Electric Water Heater Red Reset Button Tripping Troubleshooting Guide

411 plumb Many people even plumbing and electrical professionals have trouble figuring why the red reset button on the upper thermostat of an electric water heater trips. The red reset button or, high limit known as the Energy Cut Off or, ECO is designed to trip when the water in the tank becomes too hot cutting off power to the elements. The ECO is only a manually reset thermostatic switch that shuts off the power to the water heater when the water in the heater reaches 180 Degrees F. The ECO has no other function.

There are a few different things that can cause the ECO to trip all of which involve the ECO getting too hot.

A bad thermostat that does not shut off allowing continuous heating of the water even after the set temperature has been reached is a possible cause of ECO tripping. Your water heater has 2 thermostats, an upper and lower under the two access panels, as well as two elements. Either thermostat sticking in the on position could cause the element it serves to continue heating the water until the water in the tank is heated to 180 Degrees F when the ECO opens cutting power to the water heater.

A loose electrical connection either where the wires connect to the upper thermostat or an internal loose connection can generate heat caused by high resistance inside the thermostat causing the ECO to sense the heat of the bad connection rather than the temperature of the water in the tank causing the ECO to trip.

A bad element that is shorted to ground near the center of the element may also cause the water in the tank causing the ECO to trip. Because the element is shorted to ground near the center of the element the short does not have a high enough current draw to trip the circuit breaker and it continues to heat. However, the way the water heater electrical power is switched the power still is applied to the element even when the thermostat shuts off. The water heater is supplied with 240-volts which means both of the power leads are hot leads. Only 1 side is switched and in normal operation that is fine. But, when the element is shorted to ground there is still the power on the unswitched side available, which will flow through half of the element to ground as 120-volts continuing to heat the water until the ECO trips.

Wiring diagram typical to residential 240-volt non-simultaneous operation water heaters.

Wiring diagram typical to residential 240-volt non-simultaneous operation water heaters.

Your residential electric water heater is wired for 240-volt non-simultaneous operation where the power is initially applied to the upper element, then when the upper thermostat is satisfied it switches power to the lower thermostat for heating the lower section. Once the lower thermostat is satisfied the power to the element is shut off until either thermostat calls for heating again.

Troubleshooting is relatively easy with basic electrical knowledge and skills with a screwdriver and a basic multimeter. Caution is needed as the electrical voltage is 240-volts AC and severe injury or even death can result from electrical shock. The ECO is also a critical safety item of your electric water heater. If the water in the water heater was allowed to continue heating uncontrolled the one remaining safety device before a water heater explosion is a T&P valve functioning properly. If you do not have the skills required to safely and properly test your water heater please call a Licensed Plumber. 411Plumb assumes no liability for this advice or your ability to accomplish it safely.

Testing The ECO

Under the upper side access panel measure for voltage passing through the ECO switch to the thermostat section of the upper thermostat. If the voltage is present and being supplied to the thermostat section then move on to testing the thermostat and elements. If voltage is not present then the ECO switch requires resetting. If the water in the tank is still to hot it must be cooled down to allow resetting the ECO switch. Run hot water from a faucet to cool the tank. If the ECO switch will not reset replace the upper thermostat. If the Eco switch resets then move on to testing the thermostat and elements.

Testing the Elements

To test the elements turn off the power to the water heater and remove both the upper and lower side access panels. Disconnect both wires off the screw terminals on each heating element. Measure across the two screws with a multimeter set top resistance and the resistance should read about 12.8 Ohms for a 240-Volt/4500-Watt element. Then measure resistance from each screw to the water heater tank. This measurement should be an open circuit or infinite reading. If there is any connection from either screw to the tank the element is shorted and needs replacement.

Testing the Thermostat

With the tank cold turn on power to the water heater and measure for voltage from the top thermostat to the upper element, it should read 240-Volts. Check for power being fed to the lower thermostat and element, in this case it should read 0-Volts. Once the upper thermostat is satisfied the power supplied to the upper element should be 0-Volts and the voltage supplied to the lower thermostat and element should read 240-Volts. Once the lower thermostat is satisfied the lower thermostat should shut off power to the lower element.

Note: If testing reveals a fault of the internal wiring of the water on a water heater with foam insulation the wiring is generally not repairable and the water heater should be replaced.

Comments

  1. Chris says

    Found this item by way of Terry Love’s plumbing forum. Been having some issues with the ECO and Sears was no help. I’ll definitely be troubleshooting the water heater this weekend. Thanks!

    • says

      Hi Chris,

      You’re in good hands at either location on the web! Terry Love’s is a great forum and Terry is a great guy, I’m a member there as well. Hopefully this guide helps you out with your troubleshooting and you get your problem resolved this weekend. If not following the trouble shooting procedure will at least have you with some answers to put in your questions either here or, there to zero in on the problem. I’ve answered posts on Terry’s forum about this so many times I figured writing an article here could save typing.

      Minot AFB huh. Are the stories true about there? I was stationed at Mt. Home AFB myself.

      Redwood

  2. steve says

    Your hot water cylinder has two elements one at top one at bottom.Why do so many how to fix it pages start with this?Right from the start anyone with cylinder with one element is off to confusing start,and there are many,many cylinders out there with one thermostat.

    • says

      Hi Steve,
      While there may be many single element water heaters down under, here in the US a vast majority of the water heaters have 2 elements which explains why most online repair guides are written for them. You could still use the 2 element repair guide, but just realize that you can simplify the troubleshooting by having the top thermostat become an on & off for the top element that does not switch power to a lower element.
      Redwood

  3. Dennis Yule says

    The water heater is a Bradford White 80 gal cap. model # M-I-8OR-5ds-12. The top heating element works and receives 220 volts. The bottom element receives 120 volts and does not heat. OLM reading accross the bottom element 16 olms. Is one of the thermostats defective?

    • says

      Hi Dennis,
      Is the upper element satisfied and switching power on to the lower thermostat? Only 1 element should be heating at a time.
      The upper element heats first and when that is done it switches power on to the lower element thermostat.
      If the lower thermostat calls for heating it supplies power to the lower element.
      Only one side of the 240 volts is switched so if you are seeing 120 volts one of the thermostats is not on.
      Redwood

  4. says

    I do some how-to writing for pay and my client would not let me use your site as a linked reference for an article I was writing, even though I tried. This is some of the most sensible information on the internet about how to troubleshoot your water heater. One of these days I’ll get around to fixing mine, I’ve been living with a burned out lower element and barely enough hot water for a fast shower for about six months now. I think it might save money on the electric bill this way but I’m not sure.

    • says

      Hi Jimmy,
      Thanks for visiting my site. Normally I see a link and go “Uuuuugh Another Spam Comment” looking at the associated gibberish that they wrote. I quickly realized that yours was a real comment, and worthy of approval.

      The lower element being out is probably saving a minimal amount and is certainly not worth the discomfort of rushing a shower or, running out of hot water during a shower. When you do get ready to replace that element I suggest having a look at this post “How To Replace Electric Water Heater Elements” for some advice on selecting a good long lasting element.

      I visited your blog and found it quite fascinating and well written. Worthy of a visit for sure, and I’ll share it with some friends as well, these times we are facing will require your good advice. I found “Life and Death in the Minimalist Universe” of particular interest as you will find in the comment I left there regarding the DeLorme Earthmate.
      Redwood

  5. JOHN says

    I came home today and found my water heater sounds like it keeps heating the water. I just had a plumber drain my tank, clean sediment out, replace both heating elements, and install a water filtration system. There are no leaks, I turned the breaker off, hit the reset button, and turned the breaker back on. If this works okay, if not, what could be the problem?
    Thanks,
    John

    • says

      Hi John,
      It could be any number of things which should be properly troubleshot using the information in the article above. Is the water heater actually heating uncontrolled? Did the red button actually trip? Were the elements bad? Are the thermostats working properly? Is hot water being used and that is why the water heater is heating?

      Proper troubleshooting will establish what is happening and what repairs have to be made.

      Redwood

  6. Art says

    Your information has been extremely helpful. I am a retired electrician and have often had problems troubleshooting the ECO. Your information gives correct steps to troubleshooting. Saves the homeowner money when they fix it themselves and also the pro who may not have learned the correct procedure other than changing parts and coming back until all electric parts are changed. Thanks

    • says

      Hi Art,
      Thanks for the comment, and I’m glad you found the information useful.
      The function of the ECO is misunderstood by many people, pro’s included.
      Redwood

  7. steha says

    This is a great trouble shooting guide! The guy working at the Home Depot tried to convince me that it was the upper thermostat instead of the lower that was malfunctioning but I held my ground with my new found knowledge of how a water heater works…he wasn’t convinced. Anyway, it only cost about $9 to fix and I avoided any expensive visits from the plumber. Thanks for your help.

  8. Mike says

    Thanks for the troubleshooting guide. Turns out there was a short in the black wire between the lower element and the lower thermostat. Learning that the lower element comes on after the top element is satisfied, really helped explain why we got hot water to the point of almost steaming, and then the red button would trip. Prior to reading this guide I was working on the assumption that the red button was faulty or that the upper thermostat was faulty. A simple replacement of the offending wire, and it appears to be fixed. If no recurring red button tripping by this time tomorrow and I can safely presume the problem is fixed permanently. You saved me a visit from the plumber, and I learnt something, thank you!.

    • says

      Hi Mike,
      Yes a short there would make the lower element heat on 120 volts all the time causing the ECO to trip. If the upper thermostat did switch over earlier the circuit breaker would also have tripped if the lower thermostat was calling for heating. I’m glad this was able to help you fix the problem.
      Redwood

  9. Ann says

    ok we followed all this info and found everything is functioning on the water heater and can not figure out why our eco keeps tripping. should we replace the whole thing?

    • says

      Hi Ann,
      I would recommend going back through the tests as something is wrong that you have missed. The ECO can only trip because of the causes I have listed. If you are going to use the shotgun approach to fixing the water heater I’d recommend replacing both thermostats and elements rather than a new water heater, this will certainly cure anything with the exception of faulty wiring, which would probably reveal itself by tripping a circuit breaker rather than tripping the ECO.
      I hope this helps,
      Redwood

  10. jonathan says

    I have a hot point electric hot water heater it is a one element heater I replaced the thermostat and the heating element and I am still no getting hot water. My question is if the reset button on the thermostat was tripped would I still have good voltage at the heating element?

    • says

      Hi Jonathan,
      With the ECO tripped you should not read voltage at the element.
      Are you sure the water heater was filled with water before you turned it on?
      Dry Firing will kill a new element almost instantly.
      Redwood

  11. peter king says

    You mentioned that “But, when the element is shorted to ground there is still the power on the unswitched side available, which will flow through half of the element to ground as 120-volts continuing to heat the water until the ECO trips.” If I disconnect the unswitched side, can the issue with ECO trips be resolved ?

    Thanks!

    Peter

    • says

      Hi Peter,
      Have you troubleshot your water heater and found an element shorted to ground or, are you just guessing that is the problem?

      In you home’s electrical system there are 2 hot leads, and a neutral which is bonded to ground. Current flowing from hot to neutral is 120 volts, and current flowing from hot to hot is 240 volts. A water heater using 240 volts is only switched on one side by the thermostat which effectively turns the heating elements on and off. If an element is shorted to ground the unswitched hot side can continue to flow to ground heating the water with 120 volts. This heating will then continue until the water in the tank is overheated and the ECO trips, which then shuts off both hot leads supplying the water heater. If you were to shut off the unswitched side the water heater will not work as you will have shut off the electricity supply to the water heater. The exception here would be if only the unswitched side was disconnected and the upper element was shorted, then it would heat with 120 volts until the thermostat was satisfied.

      Really the only good solution is to troubleshoot the water heater and replace the faulty components so it works properly. As a rule when I repair a water heater I will replace both elements and both thermostats anyway but I do troubleshoot to be sure that the components I am replacing will indeed fix the problem and the wiring in the water heater is not faulty. To go on a paid service call and only replace a single component in the system leaves open the possibility of another old component failing in the guarantee period and a call back. Less than $100 in parts ensures reliability and the possibility of looking bad as the guy who just fixed it and it broke again as well as costing me money on an unpaid repair under the guarantee. All of the components needed for the most common electric water heater rebuild are available for purchase on this page.

      Redwood

  12. peter king says

    Hi Redwood,

    Thanks so much to answer my question. The lower element is shorted. Does the disconnection of the unswitched side just from the lower element do the trick?

    Thanks.

    Peter

    • says

      Hi Peter
      Disconnecting the lower element should stop the ECO from tripping, but your hot water supply will be very limited until you replace the element and have the water heater running right again.
      Redwood

  13. peter king says

    Hi Redwood,

    How can the both thermostats be set up? The thermostat tempture range is 90 – 150. Should the upper thermostat be set a bit higher than the lower one? Why or why not? Dose there exist a ‘best’ combination ?

    Thank you.

    Peter

    • says

      Hi Peter,

      I set both to 120ºF to avoid scalding liability issues. If you set both higher you must temper the output of the water heater to a safe temperature using a thermostatic tempering valve. The threshold of pain from hot water in an adult is approximately 116ºF, water at 120ºF takes approximately 3 minutes to scald an adult, 122ºF takes 1 minute, and 154ºF is instantaneous. Any temperature above 120ºF rapidly changes the time for a burn to occur even with the temperature being just a few degrees higher. Scalding in infants, young children and the elderly can occur much faster than the temperatures I cited.

      There are some changes to the plumbing codes in the US possibly coming soon, and these changes may already be in effect in other countries. Legionella Bacteria is present in all water in small amounts, with water temperatures below 68ºF or, 118 – 122ºF and above Legionella Bacteria can survive but not multiply. With temperatures between 77 – 108ºF being considered in the growth range where the Legionella Bacteria colony can rapidly multiply. Water temperatures above 131ºF will kill Legionella Bacteria with the time decreasing as the temperature increases, with instant death occurring at approximately 158ºF. Watch for plumbing codes to be changed to higher temperatures, with thermostatic mixing valves for scalding safety becoming a requirement in the future code revisions.

      I hope this helps,
      Keep safe,
      Redwood

  14. Andy Krause says

    I had a problem with my water heater tripping the reset button. I found your website for troubleshooting. I cannot express enough gratitude. I followed the procedure and in less than an hour and a half, I had hot water again. Thank you so much for sharing your knowledge here for us to use. If you were here, I would buy you a beer!!! :)

    • says

      Hi Andy,
      If I was there I’d take you up on that beer, perhaps one from the Russian River Brewing Company such as Pliny The Younger or, Pliny The Elder, I sure wish we could get them over here on the Right Coast. I’m glad you found the article helpful and that you were able to repair your water heater. Please share the site with others.
      Redwood

  15. Chip says

    Hi Redwood – Extremely useful page here, thanks for your efforts. I have a question:
    How can I tap into the existing thermostat on my water heater to get a live reading of the temperature? Is it a thermocouple or thermistor that is inside there somewhere?
    I should mention, it’s electric, not gas.

    Thanks! – Chip W.

    • says

      Hi Chip,
      Most electric water heaters use a mechanical snap acting thermostat that is in direct contact with the tank, some such as Whirlpool’s Energy Smart Electric Water Heater use a thermistor. On those while it may be possible to tie into the circuitry and obtain a reading I don’t have any details of the thermistor which could help you.

      I’d recommend either placing a thermistor from a commercially available thermometer in contact with the tank, using an IR thermometer to read the tank temperature or, using a snap in place temperature gauge on the outlet pipe and obtaining a reading when the water is being used. I usually just place a thermometer in the hot water stream at a faucet closest to the water heater.

      You should be aware that the water temperature in the tank will almost never be exactly at the set point of the thermostat. There will be a maximum temperature at which the elements turn off, a differential temperature range at which the elements are off, and a low temperature at which the elements turn on and the water is being heated again. The differential is probably around 10ºF which will give you the variation, in addition there is also some variation in the accuracy of the setting on mechanical thermostats.

      I hope this helps,
      Redwood

      • Chip says

        Hi Redwood – Many thanks for the help. I ended up installing my own thermocouples on the tank and the tank discharge. They come to pretty close agreement after that water line heats up.

        Chip

  16. Kris Hasler says

    Hi Redwood,
    Very helpful information. But my water heater checked out on all the tests above, but still trips the ECO like once every 3 months, usually when im not home so I come home to an unhappy family. In the last 6 months I have replaced both elements and flushed out the tank. Does that mean the wiring internally is bad??? Thanks much for the info and have a great day.

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