Is This the Element(s)?
An older State water heater came with the home we bought last year. Up until yesterday, it put out a steady amount of reasonably hot water, but it seemed that an element replacement was in our future... Then yesterday morning when I went to bathe my son, the water came out EXTREMELY hot and I had to go from adjusting the faucet from near the hottest setting to the middle just to get a reasonable temperature. My husband and I then each took showers after this.
When we returned to the house in the afternoon, there was absolutely no hot water whatsoever. Now we're contemplating replacing the elements vs. replacing the unit. The heater does not leak (so far) and it has a timer unit on top from Home Depot that was put on by the previous owner.
Does this sound like something that an element change will fix, or should we be scraping the money together for a new unit?
With an Ohmmeter and ammeter you can quickly test the elements in the tank.
But it sound likes your 8$ temperature switch is bad. There is usually a reset button on them on top and one bottom. Dont 'HOLD" them in.
A dying element does not 'overheat'.
auote; A dying element does not 'overheat'.
Oh, but they can and DO overheat.
One of the elements, (usually the bottom or maybe both), is burned out, but in such a way that it is ALWAYS heating, therefore the temperature of the water keeps increasing, giving you the extremely hot water, until the thermal overload button pops out, at which time the entire system shuts down, which is why you then have NO hot water. Adjusting the thermostats does NOTHING to prevent the problem. Call a plumber to have the heater checked and repair the part(s) which have failed.
How can an element, broken or not continue heating unless the temperature switch is bad?
I have not worked on an electric water heater in decades but back then they used only a single pole thermostat to cut power to the element. If the element shorted to ground, since the neither side of a 240V circuit is at ground potential, the element could heat the water continuously despite the thermostat being open. Back then I wondered why they didn't use double pole switches.
I have bucketfulls of bad electric elements, and they typically blow a hole through the sheath, and sometimes continue heating at a greatly reduced rate in spite of the exposure to water- without tripping the breaker. That is a mystery for our JW over at the electric forum
But cut the power to any one of the lines [i.e the temp switch] and I guarantee that no more heating will occur.
Another failure mode is just an internal breakage of the resistance wire, and the result is simply no heat and no blown breaker.
A true short to ground will trip the breaker. If you guys have some more explanations, I would like to hear it.
On a 240V element, somewhere about the midpoint of it, the voltage would be at the same potential as the centre-tap (white) neutral. A short to ground anywhere near the centre would not present an overcurrent and therefor not trip a breaker.
Originally Posted by ballvalve
You must lack an understanding of how a service transformer is wound with a centre (neutral) tap that is bonded to ground.
If the breakage causes the resistance wire to touch the outer sheath the breaker trips. Other wise I suppose you are sugesting that you have a 50% chance of a 'now' 120 volt element completing its circuit through the water. I say 50% because you mention single pole temp switches, though I never really gave mine a look.
I have 2 electric water heaters for floor heating, and very hard water, thus many failures. Both elements on at the same time. None have ever caused an 'overheat', and they failed at every point along the element, in every manner possible.
To get 240vac you go from one tap to the other...no neutral involved. If you go through that resistance loop (the element), but instead of going to the other tap (which would get the 240vac), but go to ground (which is bonded to the neutral somewhere), what you have is effectively a 120vac circuit - one leg to neutral/ground. Remember, the thermostat only opens one leg, so the thing is sitting with the other leg continuously attached to the power...but, since there's no continuity, there's no current. Connect it, and you have continuity. So, anywhere along that element, as long as it doesn't exceed the capacity of the breaker, it will heat the water as it will be drawing current when shorted to ground with the 120vac potential.