Electric water heater settings

If it's like my Rheem there should be two metal covers on the side of the tank held on by two screws each. (Only one cover if you've got a really tiny heater.)
The thermostat(s) are behind those, along with the screwed in heater elements.
The upper thermostat controls the upper heater and when it's set point temperature is reached it removes power from the upper heater element and sends it downstairs where it passes through the lower thermostat to the heating element down there.
You have to adjust BOTH thermostats to the temperature you desire.
Watch out for the 240 volts on terminals around those thermostats, may be safest to flip the breaker off while you're adjusting things.
Jeff

Yup. Standard electric water heaters have the power coming in the top, and that's just a splice box. And you better NOT see 240 amps to the heater, it's only supposed to draw about 22 to 24 amps. (They will hold on a 20A breaker if you don't use a lot of hot water, but obviously that isn't how it is supposed to be done.)
There are two covers on the side - the top one has the Overtemp Cutoff thermostat (big red reset button) and the stat for the upper element. That's the one you get to adjust, but you have to bypass the plastic Safety Blocker to turn it up past 120F that is considered "safe".
There is a bottom thermostat and element too, but the top stat does all the heavy lifting. Bottom stat is more of a safety.
If there are no children or feeble people in the house you can turn it up a bit and save money on the sanitizer heater in the Dishwasher. And the cycles are shorter because it isn't waiting for the water to heat to sanitizing levels.
You can safely crank the heater temp up if you also add Tempering Valves at the top of the water heater, or under all the sinks and behind the shower/tub valves, so they can /not/ go up past 110F to 120F at the faucet, period.
And as always, when in doubt cut the power before opening up a water heater side cover for the first time - you don't know if the last guy left you any "surprises" like a shiner on a hot wire. It IS possible to pinch a wire and make lots of spitzensparken.
Is there gas available? Heck, oil or propane would be far cheaper than electricity for heat and water heating, well worth the cost of retrofitting.
We had a few killer electric bills just from a water heater - 50 gallon monster in the attic (and no Smitty Pan to catch a leak...) that went bye-bye right after the second electric bill proved it wasn't a fluke.
-->--

A few years ago propane was far cheaper, but now you need to check the electric rates and the cost of propane before going with propane. Right now propane here is $2.50 a gallon and that is about the same cost as electricity at 12 cents a kilowatt hour. Back when gasolene was three dollars a gallon, propane was more expensive than electricity.
=20 Dan

Oh, Man don't I wish I had utility rates like that... Here we're paying 0.42 (yep forty two cents) per KWH, and propane is about $4.00 per gallon. Still way cheaper to heat water with a demand Propane fired heater (Paloma 199K BTU) than an "energy efficient" 50 gallon electric...
--Rick

OUCH! Now where is my bill.......OK. $.0.05460 /KWh for the first 621 KWh. $0.07210 /KWh for the rest.
Steve R. in BC

Mine's the same except four stages in two tanks. Four adjusters behind four covers. Owner's shouldn't be trusted to adjust settings you know.
The heater works by making the first thermostat before enabling the next, and so on. Werks grate, until you burn out the first element: no hot water. This will only happen on Saturday evening after you've been doing a greasy job all day and you're late to the inlaws for a fancy dinner. DAMHIKT
Karl

On Sat, 11 Apr 2009 16:20:00 -1000, the infamous Rick Frazier scrawled the following:
We pay 7.596 cents per kWh (residential) here in Oregon. It sure beats the rate I was paying in PRKalifornia, especially since GreyOut Davis did the devil's deal.
I'll go with on-demand heaters in kitchen and bath the next time, but I just put in an energy-efficient electric 4 years ago.
-- I define comfort as self-acceptance. When we finally learn that self-care begins and ends with ourselves, we no longer demand sustenance and happiness from others. -- Jennifer Louden

On Sun, 12 Apr 2009 02:07:25 -0700, the infamous "Steve R." scrawled the following:
Is that the combined rate, including delivery? Ours is 3.557 for delivery, 3.840 for supply, and 0.199 for tax, 7.596 combined, plus $7.50 for their bean counters as a basic fee. (I guess those are expensive BlueSky-flapped envelopes they use, touting alternative energy sources.)
-- I define comfort as self-acceptance. When we finally learn that self-care begins and ends with ourselves, we no longer demand sustenance and happiness from others. -- Jennifer Louden

Can someone please tell me how an electric heater can possibly be efficient when it's fed from a 40% (at best) efficient power station, Apart from the folks in Canada that is...
Mark Rand RTFM

When we built our home 23 years ago I had the plumbers feed the dishwasher directly from the electric water heater's outlet and install a Watts tempering valve ahead of the feed to everything else in the house.
I run the heater's temperature quite high, but set the tempering valve so the hot water throughout the house is just hot enough to get a good hot shower without needing much cold water added.
Modern water heaters seem to have such good insulation that I don't think we're wasting much energy by running the heater with a high set point temperature.
That gives us the "storage equivalent" of a somewhat larger heater, and also saves a bit of energy (and causes me less angst) when someone in the family leaves the kitchen sink water running "full hot" for what seems to my parsimonious mind an intolerable amount of time for rinsing a few dishes and some cutlery.
Jeff

Thanks Jeff, for the joys of a hot shower!

On Sun, 12 Apr 2009 15:41:26 +0100, the infamous Mark Rand scrawled the following:
When it's fed nuclear-generated trons, mon.
P.S: I used the heater mfgr's terminology. It probably should read "more energy-efficient", shouldn't it? ;)
-- I define comfort as self-acceptance. When we finally learn that self-care begins and ends with ourselves, we no longer demand sustenance and happiness from others. -- Jennifer Louden

Where do you get 40% efficiency at a power station.
Is this a theory number if I truck in the natural gas by truck and replace all the water every day and hand wrap the electrons ?
I find that number very low. Line loss by leakage and all the rest might give a 'system' a lower amount - but trim trees and spray down the high voltage insulators for their leakage...
Martin
Mark Rand wrote:

The thermodynamics equations result in a max BTU efficiency of a bit under 50% for any heat source to electrical output. This is for coal in a boiler, natural gas in a a turbine, or oil in a diesel. You can raise this by going to a co-generation situation where the by product heat goes to heat a building or green house.
Using the same natural gas input directly to a water heater runs in the 70% to 90% range. When you compare BTU's burned vs hot water out for direct fire vs fire to electricity to heat, the direct fire is almost twice as effective.
A common number is that 30% of the electrical power generated is lost in the system grid. The source of that number is fuzzy but seems to be reasonable. But it makes the above numbers even worse.
Mart> Where do you get 40% efficiency at a power station.

This is the typical "coal pile to bus bar efficiency" of a modern electric generating plant. There is lots of research on raising this, but the main limit is materials and cost.
Google on "coal pile to bus bar efficiency" for too much reading.
Transmission losses on the way from powerplant to users reduces this efficiency.
Joe Gwinn

Combined cycle gas/steam turbine can get higher. Diesel + steam turbine can get higher. PWR is much lower. AGR is a bit lower. 40% is the current state of the art for coal fired steam plant. Maximum possible efficiency (Carnot efficiency) with current material temperature limits would be about 65% but this assumes 100% efficiency in all parts of the plant, including the boiler.
Mark Rand RTFM

That doesn't match my understanding and experience.
The lower element will heat the whole tank (convection currents cause the heated water to rise, and colder water to sink, so with the lower element on eventually the whole tank gets hot). The upper element only heats the part of the tank above the element, which is pretty small. So the lower element heats the whole tank slowly, while the upper one heats a small amount of water quickly.
You can't have both elements on at the same time, since that would draw too much current. So the upper thermostat is double-throw. When the top of the tank is cold, it applies power to the upper element and removes it from the bottom. When the top of the tank is hot enough, it removes power from the upper element and passes power to the bottom thermostat, which controls the bottom element.
In normal resting operation, the tank is hot, and both thermostats are off. If you use a moderate amount of hot water, the hot water leaves from the top and cold water enters the bottom of the tank. The lower thermostat turns on to reheat the whole tank, slowly, but the upper thermostat stays off. If you use enough hot water that you're in danger of running out, the upper thermostat turns on and heats only the upper part of the tank to get *some* hot water back fast. When the upper part of the tank is hot again, the upper thermostat turns off and the lower thermostat and element heat the rest of the tank.
So the lower thermostat and element do almost all the work, and the upper thermostat and element don't do anything until you've used up almost all the hot water in the tank.
Dave

And every house I've lived in got the electric water heater removed and replaced with a NG unit. Gerry :-)} London, Canada

I just added a timer to the electric water heater to turn it off overnight, and till I got home the next day. There was still plenty of hot water to fix breakfast. At one house, the sun heated the underground line from the well so much that the 'cold' water was too hot to shower with, so it was mixed with the cooler water in the un-powered water heater.