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Fencepost
Mastercarpentry wrote:

You can also save something by not having the top element working. Here's why this works- although it takes a set amount of energy to heat the water enough to reach thermostatic cut-off, you can achieve that heating with a smaller heat source spread out over time with less energy than it takes to do the same thing quickly when the second element kicks in- the time factor makes the difference.

Most dual-element electric water heaters do not run both elements at the same time. (Some do... but it requires heavier than standard wiring.) What happens is that the bottom element runs most of the time. If you draw off too much water so the water toward the top of the tank starts getting cold, then it switches to the top element. Once the water at the top gets warm enough, it switches back to the bottom element. I guess the theory is that with only the bottom element the internal convection currents wouldn't be sufficient to get the warm water to the top. By the way, this is why the bottom element always seems to fail first: it's the one that gets the most use.

You can confirm this by looking at the info plate on the water heater. It will list the top element wattage, the bottom element wattage, and the maximum wattage. If the maximum isn't the sum of the bottom and the top (it's equal to the larger of the two), then your water heater switches rather than runs both at the same time.

Some water heaters can be rewired so that both elements will run, but that usually requires a 50A circuit. Most water heater circuits are only 30A. Here's the formula: take the maximum wattage, multiply by 1.25**, divide by 240, and you'll have the minimum amperage for the circuit. (My water heater is 4500W each element, 4500W total.)

BUT -- this discussion might not be relevant, since the product mentioned in the original post was for a GAS water heater.

**Why multiply by 1.25? Because code requires continuous loads not exceed 80% of the circuit capacity. And 0.80 is the inverse of 1.25. Trust me on this, I took math in high school.

bill

If you have a standard how water tank the heat loss from the tank into the room then heats that same room except for the non heating months . So all this talk about energy saving is for nothing . either you heat that room with what ever your heating source or the heat loss from the hot water tank help you heat that same room. even Steven.