burned water heater element

I replaced a top element on an electric water heater ( double element) at the cottage. We use lake water that is pumped up to a holding barrel above the heater then feeds the heater. After replacing the element it took quite a long time ti get water to run through the system to the tap, air pockets I guess. The new element burned after a short while , it may have been due to the air pockets and not much water in the top part of the tank.
Question: this heater has a thermostat for top and bottom element, should it not turn off the element if it gets to hot , either if water is present or not?
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GINO wrote:

It's very common for the thermostats to go bad over time also. I always replace the other element and both thermostats when I have problems. I then run the water until it comes out normal before I turn the power back on. It's just extra work to replace one element and then another and then a thermostat and etc when you can do them all at once and it will last a long time. Sorta like replacing all the hoses and belts on your car--you don't want to get broken down.
J
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Gino: No. The thermostat senses the water temperature, not the element temperature. So, no water at the upper levl, no cooling of the element. I'd bet it overheats and melts down in just a few seconds if no water. Next time run the hot water till all air is out before applying power to the tank.
Dave

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Thanks guys, I'll go up next weekend and try another again, maybe change the thermostat at the same time

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No, for several reasons.
1) The heat transfer of air and water is different. A heater element in water will distribute the heat a lot faster. Heater in air will rise temperature very fast.
2) The thermostat is touching the wall of the tank. The heater element is inside the tank. If the element comes on surrounded by air, there isn't enough heat transfer to the thermostat. The thermostat stays cool, and the element fries.
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How long it takes to get the air out of the hot water tank is irrelevant. What is important is not turning the electric back on until the tank is full of water and the air is out. If the element is not surrounded by water, it will quickly burn out.
Unless you have reason to believe the thermostat is bad, I wouldn't screw around with changing it.
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