Elec Hot Water Heater wiring amps?

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I just replaced the elements in my 80 gal hot water heater. It's wired on a 240V 30A #10 circuit. The two elements are 3800 watts and 3800 lower with optional bus bar to 5500 watts. I did the math while I was working and if they both fire at the same time, that's over 30 amps, especially if I jumper to 5500 watts on the bottom.
Am I wrong about them both firing at the same time when the recovery element comes on? Or is there something at work here that I don't understand about hot water heaters? I asked a buddy of mine who is an electrician and he says they always wire them 240v 30A #10 for residential.
Thanks,
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They don't both run at the same time.
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At the top element is a sequencer -- one element runs, and then the other one. So, they aren't on at the same time.
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A question like this is the sort of question where one should provide the brand of WH at least.
But I think they are all the same.
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The elements in a hot water heater use 0 Amps.
Hot water doesn't need to be heated. It's already hot.
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OK, Einstein, how do you keep the water hot once it's heated up? Yup, you heat the HOT water so it stays hot.
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Once the water is heated up, it's hot.
Of course water loses thermal energy and its temperature falls, but then the water is no longer hot. It is cool, maybe warm at best, and therefore needs to be heated up again to make it hot.
A water heater heats cold, cool, or warm water. Calling it a "cold, cool, and warm water heater" would get a little long in the tooth so it is simply called a WATER HEATER.
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Of course, once again you're wrong. The water heater doesn't heat up the water and then let it cool way down. It only lets the temp drop a few degrees, and then cycles the elements (or burner, if gas) back on to maintain the temperature. Otherwise, when you turned on the hot faucet, you'd never know if you'd get hot water, warm water or cool water.
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Hot water doesn't need to be heated. It's already hot.
Someone had to do it.
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How were the old elements wired?????
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Only one element heats at a time, You should connect it for the higher wattage for faster recovery
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But fwiw whichever element you use first, of a dual element lower unit, if it burns out, you can switch to the other one.
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Sorry.
The upper theromstat determines whether the upper or lower element gets power, but in the lower element of many WHs ther is a bus one can use to,optionally, connect two "filaments", actual heating wires, within one "element". The owner can use the first one, both, or afaic, the second one only. Surely if the second one burns out he can continue using only the first one, which is the way it comes wired in the first place.
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If an element burns out you need to replace it. The fact that there are 2 is not so one can be a spare.
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On Fri, 16 Apr 2010 06:55:38 -0700 (PDT), jamesgangnc

I'm sure the purpose is not so one can be a spare, but what does their purpose have to do with me? Why can't I just switch elements when one burns out. If 3800 is enough for some people and the second part of that unit burns out, why can't I go back to 3800?
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me wrote:

Both elements don't come on at the same time. your 10ga wire and 30A are just fine.
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On Fri, 16 Apr 2010 08:10:40 -0500, Steve Barker

Thanks boys... makes me feel better. Another question then:
Should the top element (adjustable only behind the panel) be set at roughly the same temp as the lower (externally adjustable) element?
If the top is supposed to be there for "recovery", I'm thinking that you'd want it to come on as soon as the temp starts to drop below the level you like the hot water at (set by the lower thermostat). Is there any reason you would NOT want it to come on fairly soon? I could see some electricity savings if it stays off, but if the tank temp has dropped below the requested lower thermostat level (which is going to happen quickly when the cold water starts coming in down there), isn't the lower element going to come on anyway... so you might as well have the upper one come on?
Also, why would the lower element have the dual 3800/5500 choice... when the upper one is the one that will have to heat water very quickly in a recovery situation?
Thanks,
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I'm going with "the engineers that designed them probably figured out what worked best"
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Well, they're both there for recovery. :)

It will.

The upper comes on first. The lower is wired to not come on until the water around the upper thermostat has reached its setting
Although the cold water comes in at the bottom, the water leaves at the top, so they want the water at the top to be hot as soon as possible. When it reaches the temp it is set for, the thermostat turns off the top element and turns on the bottom, at whatever wattage you have that part set for.

In most home usage patterns, I think the lower one does the bulk of the work. If you used hot water ALL the time, the top element would be on all the time, but since you're not running a factory that uses hot water all the time, soon you stop taking a shower, fililng the bath, washing the clothes, or the dishes, and soon after that, the water at the top reaches the thermstat temp.
Then the bottom element turns on and heats the water below the top level, about 80 or 90% of the water in the tank, I'm guessing. That water is even colder, because hot water rises and cold water sinks, and because the outlet for the cold water input is at the bottom of the tank. So I think the lower element does way more than half of the heating.
The water cools slowly even when not used. I suppose it's the bottom element that goes on when it cools enough, but maybe not.
The advantage of having both filaments at the bottom connected at once is that it will finish heating faster. I'm not sure what the disadvantage is but I'm sure there is at least one, or they would come wired the other way. I'll bet the element lasts longer when it doesn't get too hot. Maybe you might need heavier wires for 5500 watts? Maybe something else?
My previous water heater had an LED that was on when the upper element was on. I guess just so people could see that they were getting what the advertising said they were getting. I think it was an advertised feature when I bought that one**, but by now maybe it's so standard they don't.
**It was Sears but it was identical to AOSmith that came with the house in 1979.
The current WH doesn't have the LED because, I think, they filled all the empty spaces around the thermostats each with a chunk of styrofoam.
Anyhow, sometimes I watched, and the red led and the upper element came on when water was used to fill the bathtub for example. It would turn off maybe 2 to 5 minutes after I got to the basement. I'm sure the lower element went on then.
IIRC and I pretty sure I do, both thermostats should be set at the same temp. They come that way.
I've bought two wh from sears and the new one sure seems to be set not as hot. Maybe this is so it can be green. I like that it's cooler because I can't scald myself, but it is more than hot enough for what I consider a hot bath. The problem for me is that if I add even a little too much cold water, the hot water isn't hot enough to get the tub to the right temperature. I made the wh a little hotter, but maybe I need to go higher.

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