating element.
When the water is hot enough at the thermostat, the thermostat will open. If the water gets too hot, because one or the other thermostat is broken, the heat limit switch in the thermostat opens. The red button is to reset it. It won't reset itself, so if the button needs pushing, you have to push it or the element just below it won't make heat.
Two wires, but more than two screws, right?
Yes but don't do that. I think a new heating element is about 20 or
30 dollars.
When the top element heats the water at the top to the right temperature, the thermostat will turn the top element off, turn the red light off, and turn the electricity on to the bottom thermostat-element combination.
It doesn't get hot now, becuase the top heating element is broken.
No it won't work, as I just said above. The bottom won't work until the top heater warms the water at the top enough. And it's not.
So, unless we're confused, turn the WH off at the breaker, and replace the element. Use 1) or 2)
1) Drain the tank enough to lower the water level below the top element** You have to turn off the input water, and open the drain valve, and estimate how much water is coming out. Maybe you need to run a garden hose from the drain to the sump or somewhere. Although if you are only draining the top part, you could run the hose to the basement sink (or toilet I suppose) Either will be lower than the top heating element.
2) **There is also a way to not drain the tank and all which might be better since some times one can't shut the drain after he opens it. In that case the input water is turned off, the hot or cold*** (I forget which) faucet that is lowest in the house should be opened wide and let to run until no more water comes out. --- This whole method only works if you already have the new element. --- When no more water comes out, unscrew the old element, then pull it out and put in the new one as quick as you can. Maybe 3 or 4 seconds. When I did it, only a couple tablespoons of water came out. (Because the partial vacuum at the top of the tank holds the water in.)
Then tighten the heating element, close the water faucet, turn on the water to the wh, go to the water faucet and run the water until all the air comes out and give the tank time for the water to fill it and cover the new element. If you run the water heater with an element exposed to air, it will burn out, even though you just replaced it. Then connect the wires, and when you are sure the wh is full, you can turn the electricity back on.
***I guess if you are opening the cold, you have to turn off the water to the whole house, or the water will never stop running. So that's why I thought it was the hot, but it's been 20 years and I don't remember.
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