Water Heater ECO keeps tripping


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Old 06-26-16, 04:48 PM
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Water Heater ECO keeps tripping

I just noticed that the safety cover to the upper thermostat/ECO is very warm where the input 240V terminals are. I'm suspecting that the heat is causing the ECO (emergency cutoff) to trip versus a thermostat issue. I have already replaced the upper thermostat on my 1 month old electric water heater (AO SMITH ENT 50). Water from the nearest faucet to the WH is about 125 degrees so I don't think the tank water temperature is tripping the ECO (supposedly trips at 170 -180 degrees). The WH runs about 20 minutes and then the ECO pops. Any thoughts as to why the input terminals could be so hot or is it normal for 240V to throw some heat? Thanks!!
 
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Old 06-26-16, 04:57 PM
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Moved to Water Weater forum.
 
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Old 06-26-16, 09:09 PM
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That area.... the thermostat cover can get warm but should not be hot.

I've only ever seen a hot tank cause that to trip and that was due to a defective lower element. Since the element didn't shut off the water temperature rose excessively and tripped it.

In your case your water temperature appears normal..... which means it's not a hot water issue.
That leaves an upper thermostat that may have been incorrectly wired.

Is the water heater connected with #10 wiring on a 2P30A circuit breaker ?

Using the diagram you could verify the wiring.

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Old 06-26-16, 09:26 PM
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In your case your water temperature appears normal..... which means it's not a hot water issue.
It could still be a matter of excessively hot water IF this installation also has a tempering valve installed. The water heater may have a "grounded" element, which makes it heat regardless of the thermostat position. The tempering valve would then mix enough cold water with the hot to keep the water going to the house in the proper temperature range.
 
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Old 06-27-16, 01:00 AM
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Thank you for the wiring diagram. I verified and tightened all connections this weekend without any difference. I have a 2P30A circuit breaker - it's 30 years old. We've been using the breaker as a on/off switch since we don't use much hot water and it heats so quickly.

I checked the elements per instructions and they are not grounded.

We don't have a tempering device at the sink where I took the water temperature but that was a good point.

It just runs for about 20 minutes and then the ECO pops. It ran great for the first month.

We did have a thunderstorm a few days before we noticed the water heater died. Nothing else electrical around the house was affected, though. I'm just throwing this out just in case.

I had also removed the innards of a broken 30 year old Intermatic timer and connected the wires from the panel to the WH in the old timer box, white to white, black to black and bare to bare. I'm getting 240V at the thermostat so I don't think I messed anything up in there.

Thanks for the help so far!!
 
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Old 06-27-16, 08:49 AM
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At this point the only thing I can think of doing is to use a current meter (amprobe) to see what the unit is drawing.

Other than that.... I'm at a loss right now. With a one month old water heater I'd contact the manufacturer.
 
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Old 06-27-16, 12:48 PM
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Thanks for the ideas. I've tried the manufacturer but at this point they want me to get back to the installer. We ordered the water heater online and used a retired plumber to install it for us. After we met him we found out that he was 77 so I don't want to bother him yet and he didn't really offer us a warranty as such since he didn't charge us based on potential future visits.

So, is it possible that even though the upper element tested 12.2 ohms across the terminals and 0.L from each element terminal to ground that it is drawing more current than it should, thus heating up the area around the ECO and popping it? Unfortunately I don't have a meter that reads more than 10 amps but I'm willing to try replacing the upper element if the scenario is possible rather than call in an electrician for a couple hours or spending money on a meter that I would use once.

Thanks again for all the great advice!!
 
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Old 06-27-16, 01:16 PM
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Did you also test the lower element for grounds? Remember, the upper element ONLY is energized when the majority of the tank is cold, it is the lower element that does most of the work.

There is also the possibility that the high limit thermostat is bad.
 
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Old 06-27-16, 01:33 PM
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Yes, I checked the lower element and also replaced the lower thermostat. Since the water heater pops the ECO after 15-20 minutes or so, I'm assuming that it's still working on the top third.

If i'm finding that the safety cover on the upper thermostat/ECO cover is real hot, can I take my temperature probe on my multimeter and put it on one of the ECO screws after it has popped again? What would the temperature be for a hot terminal screw versus a not so hot terminal screw?

Thanks...
 
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Old 06-27-16, 04:14 PM
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The OP has already replaced the upper thermostat.

upper element tested 12.2 ohms across the terminals and 0.L from each element terminal to ground
You had me there for a minute.... you mean the meter says OL. Ok... that means no continuity.
!2.2 ohms is correct.

I was trying to see if both elements were active together. I was reading in some companies brochure that the water heater can either come with only one element on at a time or both on independently.

Both elements have one terminal connected to "always" hot so either element with a leak to ground can cause the WH to overheat.
 
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Old 06-28-16, 10:53 AM
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I called AO Smith to get the part number for an upper element and I got to talking with the parts guy and after about a half hour he asks me to check the voltage across both elements while the power was on. Both were 238V so both elements were chugging away, drawing a whole bunch of current which heated up the terminals and popped the ECO. Thermostat defective - didn't think it was possible to have both elements switched on but I guess it is. New one on the way free of charge. Thanks so much for the advice and feedback...
 
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Old 06-28-16, 01:07 PM
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So the original thermostat was defective AND the new one was too ?
 
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Old 06-28-16, 03:58 PM
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The AO Smith technical guys say that a power surge can weaken the bimetal part of the ECO switch, so maybe that's what happened with the first one. Who knows in FL with all the lightning storms. Looks like the second one was purely defective. Waiting for number 3 to get here...
 
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Old 06-28-16, 04:03 PM
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I've been servicing for over 40 years. I think I've changed one or two old thermostats. Many elements.

Two new defective stats in one month. That says inferior quality parts are being used.
 
 

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