hot water heater

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Tonight our electric hot water heater was giving no hot water at all (too late to get to Home Depot!). The circuit breaker was not tripped, the reset button on the top heating element aparantly was not tripped, and electricity was getting to the top heating element (I didn't check the bottom one). The unit is about seven years old. I took out the heating elements, and they look intact. I tested them and they showed about 12.7 ohms of resistance. Does this say anything about whether or not the heating elements are OK? Could it be anything other than the heating elements, since the element was getting electricity, and the wires weren't loose?
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The resistance you measured sounds reasonable. Are you sure you're measuring 220 at the upper element? And you're still getting no heat (even limited)?
Try here, but you've already made the important checks.
http://www.chilipepperapp.com/troublee.htm
This very week, I've been having just a miserable time getting warranty work done on a 5 month old GE unit I bought at Home Depot. They're made by Rheem, and they've taken over 5 days (and counting) just to get a service outfit to return the phone call. No service at all. You might consider buying elsewhere, or a different brand.
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wrote:

It seemed to be no heat at all, but I can't be sure. The water was slightly warmer than the cold water, but it must have gone out sometime today, so it probably has retained some of the heat.

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wrote:

Initially I only measured the voltage at the top element - 244V. I just measured the bottom one, and it was only 39V. Is that normal, or does it indicate a problem (with the thermostat, perhaps)? Replace you know what by j to email
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Jud McCranie wrote:

Please don't get offended, but it's highly unlikely you would measure 39 volts across that lower element. Are you sure you are putting the two meter leads directly onto the screws of that element?
Given an element resistance of less than 15 ohms, something else in there has to be dropping over 200 volts while feeding current into the element. Whatever that drop was across would be dissipating over 4 KW and getting hotter than hell so you'd smell it or see it pretty fast.
Are you sure you're not getting tricked by a high impedance digital voltmeter and capacitive coupling?
Jeff
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Jeff Wisnia (W1BSV + Brass Rat '57 EE)

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wrote:

I don't know much about testing AC voltage, I mainly use the meter for other things. I checked the bottom one after I had taken the elements out. I turned the electricity back on and tested at the leads. I did each one at least twice.
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Jud McCranie wrote:

OK, as I suspected, with the element disconnected, that "39 volts" is a phantom reading caused by current flow into the capacitance of the wiring. The voltage is there allright, but with only minute current capability.
I'm going to have to state that your admitted lack of ac electrical knowledge is going to make it pretty hard for us avoid getting misled by your descriptions. That's OK, I bet there are lots of things you're expert in that I know naught about.
But, that said, you probably should find someone with the requisite electrical knowledge to give you a hand getting to the root of the problem. The electrics of water heaters aren't rocket science, I f I were able to stand beside you with a meter I'd get you the right answer quicker than you could say Jill Robinson.
Good luck,
Jeff
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Jeff Wisnia (W1BSV + Brass Rat '57 EE)

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On Thu, 19 Feb 2004 12:25:43 -0500, Jeff Wisnia

It might have been 39 mV instead of volts, and I didn't to notice the "m" in front of the "V" on my meter. Now I've replaced both heating elements and I checked the voltages. The top one is reading 244V, the bottom one is reading 6 mV.
Does that indicate anything?
Could there be a problem with the bottom thermostat?
Both thermostats are set on 130 degrees, and I've replaced the heating elements and restarted the unit. It sounds like it is heating. I'll have to wait to see if I get hot water.
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Jud McCranie wrote:

Yes, it sounds like normal performance, you won't see that 244 volts on the lower element until the water at the top of the tank gets hot.
The usual way that home electric hot water heaters function is:
From a cold start, and with no hot water being drawn from the tank, the upper thermostat connects power to the upper element. When the water in the top of the tank heats up to the upper thermostat's set point temperature it switches off the power to the upper element and redirects the power downstairs where it feeds through the lower thermostat to the lower element, heating the water in the bottom of the tank. (The upper thermostat works like a single pole double throw switch, so only one element can be on at a time.)
When the water at the bottom reaches the lower thermostat's set point temperature it too opens, removing power from the lower element.
If no hot water is drawn, things will remain static with both elements unpowered until the water in the tank cools through slow gradual heat loss through the tank insulation. The water in the bottom of the tank will be a little cooler than that at the top (heat rises) and the lower thermostat will cycle the lower element on and off from time to time to maintain the water temperature in the tank.
When someone starts drawing off hot water, that brings cold water into the bottom of the tank through the dip tube. The cold water coming in will shortly cool the lower thermostat, which closes and applies power to the lower element. If enough hot water is drawn off to make the water near the upper thermostat drop in temperature, that thermostat will remove power from the lower thermostat and apply it to the upper element, to help keep the water exiting the tank hot as long as possible, which it could do forever if the flow was kept down to a trickle.
All that's left to describe is the overtemperature thermostat/reset button. It's a safety device wired in series ahead of everything else. If either of the two main thermostats stick closed, causing the water temperature to increase to an unsafe level, the overtemperature thermostat "pops", removing power from everything until the water cools down and the reset button is pressed. If that happens, it's a good idea to replace the main thermostats, as once they start sticking closed, they'll likely do it again. (Things which go away by themselves usually come back by themselves you know.)
Does that help?
Jeff
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Jeff Wisnia (W1BSV + Brass Rat '57 EE)

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On Thu, 19 Feb 2004 13:34:49 -0500, Jeff Wisnia
Yes, it does. I didn't know about only one element at the time being on, etc.
And we have hot water again!
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Jud McCranie wrote:

Good!
Now take all the money you saved by doing it yourself and take SWMBO out for a nice dinner this weekend. <G>
Jeff
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Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"My luck is so bad that if I bought a cemetery, people would stop dying."
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One good friend of mine used to say "Danger Will Robinson" and I had to ask what that meant. It was from an old science fiction program on TV where the robot would say "Danger Will Robinson" when the little boy was about to do something dangerous.
It sounds like the fellow is working on something well out of his skill range, and I'll get to say "Danger Jill Robinson" if he continues to work on it.....
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Christopher A. Young
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dying."
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*CBHVAC* wrote:

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Jud McCranie wrote:

Based on your description, and taking what you've said you've measured at face value, I'd say that the "dip tube" on the cold water supply fitting (the tube which brings the cold water down to the botom of the tank) has fallen off and cold water is moving directly across the inside top of the tank from the inlet to the outlet.
The only other thing I can think of (assuming you measured full voltage directly across the two terminals of the top heating element) is that the element has an internal break, closed when the element is cold, letting you measure a reasonable 12.7 ohm resistance, but which opens as soon as it tries to heat. If you had an "Amprobe" type clamp on ammeter handy you could measure the currrent in the leads to the upper element and know for sure if it was in fact drawing the 20 amps or so it should be.
You could try swapping the two elements, it's near impossible that they would both have that funny kind of fault.
Good luck, let us know what it is,
Jeff
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Jeff Wisnia (W1BSV + Brass Rat '57 EE)

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wrote:

Thanks for telling me about the dip tube. The unit was made in 97 and has a plastic dip tube. However, it seems to be OK. I looked at it through the holes for the heating element and as far as I could see, it is intact down to the level of the bottom heating element. I turned the water back on, and it all seemed to be coming through to the end of the dip tube.

I don't have one of those clamp ammeters.
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You might want to consider getting one. They come in *very* handy. You can get a decent one that will work fine for occasional use for about $60 - $80. If it saves you just one service call from an appliance repair person, it's paid for itself.
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Banister Stairwell wrote:

Mine came from Harbor Freight when they were on sale for about $20. (As they are right now.)
Search for Item No. 42397 at:
http://www.harborfreight.com
I've found it perfectly acceptable for my home use, though it doesn't look like it'd stand much dropping and banging around on a "real" job site.
Good luck,
Jeff
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Jeff Wisnia (W1BSV + Brass Rat '57 EE)

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On Thu, 19 Feb 2004 12:15:54 -0500, Jeff Wisnia

Wow, there have been times when I could really use one. Like seeing what the total amps drawn of a computer system to see what size of UPS for it.
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On Thu, 19 Feb 2004 12:15:54 -0500, Jeff Wisnia
It says "Measures resistance and AC and DC voltage" does it also measure amps?
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