Elec. Water Heater: Can you set the thermostats to different temps?

Factual Questions
1

At my office I have a standard, 43-gallon electric water heater, 2 years old. I decided the water wasn’t quite hot enough, so I climbed into the ceiling crawl space to adjust it. Thereupon discovered it had 2 thermostats. I decided that since not much hot water is used, it would be cheaper to heat just the top of the tank. So I turned up the top thermostat/heating element to the desired temperature, between 125 and 130°F. The bottom one I turned down to 100.

Having done this, I came home and read the SDMB archives, the How Stuff Works page, and spoke with the Rheem representative. The consensus seems to be that both thermostats should be set to the same temperature.
Nowhere could I get an answer to what will happen if I leave the heater as it is, especially whether there will be any harm. Any ideas? I really don’t want to climb up there again if I can avoid it.

Thanks in advance; I’ll check back this evening if there are any questions posed.

2

Having them set at different temps should not cause any damage, however having the recovery side set at a lower temp is less efficient. If you don’t use a lot of hot water, you probably won’t notice a difference.

3

Why won’t the hot water stay basically at the top, and the cold water at bottom, saving me energy on that half a tank that is not directly heated?

4

It will, until you start to use it. The cold water entering the tank will lower the overall water temp, so you will run out of HW faster. The lower element is usually the “recovery” element, and it is sometimes larger because it must rapidly heat the incoming cold water. Larger = more energy consumtion. Again, if you don’t use a lot of HW at any one time, your plan will work.