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Old 11-24-2013, 09:50 PM   #1
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Water Heater Electrical Question


Electric (tank) water heater quit working sometime Friday PM/Sat AM.

W/o doing anything more than confirming power to the heater, checking continuity through the cutout switch, rotating the thermostat set switches as part of checking continuity through the thermostats and pushing the reset button I'm now getting hot water. (????) As part of my investigation I checked the voltage to the top/bottom heating elements and this is what I got w/ heating elements once again actively heating the water (you could hear the water starting to hiss/sizzle): top~235v, bottom~116v. With heater still connected to electrical power and heating elements turned off: top-0v, bottom~235v. Confirmed same indications later on. Question 1: when bottom heating element is on, why doesn't it read ~240v? Question 2: when bottom heating element is off, why does it read ~240v instead of 0v?

Accurate info would be MUCH appreciated.

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Old 11-25-2013, 09:38 AM   #2
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You need two point to measure voltage. What is the reference point for top and bottom readings. Also top and bottom of what? element? switch? measuring across a switch is not a useful exercise.

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Old 11-25-2013, 09:52 AM   #3
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http://waterheatertimer.org/How-to-t...r-element.html
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Old 11-25-2013, 10:29 AM   #4
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Originally Posted by Twister View Post
Electric (tank) water heater quit working sometime Friday PM/Sat AM.

W/o doing anything more than confirming power to the heater, checking continuity through the cutout switch, rotating the thermostat set switches as part of checking continuity through the thermostats and pushing the reset button I'm now getting hot water. (????) As part of my investigation I checked the voltage to the top/bottom heating elements and this is what I got w/ heating elements once again actively heating the water (you could hear the water starting to hiss/sizzle): top~235v, bottom~116v. With heater still connected to electrical power and heating elements turned off: top-0v, bottom~235v. Confirmed same indications later on. Question 1: when bottom heating element is on, why doesn't it read ~240v? Question 2: when bottom heating element is off, why does it read ~240v instead of 0v?


Accurate info would be MUCH appreciated.
When the element is "on" there is a voltage drop across the element.
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Old 11-25-2013, 10:35 AM   #5
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Looks like your top element is not working since you had essentially the same voltage on it as the no load.
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Old 11-26-2013, 12:01 PM   #6
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You need two point to measure voltage. What is the reference point for top and bottom readings. Also top and bottom of what? element? switch? measuring across a switch is not a useful exercise.
What do you mean, "what is the reference point for top and bottom readings"? A YouTube tutorial said each element should be putting out 240v. Is that what you mean?

Perhaps to help you understand what I did....I put multimeter probes into the two wires/wire nuts that go into the top of the heater (the wires that carry power from the power cord into the heater) and verified the heater was receiving electricity. Then I unplugged the cord cutting all power to the heater. Getting electrocuted is not cool. Next, via the multimeter, I checked for good continuity through the cutout switch (this verified the problem was not a bad cutout switch). After that, once again with the multimeter, I verified that the thermostats were receving power. Last, with power restored to the water heater, I put the 2 multimeter probes right on the heating element terminals/screws that hold the wires to the heating element. First the 2 terminals on the top heating element and then the 2 terminals on the bottom heating element. That's how I got the readings I posted above. So "top" and "bottom" refers to the top/bottom heating elements, NOT the terminals.

(BTW, nice Avro Lancaster avatar!)

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When the element is "on" there is a voltage drop across the element.
So why does the top heating element go from ~235v to 0v? If the top element is bad wouldn't it read ~235v all the time?

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Looks like your top element is not working since you had essentially the same voltage on it as the no load.
But the top element did not have the same voltage reading when it was (supposedly) 'on' and 'off'/no load......when it was (supposedly) 'on' it read ~235v and when 'off' it read 0v. Pls explain.

I appreciate your replies, everyone, I'm just not fully understanding yet.
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Old 11-26-2013, 12:23 PM   #7
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Are you aware that the elements operate one at a time. They are never on together at the same time. Turn the power off, remove the wires from the element and take an ohm (resistance) measurement.
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Old 11-26-2013, 12:24 PM   #8
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Wow! Super detailed and step by step. So when testing the heating elements, what does it mean in the 1st of 3 tests when it says that a bad heating element will give an "open reading" on the multimeter?

"No" reading is pretty obvious, but what's an "open reading"?
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Old 11-26-2013, 12:28 PM   #9
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Wow! Super detailed and step by step. So when testing the heating elements, what does it mean in the 1st of 3 tests when it says that a bad heating element will give an "open reading" on the multimeter?

"No" reading is pretty obvious, but what's an "open reading"?
An open means 0 resistance, bad element. A 240 volt 4500 watt element should be about 12-13 ohms.
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Old 11-26-2013, 12:32 PM   #10
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Are you aware that the elements operate one at a time. They are never on together at the same time. Turn the power off, remove the wires from the element and take an ohm (resistance) measurement.
No, I did not know that.

Why don't they turn on at the same time? Wouldn't that heat up/maintain temperature water faster/easier?

I'll do an ohm resistance test and post what I get.
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Old 11-26-2013, 12:34 PM   #11
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An open means 0 resistance, bad element. A 240 volt 4500 watt element should be about 12-13 ohms.
OK....so "no" reading is the same as an "open" reading, correct? Basically, the needle, when set to ohms, does not move?
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Old 11-26-2013, 12:45 PM   #12
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OK....so "no" reading is the same as an "open" reading, correct? Basically, the needle, when set to ohms, does not move?
Correct.
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Old 11-26-2013, 02:22 PM   #13
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An open means 0 resistance, bad element. A 240 volt 4500 watt element should be about 12-13 ohms.
A open means infinite of resistance. Your meter will not move. 0 resistance is a short circuit and your meter will peg over just like when you touch the leads together.
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Old 11-26-2013, 03:35 PM   #14
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A open means infinite of resistance. Your meter will not move. 0 resistance is a short circuit and your meter will peg over just like when you touch the leads together.
You are correct. Bad semantics on my part.
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Old 11-28-2013, 05:43 AM   #15
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So they were not working,
You fiddled with the thermostat and the cut out,
Now it works again ?
Perhaps one of these units is faulty,
dirty contacts maybe.
Or loose connecttions.

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